Characteristics of resistive switching in ZnO/SiOx multi-layers for transparent nonvolatile memory devices

Bipolar resistive switching in ZnO/SiOx bi-layer and ZnO/SiOx/ZnO tri-layer structures was investigated for nonvolatile memory applications. ZnO thin films were grown using the radiofrequency magnetron sputtering technique at room temperature. SiOx films were grown using plasma-enhanced chemical-vapor deposition at 200 °C. Multiple high-resistance states were observed during the set process. The high/low resistance state ratio was ~10 during ~100 on/off cycles. The tri-layer memory device exhibited better endurance properties than the bi-layer device. Because an asymmetric conducting filament has a weak point for charge conduction at the oxide interfaces, we attributed the good endurance property to the reproducible formation/rupture of “micro”-conducting filaments. Moreover, the dynamics of the oxygen ions in the SiOx layer plays an important role in resistive switching.