ZnO is especially attractive among the materials showing resistance switching because of its excellent properties such as light emitting and transparency for visible light. Unfortunately, the resistance switching in a ZnO-based device is usually unstable. By dispersing Ag particles of size ∼20 nm at the electrode–ZnO interface, we significantly improved the resistance uniformity, set/reset repeatability of Ag–ZnO–Pt devices. Conducting atomic force microscope analysis revealed the appearance of micro-regions where resistance switching, with an improved stability, is more easily triggered. It is suggested that Ag particles act as seeds for conducting filaments, leading to depressed randomness and reduced diameter of the conducting paths.

Electric field-induced resistive switching (RS) and related effects are studied for the ZnO-based device Ag/AgO x /Mg 0.2 Zn 0.8 O/Pt. The system exhibits a bipolar resistive switching (BRS) for the current (I)-voltage (V) cycles, with the set/reset voltage distributing in a narrow region around 0.15 V/0.16 V. The high to low resistance ratio is ∼10, and the resistive state is well retainable. However, the RS becomes unipolar (unipolar resistive switching-URS) when electric pulses are applied, with a fairly wide distribution of the set/reset voltages, though the resistive state is still well retainable. It was further found that a backward transition from the URS to the BRS state can be occasionally triggered by simply performing I-V cycling in the negative branch, which shows the strong competition of the BRS and URS states. Both the BRS and URS states were stable and reproducible over 90 cycles. Possible mechanisms for the BRS and URS state and their mutual transition were discussed.