Iron deposition on TiO2(110): effect of the surface stoichiometry and roughness

Characterizations of ultra-thin iron films deposited on TiO2(110) surfaces with different stoichiometries, roughnesses and crystallinities have been c arried out by X-ray photoelectron spectroscopy (XPS) and Auger electron spe ctroscopy (AES), For a high initial roughness of the substrate, a 2D growth mode is observed up to three monolayers. But, if the initial roughness is low, clusters grow on the TiO2 surface. Whatever the initial surface stoichiometry, electronic exchanges occur betw een titanium and iron leading to a reduction of titanium and an oxidation o f iron. This interaction between iron and titanium dioxide surface takes pl ace only at the interface between the metal and the oxide surface: during t he completion of the first layer for deposition on a non-stoichiometric and rough surface (2D growth) and at the base and periphery of the islands for 3D growth tin the case of deposition on a flat and stoichiometric surface) . Moreover, the amount of electrons exchanged between titanium and iron is lower when the substrate oxide surface is prereduced. The interaction betwe en the deposited metal and the oxide surface is related to the amount of av ailable oxygen. (C) 1999 Elsevier Science B.V. All rights reserved.