Resistive switching behavior in copper doped zinc oxide (ZnO:Cu) thin films studied by using scanning probe microscopy techniques

Abstract

Abstract The bipolar resistive switching (RS) behavior of Cu doped ZnO (ZnO:Cu) thin film samples is studied by using the conductive Atomic Force Microscopy (c-AFM) technique without an electroforming process. It is found that, comparing with the undoped ZnO, both “set” and “reset” voltages are increased in the ZnO:Cu (8 at.%) thin film. The “set” and “reset” voltage are slightly increased with the significantly increased built-in voltage. It is also found that the electroforming process has no influence on the retaining of the RS behavior. In addition, the results indicate that the RS behavior can only be retained on the control of scan rate and scan time. Furthermore, in the endurance tests by using the Piezoresponse Force Microscopy (PFM) in spectroscopy mode, the results suggest that the fatigue of polarization switching has a severely influence on the film endurance performance. The correlation of polarization switching and RS is further investigated by conducting PFM measurement on the same area where c-AFM measurement was performed. The results suggest that the polarization reversal occurs when samples are in the high resistance state (HRS). Hence, the coupling mechanisms between the polarization and RS behavior in ZnO:Cu thin film are studied.