Effects of substrate temperature on resistive switching behavior of planar ZnO resistive random access memories

Resistive switching (RS) characteristics of ZnO films via lateral conducting filaments with a length up to 250 μm were demonstrated. The ZnO films were deposited at a low radio frequency power of 50 W. We controlled the substrate temperature during the sputtering process to modify the crystallinity and oxygen vacancy concentration of the ZnO film. At low substrate temperatures of 25-160 °C, the ZnO resistive random access memories (ReRAMs) show high conduction currents and the RS behavior is absent. Optimal temperatures of 240-320 °C were found to be suitable for obtaining RS characteristics of the ZnO ReRAMs with electrode distances of 10-250 μm. A much higher temperature of 400 °C leads to an extremely low conduction current and the electrical characteristic cannot be measured. Deposition rates, transmittances, energy bandgaps, crystallinities, grain sizes, grain orientations, and distinct RS characteristics of the ZnO films deposited at temperatures of 25-400 °C were investigated. The carrier conduction mechanism of the ZnO ReRAM was also studied.