2D and 3D silver adlayers on TiO 2(110) surfaces

Abstract

The effect of chemical defects on the growth of silver films deposited on TiO 2(110) surfaces is examined in situ in ultra-high vacuum conditions, by means of surface differential reflectance, and ex situ by atomic 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 aspect ratios (diameter/height) close to 1, as expected from the small Ag TiO 2 interface energy. However, at room temperature, where kinetics play a major role in the building of the silver overlayer, the morphology of the silver film is shown to depend strongly on the chemical state of the surface. The aspect ratio of the silver clusters goes from > 10 on clean vacancy-free TiO 2(110) surfaces to 10 in the presence of oxygen vacancies, and to 1 in the presence of carbonaceous impurities.