Epitaxial growth of continuous CeO2(111) ultra-thin films on Cu(111)

Cerium oxide was grown epitaxially on a Cu(111) substrate at 520 K in an oxygen atmosphere and resulted in a high quality CeO2(111) overlayers. The continuous single crystalline thin films were characterized by low energy electron diffraction, X-ray photoelectron spectroscopy of the Ce 3d core levels and resonant photoelectron spectroscopy of the valence band. The Ce oxide on Cu(111) grew initially in the form of islands giving a sharp (1.5 × 1.5) hexagonal diffraction pattern of the CeO2(111) structure. It covered the substrate surface completely after deposition of a 2.5-monolayer thick overlayer. Ce 3d spectra and resonant enhancement of the valence band emission show that Ce is present in the Ce4+ oxidation state.