In-situ impedance spectroscopy on copper oxide scales under potential controlled oxidation at high temperatures

Abstract

In recent years, copper oxide (Cu2O) has gained significant attention for its multifaceted role as a catalyst, photocatalyst and semiconductor. Possessing a p-type conductivity and a bandgap of 2.17 eV, Cu2O emerges as an ideal candidate for applications such as water splitting and photovoltaic cells. However, to utilize its full potential, an in-depth understanding of the electrical properties of Cu2O in terms of defect density and defect mobility is required. This knowledge forms the basis for the targeted production of oxides with precisely tuned electrical properties.Extensive research on thermal oxidation under varied conditions has been performed to clarify the mechanisms governing oxide formation and growth. However, the in-situ investigation of the electrical properties of the oxide layers during their formation process is challenging.This work introduces a new method for the controlled oxidation of copper, while concurrently offering an in-depth investigation of the electrical properties of these nanometer-thick oxide layers. The implemented arrangement of potentiostat and frequency response analyzer enables their artifact-free combination. Performing HT-CV measurements in a solid electrolyte cell-setup allows to control the (potential-dependent) oxygen pressure at the copper surface. Using HT-CV, the current represents the kinetics of the redox reactions and the electric charge corresponds to the amount of substance converted. In-situ electrochemical impedance data are used to determine the electrical properties of the controlled grown layers. As a result, the defect density is obtained as a function of the oxygen partial pressure.