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 Cu2O 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.
Reprints available from U. Diebold (diebold).
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