The low-temperature thermal oxidation of copper, Cu3O2, and its influence on past and future studies

Due to its enormous technological importance there is a renewed interest in the oxidation of copper. However, due to the complex nature of oxidation of copper, the existence and importance of Cu3O2, which is a metastable defect structure of Cu2O, have not gained enough attention from researchers working on the oxidation of copper or copper alloys. The evidence for the Cu3O2 phase has been utilized to reinterpret previous Pulse Field Desorption Mass Spectrometry (PFDMS) and X-ray Photoelectron Spectroscopy (XPS) data. With additional Linear Sweep Voltammetry (LSV) and Galvanostatic Reduction (GR) data, an attempt has been made to delineate the complex nature of the oxidation of copper based on the Modified Cabrera Mott (C-M) Model. It is also emphasized that surface scientists should recognize Cu3O2 in new studies on copper oxidation and in interpreting already existing copper oxidation data. Need for more vacuum and low-pressure-based studies is stressed to characterize the distinct overlayers that can be formed by temperature and pressure control. Surface studies of oxidation of metals and alloys need to be supported and complemented by other techniques such as chemical and electrochemical methods.