Mobility of Au on TiOx substrates with different stoichiometry and defectivity

Au nanoparticles deposited on titania films, where two nanophases of different stoichiometry and defectivity are co-present, were imaged on the same spot by scanning tunneling microscopy. The observed sizes are rather dissimilar as a consequence of the different mobility of An on the two surfaces. The role of the stoichiometry, which can influence the Au-substrate interaction, and of the defects, which can trap the metal atoms, is discussed on the basis of theoretical calculations of diffusion energy barriers on the two surfaces.