Compliance Current-Controlled Conducting Filament Formation in Tantalum Oxide-Based RRAM Devices with Different Top Electrodes

Memristive switching with digital set and multistep analog reset characteristics were demonstrated in tantalum oxide (Ta2O5)-based resistive random access memory (RRAM) devices using Ti and Ag top electrodes (TEs). The Ta2O5-based device with a Ti TE requires a forming process to initiate the switching and exhibits a gradual resistance increase behavior with the sequential increase in voltage in the reset process. The Ta2O5-based device with a Ag TE shows a slightly different switching behavior. The Ta2O5-based device with a Ag TE does not require a forming process and shows a gradual resistance increase behavior after an abrupt reset with a sequential increase in voltage in the reset process. The difference in switching behavior is because of the difference in the composition of the conducting filament in both devices. The Ta2O5-based device with a Ag TE presents a dual-mode switching mechanism with coexistence of Ag and oxygen vacancy-driven filament formation. The configuration of the conducting filament is controlled by the compliance current (Icc). The resistive switching occurs because of oxygen vacancy filaments at low Icc, whereas it is due to dual filaments consisting of Ag and oxygen vacancies at high Icc. This is confirmed by the analyses of the temperature dependence of the conducting filament and the conduction mechanism. These results with unique dual-mode switching behaviors will help identify the conducting filament mechanisms and overcome the technical limitations faced by the RRAM devices.