AVS 45th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS2-TuA

Paper SS2-TuA4
STM and LEIS Study of Oxygen-Induced Restructuring of Rutile TiO@sub 2@(110)(1x1) Surface

Tuesday, November 3, 1998, 3:00 pm, Room 309

Session: Morton M. Traum Student Award Session
Presenter: M. Li, Tulane University
Authors: M. Li, Tulane University
W. Hebenstreit, Tulane University
D.R. Jennison, Sandia National Laboratories
U. Diebold, Tulane University
Correspondent: Click to Email
The rutile TiO@sub 2@(110) surface is one of the most-popular substrate in the surface science of metal oxides. We show that the exact surface preparation conditions critically influence the surface structure and morphology of this material in a rather unexpected way. TiO@sub 2@(110) surfaces, prepared by sputtering and annealing at 850 K in UHV, exhibit a (1x1) surface termination and flat, several hundred Å wide terraces. After exposure to oxygen at elevated temperatures (onset ~470 K), the surfaces are covered with small (typically tens of Å wide) terraces with monoatomic step height and the same (1x1) structure. On top and in between these terraces appear patches of an irregular network consisting of interconnected rosettes (width ~ 7 Å) with pseudohexagonal symmetry. The positions of atoms within the network are consistent with an incomplete TiO@sub 2@(110) layer. Ab-initio LDA calculations support the stability of the proposed structural model. It contains undercoordinated atoms with an electronic structure that is distinctly different from (1x1) terminated surfaces. LEIS measurements of surfaces annealed in @super 18@O@sub 2@ clearly show that new TiO@sub 2@ layers are formed through outdiffusion of interstitial Ti cations from the reduced bulk to the surface where they react with ambient oxygen. The kinetics of this 'restructuring' mechanism as well as possible implications for the surface chemistry of TiO@sub 2@ are discussed.