MSE Seminar: “The Surface Dynamics of the Initial Stages of CU Oxidation”

Much is known about oxygen interaction with metal surfaces and about the macroscopic growth of thermodynamically stable oxides. At present, however, the transient stages of oxidation – from nucleation of the metal oxide to formation of the thermodynamically stable oxide – represent a scientifically challenging and technologically important terra incognito. These issues can only be understood through a detailed study of the relevant microscopic processes at the nanoscale in situ. We have previously demonstrated via in situ transmission electron microscopy (TEM) that the formation of epitaxial Cu₂O islands during the transient oxidation of Cu(100), (110), and (111) films bear a striking resemblance to heteroepitaxy, where the initial stages of growth are dominated by oxygen surface diffusion and strain impacts the evolution of the oxide morphologies. To deepen our understanding of the atomic-scale dynamic processes of Cu₂O island formation on Cu during oxidation in situ, we are presently using correlated in situ environmental high-resolution TEM (ETEM) and atomistic simulations. As an example of this approach, preferential monolayer-by-monolayer growth along Cu₂O (110) planes, instead of along Cu₂O (100) planes, was noted. Correlated Density Functional Theory (DFT) simulations on the surface and diffusion energies during Cu₂O growth on various Cu₂O surface orientations and terminations were carried out. Our DFT results show that the monolayer formation of Cu₂O along Cu₂O(110) was both thermodynamically and kinetically preferred over that of Cu₂O(100) during Cu₂O growth, which explains the observed phenomenon.