Influences of Cu Doping on the Microstructure, Optical and Resistance Switching Properties of Zinc OxideThin Films

Copper-doped zinc oxide films (Zn1-xCuxO) (x = 0, 2%, 4%, 6%) were fabricated on conductive substrates using the sol-gel process. The crystal structure, optical and resistive switching properties of Zn1-xCuxO films are studied and discussed. RRAM is made using Zn1-xCuxO as the resistive layer. The results show that the (002) peak intensity and grain size of Zn1-xCuxOfilms increase from 0 to 6%. In addition, PL spectroscopy shows that the oxygen vacancy defect density of Zn1-xCuxO films also increases with the increase in Cu. The improved resistive switching performance of the RRAM device can be attributed to the formation of conductive filaments and the destruction of more oxygen vacancies in the Zn1-xCuxO film. Consequently, the RRAM device exhibits a higher low resistance state to high resistance state ratio and an HRS state of higher resistance value.