Photoemission Studies of Molecular Adsorption on Oxide Surfaces

  • Victor E. Henrich
  • G. Dresselhaus
  • H. J. Zeiger
Conference paper
Part of the Springer Series in Solid-State Sciences book series (SSSOL, volume 4)

Abstract

We have used ultraviolet photoemission spectroscopy (UPS), LEED and Auger spectroscopy to study the interaction of adsorbed molecules with transition-metal-oxide surfaces. Comparison of the UPS spectra of free molecules with the UPS difference spectra for adsorbed molecules, makes it possible to observe changes in the molecular electronic structure induced by adsorption. We have studied the adsorption of O2 and H2O on both nearly perfect and ion-beam-damaged surfaces of TiO2 and SrTiO3. The interaction of O2 with all surfaces is similar for low exposures (≲ 100 L), with the difference spectra indicating strong, probably dissociative chemisorption. For O2 exposures, ≳100 L, a second adsorbed phase occurs on some surfaces. For low H2O exposures, the difference spectra give evidence for dissociative chemisorption in some cases. For high H2O exposures, the spectra indicate only a slight distortion of the free molecule. On TiO2, the a1 molecular orbital of H2O is shifted 0.5—1eV toward tighter binding, suggesting that H2O is bound to the surface via is O lone-pair orbital. On SrTiO3, both the a1 and the higher-lying b1 molecular orbitals are shifted, suggesting a more complicated bonding. The magnitude of the extramolecular relaxation-polarization shift of H2O on adsorption depends primarily on the presence or absence of defect electronic surface states in the bulk bandgap of the oxide.

Keywords

TiO2 Auger Chemisorption Wolfram 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    J.E. Demuth, D.E. Eastman: Phys. Rev. Lett. 32, 1123 (1974)CrossRefGoogle Scholar
  2. 2.
    V.E. Henrich, G. Dresselhaus, H. J. Zeiger: Phys. Rev. Lett. 36, 1335 (1976)CrossRefGoogle Scholar
  3. 3.
    D.W. Turner, C. Baker, A.D. Baker, C.R. Brundle: Molecular Photoelectron Spectroscopy ( Wiley-Interscience, New York, 1970 ), p. 113Google Scholar
  4. 4.
    C.J. Ballhausen, H.B. Gray: Molecular Orbital Theory ( Benjamin, New York, 1965 ), p. 72Google Scholar
  5. 5.
    See, for example, F. Gonzalez, G. Munuera: Revue de Chimie Minerale 7, 1021 (1971), and references thereinGoogle Scholar
  6. 6.
    S. Katsumata, D.R. Lloyd: Chem. Phys. Lett. 45, 519 (1977)CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1978

Authors and Affiliations

  • Victor E. Henrich
    • 1
  • G. Dresselhaus
    • 1
  • H. J. Zeiger
    • 1
  1. 1.Lincoln LaboratoryMassachusetts Institute of TechnologyLexingtonUSA

Personalised recommendations