Effect of incorporating copper on resistive switching properties of ZnO films

Undoped and copper-doped ZnO (ZnO:Cu) thin films of wurtzite structure with c-axis orientation were grown on F-doped SnO2 (FTO) substrates by pulsed laser deposition. Typical bipolar and reversible resistance switching effects were observed in these films, and the ratio of high and low resistance state (ON/OFF ratio) increases abruptly by introducing Cu. Based on the impedance spectra of ZnO and ZnO:Cu films, the change of resistance at high and low resistance states is found to be accompanied with the variance of depletion width. Furthermore, the depletion width of ZnO films changes little, while that of ZnO: Cu films varies greatly under different resistance states, which is consistent with the result of that ZnO: Cu films show a much larger ON/OFF ratio than ZnO films. Therefore, the resistance switchings are supposed to be due to the change of depletion width of Schottky barrier. (C) 2012 Elsevier B.V. All rights reserved.