研究者詳細 - 宇佐美　雄生

論文 - 宇佐美　雄生

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Emergence of In‐Materio Intelligence from an Incidental Structure of a Single‐Walled Carbon Nanotube–Porphyrin Polyoxometalate Random Network 査読有り国際誌

Deep Banerjee, Takumi Kotooka, Saman Azhari, Yuki Usami, Takuji Ogawa, James K. Gimzewski, Hakaru Tamukoh, Hirofumi Tanaka

Advanced Intelligent Systems 4 ( 4 ) 2100145 2022年01月

Room temperature demonstration of in-materio reservoir computing for optimizing Boolean function with single-walled carbon nanotube/porphyrin-polyoxometalate composite 査読有り

Banerjee D., Azhari S., Usami Y., Tanaka H.

Applied Physics Express 14 ( 10 ) 2021年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

A method for room temperature demonstration of in-materio reservoir computing (RC) with a single-walled carbon nanotube/porphyrin-polyoxometalate network (SWNT/Por-POM) is proposed. Boolean functions of OR, AND, NOR, NAND, XOR, and XNOR, all were reconstructed with an accuracy >90% via supervised training of linear voltage readouts. The RC pre-requisite of echo-state property and recurrent connection allowed for consistent performances over multiple test datasets and time-shifted target sequences. Moreover, a non-zero machine intelligence index confirmed the presence of negative differential resistance dynamics, incorporating in SWNT/Por-POM the mathematical equivalence of additive and subtractive functions, thereby aiding the construction of such complex Boolean functions.

DOI： 10.35848/1882-0786/ac24db

Scopus

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Performance of Ag-Ag<inf>2</inf>S core-shell nanoparticle-based random network reservoir computing device 査読有り

Hadiyawarman , Usami Y., Kotooka T., Azhari S., Eguchi M., Tanaka H.

Japanese Journal of Applied Physics 60 ( SC ) 2021年06月

記述言語：英語掲載種別：研究論文（学術雑誌）

Reservoir computing (RC), a low-power computational framework derived from recurrent neural networks, is suitable for temporal/sequential data processing. Here, we report the development of RC devices utilizing Ag-Ag2S core-shell nanoparticles (NPs), synthesized by a simple wet chemical protocol, as the reservoir layer. We examined the NP-based reservoir layer for the required properties of RC hardware, such as echo state property, and then performed the benchmark tasks. Our study on NP-based reservoirs highlighted the importance of the dynamics between the NPs as indicated by the rich high dimensionality due to the echo state property. These dynamics affected the accuracy (up to 99%) of the target waveforms that were generated with a low number of readout channels. Our study demonstrates the great potential of Ag-Ag2S NPs for the development of next-generation RC hardware.

DOI： 10.35848/1347-4065/abe206

Scopus

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Sacrificial gold coating enhances transport of liquid metal in pressurized fountain pen lithography 査読有り

Livshits G.I., Bao J., Sakamoto L., Misaka T., Usami Y., Otsuka Y., Matsumoto T.

Scientific Reports 11 ( 1 ) 4670 2021年02月

記述言語：英語掲載種別：研究論文（学術雑誌）

Liquid metals have attracted attention as functional components for moldable electronics, such as soft flexible connectors, wires or conductive ink. The relatively high surface tension (> 400 mN m−1) and the fact that liquid metals do not readily wet ceramic or oxide surfaces have led to devising unique techniques to spread the liquid and mold its shape. These techniques include surface modification, electrowetting and vacuum filling of channels. This work presents an injection technique based on pressurized fountain pen lithography with glass nanopipettes developed to directly pattern liquid metal on flat hard substrates. The liquid metals were eutectic alloys of Gallium, including Gallium-Indium (EGaIn), Gallium-Indium-Zinc and Gallium-Indium-Tin. The nanopipettes were coated internally with gold, acting as a sacrificial layer and facilitating the wetting of the pipette down to its pore, with an inner diameter of ~ 100–300 nm. By applying hydrodynamic pressure to the connected end of the pipette, the metal was extruded through the pore, forming long continuous (> 3 mm) and narrow (~ 1–15 µm) metal lines on silicon oxide and gold surfaces at room temperature and ambient conditions. With this robust platform, it is possible to pattern liquid metals on a variety of substrates and geometries down to the micron range.

DOI： 10.1038/s41598-021-84065-4

Scopus

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気相からの金ドーピングによるPCBM薄膜のコンダクタンス増加

中島剛志, 三坂朝基, 宇佐美雄生, 大塚洋一, 大山浩, 松本卓也

日本表面真空学会学術講演会要旨集 ( 公益社団法人日本表面真空学会 ) 2020 ( 0 ) 2020年12月

記述言語：日本語掲載種別：記事・総説・解説・論説等（学術雑誌）

PCBM薄膜上に少量の金を蒸着するとコンダクタンスが顕著に増加する現象を見出した。この金蒸着量では金自体のアイランド成長に伴う多重トンネル伝導は起こりえないので、金蒸着したPCBM薄膜では異なるメカニズムによる電気伝導が起きていると考えられる。このような顕著なコンダクタンス増加の起源は明らかではないが、金がPCBM薄膜のドーパントとして働く可能性がある。講演では分光学的なデータも示し議論を行う。

DOI： 10.14886/jvss.2020.0_267

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/130007959460

Frequency dependence dielectrophoresis technique for bridging graphene nanoribbons 査読有り

Aji W.W., Usami Y., Hadiyawarman , Oyabu R., Tanaka H.

Applied Physics Express 13 ( 10 ) 2020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）

© 2020 The Japan Society of Applied Physics We succeeded in bridging unzipped graphene nanoribbons (GNRs) and separating them from unwanted single-walled carbon nanotubes (SWNTs) using a frequency-dependent dielectrophoresis (DEP) method by varying the frequency and applied voltage used for future assembly. Atomic force micrographs and Raman spectra proved that unzipped GNRs were successfully bridged by the DEP method at frequencies higher than 13 MHz. The theoretical calculation also supported the finding that only GNRs were collected from a mixture of SWNTs/GNRs suspensions.

DOI： 10.35848/1882-0786/abb68d

Scopus

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Local-field-induced current noise in shape-limited self-doped polyaniline 査読有り

Bao J., Otsuka Y., Etoh R., Usami Y., Matsumoto T.

Nanotechnology 31 ( 36 ) 2020年09月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2020 IOP Publishing Ltd. Electronic noise generators are an essential component of molecular neuromorphic devices. To realize molecular noise generators with a high degree of freedom for design and integration into molecular devices, the utilization of the local electric field for the modulation of electrical conduction via a shape-limited conductive polymer is one promising strategy. Herein, a molecular noise generator composed of thin self-doped polyaniline (SPAN) lines is reported. SPAN lines fabricated via fountain pen lithography on SiO2/Si substrates were found to generate current noise upon laser irradiation. This current noise exhibited white-noise-like power spectral density in the frequency range of 1-25 Hz and was independent of temperature. Multiple independent noise generation on the same substrate was also successfully demonstrated. The present results indicate that the noise generation mechanism involves the local modulation of hopping conduction via SPAN lines owing to the spatial proximity of the conduction path in the SPAN line to the surface photovoltage region of the SiO2/Si interface. This on-site random noise generation in shape-limited conductive polymers is expected to be beneficial for the realization of molecular neuromorphic devices.

DOI： 10.1088/1361-6528/ab96e4

Scopus

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Visualization of Charge Migration in Conductive Polymers via Time-Resolved Electrostatic Force Microscopy 査読有り

Kajimoto K., Araki K., Usami Y., Ohoyama H., Matsumoto T.

Journal of Physical Chemistry A 124 ( 25 ) 5063 - 5070 2020年06月

記述言語：英語掲載種別：研究論文（学術雑誌）

© 2020 American Chemical Society. Charge dynamics play an important role in numerous natural phenomena and artificial devices, and tracking charge migration and recombination is crucial for understanding the mechanism and function of systems involving charge transfer. Tip-synchronized pump-probe electrostatic force microscopy simultaneously permits highly sensitive detection, microsecond time resolution, and nanoscale spatial resolution, where the spatial distribution in static measurement (usual EFM) reflects differences in the carrier density and the time evolution reveals the surface carrier mobility. By using this method, carrier injection and ejection in sulfonated polyaniline (SPAN) thin films were visualized. Comparison of tr-EFM results of SPAN thin films with different doping levels revealed the individual differences in carrier density and mobility.

DOI： 10.1021/acs.jpca.9b12017

Scopus

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物理リザバーに向けたポリアニリン-金微粒子ランダムネットワークの構築査読有り

川嶋悠哉, 宇佐美雄生, 琴岡匠, 田中啓文, 松本卓也

日本表面真空学会学術講演会要旨集 ( 公益社団法人日本表面真空学会 ) 2020 ( 0 ) 268 2020年01月

記述言語：日本語掲載種別：研究論文（学術雑誌）

リザバーコンピューティング(RC)は、リザバー層で行われる演算を物理現象に置換することができる情報処理システムである。我々は、自己ドープ型ポリアニリン分子(SPAN)と Au ナノ粒子(AuNP)からなるネットワーク内に非線形 I-V 特性が発生することを明らかにしている。本研究では、RCへの適用可能性を探るため、ナノギャップ電極によって多入力多出力電極間での非線形電気特性および記憶特性を検討した。

DOI： 10.14886/jvss.2020.0_268

CiNii Article

CiNii Research

その他リンク： https://ci.nii.ac.jp/naid/130007959456

Conjugated electrical properties of Au nanoparticle-polyaniline network 査読有り

Usami Y., Otsuka Y., Naitoh Y., Matsumoto T.

Japanese Journal of Applied Physics 56 ( 12 ) 2017年12月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2017 The Japan Society of Applied Physics. We investigated the electrical properties of a two-dimensional (2D) network consisting of multiple Au nanoparticles (AuNPs) and self-doped polyaniline sulfonate (SPAN). Nonlinear current-voltage (I-V) characteristics with wide variations were observed in the networks. The temperature dependence of the I-V characteristics exhibited a short localization length, suggesting conjugated electronic properties of the AuNP-SPAN network. This result provides a new direction for network-based molecular electronic devices.

DOI： 10.7567/JJAP.56.128001

Scopus

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Intra-grain conduction of self-doped polyaniline 査読有り

Usami Y., Imamura K., Akai T., Che D., Ohoyama H., Kobayashi H., Matsumoto T.

Journal of Applied Physics 120 ( 8 ) 2016年08月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

© 2016 Author(s). The conduction behavior of ultrathin films (about 10 nm thick) composed of self-doped water-soluble polyaniline sulfonate (SPAN) was investigated using nano-gap electrodes under vacuum conditions. The conductance was found to be ohmic even in the high field regime up to 105V cm-1 over a temperature range of 10-300 K. The temperature dependence of the conductance indicated that SPAN gave the extremely high value of localization length (L) = 300 nm without secondary doping, in comparison with conventional polyaniline. We propose that SPAN forms long-range highly crystalline metallic grains, and we observed intra-grain conduction due to some grains directly bridging the two nano-gap electrodes at low temperature. We conclude that inter-grain conduction becomes dominant as the temperature increases.

DOI： 10.1063/1.4961610

Scopus

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