Refractory metal reactivity towards oxide surface: W/TiO2(1Â 1Â 0) case

Reactivity of deposited tungsten towards TiO2(1 1 0) surface was studied using synchrotron radiation photoemission spectroscopy (both core levels, valence band and resonant photoemission) on Materials Science Beamline at ELETTRA. W depositions carried out at room temperature on TiO2(1 1 0) surface give rise to an interfacial reaction which leads to a metastable situation due to kinetic limitations. Annealing induces chemical changes which are function of the initial coverage; for fractional coverage, annealing induces completion of oxidation of deposit whereas reduction to metallic tungsten occurs for highest coverage. These results demonstrate that interaction of W with TiO2(1 1 0) surface is, as the one of molybdenum, driven by a balance between W-O interactions and W-W depending on tungsten atoms density on TiO2 surface.