Improved Performance of ZnO-Based Resistive Memory by Internal Diffusion of Ag Atoms

An Ag/ZnO/Pt memory device, which has much better resistive switching behaviour than Pt/ZnO/Pt device was demonstrated. The detailed resistive mechanisms for the Pt/ZnO/Pt and the Ag/ZnO/Pt systems are proposed and investigated. Microstructures are observed by transmission electron microscope (TEM), indicating that the formation of conducting path for both systems is different. For the Pt/ZnO/Pt device, the conductive filament path is constructed by the oxygen vacancies from top to bottom electrodes under a larger enough bias at a forming process. For the Ag/ZnO/Pt device, the filament path was grown by oxygen vacancies combined with an internal diffusion of Ag atoms under a large bias and can provide the lowest energy barrier for electrons transported between two electrodes during set and reset processes, which reduces formation of other conducting paths after each switching. Accordingly, the stable switching performance of the Ag/ZnO/Pt device can be achieved over 100 cycles even the thickness of ZnO film <25 nm.