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 (I-cc). The resistive switching occurs because of oxygen vacancy filaments at low I-cc, whereas it is due to dual filaments consisting of Ag and oxygen vacancies at high I-cc. 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.