AVS 47th International Symposium
    Surface Science Thursday Sessions
       Session SS1+MC-ThA

Paper SS1+MC-ThA4
Temperature Dependent Adsorption of Oxygen on TiO@sub 2@ (110): A Photoemission Study

Thursday, October 5, 2000, 3:00 pm, Room 208

Session: Oxidation and Molecule-Oxide Interactions
Presenter: H. Geisler, Xavier University of Louisiana
Authors: H. Geisler, Xavier University of Louisiana
E.L.D. Hebenstreit, Tulane University
W. Hebenstreit, Tulane University
M. Li, Tulane University
U. Diebold, Tulane University
S.N. Thornburg, University of New Orleans
C.A. Ventrice, Jr., University of New Orleans
D.A. Hite, CAMD/ Louisiana State University
P.T. Sprunger, CAMD/ Louisiana State University
Correspondent: Click to Email
The Titanium dioxide (110) surface is one of the most thoroughly studied metal oxide systems. One of the primary reasons for this interest is the fact that TiO@sub 2@ is easily reduced by annealing in vacuum. During the annealing process, oxygen vacancies and titanium interstitial are created, which can increase the conductivity of the substrate sufficiently to allow characterization with electron and ion spectroscopies. In order to heal the surface region, the reduced crystals are exposed to oxygen at various temperatures and pressures. To determine the effect of oxygen adsorption on the electronic structure of reduced TiO@sub 2@ crystals, angular resolved photoelectron spectroscopy (UPS) measurements have been performed in conjunction with scanning tunneling microscopy (STM) measurements. STM indicates that the adsorption of oxygen on TiO@sub 2@ (110) at temperatures above 400 °C or below 200 °C results in an unreconstructed surface. However, adsorption between 200 °C and 400 °C results in a rosette-like structure that represents an incomplete restructured TiO@sub 2@ (110) surface with coordinatively unsaturated surface atoms.@footnote 1@ UPS measurements of the vacuum-annealed, reduced TiO@sub 2@ surface show emission from a defect state centered at approximately 1 eV below the Fermi level. The onset of emission from the TiO@sub 2@ valence band occurs ~3 eV below the Fermi level. After dosing oxygen at room temperature the defect state disappears with only slight modifications to the valence band structure. On the other hand, UPS spectra from the rosette- structured surface show an enhancement of the emission from the defect state and strong modifications of the TiO@sub 2@ valence band emissions. @FootnoteText@@footnote 1@ M. Li, W. Hebenstreit, L. Gross, et al., Surf. Sci. 437, 173-190 (1999)