Ultrathin film growth and spectroscopic characterization of VOx (0.8⩽x⩽1.3) on Pt(1 1 1)

VOx ultrathin epitaxial films (0.8⩽x⩽1.3) have been grown on Pt(1 1 1) by evaporating vanadium in a low and well-controlled water background (1×10−7 Pa). X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and X-ray excited auger electron spectroscopy data strongly indicate that vanadium(II) in the predominant oxidation state. Angle-scanned photoelectron diffraction data are compatible with a single domain film, bearing a rock-salt VO structure and exposing the (1 1 1) plane. Such films evolve toward more oxidized species within hours, probably due to oxidation by residual water in the chamber.