Switching Model of TaO x -Based Nonpolar Resistive Random Access Memory

We report on a novel TaO x -based nonpolar resistive random access memory (RRAM) cell design with a Cr/TaO x /Al (top-to-bottom) structure. Extensive studies of the switching mechanism of the nonpolar RRAM were performed. The thermal coefficient of resistance of the RRAM in the low-resistance state is observed to adopt different polarities depending on how the preceding set operation was performed. On the basis of this observation, the coexistence of metallic ions and oxygen vacancies in the dominant filament is deduced, and a hybrid filament hypothesis is proposed for the first time to explain the observations. A switching model is provided to explain the microscopic changes in the nonpolar TaO x -based RRAM.