[22a-E102-1~8] FS.1 Focused Session "AI Electronics"

[22a-E102-3] Selectively Induced Analog and Stochastic Resistive Switching in TaO_x and Their Direct Observations by C-AFM

〇Atsushi Tsurumaki-Fukuchi¹, Takayoshi Katase², Hiromichi Ohta³, Masashi Arita¹, Yasuo Takahashi¹ (1.IST, Hokkaido Univ., 2.MSL, Tokyo Tech., 3.RIES, Hokkaido Univ.)

Keywords:analog memory, stochastic computing, amorphous TaOx

Through conductive atomic force microscopy analyses for atomically flat thin films of amorphous TaO_x, we demonstrated that the stochasticity of the field-induced resistive switching phenomena in TaO_x can be drastically changed by controlling the directions of the internal ion migration. When the cations (Ta⁵⁺) were accumulated at the tip/film interface under positive voltages, highly continuous analog resistive switching, which is known as an important phenomenon for the application to artificial synapse device, was observed in the film. By contrast, when the anions (O²⁻) were accumulated at the tip/film interface under negative voltage applications, a very stochastic resistive switching phenomenon was observed in the film. After the stochastic-type resistive switching, we observed that coarsened nanoparticle structures were formed in the TaO_x thin films, suggesting the segregation of metastable TaO₂ phase. The important involvment of the metastable phase formation was suggested in the stochastic resistive switching of TaO_x, which is a key phenomenon for hardware implementation of stochastic neural network.