バナジウム酸化物(VO2)は室温付近で金属絶縁体転移を起こすという興味深い特性を持った物質です。最近その電子デバイスへの応用研究が盛んになってきました。とくにニューロモルフィックと呼ばれる脳の中のシナプスやニューロンをと同じ機能を持つ電子素子を作ろうという研究の中にVO2はよく登場します。今回、そのような研究の分野でよく知られている、イスラエルのバルイラン大学のAmos Sharoni氏と東京大学の矢嶋赳彬氏にお越しいただき、最近の研究を解説していただくことにしました。貴重な機会ですので、ぜひご参加ください。(参加無料。事前登録不要)

We have invited Professor Amos Sharoni (Bar-Ilan University, Israel) and Dr Takeaki Yajima (University of Tokyo). They are well-known by their researches of vanadium dioxide (VO2), which shows an exciting metal-insulator transition around room temperatures. Because of the transition, researches of utilising VO2 as a functional electronic device, especially, what is called neuromorphic devices, have been rapidly pumped up recently. The speakers are giving talks along this line. Those who are interested in the exotic (functional) electronic devices without using conventional semiconductors are all welcome. You may understand some key issues if you are interested in neuromorphic devices.

language: English.

date and time: 14:00-16:00 on Friday, 27th September 2019.

venue: #2213, 2nd Floor of #5-41 building

how to come to AIST: see this page

registration: not required.

contact: Dr. Isao H. Inoue

email: isaocaius@gmail.com

program

14:00-15:00 (50min talk + 10min discussion)

A 3-terminal VO₂-based realization of an artificial synapse

Elihu Anouchi ^[1], Tony Yamin ^[1,2] and Amos Sharoni ^[1,2]

^[1] Department of Physics, Bar Ilan University, Ramat-Gan, 5290002, Israel

^[2] Bar Ilan Institute of Nanotechnology and Advanced Materials, Ramat-Gan, 5290002, Israel

Realization of an artificial brain-like computer, known as “neuromorphic computation”, is a major challenge of today's electronic industry, necessary for low-power artificial intelligent applications. Mimicking neuron-like operations and incorporating them efficiently in computers requires abilities that are not easily achieved within the CMOS framework. One element is the artificial synapse, a non-volatile multi-state programmable device, able of connecting to many elements (fan-out). We present a conceptual realization of such an artificial synapse using three-terminal FET-devices based on a VO₂channel. VO₂is a correlated oxide with a temperature-driven insulator to metal transition near room temperature. In our device the insulator and metal states act as a read and write switch, accordingly. The low-temperature insulating resistance acts as the synapse state, that can be modified in a nonvolatile and reversible manner only in the high-temperature metallic state of VO2, by application of a gate voltage. We will present the properties of our artificial synapse and how, to our understanding, field induced oxygen motion is the main driving mechanism.

15:00-15:10 break

15:10-16:00 (40min talk + 10min discussion)

Impact of scaling the VO2-channel Mott transistor below material correlation length.

Takeaki Yajima

Department of Materials Engineering, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan

The sharp ON/OFF switching in Mott transistors, orig-inating from the metal-insulator transition in the channel, is often hindered by the inherent material inhomogeneity. Yet, the sharp switching is expected to be recovered by scaling down the transistor channel to the length scale of inhomogeneity. In this study, an ultra-sharp switching in the VO2-channel Mott transistor is experimentally demonstrated by scaling down the VO2 channel to several hundred nm. The sharpness of the switching is independent of the applied drain voltage (Vd), indicating it is originated from collective nature of the phase transition, rather than the Vd-induced non-equilibrium effect as previously reported. It is concluded the ultra-sharp switching is feasible by scaling down the Mott transistor below the material correlation length, implying the great potential for its low-voltage application.