Joint contributions of Ag ions and oxygen vacancies to conducting filament evolution of Ag/TaO_x/Pt memory device

The electroforming and resistive switching behaviors in the Ag/TaO_x/Pt trilayer structure are investigated under a continual change of temperatures between 300 K and 100 K to distinguish the contributions of Ag ions and oxygen vacancies in developing of conducting filaments. For either electroforming or resistive switching, a significantly higher forming/set voltages is needed as the device is operated at 100 K, as compared to that observed when operating at 300 K. The disparity in forming/set voltages of Ag/TaO_x/Pt operating at 300 K and 100 K is attributed to the contribution of oxygen vacancies, in addition to Ag atoms, in formation of conducting filament at 100 K since the mobilities of oxygen vacancies and Ag ions become comparable at low temperature. The presence of oxygen vacancy segment in the conducting filament also modifies the reset current from a gradually descending behavior (at 300 K) to a sharp drop (at 100 K). Furthermore, the characteristic set voltage and reset current are irreversible as the operation temperature is brought from 100 K back to 300 K, indicating the critical role of filament constituents on the switching behaviors of Ag/oxide/Pt system.