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824 results on '"Tsukagoshi, Kazuhito"'

201. Oxygen-Sensitive Layered MoTe2Channels for Environmental Detection

Author

Yang, Shih-Hsien, Lin, Che-Yi, Chang, Yuan-Ming, Li, Mengjiao, Lee, Ko-Chun, Chen, Ciao-Fen, Yang, Feng-Shou, Lien, Chen-Hsin, Ueno, Keiji, Watanabe, Kenji, Taniguchi, Takashi, Tsukagoshi, Kazuhito, and Lin, Yen-Fu

Abstract

The oxygen (O2)-dependent resistance change of multilayered molybdenum ditelluride (MoTe2) channels was characterized. A variation of the channel resistance could reproducibly determine relative O2content (denoted as the O2index). We found that Joule heating in a layered MoTe2field-effect transistor caused the O2index to decrease drastically from 100 to 12.1% in back gate modulation. Furthermore, Joule heating caused effective O2desorption from the MoTe2surface and repeatable O2detection by multilayered MoTe2channels was realized. This work not only explored the influence of O2on the electrical properties of multilayered MoTe2channels but also revealed that MoTe2channels are promising for sensing O2in an environmental condition.

Published
2019
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204. ナノエレクトロニクスのためのカーボンナノチューブ(第47回物性若手夏の学校(2002年度),講義ノート)

Author

Tsukagoshi, Kazuhito

Abstract

1991年のカーボンナノチューブの発見以来、電子状態や光学的性質および応用研究が注目されている。このカーボンナノチューブは炭素を主原料にした材料であり、ナノメートルサイズの細線に自己成長的に生成する。そのうえ、良好な電気的特性を有し、単位断面積あたり銅線よりも大きな電流を伝送可能であることも我々の実験において見出している。これはカーボンナノューブの円筒形状が電子散乱を軽減し発熱を少なくすることによると考えられる。さらに独特の結晶構造によって熱伝導性が高くダイヤモンドと同等である事も高密度電流印加に重要な要素である。このためにナノチューブを電子素子材料に適応した場合、低消費電力および高効率電力利用素子を実現できる可能性を秘める。同様にC60のようなフラーレンや有機合成で生成できる高分子を単位ナノサイズ-ブロック材料として用いて、これらを組み合わせて機能素子を作製することによって従来の微細加工工程の延長によって作製可能な極微細機能電子素子を超えた機能およびサイズを比較的容易に実現できると考えている。このような未来電子素子の主要材料の一つのナノチューブの基礎特性解明を目的として電気伝導を研究している。このナノチューブ内では抵抗に寄与する後方散乱が抑制され電気抵抗がほぼ0になることが予想されている。これに加えて我々の実験によって多層カーボンナノチューブではスピン散乱が小さくスピンコヒーレント長が200nmを超えることを明らかにした。この結果は、ナノチューブが理想的な1次元伝導体でありカーボンだけで構成されている為にスピン軌道相互作用に大きくかかわる原子を含有していないことによって理解される。さらに、ナノチューブの直径がCo電極を形成する微小ドメインより小さいことから、微小ドメイン間の電気伝導の研究にも発展することを示した。これらの結果を基にしてカーボンナノチューブにおけるスピン伝導を外部からの入力によって制御する事を目指し、上記スピン注入機構の明確化およびカーボンナノチューブ電気伝導自体の制御の試みを現在行っている。本研究紹介では、上記ナノチューブの素子応用の可能性をナノチューブの電気伝導特性から考えていくために、「ナノエレクトロニクスのためのカーボンナノチューブ」と題して行われた2002年物性若手夏の学校講義テキストとしてまとめられたものであり、理化学研究所・筑波大学・産業総合研究所・米国ルイスビル大学との間で行われた共同研究の最近の成果を基にまとめた。, この論文は国立情報学研究所の電子図書館事業により電子化されました。, 講義

Published
2002

220. Double resonance Raman modes in monolayer and few-layer MoTe[subscript 2]

Author

Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Research Laboratory of Electronics, Zhou, Lin, Dresselhaus, Mildred, Guo, Huaihong, Yang, Teng, Yamamoto, Mahito, Ishikawa, Ryo, Ueno, Keiji, Tsukagoshi, Kazuhito, Zhang, Zhidong, Saito, Riichiro, Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology. Department of Physics, Massachusetts Institute of Technology. Research Laboratory of Electronics, Zhou, Lin, Dresselhaus, Mildred, Guo, Huaihong, Yang, Teng, Yamamoto, Mahito, Ishikawa, Ryo, Ueno, Keiji, Tsukagoshi, Kazuhito, Zhang, Zhidong, and Saito, Riichiro

Abstract

We study the second-order Raman process of mono- and few-layer MoTe[subscript 2], by combining ab initio density functional perturbation calculations with experimental Raman spectroscopy using 532, 633, and 785 nm excitation lasers. The calculated electronic band structure and the density of states show that the resonance Raman process occurs at the M point in the Brillouin zone, where a strong optical absorption occurs due to a logarithmic Van Hove singularity of the electronic density of states. The double resonance Raman process with intervalley electron-phonon coupling connects two of the three inequivalent M points in the Brillouin zone, giving rise to second-order Raman peaks due to the M-point phonons. The calculated vibrational frequencies of the second-order Raman spectra agree with the observed laser-energy-dependent Raman shifts in the experiment., National Science Foundation (U.S.). Division of Materials Research (Grant 1004147)

Published
2015

225. Pronounced photogating effect in atomically thin WSe2 with a self-limiting surface oxide layer.

Author

Yamamoto, Mahito, Ueno, Keiji, and Tsukagoshi, Kazuhito

Subjects
PHOTOCURRENTS, FIELD-effect transistors, SOLAR cells, PHOTOTRANSISTORS, SEMICONDUCTORS
Abstract

The photogating effect is a photocurrent generation mechanism that leads to marked responsivity in two-dimensional (2D) semiconductor-based devices. A key step to promote the photogating effect in a 2D semiconductor is to integrate it with a high density of charge traps. Here, we show that self-limiting surface oxides on atomically thin WSe2 can serve as effective electron traps to facilitate p-type photogating. By examining the gate-bias-induced threshold voltage shift of a p-type transistor based on single-layer WSe2 with surface oxide, the electron trap density and the trap rate of the oxide are determined to be >1012 cm−2 and >1010 cm−2 s−1, respectively. White-light illumination on an oxide-covered 4-layer WSe2 transistor leads to the generation of photocurrent, the magnitude of which increases with the hole mobility. During illumination, the photocurrent evolves on a timescale of seconds, and a portion of the current persists even after illumination. These observations indicate that the photogenerated electrons are trapped deeply in the surface oxide and effectively gate the underlying WSe2. Owing to the pronounced photogating effect, the responsivity of the oxide-covered WSe2 transistor is observed to exceed 3000 A/W at an incident optical power of 1.1 nW, suggesting the effectiveness of surface oxidation in facilitating the photogating effect in 2D semiconductors. [ABSTRACT FROM AUTHOR]

Published
2018
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227. Self‐Assembly Atomic Stacking Transport Layer of 2D Layered Titania for Perovskite Solar Cells with Extended UV Stability.

Author

Chen, Tzu‐Pei, Lin, Chung‐Wei, Li, Shao‐Sian, Tsai, Yung‐Han, Wen, Cheng‐Yen, Lin, Wendy Jessica, Hsiao, Fei‐Man, Chiu, Ya‐Ping, Tsukagoshi, Kazuhito, Osada, Minoru, Sasaki, Takayoshi, and Chen, Chun‐Wei

Subjects
SOLAR cells, MOLECULAR self-assembly, PEROVSKITE, ATOMIC layer deposition, TITANIUM dioxide
Abstract

Abstract: A novel atomic stacking transporting layer (ASTL) based on 2D atomic sheets of titania (Ti1−δO2) is demonstrated in organic–inorganic lead halide perovskite solar cells. The atomically thin ASTL of 2D titania, which is fabricated using a solution‐processed self‐assembly atomic layer‐by‐layer deposition technique, exhibits the unique features of high UV transparency and negligible (or very low) oxygen vacancies, making it a promising electron transporting material in the development of stable and high‐performance perovskite solar cells. In particular, the solution‐processable atomically thin ASTL of 2D titania atomic sheets shows superior inhibition of UV degradation of perovskite solar cell devices, compared to the conventional high‐temperature sintered TiO2 counterpart, which usually causes the notorious instability of devices under UV irradiation. The discovery opens up a new dimension to utilize the 2D layered materials with a great variety of homostructrual or heterostructural atomic stacking architectures to be integrated with the fabrication of large‐area photovoltaic or optoelectronic devices based on the solution processes. [ABSTRACT FROM AUTHOR]

Published
2018
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228. Characteristics of Oxide TFT Using Carbon-Doped ?n2O3 Thin Film Fabricated by Low-Temperature ALD Using Ethylcyclopentadienyl Indium (?n-EtCp) and H2O & O3

Author

Kobayashi, Riku, Nabatame, Toshihide, Kurishima, Kazunori, Onaya, Takashi, Ohi, Akihiko, Ikeda, Naoki, Nagata, Takahiro, Tsukagoshi, Kazuhito, and Ogura, Atsushi

Abstract

We investigated characteristic of the In2O3 films deposited by various atomic layer deposition (ALD) conditions such as growth temperature and doses of InEtCp precursor and H2O/O3 oxidant gases. A self-limited ALD window was observed in the In2O3 film deposition when an InEtCp and H2O/O3 doses were supplied over 27.6 umol and 0.09/2.94 mmol, respectively, regardless of the growth temperature. The ratio of In:O:C of the In2O3 films at 150, 170 and 200 oC were 1:1.16:0.04 (InO1.16C0.04), 1:1.16:0.03 (InO1.16C0.03) and 1:1.2:0 (InO1.2), respectively. We found that the carbon-doped (InO1.16C0.04, InO1.16C0.03) and carbon-free In2O3 (InO1.2) films could be easily deposited by changing the growth temperature. All films had an amorphous structure. The electrical properties of InO1.16C0.04 TFT changed dramatically from metal-like conductor to semiconductor after post-metallization annealing at 150 oC in O3 while no InO1.2 TFT changed. This is thought to be due to the suppression of excess oxygen vacancies in InO1.16C0.04 channel by effect of doped carbon. The InO1.16C0.04 TFT exhibited superior characteristics of S.S (0.37 V/dec), Ion/Ioff (1.0x108), Vth (3.5 V) and saturation field effect mobility (20.4 cm2/Vs). Therefore, carbon-doped In2O3 is a promising material as a channel of a flexible TFT where low temperature formation is essential.

Published
2019

237. Double resonance Raman modes in monolayer and few-layerMoTe2

Author

Guo, Huaihong, primary, Yang, Teng, additional, Yamamoto, Mahito, additional, Zhou, Lin, additional, Ishikawa, Ryo, additional, Ueno, Keiji, additional, Tsukagoshi, Kazuhito, additional, Zhang, Zhidong, additional, Dresselhaus, Mildred S., additional, and Saito, Riichiro, additional

Published
2015
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239. Wafer-scale fabrication of transistors using CVD-grown graphene and its application to inverter circuit

Author

Nakaharai, Shu, primary, Iijima, Tomohiko, additional, Ogawa, Shinichi, additional, Yagi, Katsunori, additional, Harada, Naoki, additional, Hayashi, Kenjiro, additional, Kondo, Daiyu, additional, Takahashi, Makoto, additional, Li, Songlin, additional, Tsukagoshi, Kazuhito, additional, Sato, Shintaro, additional, and Yokoyama, Naoki, additional

Published
2015
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245. Direct formation of micro-/nanocrystalline 2,5-dimethyl-N,N'-dicyanoquinonediimine complexes on SiO(sub 2)/Si substrates and multiprobe measurement of conduction properties

Author

Yamamoto, Hiroshi M., Ito, Hiromi, Shigeto, Kunji, Tsukagoshi, Kazuhito, and Kato, Reizo

Subjects
Quinone -- Chemical properties, Molecular dynamics -- Analysis, Chemistry
Abstract

Two wet processes are developed for the fabrication of conductive molecular devices on silicon substrates. These methods are simple, fast, convenient, and low-cost and help in scientific research on nanosized molecular conductors.

Published
2006

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