An Ag/ZnO/Pt memory device, which had 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 were proposed and investigated. Microstructures were observed by transmission electron microscope, indicating that the formation of conducting path for both systems was different. For the Pt/ZnO/Pt device, the conductive filament path was 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 could provide the lowest energy barrier for electrons transported between two electrodes during set and reset processes, which reduced the formation of other conducting paths after each switching. Accordingly, the stable switching performance of the Ag/ZnO/Pt device could be achieved over 100 cycles even when the thickness of the ZnO film was <25nm.

Improved Performance of ZnO-Based Resistive Memory by Internal Diffusion of Ag Atoms. Peng, C.N., Wang, C.W., Huang, J.S., Chang, W.Y., Wu, W.W., Chueh, Y.L.: Journal of Nanoscience and Nanotechnology, 2012, 12[8], 6271-5