研究者詳細 - 林　靖彦

論文 - 林　靖彦

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Ultrafast dynamics of carrier relaxation determining the quasi-1D and non-1D electronic behaviors in carbon nanostructures

Godai Noyama, Thomas Gauthier, Yusuke Arashida, Yui Iwasaki, Riyo Nagao, Yuri Saida, Nicolas Godin, Gaël Privault, Hiroo Suzuki, Yasuhiko Hayashi, Shota Ono, Roman Bertoni, Masaki Hada

Carbon Trends 20 100510 - 100510 2025年8月

Exploring the structural and optical properties in Cs<inf>3</inf>Fe<inf>2</inf>Cl<inf>9</inf> perovskite through ruthenium doping 査読

Thiri Htun, Hytham Elbohy, Hiroo Suzuki, Kazumasa Horigane, Chiyu Nakano, Takeshi Nishikawa, Aung Ko Ko Kyaw, Yasuhiko Hayashi

Journal of Materials Science: Materials in Electronics 36 ( 5 ) 2025年2月

担当区分：最終著者,　責任著者掲載種別：研究論文（学術雑誌）

Lead-free inorganic perovskites, such as Cs3Fe2Cl9, have emerged as promising alternatives to address the challenges of toxicity and instability issues. However, the wide bandgap of Cs3Fe2Cl9 limits its applicability in some applications. In this study, we systematically investigate the influence of ruthenium (Ru) doping on the structural and optical properties of Cs3Fe2Cl9 perovskite with the various doping concentrations (0%, 5%, 20%, 50%, 70% and 100%). Comprehensive characterization was performed through X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), UV–Vis spectroscopy, and scanning electron microscopy (SEM). Structural analysis revealed a phase transition from Cs3Fe2Cl9 (hexagonal structure) at 0% Ru doping to Cs2RuCl6 (cubic structure) at 100% Ru doping. Notably, ruthenium was successfully replaced into the pristine Cs3Fe2Cl9 perovskite due to the similar ionic radii of Fe and Ru. Optical measurements confirmed a significant bandgap reduction from 2.29 eV for pristine Cs3Fe2Cl9 to 1.79 eV at 100% Ru doping, correlating with the formation of single crystals. This tunable bandgap highlights the potential of Ru-doped Cs3Fe2Cl9 for next-generation optoelectronic applications, such as photovoltaics and photodetectors.

DOI： 10.1007/s10854-025-14382-1

Enhanced capacity of aluminum-ion batteries by adjusting the average pore size of the porous carbon cathode 査読

Yifeng Chen, Hiroo Suzuki, Shu Fukumoto, Chiyu Nakano, Takeshi Nishikawa, Shigeyuki Umezawa, Yasuhiko Hayashi

Journal of Materials Chemistry A 13 ( 11 ) 8052 - 8058 2025年2月

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）出版者・発行元：Royal Society of Chemistry (RSC)

Porous carbon materials exhibit unique performance as cathodes for aluminum-ion batteries (AIBs), with capacity primarily influenced by average pore size, while the effect of specific surface area is relatively limited.

DOI： 10.1039/d4ta08671f

Optical bandgap tuning in SnO2–MoS2 nanocomposites: manipulating the mass of SnO2 and MoS2 using sonochemical solution mixing 査読

Chinkhai Ong, Weng Nam Lee, Yee Seng Tan, Patrik Ohberg, Yasuhiko Hayashi, Takeshi Nishikawa, Yuenkiat Yap

Journal of Materials Science: Materials in Electronics 36 ( 1 ) 2024年12月

掲載種別：研究論文（学術雑誌）出版者・発行元：Springer Science and Business Media LLC

Abstract

This study investigates controlled optical bandgap tuning through precise adjustment of the SnO₂ and MoS₂ mass in nanocomposites. A sonochemical solution mixing method, coupled with bath sonication, is employed for the preparation of SnO₂–MoS₂ nanocomposite. This approach allows for comprehensive characterization using UV–Vis FTIR, XRD, EDX, Raman spectroscopies, and FESEM, providing insights into morphology, chemical, and optical properties. Increasing the SnO₂ mass leads to a linear decrease in the optical bandgap energy, from 3.0 to 1.7 eV. Similarly, increasing the MoS₂ mass also results in a decrease in the optical bandgap energy, with a limitation of around 2.01 eV. This work demonstrates superior control over optical bandgap by manipulating the SnO₂ mass compared to MoS₂, highlighting the complexities introduced by MoS₂ 2D nanosheets during sonication. These findings hold significant value for optoelectronic applications, emphasizing enhanced control of optical bandgap through systematic mass manipulation.

DOI： 10.1007/s10854-024-14061-7

その他リンク： https://link.springer.com/article/10.1007/s10854-024-14061-7/fulltext.html

Enhanced piezo-response of mixed-cation copper perovskites with Cl/Br halide engineering 査読

Amr Elattar, Christopher Munoz, Libor Kobera, Andrii Mahun, Jiri Brus, Mohammed Jasim Uddin, Yasuhiko Hayashi, Okenwa Okoli, Tarik Dickens

Materials Advances 5 ( 22 ) 8953 - 8960 2024年10月

Photoinduced dynamics during electronic transfer from narrow to wide bandgap layers in one-dimensional heterostructured materials 査読

Yuri Saida, Thomas Gauthier, Hiroo Suzuki, Satoshi Ohmura, Ryo Shikata, Yui Iwasaki, Godai Noyama, Misaki Kishibuchi, Yuichiro Tanaka, Wataru Yajima, Nicolas Godin, Gaël Privault, Tomoharu Tokunaga, Shota Ono, Shin-ya Koshihara, Kenji Tsuruta, Yasuhiko Hayashi, Roman Bertoni, Masaki Hada

Nature Communications 15 ( 1 ) 2024年5月

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 Science and Business Media LLC

Abstract

Electron transfer is a fundamental energy conversion process widely present in synthetic, industrial, and natural systems. Understanding the electron transfer process is important to exploit the uniqueness of the low-dimensional van der Waals (vdW) heterostructures because interlayer electron transfer produces the function of this class of material. Here, we show the occurrence of an electron transfer process in one-dimensional layer-stacking of carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs). This observation makes use of femtosecond broadband optical spectroscopy, ultrafast time-resolved electron diffraction, and first-principles theoretical calculations. These results reveal that near-ultraviolet photoexcitation induces an electron transfer from the conduction bands of CNT to BNNT layers via electronic decay channels. This physical process subsequently generates radial phonons in the one-dimensional vdW heterostructure material. The gathered insights unveil the fundamentals physics of interfacial interactions in low dimensional vdW heterostructures and their photoinduced dynamics, pushing their limits for photoactive multifunctional applications.

DOI： 10.1038/s41467-024-48880-3

その他リンク： https://www.nature.com/articles/s41467-024-48880-3

Phenolphthalein: A Potent Small-Molecule Additive for High-Performance and Ambient-Air-Stable FAPbI₃ Perovskite Solar Cells 査読

Hytham Elbohy, Hiroo Suzuki, Takeshi Nishikawa, Aung Ko Ko Kyaw, Yasuhiko Hayashi

ACS Applied Energy Materials 2024年3月

N‐DMBI Doping of Carbon Nanotube Yarns for Achieving High n‐Type Thermoelectric Power Factor and Figure of Merit 査読

Hiroo Suzuki, Jun Kametaka, Shinya Nakahori, Yuichiro Tanaka, Mizuki Iwahara, Haolu Lin, Sergei Manzhos, Aung Ko Ko Kyaw, Takeshi Nishikawa, Yasuhiko Hayashi

Small Methods 8 2301387 2024年3月

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：Wiley

Abstract

The application of carbon nanotube (CNT) yarns as thermoelectric materials for harvesting energy from low‐grade waste heat including that generated by the human body, is attracting considerable attention. However, the lack of efficient n‐type CNT yarns hinders their practical implementation in thermoelectric devices. This study reports efficient n‐doping of CNT yarns, employing 4‐(1, 3‐dimethyl‐2, 3‐dihydro‐1H‐benzimidazole‐2‐yl) phenyl) dimethylamine (N‐DMBI) in alternative to conventional n‐dopants, with o‐dichlorobenzene emerging as the optimal solvent. The small molecular size of N‐DMBI enables highly efficient doping within a remarkably short duration (10 s) while ensuring prolonged stability in air and at high temperature (150 °C). Furthermore, Joule annealing of the yarns significantly improves the n‐doping efficiency. Consequently, thermoelectric power factors (PFs) of 2800, 2390, and 1534 µW m⁻¹ K⁻² are achieved at 200, 150, and 30 °C, respectively. The intercalation of N‐DMBI molecules significantly suppresses the thermal conductivity, resulting in the high figure of merit (ZT) of 1.69×10⁻² at 100 °C. Additionally, a π‐type thermoelectric module is successfully demonstrated incorporating both p‐ and n‐doped CNT yarns. This study offers an efficient doping strategy for achieving CNT yarns with high thermoelectric performance, contributing to the realization of lightweight and mechanically flexible CNT‐based thermoelectric devices.

DOI： 10.1002/smtd.202301387

Influence of Dilution Upon the Ultraviolet-Visible Peak Absorbance and Optical Bandgap Estimation of Tin(IV) Oxide and Tin(IV) Oxide-Molybdenum(IV) Sulfide Solutions 査読

Chin Khai Ong, Weng Nam Lee, Mohammad Khalid, Muhammad Amirul Aizat Mohd Abdah, Patrik Ohberg, Ling Hong Lim, Yasuhiko Hayashi, Takeshi Nishikawa, Yuenkiat Yap

Analytical Letters 58 ( 2 ) 196 - 212 2024年2月

Lead-free iron-doped Cs₃Bi₂Br₉ perovskite with tunable properties 査読

Thiri Htun, Amr Elattar, Hytham Elbohy, Kosei Tsutsumi, Kazumasa Horigane, Chiyu Nakano, Xiaoyu Gu, Hiroo Suzuki, Takeshi Nishikawa, Aung Ko Ko Kyaw, Yasuhiko Hayashi

RSC Advances 14 ( 32 ) 23177 - 23183 2024年

担当区分：最終著者,　責任著者掲載種別：研究論文（学術雑誌）出版者・発行元：Royal Society of Chemistry (RSC)

The bandgap of lead-free, non-toxic Cs₃Bi₂Br₉ perovskite material is reduced from 2.54 eV to 1.78 eV by changing the crystal structure to Cs₃Bi₂₋_xFe_xBr₉, Cs₂Bi₁₋_xFe_xBr₅, and CsFeBr₄, depending on the varying Fe doping concentrations.

DOI： 10.1039/d4ra04062g

Benzophenone: A Small Molecule Additive for Enhanced Performance and Stability of Inverted Perovskite Solar Cells. 査読国際誌

Hytham Elbohy, Hiroo Suzuki, Takeshi Nishikawa, Thiri Htun, Kosei Tsutsumi, Chiyu Nakano, Aung Ko Ko Kyaw, Yasuhiko Hayashi

ACS applied materials & interfaces 15 ( 38 ) 45177 - 45189 2023年9月

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）

In this study, we investigated the impact of benzophenone (BP), a small molecule additive, on the performance and stability of inverted perovskite solar cells (PSCs). Specifically, we introduced BP into the perovskite precursor solution of FAPbI3 to fabricate PSCs with an ITO/PEDOT:PSS/BP:FAPbI3/PCBM/C60/PCB/Ag architecture. The incorporation of BP with an optimum concentration of 2 mg mL-1 significantly enhanced the power conversion efficiency (PCE) of the inverted PSC from 13.12 to 18.84% with negligible hysteresis. Notably, the BP-based PSCs retained ∼90% of their initial PCE after being stored in ambient air with 30% relative humidity at 25 °C for 700 h. In contrast, control devices showed rapid degradation, retaining only 30% of their initial value within 300 h under the same conditions. We attributed the superior performance and stability of the BP-based PSCs to the grain boundary passivation of the perovskite film. The improvement was mainly attributed to the intermolecular interaction between the O-donor Lewis base BP material and both Pb2+ and FA+ in FAPbI3. This effectively suppresses trap-assisted recombination and promotes the conversion of the δ-phase to photoactive and stable α-phase FAPbI3. Overall, our findings suggest that BP is a promising additive for improving the performance and stability of inverted PSCs.

DOI： 10.1021/acsami.3c09835

Intermediate State between MoSe₂ and Janus MoSeS during Atomic Substitution Process 査読

Hiroo Suzuki, Yijun Liu, Masaaki Misawa, Chiyu Nakano, Yingzhe Wang, Ryo Nakano, Kentaro Ishimura, Kenji Tsuruta, Yasuhiko Hayashi

Nano Letters 23 ( 10 ) 4533 - 4540 2023年5月

Self-Limiting Growth of Monolayer Tungsten Disulfide Nanoribbons on Tungsten Oxide Nanowires 査読

Hiroo Suzuki, Misaki Kishibuchi, Masaaki Misawa, Kazuma Shimogami, Soya Ochiai, Takahiro Kokura, Yijun Liu, Ryoki Hashimoto, Zheng Liu, Kenji Tsuruta, Yasumitsu Miyata, Yasuhiko Hayashi

ACS Nano 17 ( 10 ) 9455 - 9467 2023年5月

Integration of Wireless Power Transfer Technology With Hierarchical Multiwalled Carbon Nanotubes-Polydimethylsiloxane Piezo-Responsive Pressure Sensor for Remote Force Measurement 査読

Saman Azhari, Kouki Kimizuka, Gábor Méhes, Yuki Usami, Yasuhiko Hayashi, Hirofumi Tanaka, Takeo Miyake

IEEE Sensors Journal 23 ( 7 ) 7902 - 7909 2023年4月

Dispersion stability of tin(IV) oxide nanoparticles in polar solvents and water aided by ultrasonication 査読

Chinkhai Ong, Wengnam Lee, Linghong Lim, Wuyi Chong, Jingwen Chew, Yasuhiko Hayashi, Takeshi Nishikawa, Patrik Öhberg, Harith Ahmad, Yuenkiat Yap

Japanese Journal of Applied Physics 62 ( 3 ) 035002 - 035002 2023年3月

掲載種別：研究論文（学術雑誌）出版者・発行元：IOP Publishing

Abstract

Dispersion stability of tin(IV) oxide nanoparticles dispersed in N-Methy-2-Pyrrolidone (NMP), dimethylformamide (DMF) and distilled water assisted by ultrasonication was investigated, aiming to identify a suitable liquid medium to effectively disperse tin(IV) oxide for many useful applications. The dispersions’ stability was characterized using field emission scanning electron microscopy, ultraviolet–visible spectroscopy and Zeta potential. The results show that distilled water has the highest stability with optimum sonication of 1 h. NMP shows better stability and consistency than DMF at different sonication timings. Good agreement between ultraviolet–visible absorbance and Zeta potentials shows that both distilled water and NMP are good mediums to produce highly stable tin(V) oxide dispersion.

DOI： 10.35848/1347-4065/acc0b5

その他リンク： https://iopscience.iop.org/article/10.35848/1347-4065/acc0b5/pdf

Zinc‐Based Metal–Organic Frameworks for High‐Performance Supercapacitor Electrodes: Mechanism Underlying Pore Generation 査読

Shigeyuki Umezawa, Takashi Douura, Koji Yoshikawa, Daisuke Tanaka, Vlad Stolojan, S. Ravi P. Silva, Mika Yoneda, Kazuma Gotoh, Yasuhiko Hayashi

ENERGY & ENVIRONMENTAL MATERIALS 2023年3月

Tin(IV) Oxide as a Saturable Absorber for Mode-Locking of Fiber Laser 査読

C. Ong, Y. Yap, W. Chong, J. Chew, W. Lee, L. Lim, Y. Hayashi, T. Nishikawa, P. Ohberg, H. Ahmad

Optica Advanced Photonics Congress 2022 2022年12月

Mixed-halide copper-based perovskite R2Cu(Cl/Br)(4) with different organic cations for reversible thermochromism 査読

Amr Elattar, Kosei Tsutsumi, Hiroo Suzuki, Takeshi Nishikawa, Aung Ko Ko Kyaw, Yasuhiko Hayashi

NEW JOURNAL OF CHEMISTRY 46 ( 45 ) 21737 - 21745 2022年11月

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 SOC CHEMISTRY

Two-dimensional (2D) hybrid perovskites have exhibited multiple features owing to their multiple quantum well structure. Here, we show the synthesis and characterization of 2D mixed-halide Cu-based perovskite crystals, R2Cu(Cl/Br)(4), with three different alkyl chains, where R is methyl, butyl, or hexyl ammonium cations. Exfoliated perovskite flakes exhibit reversible thermochromism with changes in color darkness with temperature variation. Differential scanning calorimetry and temperature-dependent X-ray diffraction measurements reveal that the thermochromic behavior mechanism of R2Cu(Cl/Br)(4) depends on the nature of the alkyl chain.

DOI： 10.1039/d2nj04693h

Characteristics of Vertical Ga2O3 Schottky Junctions with the Interfacial Hexagonal Boron Nitride Film 査読

Venkata Krishna Rao Rama, Ajinkya K. Ranade, Pradeep Desai, Bhagyashri Todankar, Golap Kalita, Hiroo Suzuki, Masaki Tanemura, Yasuhiko Hayashi

ACS Omega 7 ( 30 ) 26021 - 26028 2022年8月

Copper-incorporation for polytypism and bandgap engineering of MAPbBr3 perovskite thin films with enhanced near-Infrared photocurrent-response 査読

Amr Elattar, Jiban Kangsabanik, Kodai Nakao, Kosei Tsutsumi, Hiroo Suzuki, Takeshi Nishikawa, Kristian S. Thygesen, Yasuhiko Hayashi

Materials Chemistry Frontiers 6 ( 18 ) 2690 - 2702 2022年8月

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})

Formation of secondary phase polytypes through incorporation of copper into MAPbBr₃ perovskite yields bandgap reduction with generation of near-IR photocarriers.

DOI： 10.1039/D2QM00491G

Structure modulation for bandgap engineered vacancy-ordered Cs3Bi2Br9 perovskite structures through copper alloying 査読

Amr Elattar, Libor Kobera, Jiban Kangsabanik, Hiroo Suzuki, Sabina Abbrent, Takeshi Nishikawa, Kristian S. Thygesen, Jiri Brus, Yasuhiko Hayashi

Journal of Materials Chemistry C 10 ( 35 ) 12863 - 12872 2022年8月

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)

Light absorption enhancement was achieved through structure modulation of the Cs₃Bi₂Br₉ perovskite crystal via Cu-alloying. The Cs₃Bi₂Br₉ perovskite retains its matrix structure with homogeneously distributed Cs₂CuBr₄ large domains.

DOI： 10.1039/D2TC01762H

Surface Diffusion-Limited Growth of Large and High-Quality Monolayer Transition Metal Dichalcogenides in Confined Space of Microreactor. 査読国際誌

Hiroo Suzuki, Ryoki Hashimoto, Masaaki Misawa, Yijun Liu, Misaki Kishibuchi, Kentaro Ishimura, Kenji Tsuruta, Yasumitsu Miyata, Yasuhiko Hayashi

ACS nano 2022年7月

記述言語：英語掲載種別：研究論文（学術雑誌）

Transition metal dichalcogenides (TMDCs), including MoS2 and WS2, are potential candidates for next-generation semiconducting materials owing to their atomically thin structure and strong optoelectrical responses, which allow for flexible optoelectronic applications. Monolayer TMDCs have been grown utilizing chemical vapor deposition (CVD) techniques. Enhancing the domain size with high crystallinity and forming heterostructures are important topics for practical applications. In this study, the size of monolayer WS2 increased via the vapor-liquid-solid growth-based CVD technique utilizing the confined space of the substrate-stacked microreactor. The use of spin-coated metal salts (Na2WO4 and Na2MoO4) and organosulfur vapor allowed us to precisely control the source supply and investigate the growth in a systematic manner. We obtained a relatively low activation energy for growth (1.02 eV), which is consistent with the surface diffusion-limited growth regime observed in the confined space. Through systematic photoluminescence (PL) analysis, we determined that a growth temperature of ∼820 °C is optimal for producing high-quality WS2 with a narrow PL peak width (∼35 meV). By controlling the source balance of W and S, we obtained large-sized fully monolayered WS2 (∼560 μm) and monolayer WS2 with bilayer spots (∼1100 μm). Combining two distinct sources of transition metals, WS2/MoS2 lateral heterostructures were successfully created. In electrical transport measurements, the monolayer WS2 grown under optimal conditions has a high on-current (∼70 μA/μm), on/off ratio (∼5 × 108), and a field-effect mobility of ∼7 cm2/(V s). The field-effect transistor displayed an intrinsic photoresponse with wavelength selectivity that originated from the photoexcited carriers.

DOI： 10.1021/acsnano.2c05076

Enhancement of the mechanical and thermal transport properties of carbon nanotube yarns by boundary structure modulation 査読

Ryo Shikata, Hiroo Suzuki, Yuta Hayashi, Taisuke Hasegawa, Yuho Shigeeda, Hirotaka Inoue, Wataru Yajima, Jun Kametaka, Mitsuaki Maetani, Yuichiro Tanaka, Takeshi Nishikawa, Satoshi Maeda, Yasuhiko Hayashi, Masaki Hada

NANOTECHNOLOGY 33 ( 23 ) 2022年6月

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

Carbon nanotubes (CNTs) exhibit extremely high nanoscopic thermal/electrical transport and mechanical properties. However, the macroscopic properties of assembled CNTs are significantly lower than those of CNTs because of the boundary structure between the CNTs. Therefore, it is crucial to understand the relationship between the nanoscopic boundary structure in CNTs and the macroscopic properties of the assembled CNTs. Previous studies have shown that the nanoscopic phonon transport and macroscopic thermal transport in CNTs are improved by Joule annealing because of the improved boundary Van-der-Waals interactions between CNTs via the graphitization of amorphous carbon. In this study, we investigate the mechanical strength and thermal/electrical transport properties of CNT yarns with and without Joule annealing at various temperatures, analyzing the phenomena occurring at the boundaries of CNTs. The obtained experimental and theoretical results connect the nanoscopic boundary interaction of CNTs in CNT yarns and the macroscopic mechanical and transport properties of CNT yarns.

DOI： 10.1088/1361-6528/ac57d5

Generation of sub-100 fs electron pulses for time-resolved electron diffraction using a direct synchronization method 査読

Kou Takubo, Samiran Banu, Sichen Jin, Misaki Kaneko, Wataru Yajima, Makoto Kuwahara, Yasuhiko Hayashi, Tadahiko Ishikawa, Yoichi Okimoto, Masaki Hada, Shinya Koshihara

Review of Scientific Instruments 93 ( 5 ) 053005 - 053005 2022年5月

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

To investigate photoinduced phenomena in various materials and molecules, ultrashort pulsed x-ray and electron sources with high brightness and high repetition rates are required. The x-ray and electron’s typical and de Broglie wavelengths are shorter than lattice constants of materials and molecules. Therefore, photoinduced structural dynamics on the femtosecond to picosecond timescales can be directly observed in a diffraction manner by using these pulses. This research created a tabletop ultrashort pulsed electron diffraction setup that used a femtosecond laser and electron pulse compression cavity that was directly synchronized to the microwave master oscillator (∼3 GHz). A compressed electron pulse with a 1 kHz repetition rate contained 228 000 electrons. The electron pulse duration was estimated to be less than 100 fs at the sample position by using photoinduced immediate lattice changes in an ultrathin silicon film (50 nm). The newly developed time-resolved electron diffraction setup has a pulse duration that is comparable to femtosecond laser pulse widths (35–100 fs). The pulse duration, in particular, fits within the timescale of photoinduced phenomena in quantum materials. Our developed ultrafast time-resolved electron diffraction setup with a sub-100 fs temporal resolution would be a powerful tool in material science with a combination of optical pump–probe, time-resolved photoemission spectroscopic, and pulsed x-ray measurements.

DOI： 10.1063/5.0086008

Single Crystals of Mixed-Cation Copper-Based Perovskite with Trimodal Bandgap Behavior 査読

Amr Elattar, Wenhui Li, Hiroo Suzuki, Takashi Kambe, Takeshi Nishikawa, Aung Ko Ko Kyaw, Yasuhiko Hayashi

CHEMISTRY-A EUROPEAN JOURNAL 28 ( 26 ) 2022年5月

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：WILEY-V C H VERLAG GMBH

Two-dimensional (2D) hybrid perovskites with novel functionalities and structural diversity are a perfect platform for emerging optoelectronic devices such as photodetectors, light-emitting diodes, and solar cells. Here, we demonstrate that excess concentration of Cesium bromide (CsBr) is key to the formation of easily exfoliated 2D Cs2Cu(Cl/Br)(4) perovskite crystal. Furthermore, by employing this trick to 2D perovskite MA(2)Cu(Cl/Br)(4) (MA=methylammonium), we achieve a phase-pure easily exfoliated 2D mixed-cation (MA/Cs)(2)Cu(Cl/Br)(4) perovskite crystal, which exhibits reduced bandgap (1.53 eV) with ferromagnetic behavior and photovoltaic property. The resultant mixed-cation structured device reveals enhanced efficiency compared to all MA and all Cs counterparts. These findings demonstrate the importance of cation-engineering in developing innovative materials with novel properties.

DOI： 10.1002/chem.202104316

Highly Oriented Carbon Nanotube Supercapacitors 査読

Kohei Komatsubara, Hiroo Suzuki, Hirotaka Inoue, Misaki Kishibuchi, Shona Takahashi, Tatsuki Marui, Shigeyuki Umezawa, Tomohiro Nakagawa, Kyohei Nasu, Mitsuaki Maetani, Yuichiro Tanaka, Miyato Yamada, Takeshi Nishikawa, Yoshifumi Yamashita, Masaki Hada, Yasuhiko Hayashi

ACS Applied Nano Materials 2022年1月

Temperature-dependent device properties of γ-CuI and β-Ga2O3 heterojunctions 査読

Rama Venkata Krishna Rao, Ajinkya K. Ranade, Pradeep Desai, Golap Kalita, Hiroo Suzuki, Yasuhiko Hayashi

SN Applied Sciences 3 ( 10 ) 2021年10月

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 Science and Business Media LLC

<sec>
<title>Abstract</title>
Temperature-dependent studies of Ga₂O₃-based heterojunction devices are important in understanding its carrier transport mechanism, junction barrier potential, and stability at higher temperatures. In this study, we investigated the temperature-dependent device characteristics of the p-type γ-copper iodide (γ-CuI)/n-type β-gallium oxide (β‐Ga₂O₃) heterojunctions, thereby revealing their interface properties. The fabricated γ-CuI/β-Ga₂O₃ heterojunction showed excellent diode characteristics with a high rectification ratio and low reverse saturation current at 298 K in the presence of a large barrier height (0.632 eV). The temperature-dependent device characteristics were studied in the temperature range 273–473 K to investigate the heterojunction interface. With an increase in temperature, a gradual decrease in the ideality factor and an increase in the barrier height were observed, indicating barrier inhomogeneity at the heterojunction interface. Furthermore, the current–voltage measurement showed electrical hysteresis for the reverse saturation current, although it was not observed for the forward bias current. The presence of electrical hysteresis for the reverse saturation current and of the barrier inhomogeneity in the temperature-dependent characteristics indicates the presence of some level of interface states for the γ-CuI/β‐Ga₂O₃ heterojunction device. Thus, our study showed that the electrical hysteresis can be correlated with temperature-dependent electrical characteristics of the β‐Ga₂O₃-based heterojunction device, which signifies the presence of surface defects and interface states.

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<title>Article Highlights</title>
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We revealed the interface properties of p-type γ-copper iodide (γ-CuI) and n-type β-gallium oxide (β-Ga₂O₃) heterojunction.

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The developed heterostructure showed a large barrier height (0.632 eV) at the interface, which is stable at a temperature as high as 473 K.

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We confirmed the current transport mechanism at the interface of the heterojunction by analyzing the temperature dependent current–voltage characterization.

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DOI： 10.1007/s42452-021-04774-3

その他リンク： https://link.springer.com/article/10.1007/s42452-021-04774-3/fulltext.html

Supercapacitor electrode with high charge density based on boron-doped porous carbon derived from covalent organic frameworks 査読

Shigeyuki Umezawa, Takashi Douura, Koji Yoshikawa, Yohei Takashima, Mika Yoneda, Kazuma Gotoh, Vlad Stolojan, S. Ravi P. Silva, Yasuhiko Hayashi, Daisuke Tanaka

Carbon 184 418 - 425 2021年10月

Challenges for developing photo-induced phase transition (PIPT) systems: From classical (incoherent) to quantum (coherent) control of PIPT dynamics 招待査読

Shinya Koshihara, Tadahiko Ishikawa, Yoichi Okimoto, Ken Onda, Ryo Fukaya, Masaki Hada, Yasuhiko Hayashi, Sumio Ishihara, Tadeusz Luty

Physics Reports 2021年10月

Photoinduced oxygen transport in cobalt double-perovskite crystal EuBaCo2O5.39 査読

Masaki Hada, Satoshi Ohmura, Tadahiko Ishikawa, Masaki Saigo, Naoya Keio, Wataru Yajima, Tatsuya Suzuki, Daisuke Urushihara, Kou Takubo, Yusuke Masaki, Makoto Kuwahara, Kenji Tsuruta, Yasuhiko Hayashi, Jiro Matsuo, Takayoshi Yokoya, Ken Onda, Fuyuki Shimojo, Muneaki Hase, Sumio Ishihara, Toru Asaka, Nobuyuki Abe, Taka-hisa Arima, Shin-ya Koshihara, Yoichi Okimoto

Applied Materials Today 24 101167 - 101167 2021年9月

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

Understanding and controlling atomic motions in solid are essential in ionic materials, such as ion con-ductors, electrolyte and electrodes of batteries, and gas separators. Although photoinduced proton trans-port in solid materials has been demonstrated, photoinduced transport of heavier ions, such as the oxide ion, in solid materials remains entirely elusive. Herein, we apply ultrafast time-resolved electron diffrac-tion to observe the large displacement of oxide ions in a strongly correlated material, EuBaCo2O5.39, under near-ultraviolet photoexcitation at room temperature. The mechanism of the photoinduced transport of oxide ions is revealed via the combination of ultrafast optical spectroscopy and density functional theory calculations. Our findings show that photoexcitation induces ionic motions in a ceramic crystal at room temperature through the charge transfer that strongly couples with large ionic displacement under the nonequilibrium condition. (C) 2021 The Authors. Published by Elsevier Ltd.

DOI： 10.1016/j.apmt.2021.101167

Memristive Behavior in One-Dimensional Hexagonal Boron Nitride/Carbon Nanotube Heterostructure Assemblies 査読

Hiroo Suzuki, Misaki Kishibuchi, Kazuma Shimogami, Mitsuaki Maetani, Kyohei Nasu, Tomohiro Nakagawa, Yuichiro Tanaka, Hirotaka Inoue, Yasuhiko Hayashi

ACS Applied Electronic Materials 3 ( 8 ) 3555 - 3566 2021年8月

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 Electronics 90 106056 - 106056 2021年3月

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

© 2021 Elsevier B.V. High room-temperature thermoelectric performance is important for low-grade waste heat power generation as there are plenty of heat thrown away uselessly in our daily life, most of which are below 100 °C. However, most of the thermoelectric materials are limited to high temperature application. In this work, room-temperature thermoelectric power factor of carbon nanotube (CNT) yarn is improved by controlled doping, which is achieved by making composite with poly 3-hexylthiophene −2, 5-diyl (P3HT) followed by doping with 2, 3, 5, 6-tetrafluo-7, 7, 8, 8-tetracyanoquinodimethane (F4TCNQ). The temperature-dependent Seebeck coefficient based on power–law model suggests that P3HT shifts the Fermi energy of CNT yarn towards the valence band edge, and reduces the ionic scattering and carrier relaxation time. As a result, the Seebeck coefficient is increased while the variation of Seebeck coefficient with temperature is reduced, and hence, the room-temperature thermoelectric power factor is improved. With controlled doping, the power factor of CNT yarn/P3HT composite reaches to 1640–2160 μW m−1K−2 at the temperature range of 25–100 °C, which is higher than that of CNT yarn alone.

DOI： 10.1016/j.orgel.2020.106056

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 C 9 ( 9 ) 3264 - 3270 2021年2月

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

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

Carbon 171 437 - 443 2021年1月

掲載種別：研究論文（学術雑誌）出版者・発行元：Elsevier BV

© 2020 Elsevier Ltd The high-strengthening mechanism of carbon nanotube (CNT) yarns subjected to Joule heating was investigated by nanostructural characterization. CNT yarns produced at two drawing speeds (40 and 120 mm/min) with a spindle rotation of 1000 min−1 were used. The mechanical properties of the CNT yarns were improved by Joule heating under a vacuum of 10−6 Pa. The mean tensile strength and Young's modulus of both yarns heated at 2273 K were approximately 1.1–1.4 GPa and 44–50 GPa, respectively; these values are approximately more than two times those of the as-spun samples. The high-strengthening of the Joule-heated CNT yarns is attributed to the synergistic effect of structural changes such as improvement in the crystallinity of the CNTs, formation of the bundle structure of individual CNTs possessing a polygonal structure, and entwining of these bundles. Meanwhile, the samples in which the high-strengthening mechanism by Joule heating did not initiate, were included in the CNT yarns produced at a drawing speed of 40 mm/min. Cross-sectional observation of the lower-strength CNT yarns revealed the presence of numerous voids in the outer portion of the yarn. The structural defects formed during the spinning of the CNT yarn strongly affected the tensile strength of the yarn.

DOI： 10.1016/j.carbon.2020.09.014

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 Letters 117 ( 25 ) 253304 - 253304 2020年12月

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

Carbon 170 165 - 173 2020年12月

掲載種別：研究論文（学術雑誌）出版者・発行元：Elsevier BV

© 2020 Elsevier Ltd Modern integrated devices and electrical circuits have often been designed with carbon nanostructures, such as carbon nanotubes (CNTs) and graphene due to their high thermal and electrical transport properties. These transport properties are strongly correlated to their acoustic phonon and carrier dynamics. Thus, understanding the phonon and carrier dynamics of carbon nanostructures in extremely small regions will lead to their further practical applications. Here, we demonstrate ultrafast time-resolved electron diffraction and ultrafast transient spectroscopy to characterize the phonon and carrier dynamics at the boundary of quasi-one-dimensional CNTs before and after Joule annealing. The results from ultrafast time-resolved electron diffraction show that the CNTs after Joule annealing reach the phonon equilibrium state extremely fast with a timescale of 10 ps, which indicates that thermal transport in CNTs improves following Joule annealing. The methodology described in this study connects conventional macroscopic thermo- and electrodynamics to those at the nanometer scale. Realistic timescale kinetic simulations were performed to further elaborate on the phenomena that occur in CNTs during Joule annealing. The insights obtained in this study are expected to pave the way to parameterize the unexplored thermal and electrical properties of carbon materials at the nanometer scale.

DOI： 10.1016/j.carbon.2020.08.026

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 Letters 117 ( 10 ) 101103 - 101103 2020年9月

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 Express 7 ( 5 ) 056402 2020年5月

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 reports 10 ( 1 ) 7307 - 7307 2020年4月

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

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 Reports 10 6486 2020年4月

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

Molecules 25 ( 5 ) 1144 - 1144 2020年3月

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

CARBON 158 662 - 671 2020年3月

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

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 Physics 152 ( 8 ) 084704 - 084704 2020年2月

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 RESEARCH 61 42 - 50 2020年

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

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 Technology 76 ( 2 ) 72 - 78 2020年

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

Synthesis and characterization of conductive flexible cellulose carbon nanohorn sheets for human tissue applications. 国際誌

Karthik Paneer Selvam, Taichi Nagahata, Kosuke Kato, Mayuko Koreishi, Toshiyuki Nakamura, Yoshimasa Nakamura, Takeshi Nishikawa, Ayano Satoh, Yasuhiko Hayashi

Biomaterials research 24 18 - 18 2020年

記述言語：英語掲載種別：研究論文（学術雑誌）

Background: Conductive sheets of cellulose and carbon nanomaterials and its human skin applications are an interesting research aspect as they have potential for applications for skin compatibility. Hence it is needed to explore the effects and shed light on these applications. Method: To fabricate wearable, portable, flexible, lightweight, inexpensive, and biocompatible composite materials, carbon nanohorns (CNHs) and hydroxyethylcellulose (HEC) were used as precursors to prepare CNH-HEC (Cnh-cel) composite sheets. Cnh-cel sheets were prepared with different loading concentrations of CNHs (10, 20 50,100 mg) in 200 mg cellulose. To fabricate the bio-compatible sheets, a pristine composite of CNHs and HEC was prepared without any pretreatment of the materials. Results: The obtained sheets possess a conductivity of 1.83 × 10- 10 S/m and bio-compatible with human skin. Analysis for skin-compatibility was performed for Cnh-cel sheets by h-CLAT in vitro skin sensitization tests to evaluate the activation of THP-1 cells. It was found that THP-1 cells were not activated by Cnh-cel; hence Cnh-cel is a safe biomaterial for human skin. It was also found that the composite allowed only a maximum loading of 100 mg to retain the consistent geometry of free-standing sheets of < 100 μm thickness. Since CNHs have a unique arrangement of aggregates (dahlia structure), the composite is homogeneous, as verified by transmission electron microscopy (TEM) and, scanning electron microscopy (SEM), and other functional properties investigated by Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), conductivity measurement, tensile strength measurement, and skin sensitization. Conclusion: It can be concluded that cellulose and CNHs sheets are conductive and compatible to human skin applications.

DOI： 10.1186/s40824-020-00194-3

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 MATERIALS 2 ( 10 ) 7700 - 7708 2019年10月

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

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 NANO 13 ( 9 ) 10103 - 10112 2019年9月

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

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 communications 10 4159 2019年9月

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 ELECTRONICS 30 ( 14 ) 13534 - 13542 2019年7月

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

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

CARBON 146 785 - 788 2019年5月

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

Transistor Application and Intercalation Chemistry of π-Conjugated Hydrocarbon Molecules

Yoshihiro Kubozono, Shino Hamao, Takahiro Mikami, Yuma Shimo, Yasuhiko Hayashi, Hideki Okamoto

Physics and Chemistry of Carbon-Based Materials 229 - 252 2019年

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 A 122 ( 49 ) 9579 - 9584 2018年11月

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 ADVANCES 8 ( 7 ) 2018年7月

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

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

CARBON 133 232 - 238 2018年7月

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

Performance limit of daytime radiative cooling in warm humid environment 査読

Takahiro Suichi, Atsushi Ishikawa, Yasuhiko Hayashi, Kenji Tsuruta

AIP Advances 8 ( 5 ) 2018年5月

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

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 PHYSICS 123 ( 16 ) 2018年4月

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

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 Physics 57 ( 2 ) 028001-1 - 028001-3 2018年2月

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

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 Experiments 135 ( 135 ) e57612-1 - e57612-13 2018年

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 publisher 2 2018年

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 ADVANCES 8 ( 64 ) 36563 - 36570 2018年

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.

DOI： 10.1039/c8ra06094k

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 SOCIETY 139 ( 44 ) 15792 - 15800 2017年11月

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

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 Society 139 15792 - 15800 2017年10月

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 DYNAMICS 4 ( 5 ) 054308-1 - 054308-13 2017年9月

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

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

CARBON 120 358 - 365 2017年8月

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

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

NANOMATERIALS 7 ( 6 ) 2017年6月

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

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

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

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

SCIENTIFIC REPORTS 7 2017年6月

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

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 ELECTRONICS 28 ( 8 ) 6217 - 6225 2017年4月

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

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 ANALYSIS 49 ( 4 ) 291 - 296 2017年4月

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

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 PHYSICS 56 ( 1 ) 2017年1月

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

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 2017 10343 2017年

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

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

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 Engineering 10369 2017年

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.

DOI： 10.1117/12.2273640

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

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.

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 Forum 900 46 - 49 2017年

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

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

Surface modification of carbon nanohorns by helium plasma and ozone treatments 査読国際誌

Yasuhiko HAYASHI

2016年12月

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 toxicology 13 ( 1 ) 54 - 54 2016年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

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

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

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 Japan 41 ( 3 ) 229 - 233 2016年9月

記述言語：英語出版者・発行元：一般社団法人日本MRS

<p>We synthesized carbon nanowalls on a Si substrate by microwave surface-wave plasma chemical vapor deposition. The Raman scattering I_D/I_G ratio was changed by altering the DC bias applied to the growth substrate and the decrease in I_D/I_G with increasing DC bias appears to arise from the growing length of the carbon nanowalls. The ultrasonically separated carbon nanowalls in ethanol exhibited strong 2D-peak intensity and significant graphitization. A graphite layer of approximately 10 nm grew parallel to the substrate initially, and the carbon nanowalls grew on top of that. When the nanowalls were dispersed in ethanol and spin-coated onto PET, they exhibited a transmittance of 81% and a sheet resistance of 52 kΩ/□ without reduction treatment used in the graphene oxide.</p>

DOI： 10.14723/tmrsj.41.229

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

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

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

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 MATERIALS 66 157 - 162 2016年6月

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

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

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 REPORTS 6 2016年2月

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

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

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 2016 9918 2016年

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

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

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

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

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

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

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

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

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 Materials 136 ( 4 ) 180 - 185 2016年

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

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

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

MICRON 74 30 - 34 2015年7月

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

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

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 SCIENCES 16 ( 1 ) 660 - 676 2015年1月

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

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

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

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

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

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 C 3 ( 28 ) 7370 - 7378 2015年

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, <mu >, 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 <mu > and average values of absolute threshold voltage, <vertical bar V-th vertical bar >, 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

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

21aCJ-9 電子線照射により拡大した積層欠陥の縮小に伴う4H-SiCエピ膜中部分転位の運動

山下善文, 下村拓也, 西川亘, 林靖彦

日本物理学会講演概要集 70 2683 - 2683 2015年

マイクロ波表面波プラズマCVD法によるグラフェンの合成

市村進, 林靖彦, 梅野正義

表面科学学術講演会要旨集 35 272 - 272 2015年

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 A 1 ( 47 ) 15135 - 15141 2013年12月

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

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

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 LETTERS 7 ( 12 ) 1080 - 1083 2013年12月

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)

DOI： 10.1002/pssr.201308169

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

Photovoltaic properties of an amorphous carbon/fullerene junction 査読

Tetsuo Soga, Takuya Kondoh, Naoki Kishi, Yasuhiko Hayashi

CARBON 60 1 - 4 2013年8月

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.

DOI： 10.1016/j.carbon.2013.02.050

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

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 IONICS 241 53 - 61 2013年6月

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.

DOI： 10.1016/j.ssi.2013.03.032

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

Phthalocyanine with Trifluoroethoxy Substituents for Organic Solar Cells 査読

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

JAPANESE JOURNAL OF APPLIED PHYSICS 52 ( 5 ) 2013年5月

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

DOI： 10.7567/JJAP.52.05DA07

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

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

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

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

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

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

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

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 PHYSICS 15 ( 4 ) 1271 - 1274 2013年

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

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

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 Letters 93 258 - 262 2013年

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

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

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

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

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 EXPRESS 2 ( 4 ) 357 - 362 2012年12月

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

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

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 SCIENCE 209 ( 12 ) 2510 - 2513 2012年12月

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 (<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

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

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 SCIENCE 386 ( 1 ) 80 - 87 2012年11月

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

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

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 NANO 6 ( 11 ) 9567 - 9573 2012年11月

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

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

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 LETTERS 7 1 - 4 2012年8月

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

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

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 LETTERS 6 ( 7 ) 303 - 305 2012年7月

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

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

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 PHYSICS 249 ( 6 ) 1254 - 1257 2012年6月

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

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

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 Letters 3 206 - 207 2012年5月

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 PHYSICS 51 ( 4 ) 2012年4月

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

DOI： 10.1143/JJAP.51.04DK09

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

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 MATERIALS 24 158 - 160 2012年4月

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

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

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 LETTERS 6 ( 4 ) 184 - 186 2012年4月

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)

DOI： 10.1002/pssr.201206037

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

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 letters 7 ( 1 ) 85 - 85 2012年1月

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.

DOI： 10.1186/1556-276X-7-85

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

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 PHYSICS 51 ( 1 ) 2012年1月

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

DOI： 10.1143/JJAP.51.01AB05

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

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 JOURNAL 179 388 - 393 2012年1月

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.

DOI： 10.1016/j.cej.2011.10.087

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

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

NANOSCALE 4 ( 24 ) 7791 - 7796 2012年

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.

DOI： 10.1039/c2nr31723k

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

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 CHARACTERIZATION 364 272 - + 2012年

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

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

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

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

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

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 NANOTECHNOLOGY 11 ( 12 ) 11011 - 11014 2011年12月

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

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

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

NANO 6 ( 6 ) 583 - 588 2011年12月

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

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

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 NANOTECHNOLOGY 11 ( 12 ) 10677 - 10681 2011年12月

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

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

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 SCIENCES 24 ( 6 ) 593 - 601 2011年12月

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

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

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

CARBON 49 ( 13 ) 4191 - 4196 2011年11月

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

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

Fabrication of Ge nanoneedles by ion-irradiation method 査読

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

SURFACE & COATINGS TECHNOLOGY 206 ( 5 ) 812 - 815 2011年11月

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

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

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 SCIENCE 208 ( 10 ) 2332 - 2334 2011年10月

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

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

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 Physics 50 ( 8 ) 08LB14 2011年8月

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

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 PHYSICS 50 ( 8 ) 2011年8月

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

DOI： 10.1143/JJAP.50.08LB14

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

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 B 29 ( 4 ) 2011年7月

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]

DOI： 10.1116/1.3591420

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

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 MATERIALS 20 ( 7 ) 859 - 862 2011年7月

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'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

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

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 TECHNOLOGY 78 ( 2 ) 208 - 213 2011年4月

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.

DOI： 10.1016/j.seppur.2011.02.003

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

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 JOURNAL 43 ( 3 ) 272 - 278 2011年3月

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

DOI： 10.1038/pj.2010.135

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

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 SCIENCE 257 ( 8 ) 3168 - 3173 2011年2月

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.

DOI： 10.1016/j.apsusc.2010.10.134

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

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 MATERIALS 20 ( 2 ) 210 - 212 2011年2月

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.

DOI： 10.1016/j.diamond.2010.12.005

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

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 PHYSICS 50 ( 1 ) 2011年1月

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

DOI： 10.1143/JJAP.50.01AF10

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

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

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

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

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 COMMUNICATIONS 47 ( 17 ) 4980 - 4982 2011年

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

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

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 COMMUNICATIONS 47 ( 16 ) 4820 - 4822 2011年

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

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

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

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

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

Simple methods for tuning the pore diameter of mesoporous carbon 査読

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

CHEMICAL COMMUNICATIONS 47 ( 38 ) 10758 - 10760 2011年

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.

DOI： 10.1039/c1cc13471j

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

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 ELECTRONICS 14 192 - 197 2011年

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

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

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

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

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

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 SCIENCES 11 ( 12 ) 5028 - 5040 2010年12月

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.

DOI： 10.3390/ijms11125027

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 Japan 35 ( 4 ) 755 - 758 2010年12月

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

The Fe-incorporated carbon nanofibers (Fe-CNFs) grew on the graphite plate surface irradiated by Ar⁺ ions with a simultaneous Fe supply. The average diameter and length of the Fe-CNFs were in the range of 10-50 nm and 0.5-3 μm, respectively. As confirmed by TEM observation, the Fe-CNFs thus grown were characterized by amorphous-like or very fine crystalline nature. Compared with bulk Fe, they possessed higher coercivities for both parallel and perpendicular directions to the substrate at room temperature. In addition, magnetic properties of the Fe-CNFs strongly depended on the Fe content: The higher the Fe content, the stronger the saturation magnetization, whereas perpendicular coercivity was obtained for lower Fe supply rates.

DOI： 10.14723/tmrsj.35.755

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 NANOTECHNOLOGY 10 ( 10 ) 6677 - 6682 2010年10月

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.

DOI： 10.1166/jnn.2010.2508

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

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

NANOTECHNOLOGY 21 ( 43 ) 2010年10月

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.

DOI： 10.1088/0957-4484/21/43/435702

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

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 MATTER 405 ( 18 ) 3952 - 3954 2010年9月

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

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

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 Science 8 2010年8月

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 PHYSICS 49 ( 8 ) 2010年8月

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

DOI： 10.1143/JJAP.49.08LB15

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 SCIENCE 256 ( 21 ) 6371 - 6374 2010年8月

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.

DOI： 10.1016/j.apsusc.2010.04.019

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

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

NANO 5 ( 4 ) 195 - 202 2010年8月

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.

DOI： 10.1142/S1793292010002104

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

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 GROWTH 312 ( 12-13 ) 1935 - 1939 2010年6月

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.

DOI： 10.1016/j.jcrysgro.2010.03.023

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

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

Rakesh A. Afre, Yasuhiko Hayashi, Tetsuo Soga

SYNTHETIC METALS 160 ( 7-8 ) 779 - 782 2010年4月

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.

DOI： 10.1016/j.synthmet.2010.01.020

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

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 SOCIETY 132 ( 12 ) 4034 - + 2010年3月

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.

DOI： 10.1021/ja909346e

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

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 B 28 ( 2 ) C2C9 - C2C12 2010年3月

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.

DOI： 10.1116/1.3318694

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

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

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.

DOI： 10.1109/INEC.2010.5424518

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

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

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

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

Formation and characterization of C<inf>60</inf>- 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

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

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

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

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

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

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

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

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

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

Hayashi, Y., Okuyama, F.

German medical science : GMS e-journal 8 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

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

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

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

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

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

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 SCIENCE 256 ( 5 ) 1481 - 1485 2009年12月

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

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

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 ELECTRONICS E92C ( 12 ) 1417 - 1420 2009年12月

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

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

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 ELECTRONICS E92C ( 12 ) 1449 - 1453 2009年12月

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

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

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 SCIENCES 64 ( 11 ) 765 - 768 2009年11月

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.

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

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 LETTERS 481 ( 1-3 ) 68 - 72 2009年10月

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 >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

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

Ferromagnetism in Cu-doped AlN films 査読

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

APPLIED PHYSICS LETTERS 95 ( 11 ) 2009年9月

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]

DOI： 10.1063/1.3232238

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

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 GROWTH 311 ( 17 ) 4270 - 4274 2009年8月

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

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

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 MAGNETICS 45 ( 6 ) 2488 - 2491 2009年6月

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

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

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 PHYSICS 246 ( 6 ) 1243 - 1247 2009年6月

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.

DOI： 10.1002/pssb.200945091

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

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 House 3 ( 15 ) 195 - 202 2009年6月

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 CHEMISTRY 130 ( 3 ) 361 - 364 2009年3月

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.

DOI： 10.1016/j.jfluchem.2008.11.005

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

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 B 27 ( 2 ) 980 - 983 2009年3月

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]

DOI： 10.1116/1.3010730

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

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 CHEMISTRY 5 2009年2月

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.

DOI： 10.3762/bjoc.5.7

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

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 MATERIALS 18 ( 2-3 ) 341 - 344 2009年2月

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

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

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 PHYSICS 42 ( 4 ) 2009年2月

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

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

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 NANOTECHNOLOGY 6 ( 7-8 ) 753 - 761 2009年

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

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

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 COMMUNICATIONS 15 ( 4 ) 263 - 272 2009年

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

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

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 Proceedings 1173 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

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 RESEARCH 9 ( 6 ) 549 - 552 2008年12月

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.

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

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 DEVICES 55 ( 11 ) 2988 - 3000 2008年11月

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

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

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 GROWTH 310 ( 23 ) 4900 - 4903 2008年11月

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

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

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 LETTERS 93 ( 5 ) 2008年8月

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

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

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 MATERIALS 17 ( 7-10 ) 1525 - 1528 2008年7月

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

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

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 SOLIDS 69 ( 5-6 ) 1276 - 1279 2008年5月

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

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

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 Japan 33 ( 4 ) 1023 - 1026 2008年4月

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 MATERIALS 17 ( 4-5 ) 525 - 528 2008年4月

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

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

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 MATERIALS 17 ( 4-5 ) 581 - 584 2008年4月

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

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

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 Japan 33 ( 4 ) 1015 - 1018 2008年4月

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 ASPECTS 313 422 - 425 2008年2月

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

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

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 MATERIALS 20 ( 1 ) 189 - + 2008年1月

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.

DOI： 10.1002/adma.200700399

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

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 TECHNOLOGY 100 ( 1 ) 2008年

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

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

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

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

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

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

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

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

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 PHYSICS 102 ( 8 ) 2007年10月

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.

DOI： 10.1063/1.2799049

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

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 MATERIALS 8 ( 6 ) 443 - 447 2007年9月

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

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

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 LETTERS 91 ( 11 ) 2007年9月

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.

DOI： 10.1063/1.2785120

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

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 MATERIALIA 57 ( 3 ) 281 - 284 2007年8月

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

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

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 SCIENCE 601 ( 13 ) 2660 - 2663 2007年7月

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

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

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 MATERIALS 16 ( 4-7 ) 1200 - 1203 2007年4月

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.

DOI： 10.1016/j.diamond.2006.11.039

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 LETTERS 90 ( 13 ) 2007年3月

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.

DOI： 10.1063/1.2718268

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

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 4 32 ( 4 ) 1247 - 1250 2007年

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 > air > 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.

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 NANOTECHNOLOGY 5 ( 5 ) 485 - 490 2006年9月

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.

DOI： 10.1109/TNANO.2006.880456

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 LETTERS 45 ( 29-32 ) L860 - L863 2006年8月

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.

DOI： 10.1143/JJAP.45.L860

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

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 LETTERS 88 ( 25 ) 2006年6月

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.

DOI： 10.1063/1.2215618

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

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 LETTERS 88 ( 24 ) 2006年6月

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.

DOI： 10.1063/1.2213202

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

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 MATERIALS 15 ( 4-8 ) 1138 - 1142 2006年4月

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

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

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

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

DIAMOND AND RELATED MATERIALS 15 ( 4-8 ) 1015 - 1018 2006年4月

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.

DOI： 10.1016/j.diamond.2006.01.009

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

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 PAPERS 45 ( 3A ) 1623 - 1628 2006年3月

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 (< 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 > 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.

DOI： 10.1143/JJAP.45.1623

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

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 - NANOELECTRONICS 5 ( 5 ) 93 - + 2006年

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.

DOI： 10.1109/TNANO.2006.880456

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

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 2 1 271 - 274 2006年

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.

DOI： 10.1109/WCPEC.2006.279443

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

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 - NANOELECTRONICS 2006 93 - + 2006年

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.

DOI： 10.1109/NANOEL.2006.1609696

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

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 Research 11-12 159 - 162 2006年

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 B 19 ( 15-17 ) 2804 - 2810 2005年7月

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.

DOI： 10.1142/S0217979205031730

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

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 MATERIALIA 52 ( 12 ) 1205 - 1209 2005年6月

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

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

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 FILMS 482 ( 1-2 ) 86 - 89 2005年6月

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

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

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 PAPERS 44 ( 3 ) 1296 - 1300 2005年3月

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'-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

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

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 MATERIALS 14 ( 3-7 ) 790 - 793 2005年3月

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

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

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 MATERIALS 14 ( 3-7 ) 970 - 974 2005年3月

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

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

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 LETTERS 86 ( 5 ) 1 - 3 2005年1月

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.

DOI： 10.1063/1.1861115

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

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 MATERIALS 6 ( 1 ) 27 - 33 2005年1月

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.

DOI： 10.1016/j.stam.2004.07.002

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

LPE法によるInGaP結晶成長のシミューション

諏澤寛源, 平松和政, 神保孝志, 曽我哲夫, 林靖彦

化学工学会研究発表講演要旨集 2005 606 - 606 2005年

Structural, optical and mechanical properties of nanostructure diamond synthesized by chemical vapor deposition 査読

Y Hayashi, T Soga

TRIBOLOGY INTERNATIONAL 37 ( 11-12 ) 965 - 974 2004年11月

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.

DOI： 10.1016/j.triboint.2004.07.014

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

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 MATERIALS 13 ( 4-8 ) 1198 - 1202 2004年4月

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

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

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 LETTERS 84 ( 15 ) 2886 - 2888 2004年4月

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.

DOI： 10.1063/1.1666998

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

Reaction of indium ate complexes with allylic compounds. Controlling S(N)2/S(N)2 ' selectivity by solvents 査読

Hirashita T, Hayashi Y, Mitsui K, Araki S

Tetrahedron Letters 45 ( 16 ) 3225 - 3228 2004年

Microstructure of metal-filled carbon nanotubes 査読

S Toh, K Kaneko, Y Hayashi, T Tokunaga, WJ Moon

JOURNAL OF ELECTRON MICROSCOPY 53 ( 2 ) 149 - 155 2004年

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.

DOI： 10.1093/jmicro/53.2.149

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

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 STATE 46 ( 4 ) 733 - 737 2004年

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".

DOI： 10.1134/1.1711461

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

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 CELLS 77 ( 1 ) 105 - 112 2003年4月

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.

DOI： 10.1016/S0927-0248(02)00461-0

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

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 CELLS 77 ( 1 ) 15 - 24 2003年4月

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.

DOI： 10.1016/S0927-0248(02)00241-6

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

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 MATERIALS 12 ( 3-7 ) 687 - 690 2003年3月

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.

DOI： 10.1016/S0925-9635(03)00031-1

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-LETTERS 42 ( 3B ) L273 - L276 2003年3月

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.

DOI： 10.1143/JJAP.42.L273

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

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-C A 151 - 154 2003年

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.

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

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-C A 144 - 147 2003年

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.

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

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-LETTERS 41 ( 9A-B ) L970 - L973 2002年9月

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

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

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 PHYSICS 91 ( 12 ) 9752 - 9756 2002年6月

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

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

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 GROWTH 237 ( 1-4 II ) 1450 - 1454 2002年4月

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

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

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 MATERIALS 11 ( 3-6 ) 499 - 503 2002年3月

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

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

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 MATERIALS 11 ( 3-6 ) 1178 - 1182 2002年3月

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

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

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 B 16 ( 6-7 ) 1096 - 1100 2002年3月

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

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

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-LETTERS 41 ( 2A ) L147 - L148 2002年2月

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

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

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 CRYSTALS 386 ( PART 1 ) 73 - 80 2002年

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

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

Preparation of carbon micro-coils involving the decomposition of hydrocarbons using PACT (plasma and catalyst technology) reactor 査読

Kuzuya C, Hayashi Y, Motojima S

Carbon 40 ( 7 ) 1071 - 1077 2002年

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 MATTER 304 ( 1-4 ) 12 - 17 2001年9月

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

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

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 LETTERS 78 ( 25 ) 3962 - 3964 2001年6月

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.

DOI： 10.1063/1.1374501

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

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 PHYSICS 89 ( 12 ) 7924 - 7931 2001年6月

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

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

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 PHYSICS 89 ( 9 ) 5215 - 5218 2001年5月

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.

DOI： 10.1063/1.1362339

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

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 MATERIALS 10 ( 3-7 ) 1002 - 1006 2001年3月

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.

DOI： 10.1016/S0925-9635(00)00566-5

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 LETTERS 78 ( 3 ) 294 - 296 2001年1月

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.

DOI： 10.1063/1.1335548

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

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 GROWTH 221 ( 1-4 ) 688 - 692 2000年12月

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.

DOI： 10.1016/S0022-0248(00)00801-0

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

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 PAPERS 39 ( 7A ) 4088 - 4093 2000年7月

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 >100W RF powers. A weak correlation between the PL peak and the optical band gap is demonstrated.

DOI： 10.1143/JJAP.39.4088

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

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 B 272 ( 1-4 ) 256 - 259 1999年12月

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.

DOI： 10.1016/S0921-4526(99)00280-X

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

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 PAPERS 38 ( 2A ) 622 - 630 1999年2月

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

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-LETTERS 37 ( 11B ) L1354 - L1357 1998年11月

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

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

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.

Hydrogen absorbing and desorbing properties of Nd-Fe-B and Nd-Co-B amorphous alloys 査読

Tanaka K, Hayashi Y, Kimura M, Yamada M

Journal of Alloys and Compounds 253-254 101 - 105 1997年

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 PROCESSING 228 189 - 194 1992年

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 GROWTH 115 ( 1-4 ) 524 - 528 1991年12月

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

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 LETTERS 29 ( 7 ) L1133 - L1135 1990年7月

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