Localized and delocalized vibrations onTiO2(110) studied by high-resolution electron-energy-loss spectroscopy

Electronic as well as localized and delocalized vibrational losses were studied on ${\mathrm{TiO}}_2$(110) by electron-energy-loss spectroscopy. Electronic loss features at defect surfaces around 0.8 eV indicate band-gap defect states. In the higher loss-energy range above 3 eV well-known interband transitions were detected, which were found to be sensitive to ion bombardment, but not to the formation of point defects produced by high-temperature pretreatment. Vibronic loss structures are characterized by three different delocalized Fuchs-Kliewer surface phonons at 46, 54, and 95 meV as well as multiple and combination losses thereof. Ion bombardment as well as high-temperature pretreatment reduces their intensities significantly. On defect-free surfaces a shift of all three fundamental frequencies of +2 meV relative to defect surfaces was observed for primary energies below 10 eV. Localized O—H stretching vibrations at 455±1 meV were detected on stoichiometric and defect surfaces after exposure to atomic hydrogen.