Initial Oxidation of Cu(hkl) Surfaces Vicinal to Cu(111): A High- Throughput Study of Structure Sensitivity

The initial stage in the oxidation of Cu single crystal surfaces has been studied on a surface structure spread single crystal (SC) exposing a continuous distribution of all Cu(hkl) surface orientations lying within 10° polar angle of the (111) plane, Cu(111) ± 10°-SC. The uptake of oxygen across the Cu(111) ± 10°-SC during exposure to O2 at 300 K has been measured using spatially resolved X-ray photoelectron spectroscopy (XPS), and the resulting Cu2O surface oxide layer has been imaged using scanning tunneling microscopy (STM). Uptake of oxygen is dependent on surface step density and increases with increasing polar angle relative to the (111) pole. In contrast, the oxygen uptake does not depend on the crystallographic orientation of the step edge or, in other words, the kink density along the step edge. STM images reveal that once oxidation of the step edges begins, all of the boundaries of the Cu2O step oxide layer are oriented along (100) step edges in the Cu(111) terrace independent of the initial orientation of the step. In other words, the oxidizing step edges have no memory of their original orientation, and thus, the step growth depends only on step density and not on the kink density along the step edge. The combined use of both spatially resolved XPS and atomic scale imaging with STM on a Cu(111) ± 10°-SC has provided unique insight into the origins of structure-sensitive surface chemistry.