Revelation on the Interrelated Mechanism of Polarity-Dependent and Multilevel Resistive Switching in TaOx-Based Memory Devices

In this study, polarity dependent and multilevel resistive switching characteristics of the Ta/TaOx/Pt device are investigated. The resistive switching polarity is decisively associated with the location of the Ta/TaOx interface while at a specific switching polarity, and multiple (four) resistance states in the Ta/TaOx/Pt device are achieved by controlling the stop voltage during the reset process and are stable for more than 104 s under continuous readout testing. X-ray photoelectron spectroscopy reveals that the Ta/TaOx interface is rich in oxygen vacancies. A schematic on the configurations of oxygen-vacancy aggregated conducting paths is proposed, where the Ta/TaOx interface acts as an oxygen vacancy reservoir, and the migration of vacancies can be driven by the applied electric field as well as the vacancy concentration gradient emanated from the Ta/TaOx interface. The polarity-dependent and multilevel resistive switching behaviors are then discussed in terms of filament configuration variation, and their interrelationship is visibly unveiled.