記述言語：英語   出版者・発行元：Carbon  

Reservoir computing, a type of neural network computing, is an energy-efficient and fast machine learning method, expected to realize low-power edge processing in sensor devices. This study constructs an electrochemical reservoir using carbon nanotube (CNT) thin-film electrodes on flexible plastic and proves the capability of the electrochemical functionalization of CNT thin films to improve the reservoir's performance. The performance of the time-series data prediction task, called the nonlinear autoregressive moving average (NARMA) task, can be improved using multiple CNT electrodes functionalized under different conditions. Based on the correlation coefficient analysis of the reservoir output, we illustrate that the reservoir dimensionality is enhanced by combining CNT electrodes with different functionalization conditions. Furthermore, the dimensionality and memory capacity of the reservoir can be improved using the displacement current of the electric double layer and the redox current in the electrochemical electrode. We demonstrate the time-series data prediction of blood glucose levels in patients with type 1 diabetes using a physical reservoir for the first time. The use of functionalized CNTs enables flexible and high-performance reservoir computing, leading to the low-power in-sensor edge processing of wearable sensors.

DOI： 10.1016/j.carbon.2023.118344

Web of Science

Scopus

記述言語：英語   出版者・発行元：ACS Applied Materials and Interfaces  

For the complementary operation of two-dimensional (2D) material-based field-effect transistors (FETs), high-performance p-type FETs are essential. In this study, we applied surface charge-transfer doping from WOx, which has a large work function of ∼6.5 eV, selectively to the access region of WS2 and WSe2 by covering the channel region with h-BN. By reducing the Schottky barrier width at the contact and injecting holes into the valence band, the p-type conversion of intrinsically n-type trilayer WSe2 FET was successfully achieved. However, trilayer WS2 did not show clear p-type conversion because its valence band maximum is 0.66 eV lower than that of trilayer WSe2. Although inorganic WOx boasts high air stability and fabrication process compatibility due to its high thermal budget, the trap sites in WOx cause large hysteresis during back gate operation of WSe2 FETs. However, by using top gate (TG) operation with an h-BN protection layer as a TG insulator, a high-performance p-type WSe2 FET with negligible hysteresis was achieved.

DOI： 10.1021/acsami.3c04052

Web of Science

Scopus

PubMed

記述言語：英語   出版者・発行元：Small  

Achieving the direct growth of an ultrathin gate insulator with high uniformity and high quality on monolayer transition metal dichalcogenides (TMDCs) remains a challenge due to the chemically inert surface of TMDCs. Although the main solution for this challenge is utilizing buffer layers before oxide is deposited on the atomic layer, this method drastically degrades the total capacitance of the gate stack. In this work, we constructed a novel direct high-κ Er2O3 deposition system based on thermal evaporation in a differential-pressure-type chamber. A uniform Er2O3 layer with an equivalent oxide thickness of 1.1 nm was achieved as the gate insulator for top-gated MoS2 field-effect transistors (FETs). The top gate Er2O3 insulator without the buffer layer on MoS2 exhibited a high dielectric constant that reached 18.0, which is comparable to that of bulk Er2O3 and is the highest among thin insulators (< 10 nm) on TMDCs to date. Furthermore, the Er2O3/MoS2 interface (Dit ≈ 6 × 1011 cm−2 eV−1) is confirmed to be clean and is comparable with that of the h-BN/MoS2 heterostructure. These results prove that high-quality dielectric properties with retained interface quality can be achieved by this novel deposition technique, facilitating the future development of 2D electronics.

DOI： 10.1002/smll.202207394

Web of Science

Scopus

PubMed

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

Raman scatterings of both pristine and defective single-walled carbon nanotubes were measured. Defects on carbon nanotubes (CNTs) were induced by UV/O3 treatment, and the correlation between the temperature dependence of the Raman shift of the G-band and the crystallinity of CNTs was investigated. In the temperature range of 250-600 K, a gradual negative change in the slope was observed; the linear shift of the Raman G-band frequency with respect to temperature increased as the crystallinity deteriorated. This phenomenon is attributed to the increase in the fourth-order phonon-phonon scattering interaction resulting from the induced defects.

DOI： 10.35848/1882-0786/ac4678

Web of Science

Scopus

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

Triboelectric nanogenerator (TENG) is a promising power source toward the realization of self-powered wearable electronics. However, because of its pulsed output, a power management circuit, such as an intermittent operation circuit and AC-DC converter, is required to drive electronic devices. In this study, we propose a simple and highly efficient intermittent operation circuit composed of a programmable unijunction transistor. The energy transfer efficiency from the storage capacitor to the load reached 89%. We demonstrated that the intermittent circuit can be used to drive electronic devices such as stopwatches and wristwatches using the electricity generated by a carbon-nanotube-based stretchable TENG. &copy; 2021 The Japan Society of Applied Physics.

DOI： 10.35848/1882-0786/abf405

Web of Science

Scopus

開催年月日： 2024年3月

記述言語：英語   会議種別：口頭発表（一般）  

国名：日本国  

開催年月日： 2024年3月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京   国名：日本国  

開催年月日： 2024年3月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東京   国名：日本国  

開催年月日： 2024年3月

記述言語：英語   会議種別：ポスター発表  

開催地：Nagoya   国名：日本国  

開催年月日： 2024年3月

記述言語：英語   会議種別：ポスター発表  

開催地：Nagoya   国名：日本国