2021/05/30 更新

写真a

ハヤシ ヤスヒコ
林 靖彦
HAYASHI Yasuhiko
所属
自然科学学域 教授
職名
教授
外部リンク

学位

  • 博士(工学) ( 1999年3月   名古屋工業大学 )

  • 修士(工学) ( 1992年3月   名古屋工業大学 )

  • 学士(工学) ( 1990年3月   名古屋工業大学 )

研究キーワード

  • スーパーキャパシタ材料・デバイス

  • ナノカーボン材料(ナノチューブ,グラフェン)合成およびデバイス

  • ペロブスカイ材料および太陽電池

  • 人工筋肉・ソフトアクチュエータ

  • 熱電変換材料・素子

  • 有機半導体太陽電池およびトランジスタ

  • フェムト秒電子分光

研究分野

  • ものづくり技術(機械・電気電子・化学工学) / 電気電子材料工学

  • ナノテク・材料 / ナノ材料科学

  • ナノテク・材料 / 有機機能材料

  • ナノテク・材料 / ナノマイクロシステム

学歴

  • 名古屋工業大学   大学院工学研究科   電気情報工学専攻

    1996年4月 - 1999年3月

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  • 名古屋工業大学   大学院工学研究科   電気情報工学専攻

    1990年4月 - 1992年3月

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    国名: 日本国

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経歴

  • 岡山大学

    2021年4月 - 現在

  • 岡山大学   副理事(研究・産学協創)

    2021年4月 - 現在

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  • 東京工業大学   科学技術創成研究院

    2016年12月 - 現在

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  • 岡山大学   大学院自然科学研究科産業創成工学専攻   教授

    2012年10月 - 現在

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  • Universiti Teknologi MARA (UiTM)

    2012年1月 - 2012年9月

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  • 名古屋工業大学   大学院工学研究科 未来材料創成工学専攻   准教授

    2008年4月 - 2012年9月

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  • 名古屋工業大学   大学院工学研究科 都市循環システム工学専攻   准教授

    2007年4月 - 2008年3月

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  • 名古屋工業大学   大学院工学研究科 都市循環システム工学専攻   助手

    1999年4月 - 2007年3月

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  • 市邨学園短期大学(現名古屋経済大学短期大学部)

    1998年4月 - 1999年3月

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  • 日本モトローラ株式会社 -   研究員

    1992年4月 - 1996年2月

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所属学協会

  • 炭素材料学会

    2020年10月 - 現在

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  • 公益社団法人 応用物理学会

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  • 日本繊維機械学会

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  • 一般社団法人日本機械学会

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  • Materials Research Society(MRS)

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  • The Institute of Electrical and Electronic Engineers (IEEE)

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委員歴

  • 独立行政法人 情報通信機構   研究評価委員会委員  

    2007年4月 - 2011年3月   

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    団体区分:学協会

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  • 電子情報通信学会   基礎境界ソサイエティー 第3種研究会 幹事  

    2001年4月 - 2003年3月   

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    団体区分:学協会

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  • 財団法人 ファインセラミックスセンター   研究開発推進委員会委員  

    2000年4月 - 2001年3月   

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    団体区分:学協会

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論文

  • Improved room-temperature thermoelectric characteristics in F4TCNQ-doped CNT yarn/P3HT composite by controlled doping 査読

    May Thu Zar Myint, Takeshi Nishikawa, Hirotaka Inoue, Kazuki Omoto, Aung Ko Ko Kyaw, Yasuhiko Hayashi

    Organic Electronics90   106056 - 106056   2021年3月

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    担当区分:責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    DOI: 10.1016/j.orgel.2020.106056

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  • Nanostructural characterization of carbon nanotube yarn high-strengthened by joule heating 査読

    Takaya Tezuka, Norio Mori, Takuya Murayama, Takuma Sano, Tomohiro Nakagawa, Hirotaka Inoue, Yasuhiko Hayashi, Toru Kuzumaki

    Carbon171   437 - 443   2021年1月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    DOI: 10.1016/j.carbon.2020.09.014

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  • Single crystal of two-dimensional mixed-halide copper-based perovskites with reversible thermochromism 査読

    Amr Elattar, Hiroo Suzuki, Ryuji Mishima, Kodai Nakao, Hiromi Ota, Takeshi Nishikawa, Hirotaka Inoue, Aung Ko Ko Kyaw, Yasuhiko Hayashi

    Journal of Materials Chemistry C9 ( 9 ) 3264 - 3270   2021年

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    担当区分:責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Royal Society of Chemistry (RSC)  

    <p>Facile synthesis of single crystal of two-dimensional mixed-halide copper-based perovskites with tunable band gaps and their capability of exfoliation and reversible thermochromism.</p>

    DOI: 10.1039/d0tc04307a

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  • A mechanistic investigation of moisture-induced degradation of methylammonium lead iodide 査読

    Masaki Hada, Md. Abdullah Al Asad, Masaaki Misawa, Yoichi Hasegawa, Ryota Nagaoka, Hiroo Suzuki, Ryuji Mishima, Hiromi Ota, Takeshi Nishikawa, Yoshifumi Yamashita, Yasuhiko Hayashi, Kenji Tsuruta

    Applied Physics Letters117 ( 25 ) 253304 - 253304   2020年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AIP Publishing  

    DOI: 10.1063/5.0021338

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  • Phonon transport probed at carbon nanotube yarn/sheet boundaries by ultrafast structural dynamics 査読

    Masaki Hada, Kotaro Makino, Hirotaka Inoue, Taisuke Hasegawa, Hideki Masuda, Hiroo Suzuki, Keiichi Shirasu, Tomohiro Nakagawa, Toshio Seki, Jiro Matsuo, Takeshi Nishikawa, Yoshifumi Yamashita, Shin-ya Koshihara, Vlad Stolojan, S. Ravi P. Silva, Jun-ichi Fujita, Yasuhiko Hayashi, Satoshi Maeda, Muneaki Hase

    Carbon170   165 - 173   2020年12月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier BV  

    DOI: 10.1016/j.carbon.2020.08.026

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  • Super-chiral vibrational spectroscopy with metasurfaces for high-sensitive identification of alanine enantiomers 査読

    Takumi Iida, Atsushi Ishikawa, Takuo Tanaka, Atsuya Muranaka, Masanobu Uchiyama, Yasuhiko Hayashi, Kenji Tsuruta

    Applied Physics Letters117 ( 10 ) 101103 - 101103   2020年9月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:AIP Publishing  

    DOI: 10.1063/5.0012331

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  • Synthesis of solvent-free conductive and flexible cellulose–carbon nanohorn sheets and their application as a water vapor sensor 査読

    Karthik Paneer selvam, Tomohiro Nakagawa, Tatsuki Marui, Hirotaka Inoue, Takeshi Nishikawa, Yasuhiko Hayashi

    Materials Research Express7 ( 5 ) 056402   2020年5月

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    担当区分:最終著者, 責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  • Controlling Electronic States of Few-walled Carbon Nanotube Yarn via Joule-annealing and p-type Doping Towards Large Thermoelectric Power Factor. 査読 国際誌

    May Thu Zar Myint, Takeshi Nishikawa, Kazuki Omoto, Hirotaka Inoue, Yoshifumi Yamashita, Aung Ko Ko Kyaw, Yasuhiko Hayashi

    Scientific reports10 ( 1 ) 7307 - 7307   2020年4月

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    担当区分:最終著者, 責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Flexible, light-weight and robust thermoelectric (TE) materials have attracted much attention to convert waste heat from low-grade heat sources, such as human body, to electricity. Carbon nanotube (CNT) yarn is one of the potential TE materials owing to its narrow band-gap energy, high charge carrier mobility, and excellent mechanical property, which is conducive for flexible and wearable devices. Herein, we propose a way to improve the power factor of CNT yarns fabricated from few-walled carbon nanotubes (FWCNTs) by two-step method; Joule-annealing in the vacuum followed by doping with p-type dopants, 2,3,5,6-tetrafluo-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). Numerical calculations and experimental results explain that Joule-annealing and doping modulate the electronic states (Fermi energy level) of FWCNTs, resulting in extremely large thermoelectric power factor of 2250 µW m-1 K-2 at a measurement temperature of 423 K. Joule-annealing removes amorphous carbon on the surface of the CNT yarn, which facilitates doping in the subsequent step, and leads to higher Seebeck coefficient due to the transformation from (semi) metallic to semiconductor behavior. Doping also significantly increases the electrical conductivity due to the effective charge transfers between CNT yarn and F4TCNQ upon the removal of amorphous carbon after Joule-annealing.

    DOI: 10.1038/s41598-020-64435-0

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  • Whitish daytime radiative cooling using diffuse reflection of non-resonant silica nanoshells 査読

    Takahiro Suichi, Atsushi Ishikawa, Takuo Tanaka, Yasuhiko Hayashi, Kenji Tsuruta

    Scientific Reports10   6486   2020年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  • The critical role of the forest morphology for dry drawability of few-walled carbon nanotubes 査読

    Hirotaka Inoue, Masaki Hada, Tomohiro Nakagawa, Tatsuki Marui, Takeshi Nishikawa, Yoshifumi Yamashita, Yoku Inoue, Kazuhiko Takahashi, Yasuhiko Hayashi

    CARBON158   662 - 671   2020年3月

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    担当区分:責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Carbon nanotube (CNT) yarns comprise few-walled CNTs (FWCNTs), mainly consisting of double- and triple-walled CNTs, and have several properties which are beneficial for practical bulk-scale carbon devices. These features include high tensile strength, electrical conductivity, thermal conductivity, chemical stability, and environmental tolerance. However, the synthesis window for fabricating CNT yarns with FWCNTs by the dry-spinning method is quite narrow and optimal conditions have yet to be determined. In this study, we fabricated CNT forests mainly comprised of FWCNTs at various synthesis conditions (temperature and time). The drawability of the CNT forests was characterized depending on the synthesis conditions. Our results show that optimum values exist for continuously drawable CNT forests in terms of both their height (>130 mu m) and bulk density (> 90 mg/cm(3)) for satisfying enough entanglement force between the CNT bundles. The diameter and number of walls of the CNTs are controlled by the temperature during the formation of catalyst particles because the sizes of catalyst particles are approximately equal to the outer diameter of CNTs. All temperature conditions in the range 350-500 degrees C, used to form catalyst particles, resulted in a drawable FWCNT forest. These insights will be useful for developing devices based on FWCNT yarns. (C) 2019 Published by Elsevier Ltd.

    DOI: 10.1016/j.carbon.2019.11.038

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  • Systematic Investigations of Annealing and Functionalization of Carbon Nanotube Yarns 査読

    Maik Scholz, Yasuhiko Hayashi, Victoria Eckert, Vyacheslav Khavrus, Albrecht Leonhardt, Bernd Büchner, Michael Mertig, Silke Hampel

    Molecules25 ( 5 ) 1144   2020年3月

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    担当区分:責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  • Liquid-like dielectric response is an origin of long polaron lifetime exceeding ten microseconds in lead bromide perovskites 招待 査読

    Kiyoshi Miyata, Ryota Nagaoka, masaki hada, Takanori Tanaka, Ryuji Mishima, Taihei Kuroda, Sota Sueta, Takumi Iida, Yoshifumi Yamashita, Takeshi Nishikawa, Kenji Tsuruta, Yasuhiko Hayashi, Ken Onda, Toshihiko Kiwa, Takashi Teranishi

    The Journal of Chemical Physics152   084704   2020年2月

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    担当区分:責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  • Reverse Engineering of Thin Films to Nanoparticles by Thermal Deposition for Large-Scale Production of Nanometals 査読

    Karthik Paneer Selvam, Zaw Lin, Inoue Hirotaka, Marui Tatsuki, Takeshi Nishikawa, Yasuhiko Hayashi

    JOURNAL OF NANO RESEARCH61   42 - 50   2020年

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    担当区分:責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TRANS TECH PUBLICATIONS LTD  

    A simple method to synthesize metal nanoparticles (Nps) has been proposed using high vacuum thermal deposition (HVTD) by reverse engineering of thin films to Nps. Metal Nps synthesized by this technique corresponds to the top-down approach of nanomaterial synthesis from bulk metals of silver and copper wires to metal Nps. A high-vacuum thermal deposition is a commonly used technique for thin-film deposition in many applications. Synthesis of metal Nps by HVTD is simple, efficient, and can provide particle of about few tens of nanometers is effortless. A precoated thin layer of polyethylene glycol (PEG) on a glass substrate (Petri dish), is allowed deposit with a metallic thin film by thermionically evaporating bulk metal wires in high vacuum. The deposited metal thin film is removed along with the PEG coating into a liquid medium and subjected to sonication, stirring, and deoxidation. Obtaining the particle size in tens of nanometer range in one step is one projecting factor by HVTD technique. Also, providing the feasibility of reusing large particles as precursors after synthesis is a unique vantage point. The Nps were analyzed by various characterizations tools to evaluate the underlying properties.

    DOI: 10.4028/www.scientific.net/JNanoR.61.42

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  • A review of dry spun carbon nanotube yarns and their potential applications in energy and mechanical devices 招待 査読

    Yasuhiko Hayashi, Yusuke Chiba, Hirotaka Inoue, Masaki Hada, Takeshi Nishikawa

    Journal of Fiber Science and Technology76 ( 2 ) 72 - 78   2020年

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    担当区分:筆頭著者, 最終著者, 責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    © 2020 The Society of Fiber Science and Technology, Japan. Carbon nanotube (CNT) yarn drawn from CNT arrays has recently attracted considerable interest for various applications in wiring harnesses, composites, smart textiles, and high strength structural materials. Although the excellent properties and functions of CNTs are expressed at nanometer scale, it is quite difficult to maintain these nanoscale properties while upscaling to bulk CNT spun yarn. This paper aims to provide an overview of the rapid synthesis of spinnable tall and dense CNT arrays, the processing and improvement of the physical properties of CNT spun yarn, and the application of CNT spun yarn in the fields of energy and mechanical devices.

    DOI: 10.2115/fiberst.2020-0013

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  • One-Minute Joule Annealing Enhances the Thermoelectric Properties of Carbon Nanotube Yarns via the Formation of Graphene at the Interface 査読

    Masaki Hada, Taisuke Hasegawa, Hirotaka Inoue, Makito Takagi, Kazuki Omoto, Daiki Chujo, Shogo Iemoto, Taihei Kuroda, Taiga Morimoto, Takuma Hayashi, Toru Iijima, Tomoharu Tokunaga, Naoshi Ikeda, Kazuhiro Fujimori, Chihiro Itoh, Takeshi Nishikawa, Yoshifumi Yamashita, Toshihiko Kiwa, Shin-ya Koshihara, Satoshi Maeda, Yasuhiko Hayashi

    ACS APPLIED ENERGY MATERIALS2 ( 10 ) 7700 - 7708   2019年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    Interfaces in nanocarbon materials are highly important, as they determine the properties of carbon-based devices. In terms of carrier and thermal transport properties, the interfacial features are often more important than the intrinsic characteristics. Herein, we describe how 1 min Joule annealing of carbon nanotube (CNT) yarns can convert the interfacial amorphous carbon into graphene fragments. After 1 min Joule annealing, we have obtained multiwalled CNT yams with extremely high Seebeck coefficients (+/- 100 mu V/K) and high thermoelectric power factor (400 and 1000 mu W/mK(2)) at room temperature, both with or without polyethylenimine doping. Theoretical simulations and experimental measurements helped to determine the optimal annealing conditions in terms of a rapid transformation of the interfacial amorphous carbon between the bundled CNTs in the yarn into graphene fragments at similar to 2000 K. The present approach represents significant progress in energy materials science, as it provides a guiding principle for the design of interfaces in nanocarbon materials with potential applications in energy-harvesting systems.

    DOI: 10.1021/acsaem.9b01736

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  • Ultrafast isomerization-induced cooperative motions to higher molecular orientation in smectic liquid-crystalline azobenzene molecules 査読

    Masaki Hada, Daisuke Yamaguchi, Tadahiko Ishikawa, Takayoshi Sawa, Kenji Tsuruta, Ken Ishikawa, Shin Ya Koshihara, Yasuhiko Hayashi, Takashi Kato

    Nature communications10   4159   2019年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  • Selective Reduction Mechanism of Graphene Oxide Driven by the Photon Mode versus the Thermal Mode 査読

    Masaki Hada, Kiyoshi Miyata, Satoshi Ohmura, Yusuke Arashida, Kohei Ichiyanagi, Ikufumi Katayama, Takayuki Suzuki, Wang Chen, Shota Mizote, Takayoshi Sawa, Takayoshi Yokoya, Toshio Seki, Jiro Matsuo, Tomoharu Tokunaga, Chihiro Itoh, Kenji Tsuruta, Ryo Fukaya, Shunsuke Nozawa, Shin-ichi Adachi, Jun Takeda, Ken Onda, Shin-ya Koshihara, Yasuhiko Hayashi, Yuta Nishina

    ACS NANO13 ( 9 ) 10103 - 10112   2019年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    A two-dimensional nanocarbon, graphene, has attracted substantial interest due to its excellent properties. The reduction of graphene oxide (GO) has been investigated for the mass production of graphene used in practical applications. Different reduction processes produce different properties in graphene, affecting the performance of the final materials or devices. Therefore, an understanding of the mechanisms of GO reduction is important for controlling the properties of functional two-dimensional systems. Here, we determined the average structure of reduced GO prepared via heating and photoexcitation and clearly distinguished their reduction mechanisms using Graphene oxide ultrafast time-resolved electron diffraction, time-resolved infrared vibrational spectroscopy, and time-dependent density functional theory calculations. The oxygen atoms of epoxy groups are selectively removed from the basal plane of GO by photoexcitation (photon mode), in stark contrast to the behavior observed for the thermal reduction of hydroxyl and epoxy groups (thermal mode). The difference originates from the selective excitation of epoxy bonds via an electronic transition due to their antibonding character. This work will enable the preparation of the optimum GO for the intended applications and expands the application scope of two-dimensional systems.

    DOI: 10.1021/acsnano.9b03060

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  • Influence of pressure of nitrogen gas on structure and thermoelectric properties of acid-treated PEDOT:PSS films 査読

    May Thu Zar Myint, Hirotaka Inoue, Susumu Ichimura, Takeshi Nishikawa, Yuta Nishina, Aung Ko Ko Kyaw, Yasuhiko Hayashi

    JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS30 ( 14 ) 13534 - 13542   2019年7月

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    担当区分:責任著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGER  

    Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most commonly investigated conductive polymer due to its unique thermoelectric properties. Several post treatments using various acids have been reported to improve the thermoelectric properties of PEDOT:PSS. In most articles, however, only the role of acids on the structure and thermoelectric properties of PEDOT:PSS were reported. In this article, we report the major role of the pressure of nitrogen gas (N-2) on the structure and thermoelectric properties of PEDOT:PSS after treatment with various acids at optimized temperatures. After treatment with acids followed by N-2 gas-passing, electrical conductivity enhances significantly. Therefore, N-2 gas-passing after acid treatments results in higher thermoelectric properties than other traditional acid treatment methods. The enhancement in electrical conductivity is attributed to the removal of insulating PSS and the conformational change of the PEDOT chain. Furthermore, the pressure of N-2 is responsible for the additional conformation of PEDOT chain, favoring the linear orientation of the PEDOT structure and resulting in an improvement of the electrical conductivity.

    DOI: 10.1007/s10854-019-01721-2

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  • Temperature dependence of pressure-driven water permeation through membranes consisting of vertically-aligned double-walled carbon nanotube arrays 査読

    Shiho Shirahama, Shaoling Zhang, Motohiro Aiba, Hirotaka Inoue, Masaki Hada, Yasuhiko Hayashi, Kenjiro Hata, Shuji Tsuruoka, Hidetoshi Matsumoto

    CARBON146   785 - 788   2019年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    We explore the temperature dependence of pressure-driven water permeation through membranes consisting of a vertically aligned double-walled carbon nanotube (VA DWCNT) array. The prepared membrane with CNT inner diameter of 3.9 nm exhibits no water permeation below the critical temperature of 26 degrees C, after which water permeability is first observed and increases with temperatures > 26 degrees C. Further, the critical temperature decreases to 18 degrees C when the CNT inner diameter increases to 6.0 nm. The water permeation in the CNT-confined space exhibits activation energy transitions around room temperature, thereby suggesting that the confined water molecules in CNTs exhibit plural ordered structures. (C) 2019 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.carbon.2019.02.031

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  • Bond Dissociation Triggering Molecular Disorder in Amorphous H2O 査読

    Masaki Hada, Yuho Shigeeda, Shin-ya Koshihara, Takeshi Nishikawa, Yoshifumi Yamashita, Yasuhiko Hayashi

    The Journal of Physical Chemistry A122 ( 49 ) 9579 - 9584   2018年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1021/acs.jpca.8b08455

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  • High-performance structure of a coil-shaped soft-actuator consisting of polymer threads and carbon nanotube yarns 査読

    Hirotaka Inoue, Takayuki Yoshiyama, Masaki Hada, Daiki Chujo, Yoshitaka Saito, Takeshi Nishikawa, Yoshifumi Yamashita, Wataru Takarada, Hidetoshi Matsumoto, Yasuhiko Hayashi

    AIP ADVANCES8 ( 7 )   2018年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    We fabricated thermally driven metal-free soft-actuators consisting of poly(ethylene terephthalate) (PET) threads as the actuator and carbon nanotube (CNT) yarns as the heating source. The mechanical force, displacement, and response behavior of various structures of the coil-shaped soft-actuators were characterized. The actuation performance of the soft-actuators containing a homogeneous arrangement of PET threads and CNT yarns in their cross-sectional profile was the highest. The results of the calculations based on the heat diffusion equations indicated that inhomogeneous heat generation in the soft-actuator causes parts of the actuator to remain unheated and this interferes with the mechanical motions. Homogeneous thermal distribution in the soft-actuators, namely, the use of a multifilament structure, yields the highest performance in terms of the mechanical force and displacement. (C) 2018 Author(s).

    DOI: 10.1063/1.5033487

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  • Resistance-heating of carbon nanotube yarns in different atmospheres 査読

    Maik Scholz, Yasuhiko Hayashi, Vyacheslav Khavrus, Daiki Chujo, Hirotaka Inoue, Masaki Hada, Albrecht Leonhardt, Bernd Buechner, Silke Hampel

    CARBON133   232 - 238   2018年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Annealing and functionalization of carbon nanotube yarns (CNYs) is a prospective way of increasing the electrical conductivity of this material. We show a novel way, the simultaneous annealing and instant coating of the CNY by its resistance-heating in atmospheres of hydrocarbons. This method is capable to preserve the lightweight properties of CNYs and increase the electrical conductivity. It could be raised by a factor of 2 through carbon deposition onto the yarns and the carbon nanotubes (CNTs) inside the yarn structure. By resistance-heating over a multistep process the conductivity could be even increased by a factor of 2.2. Comparison of annealing under atmosphere of different hydrocarbons and at different temperatures reveals the influence of resistance-heating on the structure of CNY. (C) 2018 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.carbon.2018.03.022

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  • Performance limit of daytime radiative cooling in warm humid environment 査読

    Takahiro Suichi, Atsushi Ishikawa, Yasuhiko Hayashi, Kenji Tsuruta

    AIP Advances8 ( 5 )   2018年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Institute of Physics Inc.  

    Daytime radiative cooling potentially offers efficient passive cooling, but the performance is naturally limited by the environment, such as the ambient temperature and humidity. Here, we investigate the performance limit of daytime radiative cooling under warm and humid conditions in Okayama, Japan. A cooling device, consisting of alternating layers of SiO2 and poly(methyl methacrylate) on an Al mirror, is fabricated and characterized to demonstrate a high reflectance for sunlight and a selective thermal radiation in the mid-infrared region. In the temperature measurement under the sunlight irradiation, the device shows 3.4 °C cooler than a bare Al mirror, but 2.8 °C warmer than the ambient of 35 °C. The corresponding numerical analyses reveal that the atmospheric window in λ = 16 ∼ 25 μm is closed due to a high humidity, thereby limiting the net emission power of the device. Our study on the humidity influence on the cooling performance provides a general guide line of how one can achieve practical passive cooling in a warm humid environment.

    DOI: 10.1063/1.5030156

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  • Expansion of Shockley stacking fault observed by scanning electron microscope and partial dislocation motion in 4H-SiC 査読

    Yoshifumi Yamashita, Ryu Nakata, Takeshi Nishikawa, Masaki Hada, Yasuhiko Hayashi

    JOURNAL OF APPLIED PHYSICS123 ( 16 )   2018年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    We studied the dynamics of the expansion of a Shockley-type stacking fault (SSF) with 30 degrees Si(g) partial dislocations (PDs) using a scanning electron microscope. We observed SSFs as dark lines (DLs), which formed the contrast at the intersection between the surface and the SSF on the (0001) face inclined by 8 degrees from the surface. We performed experiments at different electron-beam scanning speeds, observing magnifications, and irradiation areas. The results indicated that the elongation of a DL during one-frame scanning depended on the time for which the electron beam irradiated the PD segment in the frame of view. From these results, we derived a formula to express the velocity of the PD using the elongation rate of the corresponding DL during one-frame scanning. We also obtained the result that the elongation velocity of the DL was not influenced by changing the direction in which the electron beam irradiates the PD. From this result, we deduced that the geometrical kink motion of the PD was enhanced by diffusing carriers that were generated by the electron-beam irradiation. Published by AIP Publishing.

    DOI: 10.1063/1.5010861

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  • In-situ X-ray diffraction reveals the degradation of crystalline CH3NH3PbI3 by water-molecule collisions at room temperature 査読

    Masaki Hada, Yoichi Hasegawa, Ryota Nagaoka, Tomoya Miyake, Ulugbek Abdullaev, Hiromi Ota, Takeshi Nishikawa, Yoshifumi Yamashita, Yasuhiko Hayashi

    Japanese Journal of Applied Physics57 ( 2 ) 028001-1 - 028001-3   2018年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Japan Society of Applied Physics  

    We have developed a vacuum-compatible chamber for in-situ X-ray diffraction (XRD) studies and have used it to characterize the changing crystal structure of an inorganic-organic hybrid perovskite material, CH3NH3PbI3 (MAPbI3), during interactions with water vapor at room temperature. In the XRD spectra, we have observed the degradation of MAPbI3 and the creation of MAPbI3 hydrates, which follow simple rate equations. The time constant for the degradation of MAPbI3 during accelerated aging suggests that multiple collisions of water molecules with the MAPbI3 crystal trigger the degradation of the crystal.

    DOI: 10.7567/JJAP.57.028001

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  • Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals 査読

    M. Hada, S. Saito, R. Sato, K. Miyata, Y. Hayashi, Y. Shigeta, K. Onda

    Journal of Visualized Experiments135   e57612-1 - e57612-13   2018年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.3791/57612

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  • Rapid Growth of Dense and Long Carbon Nanotube Arrays and Its Application in Spinning Thread 査読

    Yasuhiko Hayashi, Karthik Paneer Selvam, Maik Scholz

    InTech open access publisher2   2018年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5772/intechopen.70702

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  • Simultaneous improvement in electrical conductivity and Seebeck coefficient of PEDOT:PSS by N-2 pressure-induced nitric acid treatment 査読

    May Thu Zar Myint, Masaki Hada, Hirotaka Inoue, Tatsuki Marui, Takeshi Nishikawa, Yuta Nishina, Susumu Ichimura, Masayoshi Umeno, Aung Ko Ko Kyaw, Yasuhiko Hayashi

    RSC ADVANCES8 ( 64 ) 36563 - 36570   2018年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

    As a thermoelectric (TE) material suited to applications for recycling waste-heat into electricity through the Seebeck effect, poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonic acid) (PEDOT:PSS) is of great interest. Our research demonstrates a comprehensive study of different post-treatment methods with nitric acid (HNO3) to enhance the thermoelectric properties of PEDOT:PSS. The optimum conditions are obtained when PEDOT:PSS is treated with HNO3 for 10 min at room temperature followed by passing nitrogen gas (N-2) with a pressure of 0.2 MPa. Upon this treatment, PEDOT:PSS changes from semiconductor-like behaviour to metal-like behaviour, with a simultaneous enhancement in the electrical conductivity and Seebeck coefficient at elevated temperature, resulting in an increase in the thermoelectric power factor from 0.0818 to 94.3 W m(-1) K-2 at 150 degrees C. The improvement in the TE properties is ascribed to the combined effects of phase segregation and conformational change of the PEDOT due to the weakened coulombic attraction between PEDOT and PSS chains by nitric acid as well as the pressure of the N-2 gas as a mechanical means.

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  • Structural Monitoring of the Onset of Excited-State Aromaticity in a Liquid Crystal Phase 査読

    Masaki Hada, Shohei Saito, Sei'ichi Tanaka, Ryuma Sato, Masahiko Yoshimura, Kazuhiro Mouri, Kyohei Matsuo, Shigehiro Yamaguchi, Mitsuo Hara, Yasuhiko Hayashi, Fynn Roehricht, Rainer Herges, Yasuteru Shigeta, Ken Onda, R. J. Dwayne Miller

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY139 ( 44 ) 15792 - 15800   2017年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    Aromaticity of photoexcited molecules is an important concept in organic chemistry. Its theory, Baird's rule for triplet aromaticity since 1972 gives the rationale of photoinduced conformational changes and photochemical reactivities of cyclic pi-conjugated systems. However, it is still challenging to monitor the dynamic structural change induced by the excited-state aromaticity, particularly in condensed materials. Here we report direct structural observation of a molecular motion and a subsequent packing deformation accompanied by the excited-state aromaticity. Photoactive liquid crystal (LC) molecules featuring a pi-expanded cyclooctatetraene core unit are orientationally ordered but loosely packed in a columnar LC phase, and therefore a photoinduced conformational planarization by the excited-state aromaticity has been successfully observed by time-resolved electron diffractometry and vibrational spectroscopy. The structural change took place in the vicinity of excited molecules, producing a twisted stacking structure. A nanoscale torque driven by the excited-state aromaticity can be used as the working mechanism of new photoresponsive materials.

    DOI: 10.1021/jacs.7b08021

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    その他リンク: http://orcid.org/0000-0002-4113-5548

  • Structural Monitoring of the Onset of Excited-State Aromaticity in a Liquid Crystal Phase 査読

    Hada, Masaki, Saito, Shohei, Tanaka, Sei'ichi, Sato, Ryuma, Yoshimura, Masahiko, Mouri, Kazuhiro, Matsuo, Kyohei, Yamaguchi, Shigehiro, Hara, Mitsuo, Hayashi, Yasuhiko, Röhricht, Fynn, Herges, Rainer, Shigeta, Yasuteru, Onda, Ken, Miller, R J Dwayne

    Journal of the American Chemical Society139   15792 - 15800   2017年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

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  • Time zero determination for FEL pump-probe studies based on ultrafast melting of bismuth 査読

    S. W. Epp, M. Hada, Y. Zhong, Y. Kumagai, K. Motomura, S. Mizote, T. Ono, S. Owada, D. Axford, S. Bakhtiarzadeh, H. Fukuzawa, Y. Hayashi, T. Katayama, A. Marx, H. M. Mueller-Werkmeister, R. L. Owen, D. A. Sherrell, K. Tono, K. Ueda, F. Westermeier, R. J. D. Miller

    STRUCTURAL DYNAMICS4 ( 5 ) 054308-1 - 054308-13   2017年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    A common challenge for pump-probe studies of structural dynamics at X-ray free-electron lasers (XFELs) is the determination of time zero (T-0)-the time an optical pulse (e.g., an optical laser) arrives coincidently with the probe pulse (e.g., a XFEL pulse) at the sample position. In some cases, T-0 might be extracted from the structural dynamics of the sample's observed response itself, but generally, an independent robust method is required or would be superior to the inferred determination of T-0. In this paper, we present how the structural dynamics in ultrafast melting of bismuth can be exploited for a quickly performed, reliable and accurate determination of T-0 with a precision below 20 fs and an overall experimental accuracy of 50 fs to 150 fs (estimated). Our approach is potentially useful and applicable for fixed-target XFEL experiments, such as serial femtosecond crystallography, utilizing an optical pump pulse in the ultraviolet to near infrared spectral range and a pixelated 2D photon detector for recording crystallographic diffraction patterns in transmission geometry. In comparison to many other suitable approaches, our method is fairly independent of the pumping wavelength (UV-IR) as well as of the X-ray energy and offers a favorable signal contrast. The technique is exploitable not only for the determination of temporal characteristics of the experiment at the interaction point but also for investigating important conditions affecting experimental control such as spatial overlap and beam spot sizes. (C) 2017 Author(s).

    DOI: 10.1063/1.4999701

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  • Water transport phenomena through membranes consisting of vertically-aligned double-walled carbon nanotube array 査読

    Hidetoshi Matsumoto, Shuji Tsuruoka, Yasuhiko Hayashi, Koji Abe, Kenjiro Hata, Shaoling Zhang, Yoshitaka Saito, Motohiro Aiba, Tomoharu Tokunaga, Toru Iijima, Takuma Hayashi, Hirotaka Inoue, Gehan A. J. Amaratunga

    CARBON120   358 - 365   2017年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Nanofluidics in CNTs is argumentative though it is theoretically calculated by various reports. It is because only a few of experimental reports are available, and the measured permeability is not so large as that suggested from the theoretical calculations. Also, water motion suppression in the confined space has not been exhibited by flux measurement. The present work explores these yet-unsolved discrepancies using the measurable size membrane of vertically aligned double-walled carbon nanotube array, which is borne with durability and flexibility, and a conventional measurement method is applied to the membranes. Water motion suppression occurs in the CNT confined space significantly, depending on temperature. Additionally, it is confirmed that the obtained permeability correlates to the reported experimental results with regard to the relationship between CNT length and permeability, and the correlation does not agree with permeability calculated from the Hagen-Poiseuille law. These results pose an insight into the inherent water transport characteristics in the CNT confined space. (C) 2017 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.carbon.2017.05.034

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  • Cross-Polarized Surface-Enhanced Infrared Spectroscopy by Fano-Resonant Asymmetric Metamaterials 査読

    Atsushi Ishikawa, Shuhei Hara, Takuo Tanaka, Yasuhiko Hayashi, Kenji Tsuruta

    SCIENTIFIC REPORTS7   2017年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:NATURE PUBLISHING GROUP  

    Plasmonic metamaterials have overcome fundamental limitations in conventional optics by their capability to engineer material resonances and dispersions at will, holding great promise for sensing applications. Recent demonstrations of metamaterial sensors, however, have mainly relied on their resonant nature for strong optical interactions with molecules, but few examples fully exploit their functionality to manipulate the polarization of light. Here, we present cross-polarized surface-enhanced infrared absorption (SEIRA) by the Fano-resonant asymmetric metamaterial allowing for strong background suppression as well as significant field enhancement. The metamaterial is designed to exhibit the controlled Fano resonance with the cross-polarization conversion property at 1730 cm(-1), which spectrally overlaps with the C=O vibrational mode. In the cross-polarized SEIRA measurement, the C=O mode of poly(methyl methacrylate) molecules is clearly observed as a distinct dip within a Fano-resonant transmission peak of the metamaterial. The vibrational signal contrast is then improved based on the cross-polarized detection scheme where only the light interacting with the metamaterial-molecular coupled system is detected by totally eliminating the unwanted background light. Our metamaterial approach achieves the zeptomole sensitivity with a large signal-to-noise ratio in the far-field measurement, paving the way toward the realization of ultrasensitive IR inspection technologies.

    DOI: 10.1038/s41598-017-03545-8

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    その他リンク: http://orcid.org/0000-0002-4113-5548

  • Simple Technique of Exfoliation and Dispersion of Multilayer Graphene from Natural Graphite by Ozone-Assisted Sonication 査読

    Zaw Lin, Paneer Selvam Karthik, Masaki Hada, Takeshi Nishikawa, Yasuhiko Hayashi

    NANOMATERIALS7 ( 6 )   2017年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:MDPI AG  

    Owing to its unique properties, graphene has attracted tremendous attention in many research fields. There is a great space to develop graphene synthesis techniques by an efficient and environmentally friendly approach. In this paper, we report a facile method to synthesize well-dispersed multilayer graphene (MLG) without using any chemical reagents or organic solvents. This was achieved by the ozone-assisted sonication of the natural graphite in a water medium. The frequency or number of ozone treatments plays an important role for the dispersion in the process. The possible mechanism of graphene exfoliation and the introduction of functional groups have been postulated. The experimental setup is unique for ozone treatment and enables the elimination of ozone off-gas. The heat generated by the dissipation of ultrasonic waves was used as it is, and no additional heat was supplied. The graphene dispersion was stable, and no evidence of aggregation was observed-even after several months. The characterization results show that well-dispersed MLG was successfully synthesized without any significant damage to the overall structure. The graphene obtained by this method has potential applications in composite materials, conductive coatings, energy storage, and electronic devices.

    DOI: 10.3390/nano7060125

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    その他リンク: http://orcid.org/0000-0002-4113-5548

  • Ultrasonic-assisted synthesis of ZnO nano particles decked with few layered graphene nanocomposite as photoanode in dye-sensitized solar cell 査読

    Satish Bykkam, Venkateshwara Rao Kalagadda, Bikshalu Kalagadda, Karthik Paneer Selvam, Yasuhiko Hayashi

    JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS28 ( 8 ) 6217 - 6225   2017年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGER  

    ZnO decked few layered graphene (FLG; 1.0, 2.0 and 3.0 wt%) nanocomposites were synthesized by simple and cost effective way using ultrasonic-assisted synthesis method. The morphological, optical and structural properties of as-synthesized nanocomposites were analyzed by field emission scanning electron microscopy and high-resolution transmission electron microscopy, UV-Visible spectroscopy with diffuse reflectance, fourier transform infrared spectroscopy, X-ray diffractometry and ramam spectroscopy. The synthesized FLG (1.0, 2.0 and 3.0 wt%)/ZnO nanocomposite were used as photoanode materials and deposited as thin films on fluorine-doped tin oxide substrate by doctor blade method for dye-sensitized solar cell (DSSC) fabrication. By varying the FLG weight percentage (1.0, 2.0 and 3.0 wt%) in ZnO nanocomposites the power conversion efficiency (PCE) in DSSC was optimized. Using N719 dye the current density-voltage (J-V) was measured under AM 1.5G, 100 m W/m(2) of the solar simulator. Results obtained after optimization showed PCE of 4.61% at the suitable FLG (1.0 wt%)/ZnO, compared to ZnO and other photoanodes.

    DOI: 10.1007/s10854-016-6301-8

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    その他リンク: http://orcid.org/0000-0002-4113-5548

  • Multilayer graphene/amorphous carbon hybrid films prepared by microwave surface-wave plasma CVD: synthesis and characterization 査読

    Susumu Ichimura, Yasuhiko Hayashi, Masayoshi Umeno

    SURFACE AND INTERFACE ANALYSIS49 ( 4 ) 291 - 296   2017年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY  

    Hybrid films of multilayer graphene (MG) containing amorphous carbon (a-C) were synthesized on Al substrates by microwave surface-wave plasma chemical vapor deposition. Raman scattering and surface transmission electron microscopy showed that the carbon films contained a large quantity of MG when a radio frequency (RF) substrate bias was not applied. Amorphization of graphene in the carbon film was promoted by applying an RF bias, which generated Ar+ in the plasma. The bandgaps of the films were found to increase as the Raman intensity ratios between the 2D-band (at 2700cm(-1)) and D-band (at 1350cm(-1)) decreased, indicating the formation of a-C. The MG/a-C all-sp(2) phase of carbon hybrid films exhibited an increase in current density under 5mW/cm(2) of AM1.5G solar simulated irradiation as the RF bias increased because of Ar+-induced amorphization of the graphene. Copyright (c) 2016 John Wiley & Sons, Ltd.

    DOI: 10.1002/sia.6133

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    その他リンク: http://orcid.org/0000-0002-4113-5548

  • Surface modification of carbon nanohorns by helium plasma and ozone treatments 査読

    Zaw Lin, Toru Iijima, Paneer Selvam Karthik, Mitsunobu Yoshida, Masaki Hada, Takeshi Nishikawa, Yasuhiko Hayashi

    JAPANESE JOURNAL OF APPLIED PHYSICS56 ( 1 )   2017年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    In this paper, we describe the effects of helium plasma and ozone treatments on the dispersibility of carbon nanohorns (CNHs) in water. The experimental setups have been designed to efficiently generate helium plasma and ozone by dielectric barrier discharge at atmospheric pressure. After being treated with ozone, the oxygen-containing functional groups were introduced to the surface of CNHs, and are responsible for better dispersion. Helium plasma treatment was performed separately and it resulted in hydroxyl functional groups on the surface of CNHs. It was also found that the sizes of CNHs in water were smaller after ozone treatment. However, plasma-treated CNHs were bigger than ozone treated CNHs. The dispersed CNHs modified by ozone treatment were stable for more than three months without precipitation. In contrast, though helium plasma treatment introduced hydroxyl groups to the surface of CNHs, the dispersibility decreased and the flocculation of CNHs was observed in a few minutes. (C) 2017 The Japan Society of Applied Physics

    DOI: 10.7567/JJAP.56.01AB08

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    その他リンク: http://orcid.org/0000-0002-4113-5548

  • Automated Design of Infrared Digital Metamaterials by Genetic Algorithm 査読

    Yuya Sugino, Atsushi Ishikawa, Yasuhiko Hayashi, Kenji Tsuruta

    METAMATERIALS, METADEVICES, AND METASYSTEMS 201710343   2017年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPIE-INT SOC OPTICAL ENGINEERING  

    We demonstrate automatic design of infrared (IR) metamaterials using a genetic algorithm (GA) and experimentally characterize their IR properties. To implement the automated design scheme of the metamaterial structures, we adopt a digital metamaterial consisting of 7 x 7 Au nano-pixels with an area of 200 nm x 200 nm, and their placements are coded as binary genes in the GA optimization process. The GA combined with three-dimensional (3D) finite element method (FEM) simulation is developed and applied to automatically construct a digital metamaterial to exhibit pronounced plasmonic resonances at the target IR frequencies. Based on the numerical results, the metamaterials are fabricated on a Si substrate over an area of 1 mm x 1 mm by using an EB lithography, Cr/Au (2/20 nm) depositions, and liftoff process. In the FT-IR measurement, pronounced plasmonic responses of each metamaterial are clearly observed near the targeted frequencies, although the synthesized pixel arrangements of the metamaterials are seemingly random. The corresponding numerical simulations reveal the important resonant behavior of each pixel and their hybridized systems. Our approach is fully computer-aided without artificial manipulation, thus paving the way toward the novel device design for next-generation plasmonic device applications.

    DOI: 10.1117/12.2273607

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  • Structure optimization of metallodielectric multilayer for high-efficiency daytime radiative cooling 査読

    Takahiro Suichi, Atsushi Ishikawa, Yasuhiko Hayashi, Kenji Tsuruta

    Proceedings of SPIE - The International Society for Optical Engineering10369   2017年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPIE  

    Engineered metallodielectric nanostructures offer a new platform for controlling thermal emission in a desired manner, thus promise potential applications in passive cooling devices. Here, we present optimization design of metallodielectric multilayer structures for high-efficiency daytime radiative cooling and experimentally characterize their cooling performance. The device structure consists of alternating layers of SiO2 and PMMA on an Ag mirror, which works as a selective thermal emitter at 8-13 μm with a high reflectance for sunlight. Automated design scheme based on simulated annealing method combined with photonic-thermal analysis is developed and applied to search the optimized number and thickness of the layers. The evaluation function in the optimization process is predefined such that a net emission power would be maximized at the ambient temperature of 27 °C (300 K) under the sunlight irradiation of AM1.5G. The numerical results prove efficient radiative cooling to 3.0 °C lower than the ambient temperature, corresponding to 6.6 °C below the bare Ag mirror temperature. Based on the optimized design, the device is fabricated on an Al mirror by using reactive evaporation and spin-coating process over an area of 25 × 25 mm2. The reflectance and absorption properties of the fabricated device are characterized to demonstrate the selective thermal radiation through an atmospheric window. The equilibrium temperature of the device is also investigated to demonstrate the cooling performance under the direct sunlight irradiation.

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  • Intentionally Encapsulated Metal Alloys within Vertically Aligned Multi-Walled Carbon Nanotube Array via Chemical Vapor Deposition Technique 査読

    Yasuhiko Hayashi, Hirotaka Inoue, Takuma Hayashi, Masaki Hada, Takeshi Nishikawa, Tomoharu Tokunaga, G. A. J. Amaratunga

    2017 IEEE INTERNATIONAL CONFERENCE ON MANIPULATION, MANUFACTURING AND MEASUREMENT ON THE NANOSCALE (3M-NANO)   357 - 361   2017年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    This paper presents a growth and characterization of vertically aligned PdxCo1-x alloy encapsulated inside Multi-Walled Carbon Nanotube (MWCNT) arrays on Pd/Co thin layers coated on Si substrate by a dc bias-enhanced plasma chemical vapor deposition (CVD) method. The Metal Alloy Encapsulated within MWCNTs (MAE-MWCNTs) were characterized by a scanning electron microscope (SEM) and a transmission electron microscopy (TEM). The SEM images show the teardrop-shape particles encapsulated within the tube top of MWCNTs. A vibrating sample magnetometer was used to study the magnetism of a large number of MAE-MWCNTs on Si substrate at room temperature. The hysteresis loop of the ME-MWCNTs shows clear ferromagnetic behavior and the easy axis of magnetization is parallel to the MEA-MWCNT tube axis, as can be elucidated from the large coercive fields and remanence values. Moreover, TEM off-axis electron holograms were used to study the magnetism of the individual MAE-MWCNT or the two pair of MAE-MWCNTs. Based on electron holography, we have successfully obtained the saturation magnetization of 0.7 T and 1.12 T for the individual MAE-MWCNT with diameters of 41 nm and 83 nm, respectively.

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  • Synthesis of hybrid carbon nanoparticles using multi-walled carbon nanotubes and fullerene via self-assembly 査読

    P. S. Karthik, Zaw Lin, Venkata Abhinav Korada, Masaki Hada, Takeshi Nishikawa, Yasuhiko Hayashi

    Materials Science Forum900   46 - 49   2017年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:Trans Tech Publications Ltd  

    This report deals with a simple and efficient method to develop hybrid carbon nanoparticles (Nps) employing Multi-walled carbon nanotubes (MWCNTs) and Fullerene nps. Fullerene nps were self-assembled via Ultrasonicated Liquid-Liquid Precipitation. Surface treated MWCNTs were entangled with fullerene nps during the process of assembling of the fullerene nps. Fullerene nps are formed by reaction between two solutions, one is the saturated solution which contains dissolved fullerene and other solution is a rough alcohol. This reaction increases the concentration of carbon in the solution and leads to super saturate hence self-assembling into nanoparticles. The obtained hybrid nanoparticles sizes were in the range of 100 nm to 300 nm with entangled mwcnts and were confirmed by characterization using SEM, Raman, UV-Vis, XRD, and DLS.

    DOI: 10.4028/www.scientific.net/MSF.900.46

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  • Surface modification of carbon nanohorns by helium plasma and ozone treatments 査読

        2016年12月

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  • Single- and double-walled carbon nanotubes enhance atherosclerogenesis by promoting monocyte adhesion to endothelial cells and endothelial progenitor cell dysfunction. 査読 国際誌

    Yuka Suzuki, Saeko Tada-Oikawa, Yasuhiko Hayashi, Kiyora Izuoka, Misa Kataoka, Shunsuke Ichikawa, Wenting Wu, Cai Zong, Gaku Ichihara, Sahoko Ichihara

    Particle and fibre toxicology13 ( 1 ) 54 - 54   2016年10月

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    記述言語:英語  

    BACKGROUND: The use of carbon nanotubes has increased lately. However, the cardiovascular effect of exposure to carbon nanotubes remains elusive. The present study investigated the effects of pulmonary exposure to single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) on atherosclerogenesis using normal human aortic endothelial cells (HAECs) and apolipoprotein E-deficient (ApoE-/-) mice, a model of human atherosclerosis. METHODS: HAECs were cultured and exposed to SWCNTs or DWCNTs for 16 h. ApoE-/- mice were exposed to SWCNTs or DWCNTs (10 or 40 μg/mouse) once every other week for 10 weeks by pharyngeal aspiration. RESULTS: Exposure to CNTs increased the expression level of adhesion molecule (ICAM-1) and enhanced THP-1 monocyte adhesion to HAECs. ApoE-/- mice exposed to CNTs showed increased plaque area in the aorta by oil red O staining and up-regulation of ICAM-1 expression in the aorta, compared with vehicle-treated ApoE-/- mice. Endothelial progenitor cells (EPCs) are mobilized from the bone marrow into the circulation and subsequently migrate to the site of endothelial damage and repair. Exposure of ApoE-/- mice to high-dose SWCNTs or DWCNTs reduced the colony-forming units of EPCs in the bone marrow and diminished their migration function. CONCLUSION: The results suggested that SWCNTs and DWCNTs enhanced atherosclerogenesis by promoting monocyte adhesion to endothelial cells and inducing EPC dysfunction.

    DOI: 10.1186/s12989-016-0166-0

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  • DC Biasing Effects on Properties of Carbon Nanowalls by Microwave Surface-Wave Plasma Chemical Vapor Deposition and Towards Transparent Electrode 査読

    Susumu Ichimura, Yasuhiko Hayashi, Masayoshi Umeno

    Transactions of the Materials Research Society of Japan41 ( 3 ) 229 - 233   2016年9月

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  • Ultrafast snapshots of the molecules twisting in liquid crystal state 査読

    Masaki Hada, Shohei Saito, Sei'ichi Tanaka, Ryuma Sato, Kyohei Matsuo, Mitsuo Hara, Yasuhiko Hayashi, Kazuhiro Mouri, Masahiko Yoshimura, Yasuteru Shigeta, Shigehiro Yamaguchi, Ken Onda, R.J. Dwayne Miller

    Optics InfoBase Conference Papers   2016年7月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:OSA - The Optical Society  

    We demonstrated time-resolved electron diffraction and vibrational spectroscopy to characterize the structure and dynamics of molecules in liquid crystal state. Our findings present the ultrafast local deformation triggering helical twisting motion in molecules.

    DOI: 10.1364/UP.2016.UTh2B.2

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  • Effect of ultraviolet light irradiation and ion collision on the quality of multilayer graphene prepared by microwave surface-wave plasma chemical vapor deposition 査読

    Susumu Ichimura, Yasuhiko Hayashi, Masayoshi Umeno

    DIAMOND AND RELATED MATERIALS66   157 - 162   2016年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    We successfully synthesized graphene by microwave surface-wave plasma chemical vapor deposition (CVD) and investigated the effect of UV light and ion collision from the plasma exposure during graphene synthesis. The graphene obtained here was multilayer graphene consisting of approximately 5 layers according to crosssectional transmission electron microscopy results. The quality of the graphene was compared between the.case where UV light was irradiated from the plasma and the case where the UV light was blocked by a grid inserted CVD configuration. Quality was evaluated by Raman scattering spectroscopy. There were more defects in the graphene prepared with irradiation of UV light than with blocking of UV light. Furthermore, we investigated the effects of ion collisions that occurred in the plasma, but they had no effect on graphene quality. These results suggest that during graphene synthesis, UV light from the plasma affects its crystallinity. The electrical conductivity, optical transmittance and mobility of the transferred graphene films were measured to clarify the effects of UV light irradiation. (C) 2016 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.diamond.2016.04.012

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  • Synthesis and transistor application of the extremely extended phenacene molecule, [9] phenacene 査読

    Yuma Shimo, Takahiro Mikami, Shino Hamao, Hidenori Goto, Hideki Okamoto, Ritsuko Eguchi, Shin Gohda, Yasuhiko Hayashi, Yoshihiro Kubozono

    SCIENTIFIC REPORTS6   2016年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:NATURE PUBLISHING GROUP  

    the widespread interest in the chemistry, physics and materials science of such molecules and their potential applications. In particular, extended phenacene molecules, consisting of coplanar fused benzene rings in a repeating W-shaped pattern have attracted much attention because field-effect transistors (FETs) using phenacene molecules show promisingly high performance. Until now, the most extended phenacene molecule available for transistors was [8] phenacene, with eight benzene rings, which showed very high FET performance. Here, we report the synthesis of a more extended phenacene molecule, [9] phenacene, with nine benzene rings. Our synthesis produced enough [9] phenacene to allow the characterization of its crystal and electronic structures, as well as the fabrication of FETs using thin-film and single-crystal [9] phenacene. The latter showed a field-effect mobility as high as 18 cm(2) V-1 s(-1), which is the highest mobility realized so far in organic single-crystal FETs.

    DOI: 10.1038/srep21008

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  • Controlled Fano Resonances via Symmetry Breaking in Metamaterials for High-Sensitive Infrared Spectroscopy 査読

    Shuhei Hara, Atsushi Ishikawa, Takuo Tanaka, Yasuhiko Hayashi, Kenji Tsuruta

    METAMATERIALS, METADEVICES, AND METASYSTEMS 20169918   2016年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:SPIE-INT SOC OPTICAL ENGINEERING  

    A high-sensitive polarized surface-enhanced infrared absorption (polarized SEIRA) is proposed and demonstrated by utilizing the resonant coupling of Fano-resonant mode of the asymmetric metamaterials and IR vibrational mode of a polymer nano-film. The asymmetric metamaterials consisting of an Au nano-rod pair with a coupling nano-antenna were fabricated and characterized to demonstrate the controlled Fano resonances at 1730 cm(-1), which spectrally overlapped with the C=O stretching vibrational mode. In the co-polarized SEIRA measurement, the C=O mode of the PMMA nano-film was clearly observed as a conventional anti-resonant peak within the Fano line-shape of the metamaterial. For the cross-polarized case, on the other hand, a distinctive dip appeared within a cross-polarized transmission peak of the metamaterial. Since the unwanted background is strongly suppressed in the cross-polarized detection scheme, the signal contrast was dramatically improved, allowing for the attomole detection of the C=O bond in the far-field measurement. Our metamaterial approach achieves the significant improvement of signal-to-background ratio in the far-field measurement, thus paving the way toward the high-sensitive analysis of functional group in direct IR spectroscopy.

    DOI: 10.1117/12.2237559

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  • Self-Assembled C-60 Fullerene Cylindrical Nanotubes by LLIP method 査読

    Venkata Krishna R. Rao, P. S. Karthik, Venkata K. Abhinav, Zaw Lin, May Thu Zar Myint, Takeshi Nishikawa, Masaki Hada, Yoshifumi Yamashita, Yasuhiko Hayashi, Surya Prakash Singh

    2016 IEEE 16TH INTERNATIONAL CONFERENCE ON NANOTECHNOLOGY (IEEE-NANO)   303 - 306   2016年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    In this article, we report C60 Fullerene Nano Cylindrical Tubes (FNCT). The FNCTs were synthesized by a liquid-liquid interface precipitation (LLIP) method using m-Xylene as a saturating solvent and TBA (Tetra butyl alcoholic) as precipitation agent leading to the formation of FNCTs with uniquely structured and well oriented size and shape. The experiment was conducted in a closed atmosphere maintaining a low temperature. The main advantage of these structures is that they are stable up to 5 months in normal room temperature. Characterizations were done to the FNCTs and concluded to have applications in the field of electronics. Enhanced semiconducting properties have been observed in the nanostructures which can be used in the application of solar cells, FET transistors, etc.

    DOI: 10.1109/NANO.2016.7751386

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  • Dispersion of relatively long multi-walled carbon nanotubes in water using ozone generated by dielectric barrier discharge 査読

    Zaw Lin, Mitsunobu Yoshida, Yuki Uesugi, Karthik Paneer, Takeshi Nishikawa, Yasuhiko Hayashi

    IEEJ Transactions on Fundamentals and Materials136 ( 4 ) 180 - 185   2016年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Institute of Electrical Engineers of Japan  

    This paper describes the effect of ozone treatment on water dispersibility of micrometer order long multi-walled carbon nanotubes by using simple ozone generation set up. Inverter type neon transformer was used to supply required energy. The dispersed nanotubes suspension was stable for a few months after treatment. Laser Raman Spectroscopy, Fourier Transform Infrared Spectroscopy, and Transmission Electron Miscroscope were used to characterize the resulted nanotubes. Analyzed data revealed that the multi-walled carbon nanotubes were functionalized by oxygen and hydrogen containing groups.

    DOI: 10.1541/ieejfms.136.180

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  • Carbon nanostructures synthesized via self-assembly (LLIP) and its application in FET 査読

    P. S. Karthik, Yuma Shimo, Zaw Lin, Venkata Krishna R. Rao, Xiao Gong, Mitsunobu Yoshida, Masaki Hada, Takeshi Nishikawa, Yasuhiko Hayashi, S. P. Singh

    2016 IEEE 11TH ANNUAL INTERNATIONAL CONFERENCE ON NANO/MICRO ENGINEERED AND MOLECULAR SYSTEMS (NEMS)   468 - 472   2016年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Here in, we report carbon nanostructures (nanorods) synthesized via liquid-liquid interface precipitation method (LLIP) with its application in field effect transistor as gate terminal. The carbon nanorods were synthesized by supersaturating and shape shifting Bucky ball fullerene into nanorods. The nanoparticles synthesis process is fast, efficient and the reaction is carried out in 24hrs. The obtained nanorods were found to have semiconducting property which was confirmed by analyzing TEM, SEM and RAMAN, FET analysis by IV measurements. Hence the nanorods where fabricated as gate terminal in field effect transistor.

    DOI: 10.1109/NEMS.2016.7758292

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  • In situ observation of carbon nanotube yarn during voltage application 査読

    Tomoharu Tokunaga, Yasuhiko Hayashi, Toru Iijima, Yuki Uesugi, Masaki Unten, Katsuhiro Sasaki, Takahisa Yamamoto

    MICRON74   30 - 34   2015年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Carbon nanotube (CNT) yarns are fabricated by drawing (combined with spinning) from CNT forests and grown on a substrate. Three types of phenomena occur in these CNT yarns with increasing amounts of current: yarn rotation, catalyst evaporation, and breakage of the yarn. These phenomena result from the resistive heating occurring during the current flow, and have been observed in situ under vacuum by transmission electron microscopy. If these CNT yarns are applied to electronic circuits, the rotation and breakage may lead to circuit failure. However, catalyst evaporation is a useful method for purifying CNT yarns without additional treatments prior to yarn fabrication. (C) 2015 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.micron.2015.04.004

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  • Synergistic Effect of Bolus Exposure to Zinc Oxide Nanoparticles on Bleomycin-Induced Secretion of Pro-Fibrotic Cytokines without Lasting Fibrotic Changes in Murine Lungs 査読 国際誌

    Wenting Wu, Gaku Ichihara, Naozumi Hashimoto, Yoshinori Hasegawa, Yasuhiko Hayashi, Saeko Tada-Oikawa, Yuka Suzuki, Jie Chang, Masashi Kato, Corina N. D'Alessandro-Gabazza, Esteban C. Gabazza, Sahoko Ichihara

    INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES16 ( 1 ) 660 - 676   2015年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:MDPI  

    Zinc oxide (ZnO) nanoparticles are widely used in various products, and the safety evaluation of this manufactured material is important. The present study investigated the inflammatory and fibrotic effects of pulmonary exposure to ZnO nanoparticles in a mouse model of pulmonary fibrosis. Pulmonary fibrosis was induced by constant subcutaneous infusion of bleomycin (BLM). Female C57BL/6Jcl mice were divided into BLM-treated and non-treated groups. In each treatment group, 0, 10, 20 or 30 mu g of ZnO nanoparticles were delivered into the lungs through pharyngeal aspiration. Bronchoalveolar lavage fluid (BALF) and the lungs were sampled at Day 10 or 14 after administration. Pulmonary exposure by a single bolus of ZnO nanoparticles resulted in severe, but transient inflammatory infiltration and thickening of the alveolar septa in the lungs, along with the increase of total and differential cell counts in BLAF. The BALF level of interleukin (IL)-1 beta and transforming growth factor (TGF)-beta was increased at Day 10 and 14, respectively. At Day 10, the synergistic effect of BLM and ZnO exposure was detected on IL-1 beta and monocyte chemotactic protein (MCP)-1 in BALF. The present study demonstrated the synergistic effect of pulmonary exposure to ZnO nanoparticles and subcutaneous infusion of BLM on the secretion of pro-fibrotic cytokines in the lungs.

    DOI: 10.3390/ijms16010660

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  • Improved Properties of Carbon Nanotube Yarn Spun from Dense and Long Carbon Nanotube Forest 査読

    Yasuhiko Hayashi, Toru Iijima, Daisuke Suzuki, Hiroshi Kinoshita, Hisayoshi Oshima, Tomoharu Tokunaga

    2015 INTERNATIONAL CONFERENCE ON MANIPULATION, MANUFACTURING AND MEASUREMENT ON THE NANOSCALE (3M-NANO)   298 - 301   2015年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Notable progress has been made recently on the properties and applications of Carbon nanotube ( CNT). However, CNT has not achieved any remarkable practical applications from the industrial point of view. In this article, we report our recent progress on the bulk fiber structure of CNT yarn spun from the CNT forest. The unique fiber-like structure of CNT yarns gives them exceptional mechanical toughness, electrical conductivity, resilience to bending stress, and blend with polymer materials for a composite structure. CNT yarn, which is produced by spinning of high dense and relatively long CNT forest, has emerged as a new high-performance CNT-based bulk and composite material. We have made improvements in properties of CNT yarn by applying high voltage ( HV) to the CNT yarn in a vacuum chamber. The tensile strengths of as-spun and HV-treated CNT yarns were 624 MPa and 955 MPa, respectively. The crystallization behavior of the amorphous carbon on CNTs was confirmed by a Transmission Electron Microscope ( TEM). The CNT yarns provide them mechanical properties different from those of original high-performance fiber.

    DOI: 10.1109/3M-NANO.2015.7425488

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  • Transistors fabricated using the single crystals of [8]phenacene 査読

    Yuma Shimo, Takahiro Mikami, Hiroto T. Murakami, Shino Hamao, Hidenori Goto, Hideki Okamoto, Shin Gohda, Kaori Sato, Antonio Cassinese, Yasuhiko Hayashi, Yoshihiro Kubozono

    JOURNAL OF MATERIALS CHEMISTRY C3 ( 28 ) 7370 - 7378   2015年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

    Field-effect transistors (FETs) with single crystals of a new phenacene-type molecule, [8]phenacene, were fabricated and characterized. This new molecule consists of a phenacene core of eight benzene rings, with an extended p-conjugated system, which was recently synthesized for use in an FET by our group. The FET characteristics of an [8]phenacene single-crystal FET with SiO2 gate dielectrics show typical p-channel properties with an average field-effect mobility, &lt;mu &gt;, as high as 3(2) cm(2) V-1 s(-1) in two-terminal measurement mode, which is a relatively high value for a p-channel single-crystal FET. The hmi was determined to be 6(2) cm(2) V-1 s(-1) in four-terminal measurement mode. Low-voltage operation was achieved with PbZr0.52Ti0.48O3 (PZT) as the gate dielectric, and an electric-double-layer (EDL) capacitor. The &lt;mu &gt; and average values of absolute threshold voltage, &lt;vertical bar V-th vertical bar &gt;, were 1.6(4) cm(2) V-1 s(-1) and 5(1) V, respectively, for PZT, and 4(2) x 10(-1) cm(2) V-1 s(-1) and 2.38(4) V, respectively, for the EDL capacitor; these values were evaluated in two-terminal measurement mode. The inverter circuit was fabricated using [8]phenacene and N, N'-1H, 1H-perfluorobutyldicyanoperylene-carboxydi-imide single-crystal FETs. This is the first logic gate circuit using phenacene molecules. Furthermore, the relationship between mu and the number of benzene rings was clarified based on this study and the previous studies on phenacene single-crystal FETs.

    DOI: 10.1039/c5tc00960j

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  • Phenol resin carbonized films with anisotropic shrinkage driven ordered mesoporous structures 査読

    Tatsuo Kimura, Ayhan M. Emre, Kazumi Kato, Yasuhiko Hayashi

    Journal of Materials Chemistry A1 ( 47 ) 15135 - 15141   2013年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    High surface area and accessibility to the surface are very important for designing advanced electrodes for energy storage, battery, and capacitor systems because electrons are delivered at the surfaces of carbon based electrodes after diffusion into pore spaces. In this study, phenol resin carbonized porous films with controllable mesostructures and highly accessible surfaces were fabricated using the common EOnPOmEOn-type triblock copolymer. Unique mesostructural transformation of cage-type and tubular mesopores by anisotropic shrinkage was demonstrated from analytical data of the films carbonized at different temperatures. The development of the soft-templating method to obtain surfactant assisted carbon films showing high surface areas is quite significant because further design of mesostructure (anisotropic shrinkage), composition (nitrogen doping, combination with other well-designed carbon based materials) and morphology (coating, spraying, etc.) would be possible for making high-performance electrodes for fuel cells, solar cells, batteries, and energy storage systems, as well as catalytic supports and adsorbents for functional chemical synthesis, purification, and separation. © 2013 The Royal Society of Chemistry.

    DOI: 10.1039/c3ta13026f

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  • Highly transparent and flexible field electron emitters based on hybrid carbon nanostructure 査読

    Debasish Ghosh, Pradip Ghosh, Takuto Noda, Yasuhiko Hayashi, Masaki Tanemura

    PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS7 ( 12 ) 1080 - 1083   2013年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-V C H VERLAG GMBH  

    We demonstrate a unique strategy to fabricate highly transparent and flexible field electron emitters (FEEs) based on combined carbon nanostructures, i.e., conical nanocarbon structures (CNCSs) and single-walled carbon nanotubes (SWNTs). The combined structure was prepared by spray coating of 1,2-dichloroethane (DCE) dispersed SWNTs onto neon ion (Ne+) irradiation induced CNCSs on nafion substrate. The field emission (FE) property of SWCNTs on both flat nafion and CNCSs surfaces increased with increasing the SWCNTs amount. The best FE result was attained for the highest amount of SWCNTs on the CNCSs substrate. This kind of collective structures is found to be effective emitters on transparent and flexible ion-irradiated nafion substrate. Moreover, the combined carbon nanostructures showed improved transparency and emission performance compared to the individual nanostructures. The FE properties of 0.5 ml SWCNTs solution on CNCSs surfaces were equal to those of 1.5 ml SWCNTs solution on flat nafion surface. The hybrid structure based emitters (CNCSs and SWCNTs) produced by this method are lower-cost cathode materials than hybrid structures of SWCNTs and flat nafion. Thus the combined nanostructures of SWCNTs/CNCSs might have huge prospects for the fabrication of efficient transparent and flexible FEEs and their broad application in next-generation portable display devices. ((c) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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  • Photovoltaic properties of an amorphous carbon/fullerene junction 査読

    Tetsuo Soga, Takuya Kondoh, Naoki Kishi, Yasuhiko Hayashi

    CARBON60   1 - 4   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    This paper demonstrates all-carbon photovoltaic devices made of amorphous carbon (a-C) and C-60 thin films. C-60 film is deposited by the sublimation in vacuum and a-C film is synthesized by exposing N-2 radicals to C-60 during the deposition. C-60 is converted into a-C when the rf power is larger than 150 Wand the optical band gap decreases with increasing the power. Photovoltaic properties of device with the structure of Al/C-60/a-C/indium tin oxide/glass are presented. It is shown that the present cell has a strong spectral response in the wavelength range shorter than 550 nm and a small response at around 620 nm. (C) 2013 Elsevier Ltd. All rights reserved.

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  • Study of intercalation compounds using ionic liquids into montmorillonite and their thermal stability 査読

    Chisato Takahashi, Takashi Shirai, Yasuhiko Hayashi, Masayoshi Fuji

    SOLID STATE IONICS241   53 - 61   2013年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    In the present study, we investigated the direct intercalation of three kinds of ionic liquids (ILs) of different salts (imidazolium and ammonium) and cation sizes into montmorillonite (M) clay, and successfully fabricated the IL intercalated montmorillonite (M-IL) compounds. The peak shifts of the M-IL intercalated compounds in comparison with dried montmorillonite powder as observed by XRD results showed that crystal swelling was significantly influenced by the cation sizes of the ILs. The intercalation behaviors of the M-IL compounds were also compared by TEM and the results are in good agreement with the XRD. The TEM-EDS results further confirmed the intercalation of three types of ILs into the montmorillonite. Based on the cation exchange capacity as measured by ICP and mathematical calculations, the extent of the intercalation and arrangement of cations in the interlayers of the montmorillonite are proposed. The TG-DTA results showed an improved thermal stability of all three kinds of M-IL intercalated compounds, and the XRD indicated that the remaining IL initiates a carbonization process with the montmorillonite at 1000 degrees C. Furthermore, the AC impedance results of the M-IL compounds showed an ionic conductivity. These results suggest the possible application of the M-IL intercalated compounds in electrical conductive films, solar cells, fuel cells, etc. (C) 2013 Elsevier B.V. All rights reserved.

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  • Phthalocyanine with Trifluoroethoxy Substituents for Organic Solar Cells 査読

    Ichiko Yamada, Norihito Iida, Yasuhiko Hayashi, Tetsuo Soga, Norio Shibata

    JAPANESE JOURNAL OF APPLIED PHYSICS52 ( 5 )   2013年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    The properties of soluble zinc phthalocyanines with trifluoroethoxy substituents (TFEO-ZnPcs) were studied to evaluate their possible use in organic thin-film solar cells. We prepared five TFEO-ZnPcs with different numbers and positions of the TFEO substituents. The solubilities, UV-visible absorption spectra, and cyclic voltammograms of these ZnPcs varied with their substituents. TFEO-ZnPc thin-films fabricated by spin-casting exhibited photocurrent generation at wavelengths between 600 and 850 nm. Flat heterojunction solar cells consisting of a poly(3-hexylthiophene) (P3HT) layer as a donor and a TFEO-ZnPc layer as an acceptor exhibited photocurrent generation over a wide range of wavelengths corresponding to both the P3HT and TFEO-ZnPc absorption spectra. The best solar cell performance was obtained with (beta-TFEO)(4)ZnPc film. (C) 2013 The Japan Society of Applied Physics

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  • Fabrication of metal nanoparticles from metal-filled carbon nanofibers and their size control by heating 査読

    T. Tokunaga, T. Kanematsu, T. Ota, K. Sasaki, T. Yamamoto, Y. Hayashi

    IEEE Nanotechnology Materials and Devices Conference, IEEE NMDC 2013   5 - 8   2013年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE Computer Society  

    In situ environmental transmission electron microscopy (ETEM) observation was used to reveal Sn inside Sn-filled carbon nanofibers (CNFs) during heating. Before and during heating, the Sn was covered completely by CNFs. The volume of Sn present in the Sn-filled CNFs gradually decreased during heating, with new Sn particles appearing at the top of the Sn-filled CNFs. It is thought that Sn diffused out of the Sn-filled CNFs and into the carbon wall of the metal-filled CNFs (MFCNFs). The specific surface area at the top of Sn-filled CNFs is higher specific surface than that at other parts and the temperature at the top of the MFCNF is lower than that at other parts
    therefore, diffused Sn particles were formed at only the top of the Sn-filled CNF. Fabrication of Sn metal particles was tried by heating the Sn-filled CNFs, and it was clear that the metal particle size could be controlled by controlling the heating time. © 2013 IEEE.

    DOI: 10.1109/NMDC.2013.6707468

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  • Synthesis of continuous graphene on metal foil for flexible transparent electrode application 査読

    Golap Kalita, Koichi Wakita, Masayoshi Umeno, Yasuhiko Hayashi, Masaki Tanemura

    Proceedings - Winter Simulation Conference   281 - 284   2013年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    We demonstrate synthesis of large area graphene on a metal (Ni and Cu) foil by the thermal chemical vapor deposition (CVD) process using the solid camphor (C10H16O) as a carbon source. The graphene growth process on a polycrystalline metal foil significantly influence by the gas composition and quantity of solid precursor. Synthesis of high quality continuous graphene film is achieved in the developed technique. Fully flexible transparent conductor is fabricated by transferring the graphene film on a plastic substrate. © 2013 IEEE.

    DOI: 10.1109/INEC.2013.6466023

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  • Influence of gas composition on the formation of graphene domain synthesized from camphor 査読

    Subash Sharma, Golap Kalita, Ryo Hirano, Yasuhiko Hayashi, Masaki Tanemura

    Materials Letters93   258 - 262   2013年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The domain structure of graphene films deposited by the chemical vapor deposition (CVD) process has a great influence on the electrical and physical properties. Here, we tackled the synthesis of increased domain size of single layer and bi-layer graphene along with few-layer graphene on Ni foil using solid camphor as a carbon source. To achieve this, effect of the composition of carrier gas for the evaporated camphor was investigated. Raman mapping and peak width (FWHM) analyses gave the insight of the quality and number of graphene layers. Optical and scanning electron microcopy studies show significance difference in domain structure of the synthesized graphene in different gas atmosphere. As confirmed by optical and scanning electron microscopes, the graphene domain grown with the carrier gas of Ar/H2 mixture was more than 10 times larger than those grown with pure Ar carrier gas. © 2012 Elsevier B.V.

    DOI: 10.1016/j.matlet.2012.11.090

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  • Synthesis of Continuous Graphene on Metal Foil for Flexible Transparent Electrode Application 査読

    Golap Kalita, Koichi Wakita, Masayoshi Umeno, Yasuhiko Hayashi, Masaki Tanemura

    PROCEEDINGS OF THE 2013 IEEE 5TH INTERNATIONAL NANOELECTRONICS CONFERENCE (INEC)   281 - 284   2013年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    We demonstrate synthesis of large area graphene on a metal (Ni and Cu) foil by the thermal chemical vapor deposition (CVD) process using the solid camphor (C10H16O) as a carbon source. The graphene growth process on a polycrystalline metal foil significantly influence by the gas composition and quantity of solid precursor. Synthesis of high quality continuous graphene film is achieved in the developed technique. Fully flexible transparent conductor is fabricated by transferring the graphene film on a plastic substrate.

    DOI: 10.1109/INEC.2013.6466023

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  • A photoinduced charge transfer composite of graphene oxide and ferrocene 査読

    Golap Kalita, Subash Sharma, Koichi Wakita, Masayoshi Umeno, Yasuhiko Hayashi, Masaki Tanemura

    PHYSICAL CHEMISTRY CHEMICAL PHYSICS15 ( 4 ) 1271 - 1274   2013年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

    We demonstrate the formation of a photoinduced charge transfer composite with graphene oxide (GO) and ferrocene (Fc) molecules. Derived insulating GO was partially reduced to improve the conductivity and modified with the Fc molecules. Transmission electron microscopy (TEM), elemental mapping, X-ray photoelectron and UV-visible spectroscopy studies confirm that the Fc molecules were well grafted to the surface of a GO sheet. Photoresponsivity of the prepared GO-Fc composite was investigated by fabricating a metal/GO-Fc/metal device. The fabricated device shows enhanced current density under light illumination, suggesting a photo-induced charge transfer process in the developed GO-Fc composite.

    DOI: 10.1039/c2cp43427j

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  • Synthesis of graphene by surface wave plasma chemical vapor deposition from camphor 査読

    Golap Kalita, Subash Sharma, Koichi Wakita, Masayoshi Umeno, Yasuhiko Hayashi, Masaki Tanemura

    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE209 ( 12 ) 2510 - 2513   2012年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-V C H VERLAG GMBH  

    We demonstrate synthesis of graphene using the solid precursor camphor in a microwave excited surface wave plasma chemical vapor deposition technique. Highly sublimely camphor was introduced into the plasma chamber in the vapor phase along with Ar and uniform plasma formation was obtained. Rapid deposition of a graphene film on Cu foil was achieved at a relatively low temperature (&lt;600 degrees C). Raman spectroscopy and transmission electron microscopy clearly showed that the deposited film on Cu foil consist of few-layer graphene. Fully flexible transparent electrode was fabricated by transferring the graphene film with excellent properties for device application. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    DOI: 10.1002/pssa.201228554

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  • Structural and Electrical Properties of Ozone Irradiated Carbon Nanotube Yarns and Sheets 査読

    Toru Iijima, Yasuhiro Inagaki, Hisayoshi Oshima, Takuya Iwata, Ryota Sato, Golap Kalita, Toru Kuzumaki, Yasuhiko Hayashi, Masaki Tanemura

    MATERIALS EXPRESS2 ( 4 ) 357 - 362   2012年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER SCIENTIFIC PUBLISHERS  

    Poor electrical conductivity of carbon nanotube (CNT) yarn and sheets has been one of the main hurdles in their practical application. Here, we demonstrate that the ozone irradiation can be an effective approach to reduce the resistivity of spun CNTs bundle with oxidization and induced defects. The CNT yarn and sheet are fabricated from a spinnable vertically aligned CNT forest synthesized by a thermal chemical vapor deposition. The electrical resistance of a CNT yarn and sheet reduces with a certain period of ozone irradiation; however for a long duration of ozone irradiation resistance increases with structural deformation of the CNTs. A comparative study on the effect of shapes between the CNT yarn and sheet with morphological change in the CNTs due to the ozone irradiation is performed. It was observed that the desorption energy of ozone molecules was slightly large for the CNT yarn due to the difference of adsorption sites. The fraction of defects induced by the ozone irradiated on the CNT yarn was estimated from the ultimate resistance change with temperature and Raman spectroscopy.

    DOI: 10.1166/mex.2012.1092

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  • Pre-treatment of multi-walled carbon nanotubes for polyetherimide mixed matrix hollow fiber membranes 査読

    P. S. Goh, B. C. Ng, A. F. Ismail, M. Aziz, Y. Hayashi

    JOURNAL OF COLLOID AND INTERFACE SCIENCE386 ( 1 ) 80 - 87   2012年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ACADEMIC PRESS INC ELSEVIER SCIENCE  

    Mixed matrix hollow fibers composed of multi-walled carbon nanotubes (MWCNTs) and polyetherimide (PEI) were fabricated. Pre-treatment of MWCNTs was carried out prior to the incorporation into the polymer matrix using a simple and feasible two stages approach that involved dry air oxidation and surfactant dispersion. The characterizations of the surface treated MWCNTs using TEM and Raman spectroscopy have evidenced the effectiveness of dry air oxidation in eliminating undesired amorphous carbon and metal catalyst while surfactant dispersion using Triton X100 has suppressed the agglomeration of MWCNTs. The resultant mixed matrix hollow fibers were applied for O-2/N-2 pure gas separation. Interestingly, it was found that removal of disordered amorphous carbons and metal particles has allowed the hollow structures to be more accessible for the fast and smooth transport of gas molecules, hence resulted in noticeable improvement in the gas separation properties. The composite hollow fibers embedded with the surface modified MWCNTs showed increase in permeability as much as 60% while maintaining the selectivity of the O-2/N-2 gas pair. This study highlights the necessity to establish an appropriate pre-treatment approach for MWCNTs in order to fully utilize the beneficial transport properties of this material in mixed matrix polymer nanocomposite for gas separation. (c) 2012 Elsevier Inc. All rights reserved.

    DOI: 10.1016/j.jcis.2012.07.033

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  • In Situ TEM Observation of Fe-Included Carbon Nanofiber: Evolution of Structural and Electrical Properties in Field Emission Process 査読

    Mohd Zamri Mohd Yusop, Pradip Ghosh, Yazid Yaakob, Golap Kalita, Masato Sasase, Yasuhiko Hayashi, Masaki Tanemura

    ACS NANO6 ( 11 ) 9567 - 9573   2012年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    In situ transmission electron microscopy (TEM) of single Fe-Included carbon nanofibers (CNFs) revealed that the fine polycrystalline structure in the shank region of CNFs transformed to graphitic, hollow structures during a field emission (FE) process. The iron metal platelets agglomerated during the FE process and perceptibly were emitted from the shank, which featured bamboo-like carbon nanotube (CNT) structures. The structural evolution also improved the electrical properties, and the FE current was remarkably increased, that is, 1000 times higher than the initial value (from 10(-9) to 10(-6) A). The structural transformations were effectuated by Joule heating that generated simultaneously during the FE process The in situ TEM study of room-temperature-synthesized CNFs could provide essential information regarding CNFs structural.. transformation for their possible application in future electron emitter sources.

    DOI: 10.1021/nn302889e

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  • High temperature in-situ observations of multi-segmented metal nanowires encapsulated within carbon nanotubes by in-situ filling technique 査読

    Yasuhiko Hayashi, Tomoharu Tokunaga, Toru Iijima, Takuya Iwata, Golap Kalita, Masaki Tanemura, Katsuhiro Sasaki, Kotaro Kuroda

    NANOSCALE RESEARCH LETTERS7   1 - 4   2012年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGER  

    Multi-segmented one-dimensional metal nanowires were encapsulated within carbon nanotubes (CNTs) through in-situ filling technique during plasma-enhanced chemical vapor deposition process. Transmission electron microscopy (TEM) and environmental TEM were employed to characterize the as-prepared sample at room temperature and high temperature. The selected area electron diffractions revealed that the Pd4Si nanowire and face-centered-cubic Co nanowire on top of the Pd nanowire were encapsulated within the bottom and tip parts of the multiwall CNT, respectively. Although the strain-induced deformation of graphite walls was observed, the solid-state phases of Pd4Si and Co-Pd remain even at above their expected melting temperatures and up to 1,550 +/- 50A degrees C. Finally, the encapsulated metals were melted and flowed out from the tip of the CNT after 2 h at the same temperature due to the increase of internal pressure of the CNT.

    DOI: 10.1186/1556-276X-7-448

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  • Transparent and flexible field emission display device based on single-walled carbon nanotubes 査読

    Debasish Ghosh, Pradip Ghosh, Mohd Zamri Yusop, Masaki Tanemura, Yasuhiko Hayashi, Tetsuo Tsuchiya, Tomohiko Nakajima

    PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS6 ( 7 ) 303 - 305   2012年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-V C H VERLAG GMBH  

    A fully transparent and flexible field emission device (FED) has been demonstrated. Single-walled carbon nanotubes (SWCNTs) coated on arylite substrate were used as electron emitters for the FED and a novel metavanadate phosphor coated on the SWCNTs/arylite film was used as transparent and flexible screen. The SWCNTs/arylite based emitters and the SWCNTs/arylite/metal-vanadate-based phosphor showed a transmittance value of 92.6% and 54%, respectively. The assembled device also showed satisfactory transparency and flexibility as well as producing significant current. Metavanadate phosphor is considered to be an excellent candidate due to its superior luminescence properties and easy fabrication onto transparent and flexible conductive substrate at room temperature while retaining reasonable transparency of the substrate. Thus, its transparency and flexibility will open the door to next-generation FEDs. ((c) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

    DOI: 10.1002/pssr.201206251

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  • Effect of defects in ferromagnetic C doped ZnO thin films 査読

    Munisamy Subramanian, Yuhei Akaike, Yasuhiko Hayashi, Masaki Tanemura, Hiroshi Ebisu, Daniel Lau Shu Ping

    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS249 ( 6 ) 1254 - 1257   2012年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-V C H VERLAG GMBH  

    The present work investigates the relation between ferromagnetism and intrinsic defects of C-doped ZnO thin films. The room-temperature ferromagnetism (RTFM) in C-doped ZnO is due to the charge transfer between Zn 4s and C 2p orbitals. The long-range magnetic interaction in C-doped ZnO is due to carboncarbon interaction mediated by oxygen. The oxygen- and zinc-related defects in C-doped ZnO affect the mediation of ferromagnetic interaction and the existence of hybridization between Zn and C, respectively.

    DOI: 10.1002/pssb.201147609

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  • Characterization of carbon nanotube-silver composite yarn 査読

    T. Iijima, Y. Inagaki, H. Oshima, T. Iwata, U. B. Suryavanshi, R. Sato, T. Kuzumaki, T. Tokunaga, Y. Hayashi, M. Tanemura

    AMTC Letters3   206 - 207   2012年5月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

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  • Fundamental Study on Organic Solar Cells Based on Soluble Zinc Phthalocyanine 査読

    Ichiko Yamada, Masashi Umeda, Yasuhiko Hayashi, Tetsuo Soga, Norio Shibata

    JAPANESE JOURNAL OF APPLIED PHYSICS51 ( 4 )   2012年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:JAPAN SOC APPLIED PHYSICS  

    We investigated the potential of trifluoroethoxy-coated phthalocyanine [(4TFEO)(4)-ZnPc] as an organic thin-film solar cell material. (4TFEO)(4)-ZnPc dissolves well in several organic solvents, thus a fluorinated phthalocyanine (Pc) thin film can be fabricated by a wet process. Additionally, (4TFEO)(4)-ZnPc has lowest unoccupied molecular orbital (LUMO) energy level close to that of a fullerene derivative owing to the electron-withdrawing effect of fluorine substituents. We fabricated two types of fluorinated Pc solar cells by spin casting "(4TFEO)(4)-ZnPc single-layer solar cells" and "two-layer heterojunction solar cells" consisting of a (4TFEO)(4)-ZnPc layer and a poly(3-hexylthiophene) (P3HT) layer. P3HT is a common donor solar cell material. On the other hand, we used (4TFEO)(4)-ZnPc as an acceptor material. For the single-layer solar cells, the (4TFEO)(4)-ZnPc film acts as the photoactive layer of the solar cells, and P3HT/(4TFEO)(4)-ZnPc solar cell properties were improved as compared with that of P3HT or (4TFEO)(4)-ZnPc single-layer solar cells. Additionally, the photovoltaic properties of these solar cells were significantly improved by annealing treatment. (C) 2012 The Japan Society of Applied Physics

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  • In-situ observation of carbon nanotube fiber spinning from vertically aligned carbon nanotube forest 査読

    Toru Iijima, Hisayoshi Oshima, Yasuhiko Hayashi, Ulka Bhimrao Suryavanshi, Akari Hayashi, Masaki Tanemura

    DIAMOND AND RELATED MATERIALS24   158 - 160   2012年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    Single carbon nanotube (CNT) has exceptional electrical and mechanical properties. And CNT fiber is an interesting application because it can become the wire which is more excellent than exiting one. Some groups reported the fabrication of CNT fiber spun from vertically aligned CNTs forest (VACNF), but mechanism of spinning has not clear yet. In this paper, we present the optimum parameters for spinnable VACNF via the difference between spinnable and unspinnable VACNF. (C) 2012 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.diamond.2012.01.002

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  • Controllable fabrication and characterization of conical nanocarbon structures on polymer substrate for transparent and flexible field emission displays 査読

    Pradip Ghosh, Shunsaku Satou, Takuma Tsuchiya, Yasuhiko Hayashi, Masaki Tanemura

    PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS6 ( 4 ) 184 - 186   2012年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-V C H VERLAG GMBH  

    The direct fabrication of fully transparent conical nanocarbon structures (CNCSs) of controlled nanoscopic dimension on a flexible nafion substrate was achieved, using field electron source, by a novel room temperature ion irradiation technique. By controlling the sizes (below the wavelength of visible light) of the CNCSs, the transparency of the substrate can be tailored satisfactorily. The transparency of the CNCSs was observed to be around 90% in the visible regime depending on the ion irradiation time. Our results suggest that the direct fabrication of well controlled fully transparent CNCSs on any transparent and flexible substrate at room temperature could open a novel route for potential applications in future highly transparent, flexible (bendable), low weight and portable field emission displays (FEDs). (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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  • Growth and structure analysis of tungsten oxide nanorods using environmental TEM. 査読 国際誌

    Tomoharu Tokunaga, Tadashi Kawamoto, Kenta Tanaka, Naohiro Nakamura, Yasuhiko Hayashi, Katsuhiro Sasaki, Kotaro Kuroda, Takahisa Yamamoto

    Nanoscale research letters7 ( 1 ) 85 - 85   2012年1月

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    記述言語:英語  

    WO3 nanorods targeted for applications in electric devices were grown from a tungsten wire heated in an oxygen atmosphere inside an environmental transmission electron microscope, which allowed the growth process to be observed to reveal the growth mechanism of the WO3 nanorods. The initial growth of the nanorods did not consist of tungsten oxide but rather crystal tungsten. The formed crystal tungsten nanorods were then oxidized, resulting in the formation of the tungsten oxide nanorods. Furthermore, it is expected that the nanorods grew through cracks in the natural surface oxide layer on the tungsten wire.

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  • Low-Temperature Fabrication of Germanium Nanostructures by Ion Irradiation: Effect of Supplied Particle Species 査読

    Ako Miyawaki, Toshiaki Hayashi, Tomoharu Tokunaga, Akari Hayashi, Yasuhiko Hayashi, Masaki Tanemura

    JAPANESE JOURNAL OF APPLIED PHYSICS51 ( 1 )   2012年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    Germanium (Ge) surfaces were irradiated by argon (Ar) ions at 600 eV with a simultaneous Ge, Al, or Au supply at room temperature. The surfaces thus ion-irradiated were characterized by densely distributed nanowalls, nanobelts (narrower than the nanowalls in width), and cones tipped with nanoribbons (narrower than the nanobelts in width), depending on the supplied particle species and the supply rate. The higher the melting points of the supplied materials, the narrower the width of the top of the nanostructures. Thus the melting point and the supply rate of the supplied material are the key parameters for controlling the shape and size in the fabrication of ion-induced Ge nanostructures. It was also demonstrated that for nanowalls and nanobelts, a higher particle supply rate yielded wider nanostructures. For many nanoribbon-tipped cones, the width of the nanoribbon increased with distance from the cone top, and hence resulted in a bottleneck structure. (C) 2012 The Japan Society of Applied Physics

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  • Fabrication of ZnO nanoparticles confined in the channels of mesoporous carbon 査読

    Ulka Suryavanshi, Toru Iijima, Akari Hayashi, Yasuhiko Hayashi, Masaki Tanemura

    CHEMICAL ENGINEERING JOURNAL179   388 - 393   2012年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    ZnO nanoparticles have been incorporated inside the pore system of mesoporous carbon (MC) which has been synthesized by polymerization of resorcinol and formaldehyde via soft templating approach. 5-20% of ZnO, with an interval of 5, have been incorporated almost exclusively within the mesopores by simple wet impregnation, drying and calcination procedures. The pristine MC shows high surface area (600 m(2)/g) with large pore diameter around 7 nm. After impregnation of ZnO in mesopores, the pore diameter has been decreased from 7 to 6.24 nm which may relate to shrinkage of the framework or deposition of ZnO particles on the inner wall of the pores. With the increase in the ZnO percentage, the specific surface area and pore volume decreased linearly confirming the incorporation of nanoparticles inside the mesopores. TGA confirms ZnO confined in the pores of MC which also prevents the collapsing of mesoporous carbon framework upto 325 degrees C. Interestingly, the graphitic nature of MC remains same even after impregnation of ZnO nanoparticles inside the pores. However, we strongly believe that this novel composite of ZnO and MC may play significant role in the application like oxygen reduction reactions. photocatalysis, photovoltaics, optoelectronics, catalysis and many more. (C) 2011 Elsevier B.V. All rights reserved.

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  • Synthesis of transfer-free graphene on an insulating substrate using a solid phase reaction 査読

    Ryo Hirano, Ken Matsubara, Golap Kalita, Yasuhiko Hayashi, Masaki Tanemura

    NANOSCALE4 ( 24 ) 7791 - 7796   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

    We demonstrate a solid phase reaction approach to synthesise transfer-free graphene on an insulating substrate by controlling the C diffusion process. Metal assisted crystallization by annealing of a C thin film was carried out to synthesise transfer-free graphene, in the presence of a top metal oxide and metal layer. Without the metal oxide layer, a large amount of C atoms diffused to the top of the metal surface and hence the formation of only small graphene domains was observed on the underneath of the metal layer. Introducing the metal oxide layer at the top surface, C diffusion was reduced and consequently the thin C film was crystallized to form large area graphene at the metal-insulating substrate interface. The metal oxide or metal catalyst layer was removed after graphene formation and transfer-free graphene was obtained directly on the base substrate. This finding shows that the thin metal oxide layer is critical to synthesise graphene with better quality and continuous domain structures.

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  • CARBON NANOTUBES BASED MIXED MATRIX MEMBRANE FOR GAS SEPARATION 査読

    S. M. Sanip, A. F. Ismail, P. S. Goh, M. N. A. Norrdin, T. Soga, M. Tanemura, H. Yasuhiko

    NANOMATERIALS: SYNTHESIS AND CHARACTERIZATION364   272 - +   2012年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:TRANS TECH PUBLICATIONS LTD  

    Mixed matrix membranes (MMM) combine useful molecular sieving properties of inorganic fillers with the desirable mechanical and processing properties of polymers. The current trend in polymeric membranes is the incorporation of filler-like nanoparticles to improve the separation performance. Most MMM have shown higher gas permeabilities and improved gas selectivities compared to the corresponding pure polymer membranes. Carbon nanotubes based mixed matrix membrane was prepared by the solution casting method in which the functionalized multiwalled carbon nanotubes (f-MWNTs) were embedded into the polyimide membrane and the resulting membranes were characterized. The effect of nominal MWNTs content between 0.5 and 1.0 wt% on the gas separation properties were looked into. The as-prepared membranes were characterized for their morphology using field emission scanning electron microscopy (FESEM) and Transmission Electron Microscopy (TEM). The morphologies of the MMM also indicated that at 0.7 % loading of f-MWNTs, the structures of the MMM showed uniform finger-like structures which have facilitated the fast gas transport through the polymer matrix. It may also be concluded that addition of open ended and shortened MWNTs to the polymer matrix can improve its permeability by increasing diffusivity through the MWNTs smooth cavity.

    DOI: 10.4028/www.scientific.net/AMR.364.272

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  • Large-Area CVD Graphene as Transparent Electrode for Efficient Organic Solar Cells 査読

    Golap Kalita, Koichi Wakita, Masayoshi Umeno, Yasuhiko Hayashi, Masaki Tanemura

    2012 38TH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC)   3137 - 3141   2012年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Indium tin oxide (ITO) and related oxide based materials have been widely used as transparent electrode in optoelectronic devices and organic solar cells. Here, we demonstrate application of chemical vapor deposited (CVD) graphene films as transparent electrode for organic solar cells. Large area graphene films are deposited by control pyrolysis of botanical derivative camphor (C10H16O) and transparent electrode were fabricated by direct synthesis or transfer process. Raman spectroscopy and transmission electron microcopy studies are used to characterize the synthesized graphene based materials. Direct synthesized and transferred graphene films on glass or plastic substrates show very good optical transparency, electrical conductivity and mechanical stability. P3HT:PCBM bulk heterojunction solar cells are fabricated successfully on graphene based transparent electrode and compared with ITO based device. The dark light characteristic shows very good rectification with minimum leakage current. Under illumination of light the device shows very good open circuit voltage, short circuit current density and conversion efficiency.

    DOI: 10.1109/PVSC.2012.6318244

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  • Direct Growth of Horizontally Aligned Carbon Nanotubes between Electrodes and Its Application to Field-Effect Transistors 査読

    Yasuhiko Hayashi, B. Jang, T. Iijima, T. Tokunaga, A. Hayashi, M. Tanemura, G. A. J. Amaratunga

    JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY11 ( 12 ) 11011 - 11014   2011年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER SCIENTIFIC PUBLISHERS  

    This paper presents direct growth of horizontally-aligned carbon nanotubes (CNTs) between two predefined various inter-spacing up to tens of microns of electrodes (pads) and its use as CNT field-effect transistors (CNT-FETs). Using the conventional photolithography technique followed by thin film evaporation and lift off, the catalytic electrodes (pads) were prepared, consisting of Pt, Al and Fe triple layers on SiO2/Si substrate. The grown CNTs were horizontally-aligned across the catalytic electrodes on the modified gold image furnace hot stage (thermal CVD) at 800 degrees C by using an alcohol vapor as the carbon source. Scanning and transmission electron microcopies (SEM/TEM) were used to observe the structure, growth direction and density of CNTs, while Raman spectrum analysis was used to indicate the degree of amorphous impurity and diameter of CNTs. Both single- and multi-wall CNTs with diameters of 1.1-2.2 nm were obtained and the CNT density was controlled by thickness of Fe catalytic layer. Following horizontally-aligned growth of CNTs, the electrical properties of back-gate CNT-FETs were measured and showd p-type conduction behaviors of FET.

    DOI: 10.1166/jnn.2011.3964

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  • POLY(3, 4-ETHYLENEDIOXYTHIOPHENE): POLY(STYRENESULFONATE)/SINGLE-WALL CARBON NANOTUBE COMPOSITE FILM FOR THE HOLE TRANSPORT LAYER IN POLYMER SOLAR CELLS 査読

    Naoki Kishi, Shinya Kato, Takeshi Saito, Junki Hayashi, Daiki Ito, Yasuhiko Hayashi, Tetsuo Soga, Takashi Jimbo

    NANO6 ( 6 ) 583 - 588   2011年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WORLD SCIENTIFIC PUBL CO PTE LTD  

    The composite thin film of poly(3, 4-ethylenedioxythiophene):poly(styrenesulfonate)/single-wall carbon nanotubes (PEDOT:PSS/SWCNTs) for a hole transport layer in polymer solar cells have been explored. PEDOT:PSS/SWCNT composite film exhibited higher electrical conductivity than the control PEDOT:PSS film, suggesting the increase in carrier transport passes through SWCNTs in the hole transport layer. We also demonstrated the improvement of a fill factor and short circuit current density in the polymer solar cells with the hole transport layer of PEDOT:PSS/SWCNT as compared with PEDOT:PSS.

    DOI: 10.1142/S1793292011002901

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  • Fabrication of Ion-Induced Carbon-Cobalt Nanocomposite Fibers: Effect of Cobalt Supply Rate 査読

    Zhipeng Wang, Mohd Zamri Mohd Yusop, Takehiko Hihara, Pradip Ghosh, Akari Hayashi, Yasuhiko Hayashi, Masaki Tanemura

    JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY11 ( 12 ) 10677 - 10681   2011年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER SCIENTIFIC PUBLISHERS  

    Graphite surfaces were irradiated by argon (Ar+) ions at 1 key with a simultaneous cobalt (Co) supply at room temperature. Various kinds of carbon nanocomposites, such as nanocones with and without single nanofibers on their tops, nanorods and fish-scale-like nanoprotrusions, were formed depending on Co supply rates. It has been observed that with increasing the Co supply rate the formation of nanoprotrusions without nanofibers became prominent. Both nanofibers and nanoprotrusions were surely composed of carbon and Co, as confirmed by energy-dispersive X-ray analysis. The cobalt carbon nanocomposite fibers (CCNFs), similar to 1.5 mu m in average length, were grown on the top of the nanocones at the Co supply rate of 1.0 nm/min. The field electron emission characteristics of CCNFs thus grown indicated that there is an optimum parameter for the CCNF growth to achieve the better emission performance than that of pristine Ar+-induced carbon nanofibers.

    DOI: 10.1166/jnn.2011.4021

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  • In Vitro Evaluation of Cytotoxicity and Oxidative Stress Induced by Multiwalled Carbon Nanotubes in Murine RAW 264.7 Macrophages and Human A549 Lung Cells 査読

    Chen Bo, Liu Ying, Song Wei Ming, Yasuhiko Hayashi, Ding Xun Cheng, Li Wei Hua

    BIOMEDICAL AND ENVIRONMENTAL SCIENCES24 ( 6 ) 593 - 601   2011年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHINESE CENTER DISEASE CONTROL & PREVENTION  

    Objective To investigate in vitro cytotoxicity and oxidative stress response induced by multiwalled carbon nanotubes (MWCNTs).
    Methods Cultured macrophages (murine RAW264.7 cells) and alveolar epithelium cells type II (human A549 lung cells) were exposed to the blank control, DNA salt control, and the MWCNTs suspensions at 2.5, 10, 25, and 100 mu g/mL for 24 h. Each treatment was evaluated by cell viability, cytotoxicity and oxidative stress.
    Results Overall, both cell lines had similar patterns in response to the cytotoxicity and oxidative stress of MWCNTs. DNA salt treatment showed no change compared to the blank control. In both cell lines, significant changes at the doses of 25 and 100 mu g/mL treatments were found in cell viabilities, cytotoxicity, and oxidative stress indexes. The reactive oxygen species (ROS) generation was also found to be significantly higher at the dose of 10 mu g/mL treatment, whereas no change was seen in most of the indexes. The ROS generation in both cell lines went up in minutes, reached the climax within an hour and faded down after several hours.
    Conclusion Exposure to MWCNTs resulted in a dose-dependent cytotoxicity in cultured RAW264.7 cells and A549 cells, that was closely correlated to the increased oxidative stress.

    DOI: 10.3967/0895-3988.2011.06.002

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  • Determination of Young's modulus of carbon nanofiber probes fabricated by the argon ion bombardment of carbon coated silicon cantilever 査読

    Kazuhisa Inaba, Kouji Saida, Pradip Ghosh, Ken Matsubara, Munisamy Subramanian, Akari Hayashi, Yasuhiko Hayashi, Masaki Tanemura, Masashi Kitazawa, Ryo Ohta

    CARBON49 ( 13 ) 4191 - 4196   2011年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    A single amorphous carbon nanofiber (CNF) was grown on a commercial Si cantilever by the argon ion (Ar+) bombardment of carbon coated silicon cantilever. The CNF probe was mounted on a piezo controlled arm opposing a soft cantilever to measure the axial force acting on the CNF in a scanning electron microscope (SEM). The buckling force was measured while observing the buckling behavior. The CNF probes have an elliptical cross section with short and long axis of 20-29 and 25-59 nm, respectively, and a length of 350-760 nm. The Young's modulus was determined from Euler's formula using the measured buckling force and had a value of 38-48 GPa, almost independent of the CNF size. The Young's modulus was lower than that of high quality carbon nanotubes (CNTs) and higher than that of defective CNTs. It was also demonstrated that the CNF probes were elastic, similar to the CNT probes. Thus CNF probes produced by Ar+ ion bombardment are quite promising as practical nanocarbon probes. (C) 2011 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.carbon.2011.05.051

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  • Fabrication of Ge nanoneedles by ion-irradiation method 査読

    Ako Miyawaki, M. Zamri, T. Hayashi, Y. Hayashi, M. Tanemura, T. Tokunaga

    SURFACE & COATINGS TECHNOLOGY206 ( 5 ) 812 - 815   2011年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    The Ge surfaces irradiated by Ar(+) ions at 600 eV with simultaneous Ni supply at room temperature were characterized by various kind of densely distributed nanostructures, such as tiny cones, nanorods with a bottlenecked and nanoneedles, depending on the Ni supply rate during Ar(+) ion irradiation. As the Ni supply rate decreased, the width of nanostructure formed on the cone tip became thin, and finally slender Ge nanoneedles of 60-80 nm in diameter and 100-300 nm in length were realized. Because the simultaneously supplied Ni fulfills the prerequisite for the so-called "seed" which enhances the surface texturing, size of clustered Ni atoms during of Ar(+) ion irradiation might affect the size of nanostructures formed after the prolonged sputtering. (C) 2011 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.surfcoat.2011.04.022

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  • Morphology control of a rapidly grown vertically aligned carbon-nanotube forest for fiber spinning 査読

    T. Iijima, H. Oshima, Y. Hayashi, U. B. Suryavanshi, A. Hayashi, M. Tanemura

    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE208 ( 10 ) 2332 - 2334   2011年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-BLACKWELL  

    Carbon nanotube (CNT) fibers have interesting applications because of their good electrical and mechanical properties. CNT fiber is fabricated in a simple way, that it is spun from a vertically aligned CNT forest (VACNF). Spinning occurs by joining of CNT when the CNT at the edge of a VACNF is drawn horizontally. However, the mechanism of spinning is still not clear. To investigate it, we fabricated a spinnable VACNF by thermal chemical vapor deposition (CVD) and compared it with unspinnable VACNF by scanning electron microscope (SEM) observation and polarized Raman spectroscopy. It was found that there were a few big differences between spinnable and unspinnable VACNFs. In the case of spinnable VACNF, most of the CNTs are straight and well aligned. Spinnable VACNF also contains CNT bundles consisting of 8-10 CNTs that are not vertically aligned. This CNT bundle was shared by a few adjacent thicker CNT bundles. These points are very important for continuous fiber spinning. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

    DOI: 10.1002/pssa.201084170

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  • High-resolution imaging of plasmid DNA in liquids in dynamic mode atomic force microscopy using a carbon nanofiber tip 査読

    Masashi Kitazawa, Shuichi Ito, Akira Yagi, Nobuaki Sakai, Yoshitugu Uekusa, Ryo Ohta, Kazuhisa Inaba, Akari Hayashi, Yasuhiko Hayashi, Masaki Tanemura

    Japanese Journal of Applied Physics50 ( 8 ) 08LB14   2011年8月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    To understand the motion of DNA and DNA complexes, the real-time visualization of living DNA in liquids is quite important. Here, we report the high-resolution imaging of plasmid DNA in water using a rapid-scan atomic force microscopy (AFM) system equipped with a carbon nanofiber (CNF) probe. To achieve a rapid high-resolution scan, small SiN cantilevers with dimensions of 2 (width) × 0.1 (thickness) × 9μm (length) and a bent end (tip view structure) were employed as base cantilevers onto which single CNFs were grown. The resonant frequencies of the cantilever were 1.5 MHz in air and 500 kHz in water, and the spring constant was calculated to be 0.1 N/m. Single CNFs, typically 88 nm in length, were formed on an array of the cantilevers in a batch process by the ion-irradiation method. An AFM image of a plasmid DNA taken in water at 0.2fps (5s/image) using a batch-fabricated CNF-tipped cantilever clearly showed the helix turns of the double strand DNA. The average helical pitch measured 3.4 nm (σ: 0.5 nm), which was in good agreement with that determined by the X-ray diffraction method, 3.4 nm. Thus, it is presumed that the combined use of the rapid-scan AFM system with the ion-induced CNF probe is promising for the dynamic analysis of biomolecules. © 2011 The Japan Society of Applied Physics.

    DOI: 10.1143/JJAP.50.08LB14

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  • High-Resolution Imaging of Plasmid DNA in Liquids in Dynamic Mode Atomic Force Microscopy Using a Carbon Nanofiber Tip 査読

    Masashi Kitazawa, Shuichi Ito, Akira Yagi, Nobuaki Sakai, Yoshitugu Uekusa, Ryo Ohta, Kazuhisa Inaba, Akari Hayashi, Yasuhiko Hayashi, Masaki Tanemura

    JAPANESE JOURNAL OF APPLIED PHYSICS50 ( 8 )   2011年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    To understand the motion of DNA and DNA complexes, the real-time visualization of living DNA in liquids is quite important. Here, we report the high-resolution imaging of plasmid DNA in water using a rapid-scan atomic force microscopy (AFM) system equipped with a carbon nanofiber (CNF) probe. To achieve a rapid high-resolution scan, small SiN cantilevers with dimensions of 2 (width) x 0.1 (thickness) x 9 mu m (length) and a bent end (tip view structure) were employed as base cantilevers onto which single CNFs were grown. The resonant frequencies of the cantilever were 1.5 MHz in air and 500 kHz in water, and the spring constant was calculated to be 0.1 N/m. Single CNFs, typically 88 nm in length, were formed on an array of the cantilevers in a batch process by the ion-irradiation method. An AFM image of a plasmid DNA taken in water at 0.2 fps (5 s/image) using a batch-fabricated CNF-tipped cantilever clearly showed the helix turns of the double strand DNA. The average helical pitch measured 3.4nm (sigma:0.5 nm), which was in good agreement with that determined by the X-ray diffraction method, 3.4 nm. Thus, it is presumed that the combined use of the rapid-scan AFM system with the ion-induced CNF probe is promising for the dynamic analysis of biomolecules. (C) 2011 The Japan Society of Applied Physics

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  • Structural change of ion-induced carbon nanofibers by electron current flow 査読

    Mohd Zamri, Pradip Ghosh, Akari Hayashi, Yasuhiko Hayashi, Masaki Tanemura, Masato Sasase

    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B29 ( 4 )   2011年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:A V S AMER INST PHYSICS  

    A graphite foil was irradiated with argon (Ar+) ions to fabricate conical structures with a carbon nanofiber (CNF) on top of the structure. The field emission (FE) properties of one-dimensional individual CNF-tipped cones that had been fabricated were carefully measured by in situ transmission electron microscopy (TEM) facilities. The highest FE current, 550 nA, was observed in the current-voltage (I-V) measurement of a single CNF. Almost no degradation in I-V properties were detected during the reliability test after 30 min. TEM images indicated that the CNF was amorphous in nature initially, and that the electron current flow in the FE process induced the dramatic change in the crystalline structure of both the CNF and of the tip region of the basal cone part. After performing the FE process, the crystalline structures of the amorphous CNFs were transformed into ring-shaped graphene layers, whereas nanodiamond like nanoparticles formed in the outer layer of the tip region of the basal cone. The structural changes induced can be attributed to Joule heating under the high electric field. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3591420]

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  • Growth evolution of rapid grown aligned carbon nanotube forests without water vapor on Fe/Al2O3/SiO2/Si substrate 査読

    Yasuhiko Hayashi, Toru Iijima, M. Miyake, M. Satoh, N. L. Rupesinghe, K. B. K. Teo, M. Tanmemura

    DIAMOND AND RELATED MATERIALS20 ( 7 ) 859 - 862   2011年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    This paper presents the growth evolutions in terms of the structure, growth direction and density of rapid grown carbon nanotube (CNT) forests observed by scanning and transmission electron microcopies (SEM/TEM). A thermal CVD system at around 700 degrees C was used with a catalyst of Fe films deposited on thin alumina (Al2O3) supporting layers, a very fast raising time to the growth temperature below 25 degrees C/s, and a carbon source gas of acetylene diluted with hydrogen and nitrogen without water vapor. Activity of Fe catalyst nanoparticles was maintained for 5 min during CVD process, and it results in CNT forests with heights up to 0.6 mm. SEM images suggest that the disorder in CNT alignment at the initial stage of CM&apos;s plays a critical role in the formation of continuous CNT growth. Also, the prolonged heating process leads to increased disorder in CNT alignment that may be due to the oxidation process occurring at the Fe nanoparticles. TEM images revealed that both double- and few-walled CNTs with diameters of 5-7 nm were obtained and the CNT density was controlled by thickness of Fe catalytic layer. The number of experiments at the same conditions showed a very good repeatability and reproducibility of rapid grown CNT forests. (C) 2011 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.diamond.2011.02.003

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  • Gas separation properties of functionalized carbon nanotubes mixed matrix membranes 査読

    S. M. Sanip, A. F. Ismail, P. S. Goh, T. Soga, M. Tanemura, H. Yasuhiko

    SEPARATION AND PURIFICATION TECHNOLOGY78 ( 2 ) 208 - 213   2011年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    The synergistic combinations of organic polymers for separation applications with inorganic substances such as multi-walled carbon nanotubes (MWNTs), have resulted in a new class of membrane material called mixed matrix membrane (MMM) for the separation of CO2/CH4 gases. Mixed matrix membrane incorporated functionalized MWNTs (f-MWNTs) were fabricated by the solution casting method, in which the f-MWNTs were embedded into the polyimide membrane and the resulting membranes were characterized. The effect of nominal MWNTs content between 0.5 and 1.0 wt% on the gas separation properties was investigated. The mixed matrix membranes showed 100% enhancement for the selectivity of CO2/CH4 compared to the corresponding neat polymer membrane. This new class of mixed matrix membrane has the ability to separate gases at the molecular level and has the potential to ultimately reduce the energy consumed in present-day separation operations. This study has shown that addition of CNTs to polymeric membranes has improved separation properties of the membranes to a certain extent. (C) 2011 Elsevier B.V. All rights reserved.

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  • Azidation of polyesters having pendent functionalities by using NaN3 or DPPA-DBU and photo-crosslinking of the azidopolyesters 査読

    Yosuke Shibata, Hiroki Tanaka, Akinori Takasu, Yasuhiko Hayashi

    POLYMER JOURNAL43 ( 3 ) 272 - 278   2011年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:NATURE PUBLISHING GROUP  

    In this article, we performed dehydration polycondensation of bromosuccinic acid and methylsuccinic acid with 1,4- butanediol at 80 1C to synthesize aliphatic polyesters containing pendent bromo groups without dehydrobromination using scandium trifluoromethanesulfonate (Sc(OTf) 3) as the catalyst. Azidation of the resultant polyesters was carried out readily in N, Ndimethylformamide at room temperature using sodium azide (M-n = 8.3 x 10(3) (M-w/M-n=2.17)). H-1 nuclear magnetic resonance analysis of the product revealed that 65% contained azide functionality, and dehydrobromination occurred in 35% during the azidation process. On the other hand, azidation of poly(butylene bromoadipate-co-butylene methylsuccinate) (poly(BBA-co-BMS)) proceeded successfully under the same conditions to generate poly(butylene azidoadipate-co-butylene methylsuccinate) (poly(BAA-co-BMS)) without dehydrobromination (M-n=10.4 x 10(3) (M-w/M-n=2.71)). We successfully photo-crosslinked the resultant azidopolyester by ultraviolet irradiation and examined it using scanning electron microscope. We also described azidation of polyesters having pendent hydroxyl groups by using the 'DPPA (diphenylphosphoryl azide)-DBU (1,8diazabicyclo[5.4.0] undec-7-ene) substitution strategy' to produce water-soluble polyesters containing pendent azido groups (M-n=7.5 +/- 103 (M-w/M-n=2.25)). These azidopolyesters might be extremely useful not only for their derivatization by simple chemical modification but also for their effective utilization as photolithography material. Polymer Journal (2011) 43, 272-278; doi: 10.1038/pj.2010.135; published online 12 January 2011

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  • Formation of carbon nanostructures containing single-crystalline cobalt carbides by ion irradiation method 査読

    Zhipeng Wang, Zamri Yusop, Pradip Ghosh, Yasuhiko Hayashi, Masaki Tanemura

    APPLIED SURFACE SCIENCE257 ( 8 ) 3168 - 3173   2011年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    Carbon nanofibers (CNFs) with a diameter of 17 nm, and carbon nanoneedles (CNNs) with sharp tips have been synthesized on graphite substrates by ion irradiation of argon ions with the Co supplies rate of 1 and 3.4 nm/min, respectively. Energy dispersive X-ray spectrometry, combined with selected area electron diffraction patterns has been used to identify the chemical composition and crystallinity of these carbon nanostructures. The CNFs were found to be amorphous in nature, while the structures of the CNNs consisted of cubic CoC(x), orthorhombic Co(2)C and Co(3)C depending on the cobalt content in the CNNs. The diameter of the carbide crystals was almost as large as the diameter of the CNN. Compared to the ion-induced nickel carbides and iron carbides, the formation of single-crystalline cobalt carbides might be due to the high temperature produced by the irradiation. (C) 2010 Elsevier B. V. All rights reserved.

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  • In-situ TEM observation of internal metal inside metal filled carbon fiber 査読

    Tomoharu Tokunaga, Yoshiro Horita, Takumi Kanematsu, Ikuo Nomura, Toru Iijima, Yasuhiko Hayashi, Kotaro Kuroda

    DIAMOND AND RELATED MATERIALS20 ( 2 ) 210 - 212   2011年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    There has been a considerable amount of research on MFCNTs and MFCNFs; however, research on the behavior of the internal metal used in MFCNF under heating has been limited. Therefore, in this study, an MFCNF was heated and the behavior of the internal metal was investigated using in-situ TEM observations. The internal metal used in the MFCNF did not melt. It was supposed that the non-melting was because of the high pressure of the internal metal resulting from a difference in the coefficients of linear thermal expansion of the graphite wall of the MFCNF and the internal metal. The pressure of the internal metal was calculated; it was approximately 12 GPa when the MFCNF was heated at 1500 degrees C. (C) 2010 Elsevier B.V. All rights reserved.

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  • Morphology and Size of Ion Induced Carbon Nanofibers: Effect of Ion Incidence Angle, Sputtering Rate, and Temperature 査読

    Mohd Zamri Yusop, Kohei Yamaguchi, Takahito Suzuki, Pradip Ghosh, Akari Hayashi, Yasuhiko Hayashi, Masaki Tanemura

    JAPANESE JOURNAL OF APPLIED PHYSICS50 ( 1 )   2011年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:JAPAN SOC APPLIED PHYSICS  

    Graphite surfaces were bombarded with oblique Ar+ ions at 1 keV to induce the carbon nanofiber (CNF) growth at room temperature and at high temperature (300 degrees C), and their dependence of length, diameter and number density on ion-incidence angle and sputtering rate was investigated in detail. The sputtered surface ion-irradiated at normal incidence produced huge cones and rod-like structures. It was found that some of the cones possessed the non-aligned thick carbon fibers on the top. By contrast, obliquely ion-irradiation induced the formation of densely distributed CNF-tipped cones. The higher ion-incidence angle produced CNF of smaller diameter and high fabrication temperature favors the formation of longer fiber with higher numerical density. In addition, the number density of the CNF-tipped cones strongly depended upon the ion-incidence angle rather than the sputtering rate. Thus, the diameter, length and number density of CNFs were strongly dependent upon the ion-irradiation parameters. It is believed that myriad of applications is possible with ion-induced CNFs by selecting the suitable ion-irradiation parameters. (C) 2011 The Japan Society of Applied Physics

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  • The growth and characterization of Zn nanowires covered with ZnO using plasma-assisted molecular beam irradiation 査読

    T. Tokunaga, K. Sasaki, K. Kuroda, T. Iijima, B. Jang, Y. Hayashi, R. A. Afre, M. Tanemura

    Proceedings - International NanoElectronics Conference, INEC   2011年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    The Zn nanowires covered with ZnO were grown by oxygen plasma-assisted molecular beam irradiation method and characterized, was reported. To grow these nanowires, oxygen plasma was irradiated to Zn thin film evaporated on Si(100) substrate. Scanning electron microscopy and transmission electron microscopy observation results of nanowires revealed that the nanowire has diameter of 80 nm, and nanowires was constructed with crystalline ZnO. Moreover NWs surface was covered by crystalline ZnO. Further Zn and ZnO orientation was coincident and resulted the ZnO appeared by oxidation of Zn nanowires. © 2011 IEEE.

    DOI: 10.1109/INEC.2011.5991618

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  • Influence of new fullerene derivatives with fluorocarbon substituent on performance of polymer solar cells 査読

    Ichiko Yamada, Manoj Pandey, Yasuhiko Hayashi, Norio Shibata, Tesuo Soga, Takeshi Toru

    9TH INTERNATIONAL CONFERENCE ON NANO-MOLECULAR ELECTRONICS14   192 - 197   2011年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:ELSEVIER SCIENCE BV  

    We report the polymer solar cells using newly synthesized fullerene derivatives with fluorocarbon substituent (F-PCBM). F-PCBMs were synthesized to improve a solar cell property byadding them to P3HT/PCBM mixture. According to the UV-vis absorption spectra and the cyclic voltammograms for F-PCBMs, the energy levels of the F-PCBMs couldn't be influenced by fluorocarbon substituent. We fabricated the polymer solar cells consist of P3HT/PCBM with each F-PCBM, and investigated their solar cell property. Some solar cells with F-PCBM showed increase of the short circuit current density (J(sc)). F-PCBM with short fluorocarbon chain (PCB2F) significantly increased J(sc), and it showed higher solar cell efficiency (E-ff = 2.31 %) than the solar cell with only PCBM (E-ff = 2.04 %). We also fabricated solar cells with PCB2F on the three condition of drying time before thermal annealing. As a result, the condition of "30 min" showed the highest solar cell efficiency than other tried one. (C) 2010 Published by Elsevier B.V.

    DOI: 10.1016/j.phpro.2011.05.039

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  • Growth and structure analysis of tungsten oxide nanorods using environmental transmission electron microscopy 査読

    Tomoharu Tokunaga, Tadashi Kawamoto, Kenta Tanaka, Naohiro Nakamura, Katsuhiro Sasaki, Kotaro Kuroda, Yasuhiko Hayashi

    Proceedings - International NanoElectronics Conference, INEC   2011年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    The WO3 nanorods were fabricated in environmental transmission electron microscopy (ETEM) by simply heating it in oxygen atmosphere. Altough, WO3 nanorod showed high crystalline, but the stacking fault existed in nanorod. Furthermore, the nanorod was grown on tungsten wire through slit of oxide layer on it. © 2011 IEEE.

    DOI: 10.1109/INEC.2011.5991617

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  • Highly transparent and flexible field emission devices based on single-walled carbon nanotube films 査読

    Debasish Ghosh, Pradip Ghosh, Masaki Tanemura, Akari Haysahi, Yasuhiko Hayashi, Kawasaki Shinji, Noboru Miura, Mohd Zamri Yusop, Toru Asaka

    CHEMICAL COMMUNICATIONS47 ( 17 ) 4980 - 4982   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

    Single-walled carbon nanotubes (SWNTs) have been used successfully to fabricate highly transparent and flexible field emission displays (FEDs). Field emission measurements indicated that SWNTs films have great potential to work as building blocks for next generation transparent and flexible FEDs.

    DOI: 10.1039/c0cc05677d

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  • Direct fabrication of aligned metal composite carbon nanofibers on copper substrate at room temperature and their field emission property 査読

    Pradip Ghosh, M. Zamri Yusop, Debasish Ghosh, Akari Hayashi, Yasuhiko Hayashi, Masaki Tanemura

    CHEMICAL COMMUNICATIONS47 ( 16 ) 4820 - 4822   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

    Direct growth of aligned metal composite carbon nanofibers (MCNFs) was achieved by a highly reproducible room temperature growth process on cost effective electrically conductive copper (Cu) substrate without any catalyst. The direct fabrication of MCNFs on electrically conductive substrate might offer new perspectives in the field of field emission displays (FEDs).

    DOI: 10.1039/c1cc10655d

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  • Electrical property of carbon nanotube Fiber spun from vertically aligned carbon nanotube forest 査読

    T. Iijima, Y. Hayashi, U. B. Suryavanshi, A. Hayashi, M. Tanemura, H. Oshima

    Proceedings - International NanoElectronics Conference, INEC   2011年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    Carbon nanotube (CNT) fibers are having interesting applications because of its good electrical and mechanical properties. CNT fiber is fabricated by simple way that it is spun from vertically aligned CNT forest (VACNF). Spinning is occurred by joining of CNT when the CNT at edge of VACNF is drawn horizontally. © 2011 IEEE.

    DOI: 10.1109/INEC.2011.5991734

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  • Simple methods for tuning the pore diameter of mesoporous carbon 査読

    Ulka B. Suryavanshi, Toru Ijima, Akari Hayashi, Yasuhiko Hayashi, Masaki Tanemura

    CHEMICAL COMMUNICATIONS47 ( 38 ) 10758 - 10760   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

    The organic-organic self-assembly method with Resorcinol (R)/Formaldehyde (F) and Pluronic F127 has been employed to synthesize mesoporous carbon (MC). The pore diameter of the MC has been tuned from 7 to 12.5 nm by changing the molar ratio of carbon sources to surfactant and polymerization time.

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  • Poly[(3-hexylthiophene)-block-(3-semifluoroalkylthiophene)] for Polymer Solar Cells 査読

    Ichiko Yamada, Koji Takagi, Yasuhiko Hayashi, Tetsuo Soga, Norio Shibata, Takeshi Toru

    INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES11 ( 12 ) 5028 - 5040   2010年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:MDPI AG  

    We report the synthesis of poly[(3-hexylthiophene)-block-(3-(4,4,5,5,6,6,7,7,7-nonafluoroheptyl)thiophene)], P(3HT-b-3SFT), carried out by the Grignard Metathesis Method (GRIM). The copolymers composition was determined by H-1 and F-19 NMR spectroscopies, and gel permeation chromatography (GPC). The thin films of P(3HT-b-3SFT) were investigated by ultraviolet-visible absorption spectroscopy and atomic force microscopy (AFM). We also fabricated bulk-hetero junction (BHJ) solar cells based on blends of P(3HT-b-3SFT) and [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM). Although the composition ratio of P3SFT in P(3HT-b-3SFT) was low, the influence of P3SFT on the morphology and properties of solar cells was significant. The annealing process for the BHJ solar cells induced the formation of large domains and led to poor solar cell performance. The BHJ solar cells, based on PCBM and P(3HT-b-3SFT), prepared by the non-annealing process, had a maximum power conversion efficiency of 0.84% under 100 mW/cm(2) (AM 1.5 solar illumination) in air.

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  • Synthesis and magnetic property of Fe-incorporated carbon nanofibers by ion-irradiation method 査読

    Z. P. Wang, M. Zamri, T. Hihara, Y. Hayashi, M. Tanemura

    Transactions of the Materials Research Society of Japan35 ( 4 ) 755 - 758   2010年12月

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  • Template-free electrochemical nanofabrication of polyaniline nanobrush and hybrid polyaniline with carbon nanohorns for supercapacitors 査読

    Di Wei, Haolan Wang, Pritesh Hiralal, Piers Andrew, Tapani Ryhaenen, Yasuhiko Hayashi, Gehan A. J. Amaratunga

    NANOTECHNOLOGY21 ( 43 )   2010年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    Polyaniline (PANI) nanobrushes were synthesized by template-free electrochemical galvanostatic methods. When the same method was applied to the carbon nanohorn (CNH) solution containing aniline monomers, a hybrid nanostructure containing PANI and CNHs was enabled after electropolymerization. This is the first report on the template-free method to make PANI nanobrushes and homogeneous hybrid soft matter (PANI) with carbon nanoparticles. Raman spectroscopy was used to analyze the interaction between CNH and PANI. Electrochemical nanofabrication offers simplicity and good control when used to make electronic devices. Both of these materials were applied in supercapacitors and an improvement capacitive current by using the hybrid material was observed.

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  • Fabrication and Morphological Control of Ion-Induced Zinc Nanostructures 査読

    Pradip Ghosh, Masaki Kutsuna, Masato Kudo, Akari Hayashi, Yasuhiko Hayashi, Masaki Tanemura

    JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY10 ( 10 ) 6677 - 6682   2010年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER SCIENTIFIC PUBLISHERS  

    An efficient method for the fabrication of zinc (Zn) nanostructures (nanoneedles and nanofibers) of controllable density and morphology without any catalyst, hazardous chemicals or external heat supply has been investigated. By varying the ion irradiation time and the ion current density, morphological control and the density of Zn nanostructures were successfully achieved using a fast and viable ion irradiation technique. Scanning (SEM) and transmission electron microscopy (TEM) results revealed that the sputtered surface was almost entirely covered with densely distributed conical and needle-like protrusions with linear shaped (sometimes curved) nanostructures (such as nanoneedles and nanofibers) with diameters and lengths of about 20-50 nm and several hundred nanometers, respectively. Detailed analysis of selected area electron diffraction (SAED) patterns with TEM analysis indicates that the Zn nanofibers were polycrystalline in nature. A possible mechanism of the formation of Zn nanostructures is briefly discussed. These aligned arrays of Zn nanoneedles/nanofibers could be a promising material for the fabrication of zinc oxide nanostructures by subsequent oxidation of Zn nanostructures and their future application in nanodevices. Thus, it is believed that this ion irradiation technique could open up a new approach for the fabrication of many kinds of nanomaterials of controllable density.

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  • Electron spin resonance (ESR) analysis of Cu-doped ZnO and AlN films 査読

    Fan-Yong Ran, M. Subramanian, Masaki Tanemura, Yasuhiko Hayashi, Takehiko Hihara

    PHYSICA B-CONDENSED MATTER405 ( 18 ) 3952 - 3954   2010年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    Cu-doped ZnO and AlN films both exhibiting room-temperature (RT) ferromagnetism (FM) were deposited by helicon magnetron sputtering. Magnetic anisotropy was observed for all the films; saturated magnetization was larger under the applied field perpendicular to the sample surface than the [0 0 0 2] direction. Electron spin resonance (ESR) analysis showed that spins tended to align in a perpendicular direction to the surface, which might account for the observed magnetic anisotropy. (C) 2010 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physb.2010.06.036

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  • New approach to breast tumor detection based on fluorescence x-ray analysis | Neues verfahren zum nachweis von brustkrebs auf der basis der röntgen-fluoreszenz-analyse 査読

    Hayashi Y, Okuyama F

    GMS German Medical Science8   2010年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.3205/000107

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  • Size Control of Carbon Nanofiber Probes Fabricated by Ion Irradiation 査読

    Kazuhisa Inaba, Yoshitaka Sugita, Takahito Suzuki, Masaki Tanemura, Akari Hayashi, Yasuhiko Hayashi, Masashi Kitazawa, Ryo Ohta

    JAPANESE JOURNAL OF APPLIED PHYSICS49 ( 8 )   2010年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:JAPAN SOC APPLIED PHYSICS  

    The effect of ion species and fabrication temperature on the size of ion-induced carbon nanofibers (CNFs) grown on tips of scanning probe microscope cantilevers was investigated in detail. Similarly to that using Ar(+) ions, the fabrication of CNF probes using Ne(+) and Xe(+) ions was possible. Xe(+) sputtering yielded the shortest CNF probes owing to its large sputtering effect; however, a significant difference in the size of the CNF probes between Ne(+) and Ar(+) ion irradiation was not observed. The CNFs increased in length with fabrication temperature owing to the enhanced diffusion of C atoms at elevated temperatures; however, the CNF diameter remained almost constant independent of fabrication temperature. Therefore, the fabrication at elevated temperatures was effective for the rapid fabrication of practical CNF probes. Thus, the CNF probe size was controllable by adjusting the fabrication temperature and ion species. (C) 2010 The Japan Society of Applied Physics

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  • Formation and growth mechanisms of ion-induced iron-carbon nanocomposites at room temperature 査読

    Zhipeng Wang, Mohd Zamri Mohd Yusop, Takehiko Hihara, Akari Hayashi, Yasuhiko Hayashi, Masaki Tanemura

    APPLIED SURFACE SCIENCE256 ( 21 ) 6371 - 6374   2010年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    The irradiation of graphite surfaces with a simultaneous Fe supply have resulted into the development of various types of carbon nanocomposites. Their morphologies - diameter, density, length and apex angle strongly depend on the ratios of Fe deposition rate (D(Fe)) to ion sputtering rate (S(ion)). By optimizing the ratio of D(Fe)/S(ion) (2.40%), the denser and well-aligned Fe-carbon nanocomposite fibers (Fe-CNFs) could be obtained, whose average length and diameter were 0.95 mu m and 17 nm, respectively. As confirmed by energy-dispersive X-ray analysis, the Fe-CNFs with amorphous-like or fine-polycrystalline phase were surely composed of carbon and Fe. Two types of growth models have been employed to explain the formation of metal-carbon nanocomposites. (C) 2010 Elsevier B. V. All rights reserved.

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  • PREPARATION AND CHARACTERISTICS OF FUNCTIONALIZED MULTIWALLED CARBON NANOTUBES IN POLYIMIDE MIXED MATRIX MEMBRANE 査読

    S. M. Sanip, A. F. Ismail, P. S. Goh, B. C. Ng, M. S. Abdullah, T. Soga, M. Tanemura, H. Yasuhiko

    NANO5 ( 4 ) 195 - 202   2010年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WORLD SCIENTIFIC PUBL CO PTE LTD  

    The functionalization of multiwalled carbon nanotubes (MWNTs) with beta cyclodextrin (beta-CD) is described. The functionalization using beta-CD treatment is an environmentally friendly and nondestructive method to modify carbon nanotubes. It was observed that the degree of functionalization increases with increasing ratios of beta-CD as seen from the Raman analysis. The Raman spectra also indicated that the nanotubes walls were not damaged. The presence of functional groups associated with beta-CD on the functionalized MWNTs indicated that the cyclodextrin groups were found to be adsorbed at the surface of the nanotubes walls. Mixed matrix membrane (MMM) was prepared by a phase inversion process. Enhanced selectivity and permeability for CO(2) over CH(4) was observed for MMM prepared using functionalized MWNTs.

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  • Crystallinity-controlled iron-carbon composite nanofibers-Synthesis and characteristic properties 査読

    Zhipeng Wang, Mohd Zamri Mohd Yusop, Takehiko Hihara, Yasuhiko Hayashi, Masaki Tanemura

    JOURNAL OF CRYSTAL GROWTH312 ( 12-13 ) 1935 - 1939   2010年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    Aligned Fe-carbon composite nonofibers (Fe-CNFs) grew on graphite substrates bombarded by Ar+ ions at an oblique incident angle with a simultaneous Fe supply at room temperature. Morphology alteration and crystallinity variation of Fe-CNFs were achieved by adjusting the supply rate of Fe atoms. The effects of different Fe concentrations on the morphological and crystalline structures of Fe-CNFs were discussed in detail. The higher the Fe supply rates, the higher the Fe concentration in Fe-CNFs. Higher Fe concentration in Fe-CNFs favors the graphitization of carbon materials, but destroys the directivity of Fe-CNFs pointing to ion beam incident direction. The magnetic properties of Fe-CNFs with different Fe contents were also analyzed in detail. (C) 2010 Elsevier B.V. All rights reserved.

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  • Improved open circuit voltage of the photovoltaic device using ferrocene as a donor material 査読

    Rakesh A. Afre, Yasuhiko Hayashi, Tetsuo Soga

    SYNTHETIC METALS160 ( 7-8 ) 779 - 782   2010年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    In this work, we have studied the combination of ferrocene (Fc), the donor material and fullerene derivatives such as [6,6]-phenyl C(61)-butyric acid methyl ester (PCBM) and the acceptor material, for fabricating organic photovoltaic devices. The effect of temperature on open circuit voltage (V(oc)), short-circuit current density (J(sc)), fill factor (FF) and the photoconversion efficiency (PCE), eta has been investigated. By varying the annealing temperature, the V(oc) FF and PCE, eta, were increased up to 140 degrees C and further increasing of temperature it remains constant. However, the short-circuit current density was not varied concomitantly with other parameters. The maximum PCE was observed to be 0.053% at 140 degrees C, which is the best annealing temperature in the present study. There have been many attempts to synthesize Fc and fullerene dyads but as an application wise very few report are available. Therefore here we have tried to use Fc and PCBM for photovoltaic device applications. (C) 2010 Elsevier B.V. All rights reserved.

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  • Transparent and Flexible Field Electron Emitters Based on the Conical Nanocarbon Structures 査読

    Pradip Ghosh, M. Zamri Yusop, Syunsaku Satoh, Munisamy Subramanian, Akari Hayashi, Yasuhiko Hayashi, Masaki Tanemura

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY132 ( 12 ) 4034 - +   2010年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    The fabrication of conical nanocarbon structures (CNCSs) on a transparent and flexible nafion substrate at room temperature using an ion irradiation technique and their application toward field emission displays (FEDs) have been demonstrated. The main advantage of this technique is that CNCSs can be fabricated directly on the transparent substrate while retaining the transparency of the substrate. A scanning electron microscopy (SEM) image revealed that the sputtered surface was entirely covered with CNCSs with a calculated numerical density of 6 x 10(6)/mm(2). Such nafion based CNCSs have proved to be an effective electron emitter with turn-on and threshold fields of 6.1 and 9.5 V/mu m, respectively. The field enhancement factor was estimated to be 1020 from the Fowler-Nordheim (F-N) plot. Thus the room temperature fabricated CNCSs based on transparent and flexible nafion substrate would be very promising for future flexible (roll-up) and transparent FEDs.

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  • Direct growth of carbon nanofibers on metal mesh substrates by ion irradiation method 査読

    M. Zamri, Pradip Ghosh, Z. P. Wang, M. Kawagishi, A. Hayashi, Y. Hayashi, M. Tanemura

    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B28 ( 2 ) C2C9 - C2C12   2010年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:A V S AMER INST PHYSICS  

    A direct growth of carbon nanofibers (CNFs) on the metal meshes by an ion irradiation method has been demonstrated. The average diameter and length of CNFs were found to be 50 nm and 2.0 mu m for Cu meshes, and 20 nm and 1.0 mu m for Mo meshes, respectively. Scanning electron microcopy images revealed that sputtering time and metal species of meshes influenced the morphology of the obtained nanofibers. High resolution transmission electron microscopy images indicated that the nanofibers were metal-composite CNFs in which the very fine metal crystallites dispersed in the amorphous carbon matrix. It was also demonstrated that the amorphous based structure changed to nanowires covered with graphene layers after the current flow in the composite CNFs.

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  • Low-Temperature Fabrication and Characterization of Ion-Induced Ge Nanostructures 査読

    A. Miyawaki, T. Hayashi, P. Ghosh, M. Tanemura, Y. Hayashi, T. Tokunaga

    INEC: 2010 3RD INTERNATIONAL NANOELECTRONICS CONFERENCE, VOLS 1 AND 2   398 - +   2010年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Ge surfaces were irradiated by Ar+ ions at 600 eV with and without a simultaneous supply of Ge, Au or Al at room temperature. The surfaces ion-irradiated without any simultaneous metal supply were characterized by densely distributed conical protrusions. By contrast, various kinds of nanostructures were formed on the Ge surfaces ion-irradiated with a simultaneous metal supply. They featured cones and nanobelts with a flattened top for Ge supply cases, whereas they were characterized by nanorods for Au supply cases and by nanorods, nanobelts and nanowalls for Al supply cases. Very interestingly, the nanorods formed with Au or Al supply possessed a bottleneck structure. Thus, the ion-induced Ge nanostructures were controllable in morphology by species and amount of simultaneously supplied metals.

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  • Structural change of ion-induced carbon nanofibers by electron current flow 査読

    M. Zamri Yusop, Pradip Ghosh, Masato Sasase, Akari Hayashi, Yasuhiko Hayashi, Masaki Tanemura

    Proceedings - 2010 8th International Vacuum Electron Sources Conference and Nanocarbon, IVESC 2010 and NANOcarbon 2010   43 - 44   2010年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    1-dimensional (1-D) nanocarbon materials such as carbon nanotubes [1] (CNTs) and carbon nanofibers (CNFs) are quite promising as electron emission sources[2] in the near future. These 1-D nanocarbon materials possess very high aspect ratio, thus readily allowing to emit electrons under relatively low applied electric fields even at low vacuum pressures. During the field emission (FE) process, degradation in current and structural damages of the nanocarbon emitters often occurs. Regarding these phenomena, for the practical use it is essential to fully understand the fundamental physics underlying the FE process particularly for individual nanocarbon emitters. In this paper, we are challenging to study the structural change of individual ion-induced CNF by electron current flow during FE process, using in situ transmission electron microscopy (TEM) facilities. © 2010 IEEE.

    DOI: 10.1109/IVESC.2010.5644429

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  • Formation and characterization of C60- and perylene-based bulk heterojunction solar cells 査読

    Oku T, Suzuki A, Kikuchi K, Kakuta N, Motoyoshi R, Nomura K, Kawashima A, Hayashi Y, Soga T

    Thin-Film Solar Cells   179 - 192   2010年

  • Growth and structure analysis of tungsten oxide nanorods using environmental TEM 査読

    Tomoharu Tokunaga, Tadashi Kawamoto, Kenta Tanaka, Naohiro Nakamura, Yasuhiko Hayashi, Katsuhiro Sasaki, Kotaro Kuroda

    Proceedings - 2010 8th International Vacuum Electron Sources Conference and Nanocarbon, IVESC 2010 and NANOcarbon 2010   278 - 279   2010年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    The metal oxide nanorods are widely studied, as the electronic characteristics of the metal oxide nanorods are different from the electronic characteristics of bulk metal oxide. [1-3] Tungsten oxide nanorods are one of the metal oxide semiconductors can be easily made. Therefore considering its semiconducting properties it is applied for electrical devices. But the growth mechanism of the tungsten oxide nanorods is not clarified yet, and growth control of tungsten oxide nanorods is not succeeded. Then, the tungsten oxide nanorods growth process was observed by Environmental transmission electron microscope (ETEM) observation, and the growth mechanism was examined. © 2010 IEEE.

    DOI: 10.1109/IVESC.2010.5644241

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  • Fabrication of Ion-Induced Carbon-Cobalt Nanocomposite Fibers: Effect of Cobalt Supply Rate 査読

    Zhipeng Wang, Mohd Zamri Mohd Yusop, Takehiko Hihara, Yasuhiko Hayashi, Masaki Tanemura

    INEC: 2010 3RD INTERNATIONAL NANOELECTRONICS CONFERENCE, VOLS 1 AND 2   77 - 78   2010年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Graphite surfaces were irradiated by Ar+ ions at 1 keV with a simultaneous Co supply at room temperature. Various kinds of carbon nanocomposites, such as nanocones with and without nanofibers (NFs) on top, nanorods and bean-like nanoprotrusions, formed depending on Co supply rates. The NFs, -1.5 mu m in average length, grew on the top of the nanocones at Co supply rate of 1.0 nm/min, and with increasing the Co supply rate the formation of nanoprotrusions without NFs became prominent. As confirmed by energy-dispersive X-ray analysis, NFs and nanoprotrusions were surely composed of C and Co.

    DOI: 10.1109/INEC.2010.5424534

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  • Fabrication of well ordered Zn nanorod arrays by ion irradiation method at room temperature and effect on crystal orientations 査読

    Masaki Kutsuna, Pradip Ghosh, Masato Kudo, Masaki Tanemura, Yasuhiko Hayashi

    INEC: 2010 3RD INTERNATIONAL NANOELECTRONICS CONFERENCE, VOLS 1 AND 2   436 - 437   2010年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Highly oriented and densely packed one dimensional (ID) polycrystalline Zn nanorods were fabricated on zinc plate without any catalyst at room temperature by bombardment with obliquely incident Ar(+) ion via ion irradiation method. The sputtered surfaces were fully covered with Zn nanostructures with diameter and the length around 60 nm and 1.3 mu m, respectively, confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The numerical density of Zn nanostructures (nanoneedle or nanorods) was found to be 2.1 x 10(6) to 9 x 10(6)/mm(2) depends upon the crystal orientation and the atomic density on different crystallographic faces. The outstanding feature of this growth technique is that it provides a new direction for the controllable growth of desired nanostructures of variable density at room temperature without any catalyst. These well-aligned arrays of Zn nanorods/nanoneedle might be a promising material for the future application in nanodevices.

    DOI: 10.1109/INEC.2010.5424501

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  • New approach to breast tumor detection based on fluorescence x-ray analysis. 査読

    Hayashi Y, Okuyama F

    German medical science : GMS e-journal8   2010年

  • Direct Growth of Horizontally Aligned Carbon Nanotubes between Electrodes and Its Application to Field-Effect Transistors 査読

    Yasuhiko Hayashi, B. Jang, T. Iijima, T. Tokunaga, R. A. Afre, M. Tanemura, G. A. J. Amaratunga

    INEC: 2010 3RD INTERNATIONAL NANOELECTRONICS CONFERENCE, VOLS 1 AND 2   215 - +   2010年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    This paper presents direct growth of horizontally aligned carbon nanotubes (CNTs) between two predefined various inter-spacing up to tens of microns of electrodes (pads) and its use as CNT field-effect transistors (CNT-FETs). The catalytic metals were prepared, consisting of iron (Fe), aluminum (Al) and platinum (Pt) triple layers, on the thermal silicon oxide substrate (Pt/Al/Fe/SiO2). Scanning electron microscopy measurements of CNT-FETs from the as-grown samples showed that over 80% of the nanotubes are grown across the catalytic electrodes. Moreover, the number of CNTs across the catalytic electrodes is roughly controllable by adjusting the growth condition. The Al, as the upper layer on Fe electrode, not only plays a role as a barrier to prevent vertical growth but also serves as a porous medium that helps in forming smaller nano-sized Fe particles which would be necessary for lateral growth of CNTs. Back-gate field effect transistors were demonstrated with the laterally aligned CNTs. The on/off ratios in all the measured devices are lower than 100 due to the drain leakage current.

    DOI: 10.1109/INEC.2010.5424640

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  • Morphology control of rapid grown vertically aligned carbon nanotube forest for fiber spinning 査読

    T. Iijima, H. Oshima, Y. Hayashi, U. B. Suryavanshi, A. Hayashi, M. Tanemura

    Proceedings - 2010 8th International Vacuum Electron Sources Conference and Nanocarbon, IVESC 2010 and NANOcarbon 2010   404 - 405   2010年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    Rapid grown vertically aligned carbon nanotubes forests (VACNFs) have received enormous attention for nanotube spinning. VACNFs are composed of not only straight CNTs, those are parallel to each other, but also curly CNTs. The bundle formation and alignment in VACNFs are crucial for spinnability of CNT fibers. In the present study, we present the effect of morphology control of VACNFs on fibers spinning. © 2010 IEEE.

    DOI: 10.1109/IVESC.2010.5644118

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  • Fabrication of well ordered Zn nanorod arrays by ion irradiation method at room temperature and effect on crystal orientations 査読

    Masaki Kutsuna, Pradip Ghosh, Masato Kudo, Masaki Tanemura, Yasuhiko Hayashi

    APPLIED SURFACE SCIENCE256 ( 5 ) 1481 - 1485   2009年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    Highly oriented and densely packed one-dimensional (1D) polycrystalline Zn nanorods were fabricated on zinc plate without any catalyst at room temperature by bombardment with obliquely incident Ar(+) ion via ion irradiation method. The sputtered surfaces were fully covered with Zn nanostructures with diameter and the length around 60 nm and 1.3 mu m, respectively, confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystal orientation of the Zn plate was investigated by electron back scattering pattern method (EBSP). The numerical density and morphology of Zn nanostructures (nanoneedle or nanorods) were found to be 2.1 x 10(6) to 9 x 10(6)/mm(2) depending upon the crystal orientation and the atomic density on different crystallographic faces. (2 (1) over bar(1) over bar0) faces of Zn polycrystal tended to form more dense nanostructures compared to (000 (1) over bar ) faces. This is because of lower atomic density on (2 (1) over bar(1) over bar0) faces in comparison with (000 (1) over bar )faces. This indicates that lower atomic density on any crystallographic faces is favorable to form nanostructure of higher density. The outstanding feature of this growth technique is that it provides a new direction for the controllable growth of desired nanostructures of variable density at room temperature without any catalyst. These well-aligned arrays of Zn nanorods/nanoneedle might be a promising material for the future application in nanodevices. (C) 2009 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.apsusc.2009.09.007

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  • Low-Temperature Fabrication of Ion-Induced Ge Nanostructures: Effect of Simultaneous Al Supply 査読

    Ako Miyawaki, Toshiaki Hayashi, Masaki Tanemura, Yasuhiko Hayashi, Tomoharu Tokunaga, Tetsuo Soga

    IEICE TRANSACTIONS ON ELECTRONICSE92C ( 12 ) 1417 - 1420   2009年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

    Ge surfaces were irradiated by Ar+ ions at 600eV with and without simultaneous supply of Ge or At at room temperature. The surfaces ion-irradiated without any simultaneous metal supply were characterized by densely distributed conical protrusions. By contrast, various kinds of nanostructures were formed on the Ge surfaces ion-irradiated with a simultaneous metal supply. They featured cones and nanobelts with a flattened top for Ge supply cases, whereas they were characterized by the nanorods, nanobelts and nanowalls for Al supply cases. Very interestingly, most of the nanorods and nanobelts formed with an Al supply possessed a bottleneck structure. Thus, the Ge nanostructures were controllable in morphology by species and amount of simultaneously supplied metals.

    DOI: 10.1587/transele.E92.C.1417

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  • Morphological Control of Ion-Induced Carbon Nanofibers and Their Field Emission Properties 査読

    Mohd Zamri Bin Mohd Yusop, Pradip Ghosh, Zhipeng Wang, Masaki Tanemura, Yasuhiko Hayashi, Tetsuo Soga

    IEICE TRANSACTIONS ON ELECTRONICSE92C ( 12 ) 1449 - 1453   2009年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

    Carbon nanofibers (CNFs) were fabricated on graphite plates using "Ar+ ion sputtering method" in large amount at room temperature. The morphology of CNFs was controlled by a simultaneous carbon supply during ion sputtering. CNF-tipped cones were formed on graphite plate surfaces without carbon supply whereas those with a simultaneous carbon supply featured mainly needle-like protrusions of large size. The field electron emission (FE) properties, measured using parallel plate configurations in 10(-4) Pa range, showed the threshold fields of 4.4 and 5.2 V/mu m with a current density of 1 mu A/cm(2) for CNF-tipped cones and needle-like protrusion, respectively. Reliability test results indicated that CNF-tipped cones were more stable than needle-like protrusion. The morphological change after reliability test showed a so-called "self-regenerative" process and structure damage for CNF-tipped cones and needle-like protrusions, respectively.

    DOI: 10.1587/transele.E92.C.1449

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  • Ferromagnetic and Optical Properties of Partially Cu-Doped ZnO Films 査読

    Fan-Yong Ran, Masaki Tanemura, Yasuhiko Hayashi, Norihiro Ide, Masao Imaoka, Tun-Seng Herng, Shu-Ping Lau

    ZEITSCHRIFT FUR NATURFORSCHUNG SECTION A-A JOURNAL OF PHYSICAL SCIENCES64 ( 11 ) 765 - 768   2009年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:VERLAG Z NATURFORSCH  

    Wurtzite structure ZnO films (3 x 3 mm(2)) with a partial-area Cu doping were successfully prepared using a micro-area Ar(+)-ion beam (similar to 380 mu m in diameter) and a simultaneous Cu supply at room temperature. A Cu(2)O phase was formed in the ZnO films by Cu doping. The partially Cu-doped ZnO films exhibited room-temperature ferromagnetism (RTFM) with a saturation magnetization of 1.6 x 10(-5) emu and a coercive field of 40 Oe. Since Zn, Cu, and their compounds are not ferromagnetic, the observed RTFM is attributed to the intrinsic property of Cu-doped ZnO films. As confirmed by the low temperature photoluminescence (PL) spectra, no serious optical damage was recongnized in the region without Ar(+)-ion irradiation. Thus, it was believed that the micro-area Ar(+)-ion irradiation. Thus, it was believed that the micro-area Ar(+)-ion irradiation with a simultaneous Cu supply was promising to integrate the magnetic and optical properties of ZnO-based materials.

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  • Effect of liquid nitrogen treatment on the structural, electrical and optical properties of indium tin oxide coated glass substrate 査読

    Rakesh A. Afre, Yasuhiko Hayashi, Tetsuo Soga, Golap Kalita, Masayoshi Umeno

    CHEMICAL PHYSICS LETTERS481 ( 1-3 ) 68 - 72   2009年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    Influence of liquid nitrogen on the structural, electrical and optical properties of indium tin oxide (ITO) coated glass substrates, has been studied. These studies indicate that treatment of the ITO coated glass substrates with liquid nitrogen is found to reduce the surface roughness, concomitant with the increase in contact angle up to a critical value, followed by its decrease upon prolonged treatment. Optical transmittance study of the ITO glass substrate shows the increase in transmittance of &gt;90% and X-ray diffraction studies show the negligible change in structural properties while FWHM of the peak at 2 theta = 30.48 degrees for (222) has been reduced with increase in treatment time. (C) 2009 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.cplett.2009.09.039

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  • Ferromagnetism in Cu-doped AlN films 査読

    Fan-Yong Ran, M. Subramanian, Masaki Tanemura, Yasuhiko Hayashi, Takehiko Hihara

    APPLIED PHYSICS LETTERS95 ( 11 )   2009年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    AlN films doped with 3.2-8.2 at. % Cu were deposited by helicon magnetron sputtering. The films exhibited ferromagnetism with a Curie temperature above 360 K. The observed magnetic anisotropy and exclusion of ferromagnetic contamination indicated that the ferromagnetism was the intrinsic property of Cu-doped AlN films. Room-temperature (RT) saturation magnetization (M(s)) tended to decrease with increasing Cu concentration and the maximum RT Ms obtained was about 8.5 emu/cm(3) (0.6 mu(B)/Cu). Vacuum annealing increased the RT M(s) values and meanwhile reduced ratio of N/(Al+Cu), which suggested that Al interstitial and N vacancy might contribute to the observed ferromagnetic behavior. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3232238]

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  • Effect of substrate temperature on the room-temperature ferromagnetism of Cu-doped ZnO films 査読

    Fan-Yong Ran, Masaki Tanemura, Yasuhiko Hayashi, Takehiko Hihara

    JOURNAL OF CRYSTAL GROWTH311 ( 17 ) 4270 - 4274   2009年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    Wurtzite structure ZnO films doped with similar to 2 at% Cu were deposited at substrate temperatures (T-s) from 350 to 600 degrees C by helicon magnetton sputtering. All the films exhibited room-temperature (RT) ferromagnetism (FM) and the maximum saturation magnetization (M-s) was 1.2 emu/cm(3) (similar to 0.15 mu(B)/Cu). Cu ions were mainly in a divalent state as identified by X-ray photoelectron spectroscopy. FM tended to increase with decreasing T-s, and vacuum annealing enhanced the M-s. These results suggested that oxygen vacancies and/or zinc interstitials might contribute to the ferromagnetic performance. Thus, the observed FM was explained in terms of the defect related mechanism. (C) 2009 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jcrysgro.2009.07.008

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  • Growth and Nanoscale Magnetic Properties of Ferromagnetic Nanowire Encapsulated Inside Carbon Nanotubes 査読

    Yasuhiko Hayashi, T. Fujita, T. Toicunaga, B. Jang, M. Tanemura, G. A. J. Amaratunga

    IEEE TRANSACTIONS ON MAGNETICS45 ( 6 ) 2488 - 2491   2009年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

    We synthesize ferromagnetic Co nanowire, and Co/Pd multisegment nanowires encapsulated inside multi-walled carbon nanotubes CNTs (MWCNTs) by plasma-enhanced chemical vapor deposition (PECVD). High-resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED) patterns and energy dispersive X-ray spectroscopy (EDS) were used to characterize the microstructures and elemental analyses of the nanowires. Quantitative magnetization measurements of Co nanowires encapsulated inside MWCNTs were experimentally established by TEM off-axis electron holography at room temperature. The MWCNTs grew up to 100-110 nm in diameter and 1.5-1.7 mu m in length. The typical bright-field TEM images revealed both Co nanowire and Co/Pd multisegment nanowires encapsulated inside vertically aligned MWCNTs on the same substrate. The composition of metal encapsulated inside MWCNTs were characterized by EDS. Experimental results revealed that the Co nanowire encapsulated inside MWCNT was always presented as the face-centered-cubic (fcc) Co structure. The component of magnetic induction was then measured to be 1.2 +/- 0.1 T based on TEM off-axis electron holography results, which is lower than the expected saturation magnetization of fcc Co bulk of 1.7 T. The partial oxidation of the ferromagnetic metal during the process and the magnetization direction may play an important role in the determination of the quality of the remanent states. The ferromagnetic metal nanowires encapsulated inside CNTs demonstrate very high potential in providing the required magnetic properties, low dimensionality, and small volume for future nanoscale devices.

    DOI: 10.1109/TMAG.2009.2018668

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  • Room-temperature ferromagnetism of Cu-doped ZnO films deposited by helicon magnetron sputtering 査読

    Fan-Yong Ran, Masao Imaoka, Masaki Tanemura, Yasuhiko Hayashi, Tun-Seng Herng, Shu-Ping La

    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS246 ( 6 ) 1243 - 1247   2009年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-V C H VERLAG GMBH  

    Wurtzite structure ZnO films doped with 0.5 and 1.7 at% Cu were deposited by helicon magnetron sputtering. The prepared films exhibited room-temperature (RT) ferromagnetism (FM). Maximum RT saturation magnetization of 2 emu/cm (similar to 0.3(mu B)/Cu) was observed for ZnO films with 1.7 at% Cu. Cu ions were in a bivalent state as identified by X-ray photoelectron spectroscopy (XPS). In photoluminescence spectra, the green emission peak increased and redshifted due to the incorporation of Cu or defects induced by Cu incorporation Since. Cu and Cu related oxides are not RT ferromagnetic and no trace of ferromagnetic-contamination was detected in XPs results, the observed FM is considered to be an intrinsic property of Cu-doped ZnO films. The FM was thought to originate from defect-related mechanisms. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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  • Synthesis of Covalently Linked Phthalocyanine-C60 Dyad via a Flexible Carbon Linker 査読

    Daisuke Sukeguchi, Hideyuki Yoshiyama, Surya, Prakash Singh, Norio Shibata, Shuichi Nakamura, Takeshi Toru, Yasuhiko Hayashi, Tetsuo Soga

    Heterocycl. Commun. Freund Publishing House3 ( 15 ) 195 - 202   2009年6月

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  • Synthesis and spectroscopic investigation of trifluoroethoxy-coated phthalocyanine linked with fullerene 査読

    Daisuke Sukeguchi, Hideyuki Yoshiyama, Norio Shibata, Shuichi Nakamura, Takeshi toru, Yasuhiko Hayashi, Tetsuo Soga

    JOURNAL OF FLUORINE CHEMISTRY130 ( 3 ) 361 - 364   2009年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    Synthesis and spectroscopic investigation of trifluoroethoxy-coated phthalocyanine-fullerene dyad 2 has been described. While nonfluorinated phthalocyanine-fullerene dyad 1 showed an efficient property of intramolecular photoinduced electron transfer, dyad 2, regardless of its covalently linked dyad system, appears not to show any electronic communication between fullerene and phthalocyanine. This observation is presumably due to the strong electron withdrawing nature of 12 trifluoroethoxy groups; fluorine leads phthalocyanine to become an acceptor whose electronic accepting property is equivalent to that of fullerene. This is a unique example that fluorine can terminate electronic communication in the covalently fullerene-phthalocyanine dyad system. (C) 2008 Elsevier B.V. All rights reserved.

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  • Application of ion-induced carbon nanocomposite fibers to magnetic force microscope probes 査読

    Yoshitaka Sugita, Masashi Kitazawa, M. Zamri M. Yusop, Masaki Tanemura, Yasuhiko Hayashi, Ryo Ohta

    JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B27 ( 2 ) 980 - 983   2009年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:A V S AMER INST PHYSICS  

    Small-scale batch fabrication of Co-included carbon nanofibers (Co-CNFs) onto commercially available Si cantilevers for scanning probe microscope by an Ar+-ion-irradiation method with a simultaneous Co supply was demonstrated (eight chips/batch). As confirmed by scanning and transmission electron microscopes equipped with energy dispersive x-ray spectroscopy, Co-CNFs were fibrous and contained Co and C. With increasing the Co supply rate, Co-CNFs decreased in length from similar to 600 to similar to 400 nm, whereas their diameter was almost independent of the Co supply rate, 20-30 nm. As proven by magnetic force microscope (MFM) measurements using the Co-CNF probes, they were applicable as MFM probes. Since various metals including alloys can be incorporated into CNFs, this ion-irradiation method with a simultaneous metal supply was believed to be quite promising for the functionalization of CNF probes for a variety of applications. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3010730]

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  • New diarylmethanofullerene derivatives and their properties for organic thin-film solar cells 査読

    Daisuke Sukeguchi, Surya Prakash Singh, Mamidi Ramesh Reddy, Hideyuki Yoshiyama, Rakesh A. Afre, Yasuhiko Hayashi, Hiroki Inukai, Tetsuo Soga, Shuichi Nakamura, Norio Shibata, Takeshi Toru

    BEILSTEIN JOURNAL OF ORGANIC CHEMISTRY5   2009年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:BEILSTEIN-INSTITUT  

    A number of diarylmethanofullerene derivatives were synthesized. The cyclopropane ring of the derivatives has two aryl groups substituted with electron-withdrawing and -donating groups, the latter with long alkyl chains to improve solubility in organic solvents, an important property in processing cells. First reduction potentials of most derivatives were less negative than that of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), which is possibly ascribed to their electron-withdrawing nature. Organic thin-film photovoltaic cells fabricated with poly(3-hexylthiophene) (P3HT) as the electron-donor and diarylmethanofullerene derivatives as the electron-acceptor material were examined. The {(methoxycarbonyl) phenyl[bis(octyloxy)phenyl] methano} fullerene showed power conversion efficiency as high as PCBM, but had higher solubility in a variety of organic solvents than PCBM. The V(oc) value was higher than that of PCBM, which is derived from the electron-donating (octyloxy) phenyl group, possibly raising the LUMO level. Photovoltaic effects of the devices fabricated with the derivatives having some electron-withdrawing groups were also examined.

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  • Synthesis and characterization of carbon nanotube grown on flexible and conducting carbon fiber sheet for field emitter 査読

    Yasuhiko Hayashi, K. Suzuki, B. Jang, T. Tokunaga, H. Matsumoto, M. Tanemura, A. Tanioka, G. A. J. Amaratunga

    DIAMOND AND RELATED MATERIALS18 ( 2-3 ) 341 - 344   2009年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    We have successfully demonstrated the multiwall carbon nanotube (MWCNT) based field emission cathode fabricated on highly porous, flexible and conductive carbon fiber (CF) sheet without damage of CF sheet by chemical vapor deposition. CF sheet was composed of thin fibers with diameter of about 3 pm prepared by electrospray deposition. Well aligned MWCNTs grown on, or well anchored to. the flexible CF sheet was confirmed by transmission electron microscope. The field enhancement factor for MWCNT emitter fabricated on CF sheet was about 14,000 and 1.6 times higher than that of MWCNT emitter fabricated on Si substrate. Scanning electron microscopy image indicates that the electron emission occurred from the MWCNT field emitter arrays grown on carbon fibers not only at surface but also under layers in CF sheet. Field emission measurements revealed that this flexible MWCNT field emitter array has a great potential for the flexible field emission displays. (C) 2008 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.diamond.2008.09.014

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  • Enhanced photovoltaic device performance upon modification of indium tin oxide coated glass by liquid nitrogen treatment 査読

    Rakesh A. Afre, Yasuhiko Hayashi, Tetsuo Soga

    JOURNAL OF PHYSICS D-APPLIED PHYSICS42 ( 4 )   2009年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    We demonstrate the improvement in the surface properties of an indium tin oxide (ITO) anode contact to an organic bulk-heterojunction device via cooling down the ITO glass substrate by liquid nitrogen treatment. This treatment effectively improves the smoothness of ITO glass, the transmittance and the contact angle measurement, which thereby results in fairly good contact with organic material. The enhancement of short circuit current, efficiency and fill factor of the photovoltaic devices was also achieved. The surface properties of both the untreated and the treated ITO substrates were studied by atomic force microscopy and the electrical properties of the substrates were studied by the Hall effect measurement.

    DOI: 10.1088/0022-3727/42/4/042002

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  • Efficient carbon nanotube field emitter using electrospun carbon nanofibers as a flexible electrode 査読

    Matsumoto H, Suzuki K, Tsuboi K, Minagawa M, Tanioka A, Hayashi Y, Fukuzono K, Amaratunga G.A.J

    Materials Research Society Symposium Proceedings1173   7 - 12   2009年

  • Direct growth of carbon nanofibers on metal mesh substrates by ion irradiation method 査読

    M. Zamri, Pradip Ghosh, Wang Zhipeng, Y. Hayashi, M. Tanemura

    Technical Digest - 2009 22nd International Vacuum Nanoelectronics Conference, IVNC 2009   43 - 44   2009年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    DOI: 10.1109/IVNC.2009.5271843

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  • SYNTHESIS AND SPECTRAL INVESTIGATIONS OF COVALENTLY LINKED PHTHALOCYANINE-C-60 DYAD VIA FLEXIBLE CARBON LINKER 査読

    Daisuke Sukeguchi, Hideyuki Yoshiyama, Surya Prakash Singh, Norio Shibata, Shuichi Nakamura, Takeshi Toru, Yasuhiko Hayashi, Tetsuo Soga

    HETEROCYCLIC COMMUNICATIONS15 ( 4 ) 263 - 272   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WALTER DE GRUYTER & CO  

    Phthalocyanine-C-60 dyad 1 via a flexible saturated carbon linker was synthesized. The UV/Vis and fluorescence spectra studies of I revealed that intramolecular, not intermolecular, photoinduced electronic communication was observed in the solution state. We also examined UV-Vis and fluorescence spectra of a mixture of C-60 and conventional tetra tert-Bu phthalocyanine 2 for comparison

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  • Room-temperature synthesis and characterisation of ion-induced iron-carbon nanocomposite fibres 査読

    Zhipeng Wang, Kohei Yamaguchi, Daiki Takeuchi, Yasuhiko Hayashi, Masaki Tanemura

    INTERNATIONAL JOURNAL OF NANOTECHNOLOGY6 ( 7-8 ) 753 - 761   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:INDERSCIENCE ENTERPRISES LTD  

    Graphite plates were Ar(+) ion-irradiated with and without a simultaneous Fe supply at room temperature. The surfaces ion-irradiated without an Fe supply were covered with densely distributed conical projections with a carbon nanofibre (CNF) on file top. The CNFs thus grown were 20-50 nm in diameter and 0.3-2 mu m in length. By contrast, the graphite surfaces ion-bombarded with a simultaneous Fe supply were characterised by various kinds of carbon composites, such as conical protrusions with and without a single carbon nanocomposite fibre (CNCF) on the top, depending oil the Fe supply rates. As confirmed by transmission electron microscope (TEM), the CNCFs thus grown were amorphous-like and possessed no hollow structure. Energy dispersive X-ray analysis disclosed that CNCFs consisted of carbon and iron, and quite fine Fe crystallites were dispersed over the CNCF. Since various metals can be incorporated into the room-temperature grown carbon nanofibres, this ion-irradiation method is believed to be promising as a new approach to synthesise one-dimensional (1-D) nanomaterials at low temperatures.

    DOI: 10.1504/IJNT.2009.025313

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  • Formation and characterization of MEH-PPV/PCBM-based bulk heterojunction solar cells 査読

    Takeo Oku, Syuichi Nagaoka, Atsushi Suzuki, Kenji Kikuchi, Yasuhiko Hayashi, Hayato Sakuragi, Tetsuo Soga

    JOURNAL OF CERAMIC PROCESSING RESEARCH9 ( 6 ) 549 - 552   2008年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:KOREAN ASSOC CRYSTAL GROWTH, INC  

    Polymer/fullerene bulk heterojunction solar cells with poly[2-methoxy-5-(20-ethylhexoxy)-1,4-phenylenevinylene] (MEH-PPV), zinc-phthalocyanine (ZnPc) and 6,6-phenyl C61-butyric acid methyl ester (PCBM), were produced and characterized. A device based on MEH-PPV and PCBM provided better efficiency, fill factor and short-circuit current compared to those of a device on MEH-PPV(ZnPc) and PCBM. The solar cells with a MEH-PPV and PCBM structure showed a higher photoresponse in the range of 300 to 60 nm. The energy levels of the molecules were calculated and are discussed.

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  • ZnO Nanowire and WS2 Nanotube Electronics 査読

    Husnu Emrah Unalan, Yang Yang, Yan Zhang, Pritesh Hiralal, Daniel Kuo, Sharvari Dalal, Tim Butler, Seung Nam Cha, Jae Eun Jang, Konstantina Chremmou, Georgios Lentaris, Di Wei, Rital Rosentsveig, Kenichi Suzuki, Hidetoshi Matsumoto, Mie Minagawa, Yasuhiko Hayashi, Manish Chhowalla, Akihiko Tanioka, William I. Milne, Reshef Tenne, Gehan A. J. Amaratunga

    IEEE TRANSACTIONS ON ELECTRON DEVICES55 ( 11 ) 2988 - 3000   2008年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

    In this paper, we report on the synthesis and applications of semiconducting nanostructures. Nanostructures of interest were zinc oxide (ZnO) nanowires and tungsten disulfide (WS2) nanotubes where transistors/phototransistors and photovoltaic (PV) energy conversion cells have been fabricated. ZnO nanowires were grown with both high- and low-temperature approaches, depending on the application. Individual ZnO nanowire side-gated transistors revealed excellent performance with a field-effect mobility of 928 cm(2)/V . s. ZnO networks were proposed for large-area macroelectronic devices as a less lithographically intense alternative to individual nanowire transistors where mobility values in excess of 20 cm(2)/V . s have been achieved. Flexible PV devices utilizing ZnO nanowires as electron acceptors and for photoinduced charge separation and transport have been presented. Phototransistors were fabricated using individual WS2 nanotubes, where clear sensitivity to visible light has been observed. The results presented here simply reveal the potential use of inorganic nanowires/tubes for various optoelectronic devices.

    DOI: 10.1109/TED.2008.2005166

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  • MOCVD growth of GaN on porous silicon substrates 査読

    Hiroyasu Ishikawa, Keita Shimanaka, Fumiyuki Tokura, Yasuhiko Hayashi, Yosuke Hara, Masami Nakanishi

    JOURNAL OF CRYSTAL GROWTH310 ( 23 ) 4900 - 4903   2008年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    Single-crystal GaN thin films were successfully grown on porous Si (Psi) substrates using metalorganic chemical vapor deposition. The full-width at half-maximum (FWHM) of the asymmetric rocking curve for a GaN film on a Psi substrate was narrower than that for a GaN film on a normal flat-Si substrate (Flat-Si), whereas the FWHM of the symmetric one is broader. Compared with a GaN film on Flat-Si, the extent of wafer bending was reduced and the band-edge emission from GaN was enhanced. Moreover, the tensile stress in the film was significantly reduced. (C) 2008 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jcrysgro.2008.08.030

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  • Carbon nanotubes on carbon fabrics for flexible field emitter arrays 査読

    Kenichi Suzuki, Hidetoshi Matsumoto, Mie Minagawa, Akihiko Tanioka, Yasuhiko Hayashi, Kazuyuki Fukuzono, Gehan A. J. Amaratunga

    APPLIED PHYSICS LETTERS93 ( 5 )   2008年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    Flexible carbon fabrics (CFs) prepared by electrospray deposition were used for the substrate of carbon nanotube (CNT) field emitter arrays. CNTs were grown on the CFs by chemical vapor deposition. The CNT field emitter arrays on CFs produced a higher current density at a lower turn-on voltage compared to ones on a Si substrate.

    DOI: 10.1063/1.2967868

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  • Microstructure and local magnetic induction of segmented and alloyed Pd/Co nanocomposites encapsulated inside vertically aligned multiwalled carbon nanotubes 査読

    Yasuhiko Hayashi, T. Fujita, T. Tokunaga, K. Kaneko, M. Tanemura, T. Butler, N. Rupesinghe, J. D. Carey, S. R. P. Silva, K. B. K. Teo, G. A. J. Amaratunga

    DIAMOND AND RELATED MATERIALS17 ( 7-10 ) 1525 - 1528   2008年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    We have successfully synthesized the Co/Pd magnetic and nonmagnetic multisegment nanowires encapsulated inside multiwalled carbon nanotubes (MWCNTs) by using Co and Pd thin-layers deposited on Si substrate by microwave plasma enhanced chemical vapor deposition. Energy dispersive X-ray spectroscopy revealed that MWCNTs were encapsulated with Co and Pd nanowires, separately, at the tube top and the bottom of Co nanowire, respectively. The face-centered-cubic (fcc) structure of Co nanowires was confirmed by a selected area diffraction pattern. We proposed a fruitful description for the encapsulating mechanisms of both Co and Pd multisegment nanowires. The component of magnetic induction from Co region, not Pd region, was then estimated to be 1.2 +/- 0.1 T, based on results of off-axis electron holography, which is lower than the expected saturation magnetization of fcc bulk Co of 1.7 T. We proposed a fruitful description for the mechanisms of reduced magnetic induction from Co nanowires. (c) 2008 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.diamond.2008.03.012

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  • Formation and characterization of polymer/fullerene bulk heterojunction solar cells 査読

    Takeo Oku, Syuichi Nagaoka, Atsushi Suzuki, Kenji Kikuchi, Yasuhiko Hayashi, Hironori Inukai, Hayato Sakuragi, Tetsuo Soga

    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS69 ( 5-6 ) 1276 - 1279   2008年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Polymer/fullerene bulk heterojunction solar cells with poly[3-hexylthiophene] (P3HT), poly [2-methoxy-5-(20-ethylhexoxy)-1,4-phenylenevinylene] (MEH-PPV), and 6,6-phenyl C61-butyric acid methyl ester (PCBM) were produced and characterized. A device based on P3HT and PCBM provided better efficiency, fill factor, and short-circuit current compared to those of a device based on MEH-PPV and PCBM. The solar cell with P3HT and PCBM structure showed a higher photoresponse in the range of 400-650 nm. Energy levels of the molecules were calculated and discussed. (C) 2007 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.jpcs.2007.10.117

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  • Room-temperature synthesis and characterization of Ni-doped carbon nanofibers 査読

    Z. P. Wang, D. Takeuchi, K. Yamaguchi, Y. Hayashi, M. Tanemura

    Transactions of the Materials Research Society of Japan33 ( 4 ) 1023 - 1026   2008年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  • Low-temperature fabrication of Ge nanostructures by ion irradiation 査読

    A. Miyawaki, Y. Sugita, K. Yamaguchi, T. Hayashi, Y. Hayashi, T. Tokunaga, M. Tanemura

    Transactions of the Materials Research Society of Japan33 ( 4 ) 1015 - 1018   2008年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  • Room-temperature synthesis and characterization of cobalt-doped carbon nanofibers 査読

    D. Takeuchi, Z. P. Wang, A. Miyawaki, K. Yamaguchi, Y. Suzuki, M. Tanemura, Y. Hayashi, P. R. Somani

    DIAMOND AND RELATED MATERIALS17 ( 4-5 ) 581 - 584   2008年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    The graphite surfaces were irradiated by Ar+ ions with and without a simultaneous Co supply at room temperature. The sputtered surface without Co supply was characterized by densely distributed conical protrusions with aligned carbon nanofibers (CNFs) on the tops, whereas Ar+-bombarded surfaces with a simultaneous Co supply were covered with asparagus-like (micrometer order in base diameter) or nanofibrous (10-50 nm in diameter) structures depending on the supply rate of Co atoms. No CNF-tipped cones were observed to form. For the nanofibers containing carbon and cobalt, the hysteresis behavior observed in the magnetization property by applying magnetic fields in directions perpendicular and parallel (in-plain) to the substrate was almost identical, whereas a continuous 1 mu m thick-Co film showed the strong in-plane anisotropy. Other materials could be readily incorporated into CNFs by choosing the suitable metal sources. Thus, the ion-irradiation method is expected to open up a new approach to fabricate ferromagnetic 1-D nanomaterials at room temperature. (C) 2008 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.diamond.2008.01.092

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  • Room-temperature growth of ion-induced carbon nanofibers: Effects of ion species 査読

    K. Yamaguchi, M. Kitazawa, Z. P. Wang, Y. Sugita, J. Tanaka, M. Tanemura, Y. Hayashi

    DIAMOND AND RELATED MATERIALS17 ( 4-5 ) 525 - 528   2008年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    Graphite surfaces were bombarded with Ne+, Ar+ and Xe+ ions at 450 eV-1 keV to induce the carbon nanofiber (CNF) growth at room temperature, and the dependence of size and numerical density of ion-induced CNFs on the ion species and ion energy was investigated in detail. The ion-sputtered surfaces were covered with densely distributed conical protrusions and aligned CNFs grew on the tips, except for the low-energy Xe+-sputtered surfaces. Longer CNFs grew by lighter-mass-ion irradiation, and finer CNFs formed by heavier-mass-ion bombardment. In addition, the higher the ion energy, the longer the length of the ion-induced CNFs. Because the size and numerical density were controllable by the ion-irradiation parameters, ion-induced CNFs were believed to be quite promising for myriad of applications such as high-resolution scanning probe microscope cantilevers, bio-cell manipulators and field emission source operating at low voltage. (C) 2008 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.diamond.2008.01.043

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  • Bulk heterojunction solar cells based on two kinds of organic polymers and fullerene derivative 査読

    Yasuhiko Hayashi, H. Sakuragi, I. Soga, I. Alexandrou, G. A. J. Amaratunga

    COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS313   422 - 425   2008年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    We report a study of the effect of the poly (2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) on the organic solar cell based on poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction structure (BHJ). The most obvious effect of incorporating MEH-PPV in the P3HT:PCBM BJT solar cells was the increase in the open-circuit voltage (V-oc) from 0.38 to 0.50 V. This result is interpreted in terms of the band structure of BHJ where the energy level difference between the highest occupied molecular orbital (HOMO) of the polymer (P3HT + MEH-PPV) and the lowest occupied molecular orbital (LUMO) of PCBM is increased. The highest power conversion efficiency of 1.12% under air mass 1.5 simulated solar illumination (100 mW/cm(2)) was achieved from the optimized amount of MEH-PPV. The spectral response of the P3HT:PCBM BHJ solar cells is influenced by the change of molecular packing structure (interchain spacing) of P3HT by incorporating MEH-PPV. (C) 2007 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.colsurfa.2007.04.162

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  • The inner shell influence on the electronic structure of double-walled carbon nanotubes 査読

    Yann Tison, Cristina E. Giusca, Vlad Stolojan, Yasuhiko Hayashi, S. Ravi P. Silva

    ADVANCED MATERIALS20 ( 1 ) 189 - +   2008年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-V C H VERLAG GMBH  

    We present STM and STS results obtained for double-walled carbon nanotubes. In the case displayed here, the STS results exhibit the Van Hove singularities corresponding to semi conducting tubes for both the outer and the inner shell and a finite density of states at the Fermi level (E-F) is observed for a DWNT. We associate this behavior to the presence of an intershell interaction.

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  • Room-temperature growth and characterization of iron-carbon nanocomposite fibers 査読

    Z. P. Wang, K. Yamaguchi, D. Takeuchi, Y. Hayashi, M. Tanemura

    2008 2ND IEEE INTERNATIONAL NANOELECTRONICS CONFERENCE, VOLS 1-3   154 - 157   2008年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Graphite plates were Ar+ ion-sputtered with a simultaneous Fe supply at room temperature. The sputtered surfaces were characterized by various kinds of carbon compostites, such as conical protrusions with and without single carbon nanocomposite fibers (CNCFs) on the top, depending on the Fe supply rates. The CNCFs thus grown were confirmed to be amorphous-like fibers without a hollow structure and possess no distinct boundary between the cone and the CNCF by transmission electron microscope. As revealed by their compositional analysis, CNCFs surely composed of carbon and iron. Since the various kind of metals can be doped Into the room-temperature grown carbon nanofibers, this Ion-irradiation method Is believed to be promising as a new approach to synthesize one-dimensional nanomaterials at low temperatures.

    DOI: 10.1109/INEC.2008.4585458

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  • Morphological and structural characterization of metal-doped carbon nanofibers synthesized at room temperature 査読

    D. Takeuchi, Z. P. Wang, K. Yamaguchi, M. Kitazawa, Y. Hayashi, M. Tanemura

    PROCEEDINGS OF THE 17TH INTERNATIONAL VACUUM CONGRESS/13TH INTERNATIONAL CONFERENCE ON SURFACE SCIENCE/INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY100 ( 1 )   2008年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IOP PUBLISHING LTD  

    Graphite surfaces were bombarded by Ar(+) ions with and without a simultaneous Ni supply at room temperature. The sputtered surfaces without Ni supply were characterized by densely distributed conical protrusions with aligned single carbon nanofibers (CNFs) on the tops. By contrast, an excess Ni supply during Ar(+) bombardment suppressed the CNF formation, while under the proper Ni supply conditions, single Ni-doped CNFs grew on slender needle-like structures or conical protrusions depending on the supply rate of Ni atoms. Non-doped CNFs were characterized by the amorphous-like or very fine-crystallites nature, whereas the Ni-doped CNFs were featured by polycrystalline structure. Thus, the crystalline structure was controllable by Ni doping. Because any kinds of materials can be doped into ion-induced CNFs, it is believed that the ion-irradiation method will open up a new approach to fabricate 1-dimensional composite nanomaterials at room temperature.

    DOI: 10.1088/1742-6596/100/1/012029

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  • Growth and Magnetic Properties of Ferromagnetic Co Nanorods Filled inside Carbon Nanotubes towards Nanoscale Spintronics 査読

    Yasuhiko Hayashi, T. Fujita, T. Tokunaga, N. L. Rupesinghe, K. B. K. Teo, G. A. J. Amaratunga, M. Tanemura

    2008 2ND IEEE INTERNATIONAL NANOELECTRONICS CONFERENCE, VOLS 1-3   1051 - +   2008年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    We synthesize Co nanorod filled inside multi-walled CNTs (MWCNTs) by microwave plasma enhanced chemical vapor deposition (MPECVD) and utilize off-axis electron holography to observe the remanent states of the filled metal nanorod inside MWCNTs at room. The MWCNTs grew up to 100-110 nm in diameter and 1.5-1.7 pm In length. The typical bright-field transmission electron microscope (TEM) Images revealed both Co/Pd multisegment nanorod and Co nanorod filled inside MWCNTs on the same substrate. We have also performed energy-dispersive X-ray spectrometer (EDS) measurements to characterize the composition of metal filled inside MWCNTs. Based on high-resolution TEM measurements, we observed the face-centered-cubic (fcc) Co filled Inside MWCNT. The component of magnetic Induction was then measured to be 1.2 +/- 0.1 T, which Is lower than the expected saturation magnetization of fcc Co of 1.7 T. The partial oxidation of the ferromagnetic metal during the process and the magnetization direction may play an important role in the determination of the quality of the remanent states.

    DOI: 10.1109/INEC.2008.4585664

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  • Optical properties of conjugated poly(3-hexylthiophene)/[6,6]-phenylC(61)-butyric acid methyl ester composites 査読

    Emmanouil Lioudakis, Andreas Othonos, Ioannis Alexandrou, Yasuhiko Hayashi

    JOURNAL OF APPLIED PHYSICS102 ( 8 )   2007年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    In this work, we present the evolution of optical constants as a function of [6,6]-phenyl C-61-butyric acid methyl ester (PCBM) concentration for conjugated poly(3-hexylthiophene)/[6,6]-phenylC(61)-butyric acid methyl ester composites. The PCBM concentration of the utilized samples varies from 1 to 50 wt %. The dielectric functions for all these composites reveal electronic structural changes as a result of the addition of PCBM. We have deconvoluted the contribution of the substrate using a two-layer Fabry-Perot structural model. The extracted optical properties contain crucial absorption peaks of singlet exciton states and vibronic sidebands for poly(3-hexylthiophene) (P3HT) conjugated polymer as well as two PCBM-related states at higher energies. With the addition of PCBM, we have observed a limit of 20 wt % PCBM beyond which two discrete energy levels (3.64 and 4.67 eV) appear in the spectrum. For the highest concentration composite, the results suggest that the interchain interactions provide a small excitonic contribution in the absorption spectrum at energies where the conjugated polymer absorbs (1.85-2.7 eV) and a strong rise of PCBM states (3.64 and 4.67 eV) which are responsible for the subsequent exciton dissociation. In addition, the energy gap between the higher occupied molecular orbitals and the lower unoccupied molecular orbitals of the highest concentration composite (50 wt %) is 1.85 eV. The tuning of the optical properties of P3HT with the addition of PCBM shows that ellipsometry can be used to monitor layer concentration toward optimization of plastic solar cells. (C) 2007 American Institute of Physics.

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  • Synthesis, microstructure and photoluminescence of well-aligned ZnO nanorods on Si substrate 査読

    L. Miao, Y. Ieda, S. Tanemura, Y. G. Cao, M. Tanemura, Y. Hayashi, S. Toh, K. Kaneko

    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS8 ( 6 ) 443 - 447   2007年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:NATL INST MATERIALS SCIENCE  

    Well-aligned zinc oxide (ZnO) nanorods were densely grown on Si substrate using ZnO thin-film seed layer without any catalysts and/ or additives by a simple solid-vapour phase thermal sublimation technique. The growth mechanism can be interpreted as self-catalyst of zinc particles based on vapour-solid (VS) mechanism. High-resolution transmission electron microscopy (HRTEM) image and selected area electron diffraction (SAED) pattern confirmed that the single-crystalline growth of the nanorods were preferentially along c-axis of hexagonal crystal system. High-crystal quality ZnO nanorods with strong near band edge emission centred at 380 nm can be achieved on Si substrate by the introduction of sufficient oxygen during the nanorod growth processing. (c) 2007 NIMS and Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.stam.2007.02.012

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  • Ultrafast carrier dynamics on conjugated poly(3-hexylthiophene)/[6,6]-phenylC(61)-butyric acid methyl ester composites 査読

    Emmanouil Lioudakis, Andreas Othonos, Ioannis Alexandrou, Yasuhiko Hayashi

    APPLIED PHYSICS LETTERS91 ( 11 )   2007年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    The authors have studied ultrafast carrier dynamics on poly(3-hexylthiophene)/[6,6]-phenylC(61)-butyric acid methyl ester (PCBM) composites up to 50% PCBM concentration. They have resolved the exciton intraband relaxation of composites as well as the subsequent electron/polaron relaxation of dissociated excitons. The observed fast time constant of intraband relaxation is found to be 0.5-1.5 ps, whereas the second long-live relaxation (0.5-1 ns) is strongly fullerene related. A wavelength dependent ultrafast study is performed giving fundamental information on the nonradiative exciton relaxation, exciton dissociation, and electron relaxation of PCBM-related states.

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  • Facile fabrication and structural studies of filtered Ge nanowires from aged Al-Ge alloy 査読

    Keisuke Sato, Kenji Kaneko, Tomoharu Tokunaga, Yasuhiko Hayashi, Zenji Horita

    SCRIPTA MATERIALIA57 ( 3 ) 281 - 284   2007年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Single crystalline Ge nanowires have been fabricated by filtration of rod-shaped Ge precipitates from aged Al-Ge alloy using HCl solution. The diameter of the Ge nanowires ranged from 30 to 100 nm when the aging conditions of the Al-Ge alloy was altered. The Ge nanowires grow preferentially in the [110] direction, which is the same as observed earlier for rod-shaped Ge precipitates in the aged Al-Ge alloy. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.scriptamat.2007.03.054

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  • Synthesis, morphology and random laser action of ZnO nanostructures 査読

    L. Miao, S. Tanemura, Y. Ieda, M. Tanemura, Y. Hayashi, H. Y. Yang, S. P. Lau, B. K. Tay, Y. G. Cao

    SURFACE SCIENCE601 ( 13 ) 2660 - 2663   2007年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    Three-dimensional (3-D) ZnO random-wall nanostructures and one-dimensional (I-D) ZnO nanorods were prepared on silicon substrates by a simple solid-vapour phase thermal sublimation technique. Optical pumped random lasing has been observed in the ZnO random-wall arrays with a threshold intensity of 0.38 MW/cm(2) in the emission wavelength from 380 to 395 nm. The optical gain was attributed to the closed-loop scattering and light amplification of the ZnO random-wall. The experimental result suggests that the morphology of nanostructure is the key factor to effect random lasing. (C) 2006 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.susc.2006.12.011

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  • Encapsluation of Co and Pd multi-metal nanowires inside multiwalled carbon nanotubes by microwave plasma chemical vapor deposition 査読

    Yasuhiko Hayashi, T. Fujita, T. Tokunaga, K. Kaneko, T. Butler, N. Rupesinghe, J. D. Carey, S. R. P. Silva, G. A. J. Amaratunga

    DIAMOND AND RELATED MATERIALS16 ( 4-7 ) 1200 - 1203   2007年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    We report the synthesis of multiwalled carbon nanotubes (MWCNTs) encapsulated with Co/Pd magnetic and nonmagnetic multi-metal nanowires using Co and Pd thin-layers deposited on Si substrate by microwave plasma enhanced chemical vapor deposition using a bias-enhanced growth method. Detailed structural and compositional investigations of these metal nanowires inside MWCNTs were carried out by scanning electron microscopy and transmission electron microscopy to elucidate the growth mechanisms. Energy dispersive X-ray spectroscopy revealed that MWCNTs were encapsulated with Co and Pd nanowires, separately, at the tube top and the bottom of Co nanowire, respectively. The face-centered-cubic (fcc) structure of Co nanowires was confirmed by a selected area diffraction pattern. We proposed a fruitful description for the encapsulating mechanisms of both Co and Pd multi-metal nanowires. (c) 2006 Elsevier B.V. All rights reserved.

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  • Encapsulation of segmented Pd-Co nanocomposites into vertically aligned carbon nanotubes by plasma-hydrogen-induced demixing 査読

    Takeshi Fujita, Yasuhiko Hayashi, Tomoharu Tokunaga, T. Butler, N. L. Rupesinghe, K. B. K. Teo, G. A. J. Amaratunga

    APPLIED PHYSICS LETTERS90 ( 13 )   2007年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    Vertically aligned carbon nanotubes (VA-CNTs) filled with Pd-Co nanocomposites on an Si substrate have been synthesized by microwave plasma-enhanced chemical vapor deposition. It was confirmed that adjacent Pd-Co nanocomposites in the VA-CNTs were compositionally separated. Most CNTs contained Co pillars on top; however, Pd pillars were rarely present. The strong magnetic induction from an individual Co pillar was revealed by electron holography. The simultaneous phenomenon of the demixing by plasma hydrogen irradiation and the preferential encapsulation into CNTs realized the unique Pd-Co nanocomposites. (c) 2007 American Institute of Physics.

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  • Morphological and optical characterization of post-annealed ZnO films prepared by sol-gel method 査読

    F. Y. Ran, L. Miao, S. Tanemura, M. Tanemura, Y. G. Cao, Y. Kuno, Y. Hayashi, Y. Mori

    TRANSACTIONS OF THE MATERIALS RESEARCH SOCIETY OF JAPAN, VOL 32, NO 432 ( 4 ) 1247 - 1250   2007年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:MATERIALS RESEARCH SOCIETY JAPAN-MRS-J  

    Transparent zinc oxide (ZnO) films have been prepared by sol-gel method using spin coating method on quartz glass from 0.5M zinc acetate 2-methoxyethonal solution, and using monoethanolamine(MEA) as stabilizer. The as-prepared samples were heat-treated at 550 degrees C for 90min in air, oxygen and vacuum ambient, respectively. XRD patterns show that the prepared samples exhibit wurtzite structure, the sample annealed in O-2 has best crystalline quality and biggest degree of preferential orientation of (0O2) plane, and the sample annealed in vacuum nearly has,no preferential orientation. It can be found from AFM images that surface roughness of the three films are: Vacuum &gt; air &gt; O-2. The sample annealed in O-2 has rod-like and uniform particles, the sample annealed in air with ball-like particles and sample heat treated under vacuum ambient with ball-like uniform particles. PL analysis tells that vacuum atmosphere leads to more oxygen vacancy (VO) and zinc excess, however annealed in O-2 can decrease the oxygen vacancy (VO) and zinc excess obviously. The band gap of prepared ZnO films is about 3.3eV from PL spectra. Through analyze the UV-Vis result, it can be found that the surface morphology does influence the absorptance. Generally speaking, the annealed ambient influences the intrinsic defect and extrinsic defect, and then influence the properties of prepared ZnO films.

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  • Microstructure analyses of metal-filled carbon nanotubes synthesized by microwave plasma-enhanced chemical vapor deposition 査読

    Yasuhiko Hayashi, Tomoharu Tokunaga, Kenji Kaneko, Simon J. Henley, Vlad Stolojan, J. David Carey, S. R. P. Silva

    IEEE TRANSACTIONS ON NANOTECHNOLOGY5 ( 5 ) 485 - 490   2006年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

    Pd/Co-based metal-filled carbon nanotubes (MF-CNTs) were synthesized by a microwave plasma-enhanced chemical vapor deposition method using a bias-enhanced growth technique. Pd/Co-based MF-CNTs were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) electron energy loss spectroscopy (EELS), and Raman spectroscopy. MF-CNTs were well-aligned and uniform in size on a Si substrate. Both multiwall nanotube carbon nanotubes (CNTs) and herringbone (or stacked cups structure) structures were observed. High-resolution TEM revealed that MF-CNTs were composed of highly ordered graphite layers, and the elemental maps of EELS indicate that both Co and Pd metals are present inside the nanotubes. TEM results clearly showed that both Pd and Co metals were successfully encapsulated into the CNTs. We observed a low value for the Raman intensity ratio between D (1355 cm(-1)) and G (1590 cm(-1)) bands with no shift of the G-peak position and no broadening of the G-peak, indicative of high-quality Pd/Co-based MF-CNTs. Based on TEM characterization, we propose a description for the encapsulating mechanisms.

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  • Demixing of solid-soluted Co-Pd binary alloy induced by microwave plasma hydrogen irradiation technique 査読

    Tomoharu Tokunaga, Yasuhiko Hayashi, Takeshi Fujita, S. R. P. Silva, G. A. J. Amaratunga

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS45 ( 29-32 ) L860 - L863   2006年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:INST PURE APPLIED PHYSICS  

    Demixing in a solid-soluted Co-40 at. % Pd alloy has been induced by microwave plasma hydrogen irradiation on mixture of Pd-Co island grains on Si substrate. The microstructure observation and X-ray microanalysis by a transmission electron microscope before and after the microwave plasma hydrogen irradiation provide a clear evidence of demixing in metallic Co-Pd alloys, that may indicate a possibility of the decomposition into Pd hydride and Co under a hydrogen irradiation at high temperatures.

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  • Low resistivity p-ZnO films fabricated by sol-gel spin coating 査読

    Yongge Cao, Lei Miao, Sakae Tanemura, Masaki Tanemura, Yohei Kuno, Yasuhiko Hayashi

    APPLIED PHYSICS LETTERS88 ( 25 )   2006年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    N-doped and In-N-codoped ZnO films were fabricated on quartz glass substrate by sol-gel spin coating. Their p-type conductivities were characterized by the Hall measurements, revealing low resistivities of the order of 10(-1) Omega cm. Thin-film junctions comprising an undoped ZnO layer and a N-doped ZnO layer displayed the typical rectifying characteristics, suggesting formation of p-n homojunctions at the interfaces. (c) 2006 American Institute of Physics.

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  • Cobalt nanorods fully encapsulated in carbon nanotube and magnetization measurements by off-axis electron holography 査読

    T Fujita, Y Hayashi, T Tokunaga, K Yamamoto

    APPLIED PHYSICS LETTERS88 ( 24 )   2006年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    Fully encapsulated face-centered-cubic (fcc) Co nanorods in multiwalled carbon nanotubes were produced by microwave plasma enhanced chemical vapor deposition. Quantitative magnetization measurements of the Co nanorods were carried out by off-axis electron holography using a theoretical cylindrical model. The component of magnetic induction was then measured to be 1.2 +/- 0.1 T, which is lower than the expected saturation magnetization of fcc Co of 1.7 T. The reason for the reduced magnetic component was discussed.

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  • Characterization of transport properties of multiwalled carbon nanotube networks by microwave plasma chemical vapor deposition 査読

    Yasuhiko Hayashi, T. Tokunaga, K. Kaneko, Z. Horita

    DIAMOND AND RELATED MATERIALS15 ( 4-8 ) 1138 - 1142   2006年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    We report the synthesis of multiwalled carbon nanotubes (MWCNTs) and the characterization of ternperature-dependent electrical transport properties of MWCNT networks by using a two-point configuration without the lithographical technique. MWCNTs were grown by microwave plasma chemical vapor deposition with the bias enhanced growth technique. The Raman intensity ratio between the D- (similar to 1360 cm(-1)) and G- (similar to 1590 cm(-1)) peaks (I(D)/I(G)) as well as the full width at half maximum of the G-peak decreased from 1.03 to 0.03 and 18 to 13 cm(-1), respectively, with the increase in the oxidative purification time. This indicates that the crystallinity of graphite sheets is improved by the oxidative purification process and burn-off of the defects in MWCNT networks. The metal electrodes were attached on both the top and the bottom of the insulating thin films, and the as-grown and oxidative-purified MWCNT networks were connected between the electrodes for I-V measurements at various temperatures. At room temperature, the conductance for the MWNT networks at around zero bias was 0.65 G(0) (G(0): fundamental conductance unit), which was less than the value of 1 G(0) for metallic MWCNTs. Further, the conductance increased linearly with the bias voltage until it attained its peak. In the 190-390 K range, the temperature characteristic of the I-V shows that the electron transport of the as-grown MWCNT networks was activated by a lower activation energy than that in oxidative-purified MWCNT networks. (c) 2006 Elsevier B.V All rights reserved.

    DOI: 10.1016/j.diamond.2006.01.006

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  • Characterization of amorphous carbon nitride by bottom-gated thin-film structure 査読

    Yasuhiko Hayashi, N. Kamada, T. Soga, T. Jimbo

    DIAMOND AND RELATED MATERIALS15 ( 4-8 ) 1015 - 1018   2006年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    We describe the characterization of nitrogen-incorporated amorphous carbon (a-C:N) films by using a double beam method. The carrier transport of a-C:N films deposited at various substrate temperatures was investigated using a bottom-gated thin-film transistor (TFT). At substrate temperatures below 300 degrees C, the optical band gap (E-opt) and the Raman intensity ratio between the D (similar to 1360cm(-1)) and G (similar to 1590cm(-1)) peaks (I-D/I-G) of an a-C:N film deposited at room temperature were observed to vary only marginally from 1.9eV and 0.88, respectively. The electrical conductivity of the a-C:N film increased by more than four orders of magnitude with an increase in the substrate temperature from 150 to 300 degrees C due to an improvement in the activation of the nitrogen-incorporated a-C film caused by the thermal annealing effect. Based on the E-opt and I-D/I-G values, we concluded that this behavior is not responsible for the change in the hybridization of carbon atoms. The a-C:N based TFT exhibited an ambipolar transport with the strong p-type operation. The field effect hole mobility (mu(h)) attained a value as high as 1.7 x 10(-4) cm(2)/Vs. In this study, one of the important results is that mu(h) increased with the substrate temperature due to the increase in film conductivity. We found that the highest success yield of transistor operation of 38% was obtained from the a-C:N TFTs deposited at a substrate temperature of 290 degrees C. (c) 2006 Elsevier B.V. All rights reserved.

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  • Optical properties of indium-doped ZnO films 査読

    YG Cao, L Miao, S Tanemura, M Tanemura, Y Kuno, Y Hayashi, Y Mori

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS45 ( 3A ) 1623 - 1628   2006年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:INST PURE APPLIED PHYSICS  

    Indium-doped ZnO (IZO) films with low In content (&lt; 6at.%) were fabricated by rf helicon inagnetron sputtering. The uniformity of the composites was confirmed by elemental analysis. The formation of an In-Zn-O solid Solution was verified using X-ray diffraction (XRD) patterns. A wide, high-transmittance re ion (400-2000 nm) and &gt; 80% transmittance in the window of fiber optics telecommunication (1.30-1.55 mu m) were observed. The incorporation of indium enhances the optical transmission in the designated visible and infrared wavelengths. The optical band gap shows a slight blue-shift with increasing In doping which call be explained by the Burstein-Moss effect. The Urbach tail parameter E-0 increases with increasing indium content, which coincides with the increase in the full width half maximum (FWHM) of (0002) planes in XRD patterns. A decline in crystal quality with In incorporation in IZO films is also confirmed from photoluminescence (PL) spectra.

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  • Microstructure analyses of metal-filled carbon nanotubes synthesized by microwave plasma-enhanced chemical vapour deposition 査読

    Y. Hayashi, T. Tokunaga, K. Kaneko, S. J. Henley, V. Stolojan, J. D. Carey, S. R. P. Silva

    2006 IEEE CONFERENCE ON EMERGING TECHNOLOGIES - NANOELECTRONICS5 ( 5 ) 93 - +   2006年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Pd/Co-based metal-filled carbon nanotubes (MF-CNTs) were synthesized by a microwave plasma-enhanced chemical vapour deposition method using a bias-enhanced growth technique. Pd/Co-based MF-CNTs were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) electron energy loss spectroscopy (EELS), and Raman spectroscopy. MF-CNTs were well-aligned and uniform in size on a Si substrate. Both multiwall nanotube carbon nanotubes (CNTs) and herringbone (or stacked cups structure) structures were observed. High-resolution TEM revealed that MF-CNTs were composed of highly ordered graphite layers, and the elemental maps of. EELS indicate that both Co and Pd metals are present inside the nanotubes. TEM results clearly showed that both Pd and Co metals were successfully encapsulated into the CNTs.. We observed a low value for the Raman intensity ratio between D (1355 cm(-1)) and G (1590 cm(-1)) bands with no shift of the G-peak position and no broadening of the G-peak, indicative of high quality Pd/Co-based MF-CNTs. Based on TEM characterization, we propose a description for the encapsulating mechanisms.

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  • A study on visually disabled person support system utilizing led traffic light with visible light communication technology 査読

    Suzuki K, Fujita M, Fukuzono K, Mizuno H, Hayashi Y

    13th World Congress on Intelligent Transport Systems and Services   2006年

  • Effects of indium incorporation on the optical properties of ZnO films 査読

    Cao Y, Miao L, Tanemura S, Hayashi Y, Tanemura M

    Advanced Materials Research11-12   159 - 162   2006年

  • Microstructure analyses of metal-filled carbon nanotubes synthesized by microwave plasma-enhanced chemical vapour deposition 査読

    Y. Hayashi, T. Tokunaga, K. Kaneko, S. J. Henley, V. Stolojan, J. D. Carey, S. R. P. Silva

    2006 IEEE CONFERENCE ON EMERGING TECHNOLOGIES - NANOELECTRONICS2006   93 - +   2006年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Pd/Co-based metal-filled carbon nanotubes (MF-CNTs) were synthesized by a microwave plasma-enhanced chemical vapour deposition method using a bias-enhanced growth technique. Pd/Co-based MF-CNTs were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) electron energy loss spectroscopy (EELS), and Raman spectroscopy. MF-CNTs were well-aligned and uniform in size on a Si substrate. Both multiwall nanotube carbon nanotubes (CNTs) and herringbone (or stacked cups structure) structures were observed. High-resolution TEM revealed that MF-CNTs were composed of highly ordered graphite layers, and the elemental maps of. EELS indicate that both Co and Pd metals are present inside the nanotubes. TEM results clearly showed that both Pd and Co metals were successfully encapsulated into the CNTs.. We observed a low value for the Raman intensity ratio between D (1355 cm(-1)) and G (1590 cm(-1)) bands with no shift of the G-peak position and no broadening of the G-peak, indicative of high quality Pd/Co-based MF-CNTs. Based on TEM characterization, we propose a description for the encapsulating mechanisms.

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  • Investigation of PCBM concentration on photovoltaic characteristics of polymer solar cells with blends of P3HT and PCBM 査読

    Yasuhiko Hayashi, K. Hamada, K. Takagi, A. Takasu, S. Takagi, T. Soga

    CONFERENCE RECORD OF THE 2006 IEEE 4TH WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION, VOLS 1 AND 21   271 - 274   2006年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE  

    Polymer photovoltaic cells (PVCs) consisting of a blend of p-type poly(3-hexylthiophene) (P3HT) and n-type [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) were fabricated and Investigated the role of the PCBM concentration. The photocurrent and the power conversion efficiency gradually increased with increase in PCBM concentration up to 50% and decreased with further increase In PCBM concentration. Both the root mean square and average roughnesses measured by atomic force microscopy decrease as the PCBM concentration increases from 0 to approximately 70%. The surface morphology of P3HT/PCBM blended and improved donor-acceptor proximity, leading to electron conductivity, contribute to the increase in power conversion efficiency.

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  • Structural and optical characterization of ZnO single crystalline nanobamboos 査読

    L Miao, S Tanemura, Y Hayashi, M Tanemura, RP Wang, S Toh, K Kaneko

    INTERNATIONAL JOURNAL OF MODERN PHYSICS B19 ( 15-17 ) 2804 - 2810   2005年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WORLD SCIENTIFIC PUBL CO PTE LTD  

    ZnO nanobamboos and nanowires with diameters of 10-30 nm and lengths of 2-4 mu m have been prepared by laser ablation in vacuum with precisely controlled pressure, growth and post-annealing temperature. XRD results show the annealed sample is hexagonal ZnO. Low-magnified TEM observation reveals the annealed sample includes ZnO nanobamboos and nanowires. High resolution TEM image and electron diffraction pattern confirm that the structure of ZnO nanobamboo is regular stacking of Zn and 0 layers with high crystal quality. The growth direction is determined as along [001] direction (c axis). TEM observations confirm that the formation of bamboo-shape ZnO is due to the stacking fault and cleavage. The bundle of those stacking faults seems to be the origin of the black contrast at the nodes. The uniformity of chemical composition for the nanobamboos is identified by EDS profiles. A strong-narrow UV band centred at 390 nm and a weak-broad green band centred at 515 nm are observed at room temperature in the PL spectrum recorded from the annealed ZnO nanobamboos and nanowires.

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  • Formation of wedge-shaped carbon film by chemical vapor deposition method and observation using transmission electron microscopy 査読

    K Kaneko, R Nagayama, K Inoke, WJ Moon, Z Horita, Y Hayashi, T Tokunaga

    SCRIPTA MATERIALIA52 ( 12 ) 1205 - 1209   2005年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Unusual morphologies of carbon nanofibers (CNFs) fabricated by the microwave plasma-enhanced chemical vapor deposition method were confirmed by transmission electron microscopy. In particular, the presence and distribution of wedge-shaped carbon films, consisting of amorphous carbon and CNFs, were observed by three-dimensional electron tomography (3D-ET), and their growth mechanisms were modeled. High-resolution transmission electron microscopy (HRTEM) revealed the presence of amorphous carbon on carbon nanofibers. Wedge-shaped carbon films are most likely caused by the bridging of individual CNFs by amorphous carbon from plasmarized carbon. The combination of 3D-ET and HRTEM clearly provides a successful strategy for determining 3D morphologies with characteristic sizes on the nanometer scale. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.scriptamat.2005.03.007

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  • Effect of rf power on the photovoltaic properties of boron-doped amorphous carbon/n-type silicon junction fabricated by plasma enhanced chemical vapor deposition 査読

    T Soga, T Kokubu, Y Hayashi, T Jimbo

    THIN SOLID FILMS482 ( 1-2 ) 86 - 89   2005年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    The optical and electrical properties of boron doped amorphous carbon thin films using methane and trimethylboron by plasma enhanced chemical vapor deposition are studied with varying the rf power. The optical bandgap is decreased from 2.4 to 1.4 eV with increasing the rf power due to the increase of sp(2) carbon. The boron doped amorphous carbon deposited at 300 W shows large photoconductivity (the ratio of conductivity under illumination to under dark) with high spin density. The open circuit voltage of boron doped amorphous carbon/n-Si structure photovoltaic cell is increased with the increase of rf power and then saturates over 100 W. On the other hand, the short circuit current is increased gradually with increasing the rf power up to 300 W. (c) 2004 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.tsf.2004.11.123

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  • Influence of structure and C-60 composition on properties of blends and bilayers of organic donor-acceptor polymer/C-60 photovoltaic devices 査読

    Y Hayashi, Yamada, I, S Takagi, A Takasu, T Soga, T Jimbo

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS44 ( 3 ) 1296 - 1300   2005年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:JAPAN SOC APPLIED PHYSICS  

    We have fabricated both blended and bilayered organic photovoltaic cells (OPVCs) using C-60 and poly [2-methoxy-5-(2&apos;-ethyihexoxy)-1,4-phenylenevinylene] (MEH-PPV). Improvements in photovoltaic performance are seen in blended OPVCs when the C-60 concentration is increased. It is believed that the optimized surface morphology of MEH-PPV/C-60 Composite and improved donor-acceptor proximity, leading to electron conductivity, contribute to the increase in power conversion efficiency E-ff. Two broad peaks were observed in the spectral response of the blended OPVCs, with maximum peaks at similar to 490 nm (= I-BL1) and similar to 350 nm (= I-BL2). The intensity ratio of I-BL1 to I-BL2 (I-BL1/I-BL2) decreases with an increase in the C-60 concentration. Also, I-BL1 is blue-shifted by 25-30 nm with an increase in the C-60 concentration. The significant improvement in the performance was observed in the bilayered OPVCs on the thermally induced interdiffusion Of C-60 into the MEH-PPV network, leading to the existence of C-60 molecules within the exciton diffusion radius of the MEH-PPV, network. The spectral response of bilayered OPVCs reveals two peaks at 535 nm and 345 nm. The former peak is red-shifted by 45 nm compared to that in blended OPVCs. We also investigate the effect of top electrode materials on the photovoltaic performances. To the best of our knowledge, we have obtained the best performances of blended and bilayered OPVCs fabricated with the Al and Mg electrodes, respectively. In both OPVC structures, the nanoscale composition control of the two materials, the choice of metal electrode, and the device processing techniques all play an important role in determining or enhancing the solar cell performance.

    DOI: 10.1143/JJAP.44.1296

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  • Synthesis and characterization of metal-filled carbon nanotubes by microwave plasma chemical vapor deposition 査読

    Y Hayashi, T Tokunaga, S Toh, WJ Moon, K Kaneko

    DIAMOND AND RELATED MATERIALS14 ( 3-7 ) 790 - 793   2005年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    A new type of palladium-based metal-filled carbon nanotubes (MF-CNTs) was fabricated and their characteristics were investigated. The MF-CNTs were grown on Pd/SiO2/Si substrates and Pd/Mo mesh by a microwave plasma-enhanced chemical vapor deposition method using CH4 and H-2 gasses with the technique of bias-enhanced growth method. The structure and composition of Pd-based MF-CNTs were thoroughly investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and Raman spectroscopy. TEM and EDS analyses showed that MF-CNTs were composed of thick cylindrical graphite walls, and filled with Pd metal inside their roots. Based on TEM characterizations, we proposed a fruitful description for the encapsulating mechanisms. (c) 2005 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.diamond.2004.12.008

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  • Efficient nitrogen incorporation into amorphous carbon films by double beam method 査読

    Y Hayashi, T Kamio, T Soga, K Kaneko, T Jimbo

    DIAMOND AND RELATED MATERIALS14 ( 3-7 ) 970 - 974   2005年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    Conductivity of amorphous carbon (a-C) was successfully controlled by incorporation of nitrogen atoms using a double beam method (DBM), where both rf nitrogen radical and if methane plasma sources were controlled separately to optimize the nitrogen incorporation. The as-grown a-C is p-type with a conductivity of 10(-11) Omega cm and activation energy (E-a) of 333 meV The addition of nitrogen atoms under varying nitrogen flow rate from 0 to 2.0 seem caused the conductivity to reach 10(-4) Omega cm as maximum and E-a of 41 meV at 1.5 seem. The optical band gap is shown to vary only marginally from standard of the as-grown of a-C film (1.39 eV) to 1.45 eV by nitrogen incorporation. The depth profile of a secondary ion mass spectroscopy (STMS) shows that the uniform concentration of C and N in the films and the sharp interface between nitrogen doped and undoped regions from the doped/undoped sandwich-like a-C structure. Furthermore, the changes in the chemical structure and relative bond fractions as a function of nitrogen flow rate are reported based on the results of an X-ray photoelectron spectroscopy and a Raman spectroscopy. (c) 2005 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.diamond.2005.01.003

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  • Facile fabrication method for p/n-type and ambipolar transport polyphenylenevinylene-based thin-film field-effect transistors by blending C-60 fullerene 査読

    Y Hayashi, H Kanamori, Yamada, I, A Takasu, S Takagi, K Kaneko

    APPLIED PHYSICS LETTERS86 ( 5 ) 1 - 3   2005年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    We have demonstrated the solution-processed p- and n-type transports including ambipolar transport organic thin-film transistors (OTFTs), required for complementary thin-film integrated circuit technology, by. a facile method of blending the n-type C-60 and the p-type [poly2-methoxy-5-[2'-ethyl-hexyloxy]-1,4-phenylene vinylene] (MEH-PPV). The carrier transport of PPV-based thin-film field-effect transistors with various C60 compositions are investigated by using the field-effect gated structure. One of the important findings is that tunable electronic properties of OTFTs are achieved by controlling C60 composition using a simple and an inexpensive spin-cast technology. The mobility increases with increase in the C60 composition in both n- and p-type OTFTs. Temperature measurements on n-type OTFTs revealed that transport follows a thermally activated hopping transport model with small activation energy. (C) 2005 American Institute of Physics.

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  • Development of new materials for solar cells in Nagoya Institute of Technology 査読

    T Jimbo, T Soga, Y Hayashi

    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS6 ( 1 ) 27 - 33   2005年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IOP PUBLISHING LTD  

    Solar cells with high efficiency and low price have long been desired, however, the commercially available solar cells are still expensive and the efficiencies of them are not high enough yet. A tandem solar cell was fabricated to develop a high-efficiency solar cell, and amorphous carbon solar cells were fabricated to develop a low-price solar cell.
    An AlGaAs/Si tandem solar cell was successfully fabricated by heteroepitaxial growth of AlGaAs on Si substrate. At first, a p-n junction was formed in Si substrate by the impurity diffusion method. Then, an AlGaAs p-n junction was grown by MOCVD. Since the AlGaAs p-n junction has a graded band gap emitter, the photo-excited minority carriers can be collected efficiently. The energy conversion efficiency of AlGaAs/Si tandem solar cell was 21.4% (AM0) in spite of large lattice mismatch and difference in thermal expansion coefficients between AlGaAs and Si.
    Solar cells were fabricated by using amorphous carbon films deposited by Ion Beam Sputtering and Pulse Laser Deposition (PLD). The highest efficiency of 1.82% (AM0) was attained with a-C(IBS)/p-C(pyrolysis)/p-Si structure. Solar cells using a-C:H were also fabricated by PLD and Plasma CVD, and the efficiencies of them were 2.1% (AM1.5) and 0.04% (AM0), respectively.
    Other research activities on solar cells in Nagoya Institute of Technology are briefly mentioned. (c) 2004 Elsevier Ltd. All rights reserved.

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  • Structural, optical and mechanical properties of nanostructure diamond synthesized by chemical vapor deposition 査読

    Y Hayashi, T Soga

    TRIBOLOGY INTERNATIONAL37 ( 11-12 ) 965 - 974   2004年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCI LTD  

    Nanostructure diamond (NSD) films on Si substrate are prepared by microwave plasma enhanced chemical vapor deposition (MPECVD) using methane and hydrogen as the reactants with two-step negative substrate bias (SB). The dependencies of the NSD film morphology, grains, surface roughness, crystal and bonding structures and hardness on the negative SB at the bias-enhanced growth (BEG) step and substrate temperature during growth have been investigated by conducting atomic force microscopy (CAFM), X-ray diffraction (XRD), Raman spectroscopy and nanoindentation. The hardness of the NSD film is found to be as high as 80 GPa with CAFM average and root mean square roughness of 7 and 9 nm, respectively, under optimal negative SB at the BEG step. From the studies of substrate temperature effect, the hardness of the NSD film is as high as 70 GPa, with average and root mean square CAFM roughness of 9 and 11 nm, respectively, which were obtained at a substrate temperature of 500 degreesC. In both cases, the film hardness was found to be affected by the size of clusters, which are composed of many small NSD particles, the amount of NSD in an amorphous matrix as well as surface roughness. We also synthesized transparent NSD films by MPECVD under optimized single-step growth conditions on quartz substrates, which are scratched with several micrometers diamond powder. A hardness as high as 60 GPa and a maximum transmittance of 60% in the visible light region are achieved for an NSD coating of 1.0 mum thickness with small surface roughness. (C) 2004 Elsevier Ltd. All rights reserved.

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  • Synthesis of corn-shape carbon nanofibers on Si and Mo substrates by bias-enhanced microwave plasma chemical vapor deposition 査読

    Y Hayashi, T Tokunaga, Y Yogata, S Toh, K Kaneko, T Soga, T Jimbo

    DIAMOND AND RELATED MATERIALS13 ( 4-8 ) 1198 - 1202   2004年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    A new type of corn-shape carbon nanofibers (CCNFs) with metal-free tips was fabricated and their characteristics were investigated. The CCNFs were grown on Ni/SiO2/Si and Ni/Mo mesh substrates by a microwave plasma-enhanced chemical-vapor deposition method using CH4 and H-2 gases with the technique of bias enhanced growth method. Transmission electron microscopy and selected area electron diffraction show that CCNFs were composed of thick cylindrical pure graphite walls, and had nanometer-sized tips with roots. The tips' apex angles of CCNFs were dependent on the substrate temperature, as the cone angles of 20, 39 and 60degrees. (C) 2004 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.diamond.2004.01.020

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  • Corn-shape carbon nanofibers with dense graphite synthesized by microwave plasma-enhanced chemical vapor deposition 査読

    Y Hayashi, T Tokunaga, T Soga, T Jimbo, Y Yogata, S Toh, K Kaneko

    APPLIED PHYSICS LETTERS84 ( 15 ) 2886 - 2888   2004年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    Corn-shape carbon nanofibers (CCNFs) with metal-free tips have been synthesized by a microwave plasma-enhanced chemical-vapor deposition method using CH4 and H-2 gasses. The CCNFs were grown on Ni/SiO2/Si and Ni/Mo mesh substrates using a bias-enhanced growth method, and they were analyzed by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The cones are composed of cylindrical pure graphite sheets, and have nanometer-sized tips and roots. The tips' apex angles of CCNFs have cone angles of 20degrees, 39degrees, and 60degrees depending on the growth conditions such as substrate temperature. (C) 2004 American Institute of Physics.

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  • Reaction of indium ate complexes with allylic compounds. Controlling S(N)2/S(N)2 ' selectivity by solvents 査読

    T Hirashita, Y Hayashi, K Mitsui, S Araki

    TETRAHEDRON LETTERS45 ( 16 ) 3225 - 3228   2004年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Vinyl and methylindium ate complexes (indates) were prepared and both the tendency of immigration and regioselectivity toward cinnamyl bromide were investigated. The vinyl group was more preferably transferred than the Me group, giving a regio-isomeric mixture of S(N)2 and S(N)2' products. The ratio of S(N)2/S(N)2' selectivity can be controlled by solvents; in the presence of polar solvents, such as N-butylpyrrolidone (NBP) and THF, the S(N)2' product was mainly obtained, whereas the S(N)2 product was selectively prepared in solutions containing hexane. The vinylindium compound, generated by the reaction of allylic-type diindium reagents with imine, was also converted to the corresponding vinyl indate, which was allowed to react with allyl chloride to give a three-component coupling product. (C) 2004 Elsevier Ltd. All rights reserved.

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  • Modification of the physical properties of chemical vapor-deposited nanostructure diamond by argon-hydrogen plasma surface treatment 査読

    Y Hayashi, D Mori, T Soga, T Jimbo

    PHYSICS OF THE SOLID STATE46 ( 4 ) 733 - 737   2004年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    Nanostructure diamond (NSD) film with a hardness as high as 70 GPa and an average surface roughness of 10 nm has been synthesized by the two-step negative substrate bias method combined with post-growth Ar-H-2 plasma irradiation. The Ar-H-2 plasma irradiation has been confirmed to improve the uniformity of grain size and shape and increase the hardness of the NSD film. (C) 2004 MAIK "Nauka / Interperiodica".

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  • Microstructure of metal-filled carbon nanotubes 査読

    S Toh, K Kaneko, Y Hayashi, T Tokunaga, WJ Moon

    JOURNAL OF ELECTRON MICROSCOPY53 ( 2 ) 149 - 155   2004年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:OXFORD UNIV PRESS  

    Catalysts are usually required to produce carbon nanotubes (CNTs) and play important roles during the growth process. Any catalysts that remain after processing are expected to add extra properties and removal of the catalysts is usually required to achieve the original properties of CNTs. Recently, CNTs have been filled incidentally by catalysts, such as Pb, Sn, Ni and Bi. This has led to success in obtaining additional properties and a few models have been proposed to describe the encapsulating mechanisms. In the present study, CNTs were filled with palladium by a microwave plasma-assisted chemical vapor deposition method. Detailed structural and compositional investigations of these metal-filled CNTs were carried out by transmission electron microscopy to elucidate the growth mechanisms.

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  • A photovoltaic cell from p-type boron-doped amorphous carbon film 査読

    XM Tian, M Rusop, Y Hayashi, T Soga, T Jimbo, M Umeno

    SOLAR ENERGY MATERIALS AND SOLAR CELLS77 ( 1 ) 105 - 112   2003年4月

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    記述言語:英語   出版者・発行元:ELSEVIER SCIENCE BV  

    Boron-doped amorphous carbon (a-C(B)) films,here prepared on n-type silicon using pulsed laser deposition technique of a graphite target. The a-C(B) films have been proved to be p-type by the formation of a heterojunction between the a-C(B) film and n-Si. The device of aC(B)/n-Si structure yielded an open-circuit voltage (V-oe) of 0.27 V and a short-circuit current density (J(sc)) of 2.2 mA/cm(2) under illumination (AM1.5 100mW/cm(2)). According to calculation, the energy conversion efficiency and fill factor were found to be about 0.3% and 0.53. respectively. (C) 2002 Elsevier Science B.V. All rights reserved.

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  • An approach for utilization of organic polymer as a sensitizer in solid-state cells 査読

    PM Sirimanne, T Shirata, L Damodare, Y Hayashi, T Soga, T Jimbo

    SOLAR ENERGY MATERIALS AND SOLAR CELLS77 ( 1 ) 15 - 24   2003年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    A solid-state cell,vas fabricated by sand viching poly[2-methox,-5(2'-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) in between micro-porous n-TiO2 and p-CuI films. The photo-excited polymer is found inject electrons into the conduction band of n-TiO2 and holes into the valance band of p-Cul. Maximum open-circuit voltage of 400 mV and short-circuit current of about 0.3 mA cm(-2) were observed for the TiO2\MEH-PPV\Cul cell, under white light illumination (100mW cm(-2)). (C) 2002 Elsevier Science B.V. All rights reserved.

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  • Photovoltaic characteristics of boron-doped hydrogenated amorphous carbon on n-Si substrate prepared by rf plasma-enhanced CVD using trimethylboron 査読

    Y Hayashi, S Ishikawa, T Soga, M Umeno, Jimbo, I

    DIAMOND AND RELATED MATERIALS12 ( 3-7 ) 687 - 690   2003年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    An attempt has been made on the device fabrication with boron-doped hydrogenated amorphous carbon (a-C:H) thin film deposited on n-type Si (100) by r.f. plasma-enhanced CVD. In order to identify the optimal doping condition, the various CH4 partial pressure has been examined. a-C:H/n-Si heterojunction solar cells with a conversion efficiency as high as 0.04% have been fabricated. The spectral response of cell photocurrents in the short wavelength region below 700 nm is determined to be due to the optical absorption of the boron-doped a-C:H film. The photovoltaic properties of the a-C:H based heterojunction solar cell structures are discussed with the dark and illuminated J-V as well as optical properties of boron-doped a-C:H film. (C) 2003 Elsevier Science B.V. All rights reserved.

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  • Photovoltaic properties of boron-incorporated amorphous carbon on n-Si heterojunction grown by radio frequency plasma-enhanced chemical vapor deposition using trimethylboron 査読

    Y Hayashi, T Soga, T Jimbo

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS42 ( 3B ) L273 - L276   2003年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:INST PURE APPLIED PHYSICS  

    Boron-incorporated hydrogenated amorphous carbon (a-C:H) thin film, which is thought to be promising for p-type conductivity, on n-type Si(100) heterojunction photovoltaic devices has been grown by radio frequency plasma-enhanced chemical vapor deposition using trimethylboron. In order to identify the effect of boron incorporation, various CH4 partial pressures have been examined. a-C:H/n-Si heterojunction solar cells with a conversion efficiency as high as 0.04% under 100 mW/cm(2) have been fabricated. The spectral response of cell photocurrents in the short wavelength region below 700 nm is determined to be due to the optical absorption of the boron-incorporated a-C:H film. The photovoltaic properties of the a-C:H-based heterojunction solar cell structures are discussed with the dark and illuminated current density-voltage characteristics as well as the optical properties of boron-incorporated a-C:H film. The possibility of improving the conversion efficiency is also discussed.

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  • Photovoltaic cells based on boron-doped amorphous carbon on n-Si prepared by rf plasma-enhanced chemical vapor deposition using trimethylboron 査読

    Y Hayashi, T Soga, T Jimbo

    PROCEEDINGS OF 3RD WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION, VOLS A-CA   151 - 154   2003年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:WCPEC-3 ORGANIZING COMMITTEE  

    Photovoltaic cells based on boron-doped p-type amorphous carbon on n-Si have been synthesized by rf plasma-enhanced CVD using trimethylboron (TMB). In order to identify the optimal doping condition, various TMB/CH4 flow ratios have been investigated. A p-type a-C:H/n-Si heterojunction solar cells with a conversion efficiency as high as 0.007 % have been fabricated. The spectral response of cell photocurrents in the short wavelength region below 700 nm is determined to be due to the optical absorption of the boron-doped a-C:H film based on the optical gap measured by UV-visible spectroscopy. The photovoltaic properties of the a-C:H based solar cell structures are discussed with the dark and illuminated current density-voltage characteristics (efficiency, short-circuit current, open-circuit voltage, fill factor and series resistance) as well as optical properties of boron-doped a-C:H film characterized by UV-visible spectroscopy.

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  • Photovoltaic properties of boron-doped amorphous carbon on n-Si with C-60 intermediate layer deposited by rf nitrogen plasma co-sputtering of graphite and boron 査読

    Y Hayashi, T Soga, T Jimbo

    PROCEEDINGS OF 3RD WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION, VOLS A-CA   144 - 147   2003年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:WCPEC-3 ORGANIZING COMMITTEE  

    Photovoltaic cells based on boron-doped amorphous carbon on n-Si with C-60 intermediate thin layer between them have deposited by rf nitrogen plasma co-sputtering of graphite and boron targets in a UHV chamber. In order to identify the effect of rf input power of graphite sputtering, the rf power was varied between 15 W and 100 W by keeping that of boron was constant at 300 W. A p-type a-C/C-60/n-Si heterojunction solar cells with conversion efficiency as high as 0.00015 % have been fabricated. The spectral response of cell photocurrents in the short wavelength region below 400 nm and 700 nm are determined to be due to the optical absorption of the borondoped a-C and C-60 layers, respectively, based on the absorption peaks measured by UV-visible spectroscopy. The photovoltaic properties of the a-C based solar cell structures are discussed with the dark and illuminated current density-voltage characteristics as well as optical properties of boron-doped a-C film.

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  • Boron-incorporated amorphous carbon films deposited by pulsed laser deposition 査読

    XM Tian, M Rusop, Y Hayashi, T Soga, T Jimbo, M Umeno

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS41 ( 9A-B ) L970 - L973   2002年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:INST PURE APPLIED PHYSICS  

    Boron-incorporated carbon films (a-C(B)) were deposited on a silicon substrate by pulsed laser deposition (PLD) of a graphite target at room temperature. The boron content was determined by X-ray photoelectron spectroscopy (XPS) to be in the range of 0.2-1.7 at.% in the films. These films were confirmed to be p-type due to the formation of a heterojunction between the a-C(B) carbon film and silicon substrate. The devices of C(B)/n-Si configuration show a maximum [open-circuit voltage] V-oc = 0.25 V, and [short-circuit current density] J(sc) = 2.1 mA/cm(2) under illumination (AM 1.5, 100 mW/cm(2)).

    DOI: 10.1143/JJAP.41.L970

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  • Role of cyclic process in the initial stage of diamond deposition during bias enhanced nucleation 査読

    Y Hayashi, Y Matsushita, T Soga, M Umeno, T Jimbo

    JOURNAL OF APPLIED PHYSICS91 ( 12 ) 9752 - 9756   2002年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    The initial nucleation of diamond film on a Si substrate, deposited by a three-step growth process together with a cycle bias enhanced nucleation (BEN) growth/H-2 plasma etching technique in a microwave plasma enhanced chemical vapor deposition system has been investigated by atomic force microscopy, Raman spectroscopy and x-ray photoelectron spectroscopy. The surface morphology and the uniformity of {100}-oriented textured grains at the BEN step were found to be greatly increased by applying the cyclic process with some optimal H-2 plasma etching time during the BEN stage. (C) 2002 American Institute of Physics.

    DOI: 10.1063/1.1480116

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  • Growth of GaAs epitaxial layers on Si substrate with porous Si intermediate layer by chemical beam epitaxy 査読

    S Saravanan, Y Hayashi, T Soga, T Jimbo, M Umeno, N Sato, T Yonehara

    JOURNAL OF CRYSTAL GROWTH237 ( 1-4 II ) 1450 - 1454   2002年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    In order to reduce the residual thermal stress in GaAs layer on Si substrate, we have introduced a porous region and a thin (similar to 10 nm) Si layer over that in between GaAs and Si substrate. A 1-mum-thick undoped GaAs layers were grown by using chemical beam epitaxial technique at different temperatures. Because of the presence of porous region the morphology of the grown layers was slightly rough. Photolumineseence improvement and reduction of surface roughness have been achieved by chemical mechanical polishing (CMP). The ex situ non-contact optical interferometer observation shows that the rms roughness values of GaAs epilayer after CMP is 4.6 nm, whereas the as-grown is 9.5 nm, From the result of low-temperature photoluminescence, it was found that a significant reduction of the biaxial tensile stress has been achieved. The results prove that the growth of GaAs on Si substrate with intermediate porous region is a promising approach for obtaining GaAs epilayers with less biaxial tensile stress. (C) 2002 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0022-0248(01)02287-4

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  • The formation of a (111) texture of the diamond film on Pt/TiO2/SiOx/Si substrate by microwave plasma chemical vapor deposition 査読

    Y Hayashi, Y Matsushita, T Soga, M Umeno, T Jimbo

    DIAMOND AND RELATED MATERIALS11 ( 3-6 ) 499 - 503   2002年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    Heteroepitaxial diamond films were grown on Pt(111)/Si with a SiQ(x) intermediate layer between them to prevent silicidation by microwave plasma enhanced chemical vapor deposition. We found that adhesion of Pt films could be improved by depositing a TiO2 thin film between Pt and SiOx. During the diamond growth, the change of preferred orientation of the Pt film was observed by X-ray diffraction (XRD) measurements. The films grown on a Pt(111)/SiOx/Si substrate had a (111)-oriented diamond with full-width at half-maximum (FWHM) values of 3-5degrees in XRD rocking curve of diamond(l 11) diffraction. Raman spectroscopy revealed that the FWHM of the diamond peak at 1332.8 cm(-1) was approximately 7-10 cm(-1) over the growth temperature range 700-850 degreesC. All the films contained disordered graphitic carbon components or an amorphous carbon phase. (C) 2002 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0925-9635(02)00021-3

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  • Deposition of amorphous CNx by d.c. and rf plasma sputtering using a rf radical nitrogen beam source 査読

    Y Hayashi, MM Rahman, K Kaneko, T Soga, M Umeno, T Jimbo

    DIAMOND AND RELATED MATERIALS11 ( 3-6 ) 1178 - 1182   2002年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    Amorphous CNx thin films were deposited by d.c. and if Ar plasma sputtering combined with a nitrogen if radical beam source which supplies active nitrogen species to the growing film surface. The dependence modifications of the optical and the structural properties on nitrogen incorporation were investigated using ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, a four-point-probe method and electron energy-loss spectroscopy. For the rf-sputtered films, the optical band gap was found to increase with the increase in the nitrogen content. For the d.c.-sputtered films, the optical gap first decreased to zero at low nitrogen content, and then increased with a further increase in the nitrogen content, C-K energy-loss near-edge structure (ELNES) showed a slight broadening on the lower energy side. The local environment of C and N atoms are almost similar as observed by comparing the C-K and N-K ELNESs. (C) 2002 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0925-9635(02)00013-4

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  • Optical properties of trimethylboron and nitrogen codoped amorphous carbon films 査読

    Y Hayashi, S Ishikawa, T Soga, T Jimbo, M Adachi, M Umeno

    INTERNATIONAL JOURNAL OF MODERN PHYSICS B16 ( 6-7 ) 1096 - 1100   2002年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WORLD SCIENTIFIC PUBL CO PTE LTD  

    We report on the efficient photoluminescence (PL) and optical properties of hydrogenated amorphous carbon thin films codoped with nitrogen and trimethylboron (TMB) grown by rf plasma-enhanced chemical vapor deposition at room temperature. The study clearly shows the observation of discrete PL emission peaks. The PL intensity of the film deposited with 20 seem TMB is more than 10(3) times than that of the film deposited without TMB, The change of optical bandgap and PL emission energy with TMB flow rate are discussed based on sp(3) and sp(2) C networks. Angular dependence of the PL spectra revealed that the origin of multiple sharp peaks is due to Fabry-Perot cavity interference effect.

    DOI: 10.1142/S0217979202010920

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  • Fabrication of a TiO2-based solid-state cell with an organic polymer as a sensitizer 査読

    PM Sirimanne, T Soga, Y Hayashi, T Jimbo

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS41 ( 2A ) L147 - L148   2002年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:INST PURE APPLIED PHYSICS  

    Poly [2-methoxy-5(2'-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) was used as a sensitizer in a photovoltaic cell. The cell was fabricated by depositing MEH-PPV in between wide band gap n-TiO, and p-Cul films. A maximum open circuit voltage of 390 mV and short circuit current of 0.29 mA.cm(-2) were observed for the TiO2[MEH-PPV]CuI cell, under AM 1.5 conditions (100mW.cm(-2) of white light illumination).

    DOI: 10.1143/JJAP.41.L147

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  • Photovoltaic characteristics of boron doped amorphous carbon films deposited by pulsed laser deposition using graphite target 査読

    XM Tian, M Rusop, Y Hayashi, T Soga, T Jimbo, M Umeno

    MOLECULAR CRYSTALS AND LIQUID CRYSTALS386 ( PART 1 ) 73 - 80   2002年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TAYLOR & FRANCIS LTD  

    This paper reports on the successful deposition of boron (B) doped carbon films (p-C(B)) and fabrication of p-C(B)/n-Si solar cells by pulsed laser deposition (PLD) technique at room temperature using graphite target. The B content in the film was determined by X-ray photoelectron spectroscopy (XPS) to be in the range of 0.2-1.7 atomic percentage. The photovoltaic values of the device, a maximum open circuit voltage, V-oc =250 mV and short circuit current density, J sc =2.113 mA/cm(2) were obtained, when exposed to AM 1.5 illumination (100 mW/cm(2) , 25degreesC). The maximum energy conversion efficiency was found tentatively to be about, eta=0.2%, together with the fill factor, FF=45%. In this paper, the dependence of the B content on electrical and optical properties of the p-C(B) films and the photovoltaic characteristic of the p-C(B)/n-Si structure photovoltaic solar cells are discussed.

    DOI: 10.1080/10587250290113222

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  • Preparation of carbon micro-coils involving the decomposition of hydrocarbons using PACT (plasma and catalyst technology) reactor 査読

    C Kuzuya, Y Hayashi, S Motojima

    CARBON40 ( 7 ) 1071 - 1077   2002年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    Carbon micro-coils as well as carbon fibers with various morphologies were prepared by the decomposition of hydrocarbons, such as acetylene, methane, propane, ethylene, etc., at 770degreesC using a PACT (plasma and catalyst technology) reactor. The preparation conditions, growth mechanism and morphology of the carbon micro-coils were examined. The Ni electrode of the PACT reactor was used as the catalyst as well as a plasma source electrode. It was found that hydrocarbons, such as methane, propane and ethylene, decomposed under the plasma and catalyst atmosphere to form acetylene as the main decomposition product, and then this acetylene was further decomposed to form carbon micro-coils. Using a Ni powder catalyst dispersed on the substrate, the carbon micro-coils with a double helix structure, in which two pieces of carbon coils entwine each other in the same coiling direction, grew among the single straight carbon fibers and paired straight fibers. On the other hand, the carbon micro-coils with a single helix structure and wide coil pitch were obtained by the indirect decomposition of acetylene using the N-2 plasma formed by the PACT reactor. (C) 2002 Elsevier Science Ltd. All rights reserved.

    DOI: 10.1016/S0008-6223(01)00248-2

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  • Origin of yellow luminescence in n-GaN induced by high-energy 7 MeV electron irradiation 査読

    Y Hayashi, T Soga, M Umeno, T Jimbo

    PHYSICA B-CONDENSED MATTER304 ( 1-4 ) 12 - 17   2001年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    The yellow luminescence band in high-energy 7 MeV electron-irradiated n-GaN is investigated as a function of electron irradiation dose. Both the yellow-band intensity and the near-bandedge photoluminescence (PL) intensity decrease continually with increasing electron irradiation dose. The decrease rate for the yellow-band intensity is less compared to the near-bandedge intensity; however, it is found that the ratio of the yellow-band intensity to the near-bandedge PL intensity increases with increasing electron irradiation dose. To interpret this phenomenon. a theoretical model is developed for the yellow-to-near-bandedge intensity ratio based on rate equations. The proposed model is in good agreement with the experimental observation. The electron spin resonance (ESR) and light-induced ESR (LESR) spectra are measured to investigate deep defects induced by electron irradiation. The ESR signal intensity at g = 1.9451 decreases with increasing electron irradiation dose and increases with the light-induced time. (C) 2001 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0921-4526(01)00499-9

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  • Determination of optical properties of nitrogen-doped hydrogenated amorphous carbon films by spectroscopic ellipsometry 査読

    Y Hayashi, G Yu, MM Rahman, KM Krishna, T Soga, T Jimbo, M Umeno

    APPLIED PHYSICS LETTERS78 ( 25 ) 3962 - 3964   2001年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    Nitrogen-doped hydrogenated amorphous carbon films have been deposited on silicon substrates by radio-frequency plasma-enhanced chemical vapor deposition using different N-2/CH4 gas ratios from 0 to 3. The real and imaginary parts, n and k, of the complex index of refraction of these films-have been determined for wavelengths between 300 and 830 nm by spectroscopic ellipsometry. Excellent agreement has been found between measured and modeled spectra, in which an empirical dielectric function based on classical Lorentz oscillator and Tauc joint density of states, and a linear void distribution along the thickness of the films have been assumed. Decrease in the optical energy gap and increase in the extinction coefficient, k, with increase in nitrogen concentration:have been observed. Refractive index, n, increases rapidly with increase in nitrogen concentration up to 6.8 at. % (similar to7.0 at. %) and then increases slowly with further increase in nitrogen concentration. For all the samples, n is found to be highest: at the film-substrate interface which gradually decreases towards the film surface. (C) 2001 American Institute of Physics.

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  • Spectroscopic properties of nitrogen doped hydrogenated amorphous carbon films grown by radio frequency plasma-enhanced chemical vapor deposition 査読

    Y Hayashi, G Yu, MM Rahman, KM Krishna, T Soga, T Jimbo, M Umeno

    JOURNAL OF APPLIED PHYSICS89 ( 12 ) 7924 - 7931   2001年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    Nitrogen doped hydrogenated amorphous carbon thin films have been deposited by rf plasma-enhanced chemical vapor deposition using CH4 as the source of carbon and with different nitrogen flow rates (N-2/CH4 gas ratios between 0 and 3), at 300 K. The dependence modifications of the optical and the structural properties on nitrogen incorporation were investigated using different spectroscopic techniques, such as, Raman spectroscopy, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, ultraviolet-visible (UV-VIS) spectroscopy, electron spin resonance (ESR), photoluminescence (PL) and spectroscopic ellipsometry (SE). Raman spectroscopy and IR absorption reveal an increase in sp(2)-bonded carbon or a change in sp(2) domain size with increasing nitrogen flow rate. It is found that the configuration of nitrogen atoms incorporated into an amorphous carbon network gradually changes from nitrogen atoms surrounded by three (sigma bonded) to two (pi bonded) neighboring carbons with increasing nitrogen flow rate. Tauc optical gap is reduced from 2.6 to 2.0 eV, and the ESR spin density and the peak-to-peak linewidth increase sharply with increasing nitrogen flow rate. Excellent agreement has been found between the measured SE data and modeled spectra, in which an empirical dielectric function of amorphous materials and a linear void distribution along the thickness have been assumed. The influence of nitrogen on the electronic density of states is explained based on the optical properties measured by UV-VIS and PL including nitrogen lone pair band. (C) 2001 American Institute of Physics.

    DOI: 10.1063/1.1371268

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  • Growth and characterization of GaAs epitaxial layers on Si/porous Si/Si substrate by chemical beam epitaxy 査読

    S Saravanan, Y Hayashi, T Soga, T Jimbo, M Umeno, N Sato, T Yonehara

    JOURNAL OF APPLIED PHYSICS89 ( 9 ) 5215 - 5218   2001年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    The initial growth of GaAs films on a Si/porous Si/Si (SPS) substrate has been investigated using reflection high-energy electron diffraction. The morphology and the thickness have been examined by a Nomarski optical microscope and scanning electron microscope, respectively. The results of the low temperature photoluminescence studies have shown that a significant reduction in the residual thermal tensile stress can be achieved with reduced growth temperature. The 77 K photoluminescence spectra for GaAs/Si show a strain-induced splitting between the heavy and light hole valence bands which corresponds to a biaxial tensile stress of 2.45 kbar acting on the GaAs layer where the same for GaAs/SPS grown at 450 degreesC is 1.69 kbar. The results have shown that a SPS substrate with the combination of low temperature growth is a promising candidate for obtaining GaAs films with low stress. (C) 2001 American Institute of Physics.

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  • Optical and structural properties of nitrogen doped amorphous carbon films grown by rf plasma-enhanced CVD 査読

    Y Hayashi, KM Krishna, H Ebisu, T Soga, M Umeno, T Jimbo

    DIAMOND AND RELATED MATERIALS10 ( 3-7 ) 1002 - 1006   2001年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA  

    Nitrogen doped hydrogenated amorphous diamond-like carbon thin films have been synthesized by radio frequency (rf) plasma-enhanced chemical vapor deposition (PECVD) using CH4 as the source of carbon and with different N-2 flow rates (N-2/CH4 gas ratios between O and 3), at 300 K. The dependence of optical and structural properties/modifications on the nitrogen incorporation was investigated using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), UV-visible spectroscopy and electron spin resonance (ESR) measurements. It was found that the configuration of nitrogen atoms incorporated into an amorphous carbon network gradually changed from nitrogen atoms surrounded by three (cr bonding) to two (pi bonding) neighbor carbons with increasing nitrogen flow rate. The Tauc optical gap was reduced from 2.6 to 2.0 eV with increasing nitrogen flow rate. The ESR spin density and the peak-to-peak linewidth increased drastically with increasing nitrogen flow rate. Significant structural modifications were observed above a gas ratio N-2/CH4 of 1. (C) 2001 Elsevier Science B.V. All rights reserved.

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  • Low density of defect states in hydrogenated amorphous carbon thin films grown by plasma-enhanced chemical vapor deposition 査読

    KM Krishna, H Ebisu, K Hagimoto, Y Hayashi, T Soga, T Jimbo, M Umeno

    APPLIED PHYSICS LETTERS78 ( 3 ) 294 - 296   2001年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER INST PHYSICS  

    The density of electronic defect states in most forms of amorphous carbon deposited at room temperature is found so far to be very high (10(18)-10(22) spins cm(-3)). In this letter, we demonstrate that the radio-frequency plasma-enhanced chemical vapor deposited hydrogenated amorphous carbon (a-C:H) thin film exhibits the lowest spin density of the order of 10(16) cm(-3), investigated by using electron spin resonance (ESR) spectroscopy, a very promising reproducible result comparable with high-quality a-Si:H. In addition, the optical gap of a-C:H has been tailored between a wide range, 1.8-3.1 eV. The ESR spectra of all the films reveal a single Lorentzian line whose linewidth DeltaH(pp) varies strongly with the optical gap. Also, there is a strong dependence of spin density on the optical gap, and we show that this dependency is a direct result of structural changes due to sp(3)/sp(2) carbon bonding network. (C) 2001 American Institute of Physics.

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  • Low-temperature growth of GaAs polycrystalline films on glass substrates for space solar cell application 査読

    M Imaizumi, M Adachi, Y Fujii, Y Hayashi, T Soga, T Jimbo, M Umeno

    JOURNAL OF CRYSTAL GROWTH221 ( 1-4 ) 688 - 692   2000年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    Preliminary results of growth of gallium arsenide poly-crystalline films on quartz glass substrate are reported. The films were grown using chemical beam epitaxy apparatus at substrate temperatures varied between 400 degreesC and 500 degreesC, The growth of polycrystalline GaAs has been realized at temperatures above 450 degreesC. X-ray diffraction (XRD) and Raman scattering show that the film grown at 500 degreesC has good crystallinity. Also, XRD and atomic force microscopy (AFM) have confirmed preferential columnar growth toward the (1 1 1) direction. Furthermore, AFM image reveals a naturally textured surface with a grain size of 0.5 - 1.0 mum. Optical energy gap, deduced from absorption coefficient of the film, is about 1.4eV. Hall measurement indicates electrical properties such as resistivity, carrier concentration, and carrier mobility of similar to 10(3) Omega cm, similar to 10(15) cm(-3), and less than a few cm(2)/Vs, respectively. The results reveal future prospects of the film for application in space solar cells. (C) 2000 Elsevier Science B.V, All rights reserved.

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  • Effect of radio frequency power on the properties of hydrogenated amorphous carbon films grown by radio frequency plasma-enhanced chemical vapor deposition 査読

    Y Hayashi, K Hagimoto, H Ebisu, MK Kalaga, T Soga, M Umeno, T Jimbo

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS39 ( 7A ) 4088 - 4093   2000年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:JAPAN J APPLIED PHYSICS  

    We have studied the influence of radio frequency (RF) power on material properties of hydrogenated amorphous carbon (a-C:H) films prepared by RF plasma-enhanced chemical vapor deposition (CVD). The RF power has a significant impact on film properties such as electron spin resonance (ESR) spin density, the optical band gap, chemical bonding and photoluminescence (PL). Raman spectroscopy, infrared (IR) absorption and ESR measurements reveal that the residual defect density (ESR spin density) increases with increasing RF power due to the increase of sp(2) C-H-x components. We obtained an ESR spin density as small as 8 x 10(16) spins/cm(3) at a low RF power, which is comparable to that of high-quality amorphous silicon films. Plasma optical emission spectroscopy indicates that the intensity ratio (IC-H/I-H) between hydrogen peaks (I-H) and hydrocarbon peaks (IC-H) significantly decreases with increasing RF power. The optical band gap, obtained from UV-visible spectroscopy, varies from 3.0 to 1.9 eV with increasing RF power. The broad emission band centered around 2.4 eV was observed in the PL spectra of the samples deposited at lower RF powers. We found a 0.5-0.3 eV Stokes shift by comparing the PL emission and the absorption coefficient spectrum from the films deposited at less than or equal to 100W RF powers, whereas, we failed to observe a clear Stokes shift from the films deposited at &gt;100W RF powers. A weak correlation between the PL peak and the optical band gap is demonstrated.

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  • Analysis of hole transport in cubic phase of p-type GaN by relaxation time approximation 査読

    Y Hayashi, T Soga, M Umeno, T Jimbo

    PHYSICA B272 ( 1-4 ) 256 - 259   1999年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    The theoretical hole transport characteristics of the cubic phase of p-type GaN, that takes the Hall coefficient anisotropy factor of the energy surface for heavy- and light-hole bands into consideration, are investigated over a wide range of temperature using the "relaxation time approximation". The calculations show that the dominant lattice scattering mechanism for holes is the acoustic deformation potential. We show that Hall factors are very important when me attempt to compare the calculated drift mobility with measured Hall ones. (C) 1999 Elsevier Science B.V. All rights reserved.

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  • Theoretical studies on hole transport and the effective hall factor in cubic phase of p-type GaN 査読

    Y Hayashi, K Watanabe, T Jimbo, M Umeno

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS38 ( 2A ) 622 - 630   1999年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:JAPAN J APPLIED PHYSICS  

    The theoretical hole transport characteristics (Hall and drift mobilities, and effective Hall factor) are reported for the cubic phase of p-type GaN. These characteristics are calculated using the "relaxation time approximation" as a function of temperature. The calculations show that the dominant lattice scattering mechanism for heres is the acoustic deformation potential. In the calculation of the scattering rate for ionized impurity mechanism the activation energy of 120 or 250 meV is used at different compensation ratios of given acceptor concentrations. Comparing the scattering lime in these activation energies, it is found that the activation energy difference is negligible at high compensation ratios. We determined the anisotropy factors separately, due to the anisotropy of the energy surface for heavy- and light-hole bands, and these parameters are taken into account in the Hall factor calculations. The Hall factors are very important when we attempt to compare the calculated drift mobility with measured Hall ones. The theoretical Hall mobilities at total hole concentrations of 3.5 x 10(15) and 3.5 x 10(16) cm(-3) are about 312 and 225 cm(2)V(-1)s(-1), respectively, with the activation energy of 120 mt V and the compensation ratio of 0.5 at 300 K. It is found that Hall mobilities are strongly affected by the compensation ratios. The obtained effective Hall factor in the cubic phase of GaN is in the range of 1.4 (T = 120 K) to 1.8 (T = 400 K).

    DOI: 10.1143/JJAP.38.622

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    その他リンク: http://orcid.org/0000-0002-4113-5548

  • Thermal stress relaxation in GaAs layer on new thin Si layer over porous Si substrate grown by metalorganic chemical vapor deposition 査読

    Y Hayashi, Y Agata, T Soga, T Jimbo, M Umeno, N Sato, T Yonehara

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS37 ( 11B ) L1354 - L1357   1998年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:JAPAN J APPLIED PHYSICS  

    We have proposed and introduced a thin Si layer over porous Si (SPS) substrate instead of the conventionally used Si substrate to overcome the residual thermal stress in GaAs layer on Si substrate (GaAs/Si). From the results of X-ray diffraction, low-temperature photoluminescence and Raman scattering, it was found that a significant reduction of the residual thermal tensile stress has been achieved. Our data clearly show that the SPS substrate is a promising substrate for overcoming the problems in GaAs/Si.

    DOI: 10.1143/jjap.37.L1354

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    その他リンク: http://orcid.org/0000-0002-4113-5548

  • Micro-Raman scattering study of internal strain relaxation in post-growth patterned GaN film grown on sapphire substrate 査読

    Y Hayashi, H Ishikawa, T Egawa, T Soga, T Jimbo, M Umeno

    BLUE LASER AND LIGHT EMITTING DIODES II   628 - 631   1998年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:OHMSHA LTD  

    The internal strain in n-type GaN epilayer is investigated as a. function of post-patterned square area by spatially resolved Micro-Raman, scattering measurements. The relationship between the post-patterned area and the internal residual strain. distribution have been obtained. Results demonstrate a, drastic, strain relaxation in the patterned area. smaller than 40 mu m square. The spectral line shape of the LO-phonon-plasmon coupled (LPPC) mode shows little variation with the, internal strain.

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  • Hydrogen absorbing and desorbing properties of Nd-Fe-B and Nd-Co-B amorphous alloys 査読

    K Tanaka, Y Hayashi, M Kimura, M Yamada

    JOURNAL OF ALLOYS AND COMPOUNDS253   101 - 105   1997年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE SA LAUSANNE  

    Hydrogen absorbing and desorbing rates are measured for melt-spun Nd-Fe(or Co)-B amorphous alloys containing 5-30% Nd and 0-15% B. The hydrogen capacity changes with the Nd concentration roughly as similar to 3.0 H/Nd, although it is also affected by the B concentration. In alloys where Nd concentration does not exceed 20%, most of the absorbed hydrogen is desorbed from the amorphous phase. X-ray structure analysis shows that the short-range order of the amorphous alloy is maintained before and after the hydrogenation.

    DOI: 10.1016/S0925-8388(96)03060-5

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    その他リンク: http://orcid.org/0000-0002-4113-5548

  • ROOM-TEMPERATURE CW OPERATION OF SQW LASERS ON SI GROWN WITH ALGAAS/ALGAP INTERMEDIATE LAYERS BY MOCVD 査読

    T EGAWA, Y HAYASHI, T GEORGE, T SOGA, T JIMBO, M UMENO

    MATERIALS FOR OPTICAL INFORMATION PROCESSING228   189 - 194   1992年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:MATERIALS RESEARCH SOC  

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  • MOCVD-GROWN SQWS ON SI WITH ALGAAS/ALGAP INTERMEDIATE LAYERS AND/OR THERMAL CYCLE ANNEALING - APPLICATION TO ROOM-TEMPERATURE CW LASERS 査読

    T EGAWA, Y HAYASHI, T JIMBO, M UMENO

    JOURNAL OF CRYSTAL GROWTH115 ( 1-4 ) 524 - 528   1991年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    We have studied the heterointerfaces of single quantum wells (SQWs) and the characteristics of SQW lasers on Si grown with Al0.5Ga0.5As/Al0.55Ga0.45P intermediate layers (AlGaAs/AlGaP ILs) by the metalorganic chemical vapor deposition (MOCVD) technique, and compare them with those grown by the two-step growth technique. The surface morphology and the heterointerfaces of SQWs on Si substrates grown with AlGaAs/AlGaP ILs are smoother than those of the two-step-grown sample. This is caused by the two-dimensional growth of the AlGaAs/AlGaP ILs. Thermal cycle annealing is found to reduce the propagation of the dislocations into the GaAs layers on Si. Excellent lasting characteristics are obtained by the AlGaAs/AlGaP ILs, which are caused by the smooth heterointerfaces. It is shown that the AlGaAs/AlGaP ILs have played an important role in achieving smooth heterointerfaces and the excellent characteristics of the SQW laser on a Si substrate.

    DOI: 10.1016/0022-0248(91)90798-A

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  • ROOM-TEMPERATURE CW OPERATION OF ALGAAS/GAAS SQW LASERS ON SI SUBSTRATES BY MOCVD USING ALGAAS/ALGAP INTERMEDIATE LAYERS 査読

    T EGAWA, Y KOBAYASHI, Y HAYASHI, T SOGA, T JIMBO, M UMENO

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS29 ( 7 ) L1133 - L1135   1990年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:JAPAN SOC APPLIED PHYSICS  

    DOI: 10.1143/JJAP.29.L1133

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    その他リンク: http://orcid.org/0000-0002-4113-5548

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書籍等出版物

  • 可視光通信の世界LEDが拓く「あかりコミュニケーション」

    林 靖彦( 担当: 共著 ,  範囲: 第4章 可視光通信のための送受信の仕組み)

    株式会社工業調査会  2006年 

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  • Properties of Amorphous Carbons

    林 靖彦( 担当: 共著)

    2002年 

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MISC

  • Water permeation behavior thorough vertically-aligned carbon nanotube array/polymer composite membranes: Effect of temperature

    Hidetoshi Matsumoto, Shiho Shirahama, Shaoling Zhang, Akito Saeki, Minoru Ashizawa, Hirotaka Inoue, Yasuhiko Hayashi, Shuji Tsuruoka

    ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY258   2019年8月

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    記述言語:英語   掲載種別:研究発表ペーパー・要旨(国際会議)   出版者・発行元:AMER CHEMICAL SOC  

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  • 研究最前線 高速成長した長尺・高密度2層カーボンナノチューブから乾式紡績による線材の開発

    林 靖彦, 井上 寛隆, 林 拓磨, 徳永 知春, 羽田 真毅, 西川 亘

    Nanofiber : ナノファイバー学会誌8 ( 1 ) 29 - 33   2017年7月

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    記述言語:日本語   出版者・発行元:ナノファイバー学会  

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  • 酸化グラフェンの光還元によるsp3からsp2への構造ダイナミクス

    羽田 真毅, 鈴木 貴之, 南 康夫, 武田 淳, 仁科 勇太, 林 靖彦, 徳永 智春, 腰原 伸也, 一柳 光平, 野澤 俊介, 足立 伸一, 片山 郁文

    日本物理学会講演概要集71 ( 0 ) 1279 - 1279   2016年

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    記述言語:日本語   出版者・発行元:一般社団法人 日本物理学会  

    &lt;p&gt;酸化グラフェンはグラフェンの化学誘導体であり、光照射や加熱、還元剤の添加によりグラフェンに近い特性を持つ物質に変化することが知られている。この酸化グラフェンは、液中における化学操作が可能となるため、グラフェン誘導体に関する幅広い応用へと期待されている。本講演では、フェムト秒時間分解電子線回折法及びシングルショット過渡透過率測定によって解明した酸化グラフェンの光還元反応のダイナミクスを議論する。&lt;/p&gt;

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  • Fabrication of tin-filled carbon nanofibres by microwave plasma vapour deposition and their in situ heating observation by environmental transmission electron microscopy. 査読 国際誌

    Tomoharu Tokunaga, Takumi Kanematsu, Takahumi Ito, Takahisa Ota, Yasuhiko Hayashi, Katsuhiro Sasaki, Takahisa Yamamoto

    Nanoscale research letters8 ( 1 ) 302 - 302   2013年6月

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    記述言語:英語  

    Sn-filled carbon nanofibres (CNFs) are fabricated by microwave plasma chemical deposition. Scanning electron microscopy observations revealed the existence of a Sn island under the CNFs. The structure of the CNFs is investigated, and the behaviour of Sn in the internal space of CNFs is revealed by performing in situ heating observations by environmental transmission electron microscopy (ETEM). ETEM observations reveal that they have low-crystallized carbon wall and Sn occupies not only the CNF's internal space but also its carbon wall. The Sn inside the CNF is completely covered by the carbon wall. Further, the in situ heating observations reveal that Sn within the internal space and the carbon wall of the CNFs diffused to the outside during heating. Moreover, it is found that higher membered carbon rings and defects in the graphite layer act as diffusion routes between disordered carbon layers.

    DOI: 10.1186/1556-276X-8-302

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  • 金属充填カーボンナノチューブの成長と磁化特性

    堀田義朗, 徳永智春, 佐々木勝寛, 黒田光太郎, 伊藤陽一, 張奉鎔, 林靖彦, 藤田武志

    日本金属学会講演概要144th   308   2009年3月

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    記述言語:日本語  

    J-GLOBAL

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  • 金属充填カーボンナノチューブの成長と磁化特性

    堀田義朗, 徳永智春, 佐々木勝寛, 黒田光太郎, 伊藤陽一, 張奉鎔, 林靖彦, 藤田武志

    日本金属学会講演概要143rd   472   2008年9月

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    記述言語:日本語  

    J-GLOBAL

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  • 磁性金属内包カーボンナノチューブの作製と評価

    林靖彦, 藤田武志, 徳永智春, 内藤綱彦, 種村眞幸

    応用物理学会学術講演会講演予稿集68th ( 1 ) 534   2007年9月

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    記述言語:日本語  

    J-GLOBAL

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  • 電子顕微鏡法による材料開発のための微細構造研究最前線(6)ホログラフィー・ローレンツ顕微鏡 カーボンナノチューブに充填した円柱状コバルトの磁化測定

    藤田武志, 林靖彦, 徳永智春, 山本和生

    まてりあ45 ( 12 ) 896   2006年12月

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    記述言語:日本語  

    DOI: 10.2320/materia.45.896

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  • カーボンナノチューブに充填した円柱状コバルトの磁化測定

    藤田 武志, 林 靖彦, 徳永 智春, 山本 和生

    まてりあ : 日本金属学会会報45 ( 12 )   2006年12月

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    記述言語:日本語   出版者・発行元:公益社団法人 日本金属学会  

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産業財産権

  • ダイヤモンド薄膜用基板及びダイヤモンド膜の作製法

    林 靖彦, 曽我 哲夫, 神保 孝志

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    出願番号:特願2001-281223  出願日:2001年9月17日

    特許番号/登録番号:特許3856201  発行日:2006年9月22日

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受賞

  • 中国四国支部第 25 回発表奨励賞

    2020年9月   (公社)応用物理学会 中国四国支部   カーボンナノチューブ高配向シートを用いたフレキシブルスーパーキャパシタの高容量化

    小松原康平, 井上寛隆, 中川智広, 西川亘, 鈴木弘朗, 山下善文, 林靖彦

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  • 中国四国支部第25回発表奨励賞

    2020年9月   (公社)応用物理学会 中国四国支部   二元触媒による乾式紡績可能なCNTアレイ作製条件の検討

    中川智広, 井上寛隆, 前谷光顕, 鈴木弘朗, 西川亘, 山下善文, 林靖彦

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  • 中国四国支部第25回発表奨励賞

    2020年9月   (公社)応用物理学会 中国四国支部   多結晶Si中の2つのNi関連準位の逆バイアス電圧下消滅過程

    安田 佳史,山下善文,西川亘,鈴木弘朗,林靖彦

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  • 2019年(第6回)ZAIKENフェスタ 奨励賞

    2019年10月   早稲田大学 各務記念材料技術研究所   細径かつ紡績可能なカーボンナノチューブアレイ合成におけるアレイ高さ・嵩密度の重要性

    井上寛隆

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  • 第24 回(2019 年度)応用物理学会中国四国支部 学術講演会発表奨励賞

    2019年9月   (公社) 応用物理学会 中国四国支部  

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  • 2019年 ナノファイバー学会第9回年次大会 最優秀ポスター賞

    2019年6月   特定非営利活動法人 ナノファイバー学会   カーボンナノチューブシートを用いた混錬物フリーなフレキシブルスーパーキャパシタの開発

    丸井竜輝

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  • 2017年(弟22回)応用物理学会中四国支部学術講演会

    2018年11月   公益社団法人 応用物理学会  

    林 靖彦

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  • 学術奨励賞

    2018年6月   日本繊維機械学会  

    林 靖彦

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  • 2017年(弟22回)応用物理学会中四国支部学術講演会

    2017年11月   公益社団法人 応用物理学会  

    林 靖彦

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  • 最優秀ポスター賞

    2017年7月   ナノファイバー学会  

    林 靖彦

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  • 2016年(弟21回)応用物理学会中四国支部学術講演会発表奨励賞

    2016年11月   公益社団法人 応用物理学会   「赤外メタマテリアルの構造対称性制御によるファノ共鳴励起と交差偏光特性」,「走査電子顕微鏡による電子線照射で促進された4H-SiC中部分転位の運動速度」,「太陽電池用多結晶シリコン中Ni関連準位の電界印加による消滅の機構」,「炭化水素ガス流量によるカーボンナノチューブの層数変化」の4件

    林 靖彦

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  • 2015年(弟20回)応用物理学会中四国支部学術講演会発表奨励賞

    2015年11月   公益社団法人 応用物理学会   「多環フェナセン単結晶電界効果トランジスタの伝導特性と論理回路応用」,「還元法により変化する酸化グラフェン電極の電気容量」の2件

    林 靖彦

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  • 平成23年度 教員評価 特別優秀賞

    2012年1月   名古屋工業大学  

    林 靖彦

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  • 平成22年度 教員評価 優秀賞

    2011年1月   名古屋工業大学  

    林 靖彦

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  • ポスター賞

    2008年11月   International Symposium on Nanoscience and Nanotechnology  

    林 靖彦

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  • 平成19年度 教員評価 優秀賞

    2008年1月   名古屋工業大学  

    林 靖彦

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  • 第57回金属組織写真賞 A部門「奨励賞」

    2006年12月   公益社団法人日本金属学会  

    林 靖彦

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共同研究・競争的資金等の研究

  • 医療・介護現場での作業負担を軽減するカーボンナノチューブ紡績糸を⽤いた装着型排泄検知ガスセンサー の開発

    2021年05月 - 2022年03月

    国⽴研究開発法⼈科学技術振興機構  研究成果展開事業  A-STEPトライアウトタイプ

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    担当区分:研究代表者 

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  • 高効率熱電発電を実現するカーボンナノチューブ糸の材料設計・制御技術の開拓

    研究課題/領域番号:21H01371  2021年04月 - 2024年03月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    林 靖彦

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    配分額:17810000円 ( 直接経費:13700000円 、 間接経費:4110000円 )

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  • ナノ界面における水分子の拘束に注目した人工輸送チャネル膜におけるゲート機能の創出

    研究課題/領域番号:20K21120  2020年07月 - 2022年03月

    日本学術振興会  科学研究費助成事業 挑戦的研究(萌芽)  挑戦的研究(萌芽)

    松本 英俊, 林 靖彦

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    配分額:6370000円 ( 直接経費:4900000円 、 間接経費:1470000円 )

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  • 真なる人間支援を目指すポリマー糸/カーボンナノチューブ複合繊維軽量人工筋肉の開発

    研究課題/領域番号:19K21946  2019年06月 - 2021年03月

    日本学術振興会  科学研究費助成事業 挑戦的研究(萌芽)  挑戦的研究(萌芽)

    林 靖彦, 松本 英俊, 西川 亘

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    配分額:6370000円 ( 直接経費:4900000円 、 間接経費:1470000円 )

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  • 低消費電力で大変位・高出力の限界を極める熱刺激型軽量コイルアクチュエータの開発

    研究課題/領域番号:19H05332  2019年04月 - 2021年03月

    日本学術振興会  科学研究費助成事業 新学術領域研究(研究領域提案型)  新学術領域研究(研究領域提案型)

    林 靖彦

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    配分額:10400000円 ( 直接経費:8000000円 、 間接経費:2400000円 )

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  • 垂直配向カーボンナノチューブ膜を用いた1次元ナノ空間における物質輸送機構の解明

    研究課題/領域番号:18K18994  2018年06月 - 2020年03月

    日本学術振興会  科学研究費助成事業 挑戦的研究(萌芽)  挑戦的研究(萌芽)

    松本 英俊, 林 靖彦

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    配分額:6370000円 ( 直接経費:4900000円 、 間接経費:1470000円 )

    本研究の目的は、垂直配向カーボンナノチューブ(CNT)/高分子複合膜を用いて、CNT内の水透過挙動に与える温度とCNT長の影響を詳細に調査することによって、CNT内部空間における水輸送メカニズムの解明に挑戦することである。
    本年度は、CNT内における水透過挙動の特徴を明らかにするためにCNT内の透水性の温度依存性と水存在状態の関係を調べた。先ず、化学気相成長(CVD)法とフッ素系高分子の気相蒸着重合を用いて、反応試薬と反応条件を詳細に検討することによって化学的安定性に優れた垂直配向CNTアレイ/高分子複合膜を作製することに成功した。得られた複合膜について全量濾過方式のセルを用いて、圧力差0.1 MPa、測定温度=15~45℃の条件下で水および有機溶媒の透過流束を測定した。水は26℃以下では膜を透過せず、透水挙動の温度依存性は36℃付近で活性化エネルギーが変化する挙動を示した。一方比較のために実施した有機溶媒の透過実験では、このような温度依存性は観察されなかった。さらに透水実験後の膜について行った示差走査熱量分析測定から、36℃付近で水の融解ピークが観察された。

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  • 光と物質の一体的量子動力学が生み出す新しい光誘起協同現象物質開拓への挑戦

    研究課題/領域番号:18H05208  2018年04月 - 2023年03月

    日本学術振興会  科学研究費助成事業 特別推進研究  特別推進研究

    腰原 伸也, 石川 忠彦, 沖本 洋一, 東 正樹, 林 靖彦, 羽田 真毅, 桑原 真人, 宮坂 等, 石原 純夫

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    配分額:630110000円 ( 直接経費:484700000円 、 間接経費:145410000円 )

    本研究では、物質と光子が一体化した場で極短時間に発現する、光励起特有の新秩序状態(Hidden State)の特性や生成過程を、フェムト秒分光・電子線構造観測手法を用いて解明し、超高速可逆光相換物質の開拓や新奇(光誘起マルチフェロイクス)物質の開拓に挑戦することを目的としている。
    本年度は研究初年度であるため、この物質開発に必要不可欠な、30fs超短パルス電子線回折装置のデザインと構築を当初計画通り実施した。電子銃、加速装置、パルス幅圧縮装置やそのRF回路等市販品は皆無なため、全て独自にデザインし導入した。特に後年度実施のパルス圧縮用RF空洞、スピン偏極線源導入に備えた独自デザインチャンバーに、昨今の物質探索面から必要性が急速に増しているTHz域励起光導入を可能とする設計変更を施した。現在真空槽を組み上げ真空度の向上を行っている。さらに超広帯域励起光源(含むTHz域:自作)の構築準備設計も開始した。
    観測装置の準備と並行して、超高速光学測定によって超高速光スイッチ・マルチフェロイック物質開拓にとって有望な有機物(複合スピンクロスオーバー系や磁性転移を伴う中性-イオン性転移系)、Co酸化物系に関して(浅香とも密接に薄膜試料準備で連携)、現有のサブピコ秒電子線発生装置を活用して構造変形と光電機能の関連解析に集中的に取り組んだ。この結果、Co系酸化物絶縁体で、巨大光学特性変化を伴う酸素イオンの大規模な光誘起移動現象や強誘電性変化が起きることを発見した。これらの結果は、スピン状態の変化も伴った、光励起状態特有のHidden Stateの出現を強く示唆している。これらの成果は理論解析グループにとっても格好のターゲットであり、データ解釈の物理基本モデルに関して理論との密接な協力を行い、光励起による高スピンポーラロン相出現の可能性の検討など新概念提案に向けた計算を開始した。

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  • 引張強度6GPaを超える超高強度 ・超軽量カーボンナノチューブ 紡績糸の創製

    2018年04月 - 2021年03月

    文部科学省  科学研究費補助金 基盤研究(B) (一般) 

    林 靖彦

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    担当区分:研究代表者  資金種別:競争的資金

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  • 引張強度6GPaを超える超高強度・超軽量カーボンナノチューブ紡績糸の創製

    研究課題/領域番号:18H01708  2018年04月 - 2021年03月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    林 靖彦, 鶴田 健二, 羽田 真毅, 西川 亘, 徳永 智春

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    配分額:17810000円 ( 直接経費:13700000円 、 間接経費:4110000円 )

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  • 垂直配向カーボンナノチューブ 膜を用いた1次元ナノ空間にお ける物質輸送機構の解明

    2018年04月 - 2020年03月

    文部科学省  科学研究費補助金 挑戦的研究( 萌芽) 

    松本 英俊

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    資金種別:競争的資金

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  • 2025年に人類が直面する水不足を解決する究極のカーボンナノチューブ分離膜創製

    研究課題/領域番号:17K20065  2017年06月 - 2019年03月

    日本学術振興会  科学研究費助成事業 挑戦的研究(萌芽)  挑戦的研究(萌芽)

    林 靖彦, 松本 英俊, 羽田 真毅, 井上 寛隆, 白濱 志帆, 張 紹玲, 相羽 誉礼

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    配分額:6370000円 ( 直接経費:4900000円 、 間接経費:1470000円 )

    熱化学気相成長法(熱CVD)により,基板に垂直配向した長尺・高密度二層カーボンナノチューブ(DWCNT)アレーを高速で合成し,炭化水素高分子でコートし,DWCNTのチューブ空間を水流チャネルとする「水処理膜(分離膜)」を作製する.透過型電子顕微鏡からDWCNTの平均チューブ径は3.4nmで,チューブ径の細径化ができた.この膜を全量濾過方式のセルにより透水実験を行い,室温付近では透水性を示さず,温度上昇とともに透水流速が急増する特異的な現象を実験で突き止めた.時分解電線回折装置により水分子薄膜をその場で堆積させるシステムを開発した.

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  • 2025年に人類が直面する水不足 を解決する究極のカーボンナノ チューブ分離膜創製

    2017年04月 - 2019年03月

    文部科学省  科学研究費補助金 挑戦的研究( 萌芽) 

    林 靖彦

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    担当区分:研究代表者  資金種別:競争的資金

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  • 高強度・高耐食性の実現に向けたマグネシウムとカーボンナノチューブの複合化技術および複合線材の開発

    2016年06月 - 2017年03月

    国立研究開発法人科学技術振興機構  平成28年度 マッチングプランナープログラム「企業ニーズ解決試験」 

    林 靖彦

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    担当区分:研究代表者  資金種別:競争的資金

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  • 二層カーボンナノチューブのナノからマクロへの展開

    研究課題/領域番号:26600045  2014年04月 - 2016年03月

    日本学術振興会  科学研究費助成事業 挑戦的萌芽研究  挑戦的萌芽研究

    林 靖彦

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    配分額:3900000円 ( 直接経費:3000000円 、 間接経費:900000円 )

    本研究では,熱化学気相成長法(CVD)により高速に成長した長尺・高密度カーボンナノチューブ(CNT)を成長し,バインダー無しの乾式紡糸で,高強度で高導電率を兼ね備えた連続繊維化可能な超軽量・長距離CNT線材を実現する.
    このため,基板温度および炭化水素ガスの導入・流量を最適化し,パーティクルサイズと触媒微粒子の構造を制御することで,紡糸可能な2層CNTの成長割合を高める.また,CNT線材はCNTを束ねたものであり,それぞれのCNTは分子間力で結合しているため,真空チャンバー中で導入するガスや圧力を制御し,CNT線材にバイアスを印加し結合を強固なものにすることで機械的および電気的特性向上を目指す.

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  • 二層カーボンナノチューブのナノからマクロへの展開

    2014年04月 - 2016年03月

    文部科学省  科学研究費補助金 挑戦的萌芽研究 

    林 靖彦

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    担当区分:研究代表者  資金種別:競争的資金

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  • カーボンナノチューブ・シームレス接合技術の開拓

    2013年10月 - 2014年09月

    独立行政法人科学技術振興機構  平成25年度先端的低炭素化技術開発事業 フィジビリティースタディー 

    林 靖彦

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    担当区分:研究代表者  資金種別:競争的資金

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  • 超高強度で超低抵抗の超軽量カーボンナノチューブ線材の開発

    2013年10月 - 2014年03月

    独立行政法人科学技術振興機構  研究成果最適展開支援プログラムA-STEPフィージビリティスタディステージ探索タイプ 

    林 靖彦

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    担当区分:研究代表者  資金種別:競争的資金

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  • ナノカーボンを基盤とする超軽量・大面積放射性物質吸着フレキシブルシートの開発

    2012年10月 - 2013年09月

    独立行政法人科学技術振興機構  研究成果最適展開支援プログラム復興促進プログラム(A-STEP) 

    林 靖彦

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    担当区分:研究代表者  資金種別:競争的資金

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  • カーボンナノホーンによる高導電性・高熱伝導性ゴムペーストの開発

    2010年10月 - 2011年03月

    独立行政法人科学技術振興機構  研究成果最適展開支援プログラムA-STEPフィージビリティスタディステージ探索タイプ 

    林 靖彦

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    担当区分:研究代表者  資金種別:競争的資金

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  • スピントロニクスを目指した鉄コバルトナノワイヤー内包カーボンナノチューブ作製評価

    2009年04月 - 2011年03月

    独立行政法人日本学術振興会  平成21年度(2009年度)英国との共同研究(RS) 

    林 靖彦

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    担当区分:研究代表者  資金種別:競争的資金

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  • フラーレン内包1次元カーボンナノチューブ複合体による3端子スイッチング素子の開発

    2009年04月 - 2011年03月

    文部科学省  科学研究費補助金 挑戦的萌芽研究 

    林 靖彦

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    担当区分:研究代表者  資金種別:競争的資金

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  • フラーレン内包1次元カーボンナノチューブ複合体による3端子スイッチング素子の開発

    研究課題/領域番号:21655067  2009年 - 2010年

    日本学術振興会  科学研究費助成事業 挑戦的萌芽研究  挑戦的萌芽研究

    林 靖彦

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    配分額:3000000円 ( 直接経費:3000000円 )

    本研究では,基板上に垂直配向させた3本の金属内包フラーレン(以後CNTとよび,3本の金属内包CNT_sのそれぞれをT1,T2,T3と呼ぶ)とカーボンナノチューブで構成した「ピーポッド」(以後「ピーポッド」と呼ぶ)の電気・磁気的相互作用を利用し,高周波ナノエレクトロメカニカルスイッチなど新規ナノ磁性素子を開発する.本年度は,以下の研究を実施した.
    1.CNT成長とピーポッド作製(担当:岸,種村)
    【素子構造に基づくピーポッド】
    前年度と同様な方法により,Si基板上に垂直に配向したCNTの先端をプラズマ処理により開管させ,その後フラーレンとCNT基板を石英官に封入し加熱することで,ピーポッドNEMS構造を作製した.CNTの両端を開管させた場合と異なり,フラーレンがチューブ内に密に内包させることが困難であった.本研究では,分子線エピタキシー装置を用いて,分子線セル(クヌーセンセル)からフラーレンを加熱昇華させ,超高真空中でかつ基板温度を最適化することで,チューブ内に密に充填させることができた.
    2.ピーポッドNEMSの微細構造評価(担当:徳永)
    電気的測定を前後でピーポッドの高分解TEM観察し,内包する金属の位置の変化に注目して評価を行った.しかし,金属の位置の明瞭な変化を観測することができなかった.電気的測定における印可バイアス条件にも依存することが考えられ,今後は印可バイアスの異なる試料の観察を行う.

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  • 鉛蓄電池再生を目指した活性・強化液添加剤カーボンナノ粒子懸濁液製造法の開発

    2008年10月 - 2010年03月

    独立行政法人科学技術振興機構  平成20年度地域ニーズ即応型 

    林 靖彦

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    担当区分:研究代表者  資金種別:競争的資金

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  • FeCo単結晶ナノワイヤ内包CNT垂直磁化強磁性材料の作製と評価

    2008年04月 - 2011年03月

    文部科学省  科学研究費補助金 基盤研究(B) 

    林 靖彦

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    担当区分:研究代表者  資金種別:競争的資金

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  • FeCo単結晶ナノワイヤ内包CNT垂直磁化強磁性材料の作製と評価

    研究課題/領域番号:20360313  2008年 - 2010年

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    林 靖彦, 種村 眞幸, 金子 賢治, 藤田 武志

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    配分額:19240000円 ( 直接経費:14800000円 、 間接経費:4440000円 )

    本研究は,カーボンナノチューブ(以後CNTと呼ぶ)を成長する際にFeCoナノワイヤをチューブ内に内包することで,ナノ領域でアスペクト比が大きな形状, CNTにより大気から遮断した,「FeCo単結晶ナノワイヤ」を作製しナノ磁性を評価する.本研究から,スピントロニクス・デバイスとして活用できる機能を見出し,(1)空気中で安定,(2)室温で大きな保持力,(3)大きな磁気異方性を併せ持っ機能の発現をより顕在化させる材料設計の知見を得る.

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  • Synthesis and characterization of carbon nanotube encapsulated ferromagnetic metal nanowires: Towards spin electronic applications

    2008年

    独立行政法人日本学術振興会  平成20年度第I期 国際学会等派遣事業 

    林 靖彦

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    担当区分:研究代表者  資金種別:競争的資金

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  • ナノインプリント技術による産業用カーボンナノチューブ光輝度光源の開発

    2006年09月 - 2007年02月

    独立行政法人科学技術振興機構  シーズ発掘試験研究 

    林 靖彦

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    担当区分:研究代表者  資金種別:競争的資金

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  • 金属内包ナノチューブの合成とスピンエレクトロニクスデバイスへの応用

    2004年04月 - 2006年03月

    文部科学省  科学研究費補助金 萌芽研究 

    林 靖彦

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    担当区分:研究代表者  資金種別:競争的資金

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  • 金属内包ナノチューブの合成とスピンエレクトロニクスデバイスへの応用

    研究課題/領域番号:16651065  2004年 - 2005年

    日本学術振興会  科学研究費助成事業 萌芽研究  萌芽研究

    林 靖彦, 曽我 哲夫, 金子 賢治

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    配分額:3400000円 ( 直接経費:3400000円 )

    平成16年度に引き続き,基板バイアス印可プラズマ化学気相成長法により,強磁性金属内包多層カーボンナノチューブ(MWCNTs)の基板配向性の制御,基板バイアスが内包金属へ与える影響を明らかにした.MWCNTsに内包する金属として,予めSi基板に積層したPd/Co金属薄膜を用いて,チューブ内にMWCNTsを成長すると同時に強磁性金属を内包させた.
    Si基板に垂直に配向したPd/Co内包MWCNTs基板を用い,試料振動型磁力計(VSM)で磁性体の磁気特性の評価を行い,磁気ヒステリシス曲線(B-H曲線)より保磁力,飽和磁束密度,残留磁束密度時期特性の評価を行った.Pd/Co内包MWCNTsに平行および垂直に磁化することで,容易磁化方向はMWCNTsに平行であることが分かり,デバイス開発に必要な情報を得ることが出来た.
    基板に配向したPd/Co内包MWCNTs試料を,高角度まで傾斜させながら連続的にTEM像を取得し,得られた一連の連続傾斜像からその切片の三次元情報を再構築する電子線トモグラフィを用いて,強磁性金属内包CNTsの形状の詳細な分析を行った.金属はチューブ内に一様に内包されていることを確認した.この他,TEMを用いた電子線ホログラフィにより内包した単一の金属の評価から,ナノ領域での磁束分布や磁化の様子を明らかにした.
    平成16年〜平成17年で行った本研究結果から,Pd/Co内包MWCNTsを用いた新規な物質やスピンエレクトロニクスデバイスなどの広範な応用が期待できると考えている.

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  • 高効率・低コスト次世代太陽電池素子用環境考慮型炭素系半導体材料の研究

    2002年04月 - 2004年03月

    文部科学省  科学研究費補助金 若手研究(B) 

    林 靖彦

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    担当区分:研究代表者  資金種別:競争的資金

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  • 高効率・低コスト次世代太陽電池素子用環境考慮型炭素系半導体材料の研究

    研究課題/領域番号:14750232  2002年 - 2003年

    日本学術振興会  科学研究費助成事業 若手研究(B)  若手研究(B)

    林 靖彦

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    配分額:3000000円 ( 直接経費:3000000円 )

    平成15年度は,具体的な技術確立目標として,Phase 2.(n型伝導性・抵抗率制御技術)およびPhase 3.の研究を行った。
    Phase 2.a-C膜への不純物添加とn伝導性・抵抗率制御技術の確立
    様々な方法でa-C膜への不純物導入が試みられたが,光学ギャップやスピン密度等薄膜物性への影響を及ぼすことなく伝導性・抵抗率制御を行った報告は無い.本研究では,カーボン薄膜堆積用と不純物導入用窒素プラズマ条件を別々に制御・最適化することで,不純物を導入しない場合と比較し,最大6桁の導電率上昇を観測し,a-C膜への不純物導入技術を確立した.窒素導入条件(不純物量)を層ごとに変えた多層a-C膜を,2次イオン質量分析装置を用いて評価し,不純物量に応じた2次イオンカウント数を観測した.本方法により,薄膜物性に影響を及ぼすことなく,抵抗率の制御を広範に行うことが可能となった.太陽光に対する抵抗率を室温で観測したが,暗状態の1.3倍程度の導電率の変化で,欠陥密度の低減が今後重要な課題になると思われる.
    Phase 3.太陽電池の試作と電池特性の評価
    n型a-C膜をp型Si基板上堆積した,ヘテロ構造a-C膜太陽電池の試作と太陽電池の諸特性(変換効率,量子効率等)を評価し,n型a-C膜の太陽電池材料としての特性を明らかにした.本構造により,変化効率0.02%を達成し,量子効率に結果からa-C膜からの発電が寄与していることを確認した.また,a-C膜のみから構成する太陽電池を作製しp/nの整流性を観測したが,疑似太陽光下での発電を確認することが出来なかった.
    平成15年度に得られた結果は,現在論文誌に投稿中です.

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  • 多波長光デバイス集積化のための異種材料一体化技術

    研究課題/領域番号:13026213  2001年 - 2003年

    日本学術振興会  科学研究費助成事業 特定領域研究  特定領域研究

    神保 孝志, 林 靖彦, 曽我 哲夫, 江川 孝志, 梅野 正義, 石川 博康

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    配分額:35800000円 ( 直接経費:35800000円 )

    種々の発光デバイスをSi基板上に集積することを目的として,GaN系及びGaAs系発光デバイスをSi基板上に作製した。
    GaN系ではSi基板上に高品質結晶を成長させるには高温成長AlNを緩衝層に使うと高品質結晶が得られるがAlNとSi接触部の電気抵抗が高いという問題があった。この原因として考えられていたAlNとSiのバンドオフセットを測定し,AlN層の高抵抗化の原因を確かめた。また,薄いAlNを使うことによりSi基板上GaInN LEDで従来7〜10Vであった20mA注入時の動作電圧を4.1Vまで下げることができ,発光特性も改善できた。
    Si基板上GaAs系素子では,初年度にSiO_2マスクの開口部から結晶成長させ,更に横方向成長させることにより240時間というレーザの動作寿命を達成した。
    プラズマ処理による欠陥不活性化を目指した実験を行い,PH_3系プラズマ処理が有効である可能性を確かめた。しかし,素子寿命改善のためには更に研究を進める必要がある。
    Si基板と発光デバイスの接着ではSeS_2を用いる接着法および新たに考案した2段階接着法により,GaAs基板上に成長させたGaAs系受光デバイスをその特性を大きく損ねることなくSi基板に接着し,GaAs基板を分離することができた。発光素子への応用は今後の課題として残った。
    活性領域の微細化により,欠陥を避けてデバイスを作製し素子寿命を延ばそうとする方法では初年度にInGaAsドットを活性領域とするレーザで80時間の動作寿命を得たが,その後大きな改善は得られなかった。
    GaInN系発光素子はSi基板上でも良好な特性を示し,実用化に近いが,Si基板上のGaAs系発光素子の実用化には更に多くの研究が必要である。

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  • シリコン基板上ガリウム砒素・ガリウム窒素の結晶成長と機能デバイスの研究

    研究課題/領域番号:12305021  2000年 - 2002年

    日本学術振興会  科学研究費助成事業 基盤研究(A)  基盤研究(A)

    梅野 正義, 江川 孝志, 井戸 敏之, 脇田 紘一, 石川 博康, 曽我 哲夫, 神保 孝志, 林 靖彦

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    配分額:41090000円 ( 直接経費:35900000円 、 間接経費:5190000円 )

    シリコン(Si)基板上に化合物半導体(GaAsとGaN)をヘテロエピタキシャル成長を行い、その結晶性を評価し、デバイスとしてレーザー、太陽電池、発光ダイオードおよび高移動度トランジスタ(HEMT)を試作した。
    (1)GaAs/Si
    Si上にH_2プラズマやPH_3プラズマの照射することにより、GaAsを成長した場合に、非常に多くの転位欠陥を発生するが、その転位を再結合センターとして働かないようにして、少数キャリアデバイスとしての発光ダイオード、レーザーおよび太陽電池の効率および寿命の大幅な改善を行った。
    (2)GaN/Si
    これまでのGaNのエピタキシャル成長はサファイア基板上に行っていたが、サファイアが絶縁体であるので、多くの欠陥密度の発生を供うと共に静電破戒でデバイスを損うことが多かった。それを大面積で、導電性があり、しかも低コストのSi基板を用いて、その上にGaNのヘテロエピ成長を行い良好な結晶成長を得ることができた。最近では、4インチのSi基板に一様性の良いGaN結成長にも成功した。そして、InGaN/Si LEDを試作し、明るい青色および緑色のLEDが出来、安価で静電破戒も無く明るい実用的なSi基板上LEDが出来た。
    以上の成果は、8件の論文として、国内外の国際的学術誌に発表すると共に、学術誌「応用物理」2003年3月号に招待論文「Si基板上へのGaAs系およびGaN系結晶のヘテロエピタキシーとデバイス応用」として総合研究報告を行った。

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    資金種別:競争的資金

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    資金種別:競争的資金

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担当授業科目

  • ナノテクノロジー工学論 (2020年度) 後期  - その他

  • ナノデバイス・材料物性学演習 (2020年度) 前期

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  • ナノデバイス・材料物性学演習 (2020年度) 通年  - その他

  • ナノ物性特論 (2020年度) 前期  - 木5,木6

  • 技術英語 (2020年度) 後期  - 木3,木4

  • 技術表現法 (2020年度) 3・4学期  - 水3,水4

  • 技術表現法 (2020年度) 3・4学期  - 水3,水4

  • 線形代数B (2020年度) 第1学期  - 木1,木2

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  • 線形代数Ⅱ (2020年度) 第1学期  - 木1,木2

  • 表現技法1 (2020年度) 前期  - その他

  • 表現技法2 (2020年度) 後期  - その他

  • 電子情報システム工学特別研究 (2020年度) 通年  - その他

  • 電子情報システム工学論 (2020年度) 前期  - 金1,金2

  • 電子物性工学 (2020年度) 第2学期  - 火3,火4,金3,金4

  • 電子物性工学Ⅱ (2020年度) 第2学期  - 火3,火4,金3,金4

  • 電気通信系概論 (2020年度) 夏季集中  - その他

  • 電気通信系概論 (2020年度) 夏季集中  - その他

  • Nanostructured Materials (2020年度) 前期

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メディア報道

  • エディター:Journal of Nanotechnology,

    2012年10月

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