Analog Resistive Switching and Synaptic Functions in WO_x/TaO_x Bilayer through Redox-Induced Trap-Controlled Conduction

The abrupt set/reset behavior of the Ta/TaOx/Pt resistive switching (RS) device is reformed to a gradual mode by inserting a WOx layer between the TaOx active layer and the Ta top electrode. With the WOx acting as a redox layer to exchange oxygen vacancies at the interface, the defect states in TaOx are regulated via applying bias, and the analog resistive switching is rationalized by trap-controlled space-charge-limited conduction mechanism. Continual change in device resistance can be achieved by repeated voltage sweeping. Based on the analogue RS behavior, the potentiation and depression behaviors with excellent linearity are also demonstrated by identical voltage pulse stimulation, and the operating current is maintained at <10–6 A. Furthermore, essential synaptic functions, such as paired-pulse facilitation (PPF), long- and short-term potentiation (LTP and STP), experience-dependent plasticity (EDP), and learning–relearning are also demonstrated to mimic the biological synapses for the application of neuromorphic computing.