Resistive Switching Tuning Ferromagnetism and Near Band Edge Emission in Metal/ZnO:Cu/n+-ZnO:Ga/c-Sapphire Structure

Abstract

A metal/ZnO:Cu/n+-ZnO:Ga/c-sapphire structure was fabricated using the pulsed laser deposition. With biased applied across the metal and the n+-Ga-doped ZnO whereas the Ga-doped ZnO was grounded and I–V-measurement conducted with the voltage sequence of 0 V→+ve bias→0 V→-ve bias→0 V, resistive switching was observed while the resistance transited from high state to low state at ≈ +1.5 V and reset to high state while the sample was reversely biased. SQUID measurement shows that the sample is ferromagnetic at room temperature, and the magnetic moment is tunable, having a reduction of ≈ 30% during the high state to low state switching. X-ray photoelectron spectroscopy study shows an increase in Cu+:Cu2+ oxidation state ratio during the high state to low state transition. Similar resonance state tunable on near band edge emission intensity is observed, with the intensity reduced by ≈ 30% during the high state to low state transition but the defect emission intensity does not change. The physics leading to the resonance state tuning of magnetic moment and near band edge emission intensity is discussed.