Electron-energy-loss study of theTiO2(110) surface

Electron-energy-loss measurements on the stoichiometric ${\mathrm{TiO}}_2$(110) surface which include electronic excitations from both the O 2p valence states and the O 2s, Ti 3p, and Ti 3s core levels have been performed. The observed features have been empirically interpreted within the framework of the molecular-orbital description of an octahedral complex. The effects of surface defects created by ${\mathrm{Ar}}^{+}$-ion bombardment and by the evaporation of a thin Ti overlayer on the energy-loss results have also been studied and were found to cause marked changes in both the valence and core loss spectra. This sensitivity arises from changes in the screening between surface cations that occur when the oxygen-titanium ratio at the surface is varied.