EGaIn Microelectrode for Electrical Characterization of ITO-Based van der Waals Interface and Airborne Molecular Contamination of ITO Surface

This paper describes the electrical characterization of the van der Waals interfaces formed between indium-tin oxide (ITO) and a liquid metal-based microelectrode. We examined the influence of the adventitious contamination of the ITO surface by airborne molecular contaminants on the electrical transport across an ITO-based van der Waals interface. We constructed large-area junctions of the form ITO//Ga2O3/EGaIn, where EGaIn is a liquid eutectic gallium-indium alloy covered with a self-passivating thin oxide film (Ga2O3 of similar to 0.7 nm), and "//" denotes the van der Waals interface formed between the ITO and EGaln electrodes. Comparisons of the current density data for junctions formed with ITO surfaces prepared via five different surface cleaning methods utilizing UV light, ozone and/or organic solvent (ethanol) indicated that the electrical conductance of the ITO//Ga2O3 van der Waals interface was significantly enhanced (by three orders of magnitude) by UV/ozone surface cleaning, based on comparisons of the median value of the log-current density, and the dispersion of the data was significantly narrowed. The results reported in this work show that the electrical characterization of surfaces using the EGaIn-based microelectrode is an attractive method for investigating the electrical behavior of a conducting surface and the molecular adsorption phenomena on it. (C) 2015 The Electrochemical Society. All rights reserved.