Humidity effects on the redox reactions and ionic transport in a Cu/Ta₂O₅/Pt atomic switch structure

Abstract

Abstract Redox reactions at the Cu/Ta 2 O 5 interface and subsequent Cu ion transport in a Ta 2 O 5 film have been investigated by means of cyclic voltammetry (CV) measurements. Under positive bias to the Cu electrode, Cu is preferentially oxidized to Cu 2+ and then to Cu + . Subsequent negative bias causes a reduction of the oxidized Cu ions at the interface. It was found that CV curves change drastically with varied relative humidity levels from 5 to 85%. At higher humidity levels, the ion concentrations and diffusion coefficients, estimated from the CV curves, suggest increased redox reaction rates and a significant contribution of proton conduction to the ionic transport. The results indicate that the redox reactions of moisture are rate-limiting and highlight the importance of water uptake by the matrix oxide film in understanding and controlling the resistive switching behavior of oxide-based atomic switches.