Ultrathin metal films on a metal oxide surface: Growth of Au onTiO2(110)

Abstract

We have studied the growth of ultrathin Au films on the ${\mathrm{TiO}}_{2}$ (110) surface using low-energy ion scattering (LEIS), x-ray photoelectron spectroscopy (XPS), and low-energy electron diffraction (LEED). For substrate temperatures of 160 and 300 K, for fractional monolayer Au coverages, Au evaporated under UHV conditions appears to grow initially on the stoichiometric ${\mathrm{TiO}}_{2}$ (110) surface in a quasi-two-dimensional (2D) form. As the average Au coverage increases to one monolayer (1 ML) and higher, Au forms three-dimensional (3D) islands. The coverage at which 3D islands become apparent in LEIS data decreases as the surface temperature increases. No evidence of significant chemical interactions has been found between the Au and ${\mathrm{TiO}}_{2}$ substrate. By annealing ${\mathrm{A}\mathrm{u}/\mathrm{T}\mathrm{i}\mathrm{O}}_{2}$ to temperatures up to 775 K, the Au islands continue to grow; encapsulation of the Au islands by Ti suboxides is not observed. There is little or no CO adsorption on small Au clusters at 300 K (upper limit of \ensuremath{\sim}0.05 ML), based on sensitive LEIS measurements.