Effect of defect content on the unipolar resistive switching characteristics of ZnO thin film memory devices

In this study, unipolar resistive switching (URS) characteristics in ZnO thin film memory devices were systematically investigated with variable defect content. ZnO films displayed typically URS behavior while oxygen-deficient ZnO1−x films did not show resistive switching effects. The devices with two intentional Ohmic interfaces still show URS. These results show that appearance of URS behavior can be dominated by initial oxygen vacancy content in ZnO thin films. Modest increase in oxygen vacancy content in ZnO films will lead to forming-free and narrower distributions of switching parameters (set and reset voltage, high and low resistance states). It indicates that controlling the initial oxygen vacancy content was an effective method to enhance the URS performance.