Application of resistance change memory to ultrasensitive sensors -Exploration of new excitation processes in metal oxides-

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K04476
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 21050:Electric and electronic materials-related
• Research Institution: Tokyo University of Science
• Principal Investigator: Kinoshita Kentaro 東京理科大学, 理学部第一部応用物理学科, 教授 (60418118)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 欠陥 / 抵抗変化メモリ / 学習デバイス / 物理リザバー / 金属酸化物

Outline of Final Research Achievements

Focusing on Sn-doped In2O3 (ITO)/Nb-doped SrTiO3 (Nb:STO) junctions, whose electrical conductivity is modulated by both electrical and optical stimulation, we attempted to electrically control the photoresponse characteristics. In the fabricated ITO/Nb:STO junctions, both voltage-induced resistance change and photo-induced current generation due to UV light irradiation were confirmed. As a result of evaluating the relaxation characteristics of the increase/decrease of the photo-induced current while applying a bias voltage to the junction, it was found that the relaxation time of the photo-induced current can be controlled over two orders of magnitude in the voltage range of ±0.5 V. To evaluate the junction's physical reservoir performance, we performed an image classification task of handwritten digits, and found that learning was optimized by selecting an appropriate voltage according to the time scale of the input signal.

Free Research Field

デバイス物理

Academic Significance and Societal Importance of the Research Achievements

物理リザバー計算（RC）は時系列信号の低電力かつ高速リアルタイム処理に適し、エッジ領域での学習適用性が高いため注目されている。RCのコアであるリザバーを物理系のダイナミクスに置き換えることでリザバーの物理実装が可能となり、計算コストと時間の削減が期待される。本研究はITO/Nb:STO接合におけるUV照射による光電流の緩和時間を、±0.5 V以内の微小電圧の印加により数桁にわたって変調できることを明らかにした。これにより様々な時間スケールの時系列信号を、単一のデバイスにより処理できることから、社会的意義は大きい。その機構は永続光伝導等、欠陥物理との関連性が考えられ、学術的にも大変興味深い。