In-Situ Raman Spectroscopy of Defined Copper Oxide Surfaces Formed by Electrochemically Controlled High-Temperature Oxidation

Abstract

The oxidation processes of copper are of great importance since its occurrence leads to various problems, both in further processing and in operation of electronic devices and other technical applications. Extensive research on the thermal oxidation of copper has demonstrated that temperature and oxygen partial pressure affect the formation of oxides, oxidation rates and the chemical composition.In this work powerful electrochemical methods for controlled oxidation are presented, where the oxygen partial pressure on the metal surface can be varied over a range of 10-25 to 100 bar in a single experiment. A specific arrangement of the setup extends its capabilities to enable in-situ Raman spectroscopy measurements of the produced oxide. Controllable oxidation states are achieved in a solid-state electrochemical cell by polarizing a copper sample in contact with a single crystal of yttria-stabilized zirconia, which is conductive for oxygen ions at high temperatures. Optical transparency of the single crystal allows the Raman laser to pass through the crystal to measure the copper oxide formed on the copper-electrolyte interface. Cyclic voltammograms contain kinetic and thermodynamic information about the oxidation processes. Thus, the various oxidation reactions are controlled by the potential that corresponds to the oxygen partial pressure, while the current measures the rate of layer growth as well as the thickness of the oxide layer. In situ Raman measurements allow more detailed analyses of the oxides. The combined data will be used to build a model for oxide layer growth, with particular attention to the defect chemistry of the copper oxide.