Coexistence of diode-like volatile and multilevel nonvolatile resistive switching in a ZrO2/TiO2 stack structure

Diode-like volatile resistive switching as well as nonvolatile resistive switching behaviors in a Cu/ZrO2/TiO2/Ti stack are investigated. Depending on the current compliance during the electroforming process, either volatile resistive switching or nonvolatile resistive switching is observed. With a lower current compliance (< 10 mu A), the Cu/ZrO2/TiO2/Ti device exhibits diode-like volatile resistive switching with a rectifying ratio over 10(6). The permanent transition from volatile to nonvolatile resistive switching can be obtained by applying a higher current compliance of 100 mu A. Furthermore, by using different reset voltages, the Cu/ZrO2/TiO2/Ti device exhibits multilevel memory characteristics with high uniformity. The coexistence of nonvolatile multilevel memory and diode-like volatile resistive switching behaviors in the same Cu/ZrO2/TiO2/Ti device opens areas of applications in high-density storage, logic circuits, neural networks, and passive crossbar memory selectors.