Characterization of Pt/TiO2 surfaces by means of photoelectron spectroscopy of adsorbed xenon

Abstract

Low lying electronic states of rare gas-oxide anions: Photoelectron spectroscopy of complexes of O − with Ar, Kr, Xe, and N 2 Photoelectron spectroscopy of adsorbed Xe (PAX) was used to characterize various PtlTi0 2 ( 100) surfaces on an atomic scale. The PAX data provide useful information on both geometrical and electronic states of various surface sites. For example, both Ar ion sputtering and high temperature annealing (850°C) in vacuum produce a distribution of (high charge density) surface defect sites, most likely Ti3+ and Ti2+, whose local surface potentials are higher than on a stoichiometric Ti0 2 surface by 0.5 and 1 eV, respectively. Submonolayer deposits of Pt on a stoichiometric Ti0 2 exhibits much lower local surface potentials (0.5-1 eV) than sputterroughened bulk Pt, suggesting modified charge densities at these sites.

Photoemission of Adsorbed Xenon, X-ray Photoelectron Spectroscopy, and Temperature-Programmed Desorption Studies of H2O on FeS2(100)

“…It might be that further S loss at the defect may enhance this effect, consistent with the association of this site with the lower binding energy −669 eV feature in the PAX spectrum of FeS 2 (100). It also is mentioned that prior PAX research of TiO 2 has shown that Xe atoms associated with oxygen-deficient sites exhibit a lower binding energy than do Xe atoms adsorbed on stoichiometric TiO 2 , analogous to our experimental observations for a metal sulfide.…”

Surface Characterization Using Metastable Impact Electron Spectroscopy of Adsorbed Xenon

“…This feature does not appear if the metastable He is quenched in the MIES source chamber and only UPS spectra collected, implying that this feature might result from simultaneous interactions among Xe's, metastable He's, and UV photons. The intensities of the two Xe features and the fwhm's of the PAX spectra of Figure a are somewhat unusual in comparison with other studies; ,,, however, it is noteworthy that difference spectra often fail to yield accurate binding energies, fwhm's, and intensities of adsorbate features 1 (a) UPS spectra for the bare and the Xe-adsorbed MgO(100)/Mo(100) surface.…”