UPS and XPS studies of the chemisorption of O2, H2 AND H2O on reduced and stoichiometric SrTiO3(111) surfaces; The effects of illumination |
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| Authors: | Salvador Ferrer GA Somorjai |
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| Institution: | Materials and Molecular Research Division, Lawrence Berkeley Laboratory and Department of Chemistry, University of California, Berkeley, California 94720, USA |
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| Abstract: | About one monolayer of Ti3+ species is detectable at the surface of reduced SrTiO3(111) single crystals by XPS and UPS. O2, H2 and H2O have been adsorbed in the dark and the decrease on the concentration of the Ti3+ species has been monitored as a function of the gas exposures. Subsequent band gap illumination partially restores the Ti3+ initial concentration in the cases of O2 and H2 exposures but not in the case of H2O. The Ti3+ photogeneration on the oxygen covered surface is associated with oxygen photodesorption as indicated by XPS and UPS. UPS measurements give evidence for surface hydroxylation resulting from water and hydrogen adsorption. The activity of the stoichiometric SrTiO3(111) crystal face for O2 and H2 adsorption is very low when compared with the reduced SrTiO3 samples. |
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