TITANIUM AND REDUCED TITANIA OVERLAYERS ON TITANIUM DIOXIDE(110)

The adsorption of titanium on titanium dioxide TiO2(110) has been studied by X-ray photoelectron spectroscopy (XPS) and low energy ion scattering (LEIS). The XPS data for Ti overlayers are interpreted using peak fitting based on experimental standard spectra. 4 Angstrom of Ti deposited at 150 K reacts with the substrate to produce approximate to 12 Angstrom of intermediate oxidation state Ti. Adsorption of neutral metal begins on top of this interface oxide film, but 20 Angstrom of deposited Ti are needed to cover the oxide completely. LEIS data indicate a tendency for clustering of Ti on top of the interface oxide. Ar+ sputtering of stoichiometric TiO2 leads to preferential loss of O from the near surface region. This reduction of the clean, annealed oxide surface by Ar+ ion bombardment starts immediately and does not reach a steady state until 3 x 10(17) ions cm(-2), at which point the reduced overlayer is 17 Angstrom thick.