Characterization of vacuum ultraviolet-irradiated surface modification of CoO(111) crystal by low-energy atom scattering spectroscopy

The surface of a CoO(111) single crystal was treated with vacuum ultraviolet (VUV) light at a wavelength of 172 nm without heat treatment. We studied the surface structural analysis of CoO(111) before and after VUV light irradiation in air using low-energy atom scattering spectroscopy. The primary beam was 3 keV-4He0, and backscattered 4He particles from Co atoms were detected using a microchannel plate detector. We compared the experimental spectra to simulation results, and the results demonstrated that the rock-salt CoO(111) surface was transformed to a spinel Co3O4(111) surface after VUV light irradiation. We also identified details about the chemical properties and topmost layers of CoO(111) surfaces before and after VUV light irradiation.