研究者詳細 - 林　靖彦

論文 - 林　靖彦

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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

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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

PubMed

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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

Web of Science

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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

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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

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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

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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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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

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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

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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

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

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

Journal of Materials Chemistry 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

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

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

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

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

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

Applied Physics 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

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

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

Applied Physics 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

PubMed

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

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

Scientific Reports 10 6486 2020年4月

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