Abstract

We hereby describe the modifications induced in a Cu thin film induced by different oxidation processes. By using plasma assisted deposition, we have adsorbed oxygen onto the Cu ZnO (0001)-Zn surface. Cu was deposited on the sputtered-annealed ZnO substrate at room temperature, which was later exposed to oxygen. Using x-ray photoelectron spectroscopy, we verified the effect of the surface treatment on the electronic structure. Our findings are consistent with a partially oxidized Cu layer, with the CuO located at the interface between ZnO and the adsorbed Cu islands. Further Cu deposition induces the formation of Cu2 O as judged by the evolution of the spectra. Annealing the sample up to 750°C in UHV induces further reduction of the oxide, metallic Cu is recovered on the top layer, with evidence of Cu desorption into the vacuum or incorporation into the substrate. © 2008 The American Physical Society.