Bipolar Switching Behavior of ZnO x Thin Films Deposited by Metalorganic Chemical Vapor Deposition at Various Growth Temperatures

The bipolar resistive switching behaviors of ZnO films grown at various temperatures by metalorganic chemical vapor deposition have been investigated. The ZnO films were grown on Pt/Ti/SiO2/Si(100) substrate, and the ZnO growth temperature was varied from 300A degrees C to 500A degrees C in steps of 100A degrees C. Rutherford backscattering spectroscopy analysis results showed that the chemical compositions of the ZnO films were oxygen-poor Zn1O0.9 at 300A degrees C, stoichiometric Zn1O1 at 400A degrees C, and oxygen-rich Zn1O1.3 at 500A degrees C. Resistive switching properties were observed in the ZnO films grown at 300A degrees C and 400A degrees C. In contrast, high current, without switching properties, was found in the ZnO film grown at 500A degrees C. The ZnO film grown at 500A degrees C had higher concentration of both nonlattice oxygen (4.95%) and oxygen vacancy (3.23%) than those grown at 300A degrees C or 400A degrees C. The resistive switching behaviors of ZnO films are related to the ZnO growth temperature via the relative amount of oxygen vacancies in the film. Pt/ZnO/Pt devices showed asymmetric resistive switching with narrow dispersion of switching voltage.