Modulation of resistive switching characteristics of WO3-x based MIM structure by ambient moisture

Abstract

Resistive switching (RS) devices are considered promising among other emerging devices to meet the demand for future memory device applications. Various transition metal oxides have been investigated for their RS properties. Out of different binary transition metal oxides, WO3-x is attractive because of its promising switching result and compatibility with CMOS process technology. While RS properties depend strongly on the defect concentration in the oxides and metal/oxide interfaces, it has been found that in various metal oxides the RS characteristics are also strongly affected by atmospheric moisture content. In this work the RS characteristics of Au/WO3-x/Pt device and its influence by the atmospheric moisture has been investigated. The non-stoichiometry and the adsorbed water molecule on the tungsten oxide’s surface is confirmed by the X-ray photoelectron spectroscopy. The device exhibited rectification and stable bipolar RS characteristics without the need of any forming step. DC conduction mechanism investigated at different temperature suggested the switching is primarily dominated by the Schottky type Au/WO3-x interface. Current conduction through the active layer has been found to be dominated by Schottky emission at low electric field and Poole–Frenkel emission at high electric field. The reverse current has been found to increase significantly on subjecting the device to ambient moisture. Modification of the Schottky barrier due to defect redistribution and molecular dipole at the Au/WO3-x interface have been discussed as a possible mechanism of the observed RS modulation. The modification of Schottky barrier height with ambient moisture reveals an important challenge the WO3-x based interface type resistive switching material faces which must be considered for the devolvement of resistive switching based future memory devices.