AVS 49th International Symposium
    Surface Science Tuesday Sessions
       Session SS3-TuM

Paper SS3-TuM8
The Influence of Subsurface, Charged Impurities on the Adsorption of Chlorine at TiO@sub 2@(110)

Tuesday, November 5, 2002, 10:40 am, Room C-112C

Session: Metals, Adsorbates, and Defects on TiO@sub 2@
Presenter: M. Batzill, Tulane University
Authors: M. Batzill, Tulane University
B. Katsiev, Tulane University
E.L.D. Hebenstreit, Lawrence Berkeley National Laboratory
W. Hebenstreit, Optical Coating Laboratory, Inc.
U. Diebold, Tulane University
Correspondent: Click to Email
A fundamental surface science study on the influence of single, subsurface dopants on the chemical surface properties is presented. In particular the adsorption of chlorine atoms on TiO@sub 2@(110) samples modified by low concentrations of impurities were investigated. Subsurface impurity atoms were identified by scanning tunneling microscopy and spectroscopy. This analysis established that positively charged impurity atoms, most likely substitutional vanadium atoms, are present in some samples. Areas of about 2 nm in diameter around these impurities are imaged as protrusions in empty state STM images. This is consistent with a downward band bending induced by positively charge impurity atoms. Adsorption studies of Cl at room temperature on these samples showed that Cl atoms avoid chemisorption in the vicinity of these impurity atoms. Cl is an acceptor-like adsorbate that is negatively charged at the surface. The suppressed adsorption is explained by an increased local electron affinity due to the only partially screened positively charged impurities. This lowers the energy gain for adsorption of Cl at the surface and thus renders adsorption sites close to impurities as energetically disfavored compared to unaltered surface areas.