The adsorption of chlorine on TiO2(110) studied with scanning tunneling microscopy and photoemission spectroscopy

E. L. D. Hebenstreit, W. Hebenstreit, H. Geisler, C. A. Ventrice, D. A. Hite, P. T. Sprunger, U. Diebold

Department of Physics, Tulane University, New Orleans, LA 70118, U.S.A.
Institut für Angewandte Physik, TU Wien, 1040 Wien, Austria
Department of Chemistry, Xavier University of Louisiana, New Orleans, LA 70125, U.S.A.
Department of Physics, University of New Orleans, New Orleans, LA 70148, U.S.A.
Center for Advanced Microstructures and Devices (CAMD), Louisiana State University, Baton Rouge, LA 70806, U.S.A.
Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803, U.S.A.

Surf. Sci. 505 (2002) 336-348

The adsorption of chlorine, dosed from an electrochemical cell, on the (110)-surface of a bulk-reduced TiO2 crystal was studied with scanning tunneling microscopy, X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy (UPS). At room temperature chlorine adsorbs on the fivefold coordinated Ti atoms and on the vacancies in the bridging oxygen rows. Chlorine exposure at 200 and 300 °C leads to adsorption at the position of bridging oxygen atoms. In addition, ~15 Å wide protrusions are formed that contain several chlorine atoms. No long-range ordering was found in the adsorbed layer. UPS shows that adsorption of Cl on the hot surface leads to an increase in the Ti 3d-related defect state. This indicates a replacement of bridging oxygen atoms by chlorine. Interestingly, the rate of the site exchange depends on the bulk reduction state of the TiO2 crystal. After dosing Cl at 200 °C, negligible adsorption was found on a slightly reduced, light blue crystal. The data are compared and contrasted with similar experimental results on the S/TiO2(110) system.

Corresponding author: Ulrike Diebold (diebold at iap_tuwien_ac_at).

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