2D AND 3D SILVER ADLAYERS ON TIO2(110) SURFACES

The effect of chemical defects on the growth of silver films deposited on TiO2(110) surfaces is examined in situ in ultra-high vacuum condit ions, by means of surface differential reflectance, and ex situ by ato mic force microscopy. Annealing at 620 K of a film deposited at 300 K or direct deposition at 520 K both lead to 3D silver clusters with asp ect ratios (diameter/height) close to 1, as expected from the small Ag /TiO2 interface energy. However, at room temperature, where kinetics p lay a major role in the building of the silver overlayer, the morpholo gy of the silver film is shown to depend strongly on the chemical stat e of the surface. The aspect ratio of the silver clusters goes from >1 0 on clean vacancy-free TiO2(110) surfaces to 10 in the presence of ox ygen vacancies, and to 1 in the presence of carbonaceous impurities.