Stretching Effect on Resistive Switching of TiO2/ZnO n–n Heterojunction Films

In this study, the switching characteristics of the GaIn/ZnO–TiO2/AgNWs devices under mechanical stretching conditions are investigated. It is shown that the maximum ON/OFF ratio of the unstretched sample is above 103, which exhibits reversible bipolar resistive switching. Upon stretching, the device ON/OFF ratio deteriorates by 1 order of magnitude. The switching mechanism can be ascribed to the formation/rupture of oxygen vacancy filaments. Finite element analysis demonstrates that the mechanical fatigue under repetitive stretching can be explained by the channel extrusion cracks and ductile failure with local necking at the interface. The microcracks may act as blocking layers, which limit the migration of the electrons and holes. Moreover, oxygen can easily get into the cracks, leading to the acceleration of the interfacial filament oxidation and decreasing the oxygen vacancy density. The interfacial adhesion and extrusion cracks may thus lead to the deterioration of switching performance. Our work may provide an approach to understand how to improve switching performance for the n–n heterojunction under stretching conditions.