Growth and Characterization of Ultrathin V2Oy (y ≈ 5) Films on Au(111)

The growth of vanadium oxide ultrathin films on Au(111) using physical vapor deposition of V and oxidation under 50 mbar of oxygen has been investigated with scanning tunneling microscopy, low-energy electron diffraction, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure analysis. Depending on the coverage, two different well-ordered coincidence monolayer structures with a V∼5+ oxidation state are observed. These arrangements do not correspond to any known bulk structures, and they are determined by the interaction between the oxide layer and the Au(111) surface, a finding that highlights the ability of vanadium oxides to adopt different structures. After completion of the first layer, a two-layer thick film which wets the substrate and has a surface structure similar to that of V6O13(001) is formed. This film does not exhibit a well-defined azimuthal orientation, which leads to ringlike structures in the low-energy electron diffraction pattern. The formation of the V6O13(001...