Cu₂O island growth during Cu oxidation revealed by correlated in situ ETEM and multiscale simulations

Fundamental understanding of the surface oxidation process is essential for controlling and predicting oxide growth for catalysts and electronic devices applications. Despite numerous studies on the bulk oxidation process, the initial oxide growth process is still less explored, especially at the atomic scale. In this work, by combining in situ Environmental TEM (ETEM) with multiscale atomistic simulation, the dynamic process of initial Cu₂O nano island growth was explored. Our ETEM result shows during Cu(100) oxidation, Cu₂O nano islands grow through a layer-by-layer adatom growth mechanism along Cu₂O(110) surface. Our simulation results show that comparing with Cu₂O(100), Cu₂O(110) has lower surface energy, lower Cu diffusion energy and more favorable Cu adsorption energy, leading to easier Cu₂O monolayer formation along Cu₂O(110) that ultimately caused the observed layer-by-layer oxide growth. These results will enhance the understanding of surface oxidation and will also provide insights into understanding initial oxide growth mechanisms of other metal/alloy systems.