OXIDATION OF ULTRATHIN COPPER LAYERS ON ZINC-OXIDE POLAR SURFACES - UNOCCUPIED ELECTRONIC STATES

Total current spectroscopy (TCS) was used to study an evolution of uno ccupied states through the process of thin-layer copper deposition and its oxidation on polar ZnO(0001) and (<000(1)over bar>) surfaces. Zn- derived and O-derived unoccupied;bands were identified in the TC spect rum at 7.7 and 9.8 eV, respectively, from the clean and well ordered p olar ZnO faces, while the spectra from a thin CuO layer reveal an inte nsive fine structure in the 6-25 eV energy range above the Fermi level , which is discussed in comparison with previously reported results of experimental and theoretical investigations. The obtained data provid e additional information on the energy location of the edges of unoccu pied bands in CuO in the 6-25 eV range relative to E-F.