(Invited) Nanoscale Probing of Field-Driven Ion Migration in TaOx for Neuromorphic Memristor Applications

Stable operations as resistive switching memory were demonstrated in amorphous TaOx (a-TaOx) thin films with very flat surfaces by conductive atomic force microscopy (c-AFM). The a-TaOx thin films fabricated on glass and Nb-doped SrTiO3 substrates by pulsed laser deposition showed high surface flatness with root-mean-square roughness of less than 0.2 nm. The c-AFM observations on the surfaces revealed that the resistive switching in a-TaOx causes almost no change in the topographic structures, and the significant structural deformation appears after the electrical breakdown by longer-range migration of the constituent ions. The possible mechanisms of the resistive switching phenomena were discussed based on the changes in the topographic structures and conduction states.