Growth and structure of WOx nanolayers on bare Cu(110) and Cu(110)(2x1)O surfaces

Full text: Tungsten trioxide (WO3) is deposited through direct thermal evaporation of WO3 powder under ultra high vacuum (UHV) conditions onto a bare Cu(110) and onto a Cu(110)(2x1) oxide reconstructed crystal surfaces at room temperature. The growth characteristics have been documented with scanning tunnelling microscopy (STM), low energy electron diffraction (LEED) and synchrotron x-ray photoemission (XPS) systematically through the range of low, i.e. 0.1 monolayer (ML) to high (2.0 ML) coverage of WOx and annealing of the sample to temperatures from room temperature to 7000C. Several phases of WOx structures have been observed and analyzed. Under particular growth conditions, i.e. 0.6 ML WO3 and a sample temperature of 3000C a well ordered single phase surface with a quasi-square structure could be prepared onto the Cu(110)(2x1)O surface. As the unit cell dimensions of this phase are similar to those of the (ac) projected surface of CuWO4 single crystals a model with a CuWO4 stoichiometry has been proposed and analyzed in DFT calculations. (author)