Parameters controlling microstructures and resistance switching of electrodeposited cuprous oxide thin films

Abstract

Cuprous oxide (Cu2O) thin films were electrodeposited cathodically from a highly alkaline bath using tartrate as complexing agent. Different microstructures for Cu2O thin films were achieved by varying the applied potential from −0.285 to −0.395V versus a reference electrode of Ag/AgCl at 50°C in potentiostatic mode, and separately by changing the bath temperature from 25 to 50°C in galvanostatic mode. Characterization experiments showed that both grain size and orientation of Cu2O can be controlled by changing the applied potential. Applying a high negative potential of −0.395V resulted in smaller grain size of Cu2O thin films with a preferred orientation in [111] direction. An increase in the bath temperature in galvanostatic electrodeposition increased the grain size of Cu2O thin films. All the films in Au/Cu2O/Au-Pd cell showed unipolar resistance switching behavior after an initial FORMING process. Increasing the grain size of Cu2O thin films and decreasing the top electrode area increased the FORMING voltage and decreased the current level of high resistance state (HRS). The current in low resistance state (LRS) was independent of the top electrode area and the grain size of deposited films, suggesting a filamentary conduction mechanism in unipolar resistance switching of Cu2O.