Oxygen-Induced Restructuring of Rutile TiO(2)(110): Formation Mechanism, Atomic Models, and Influence on Surface Chemistry
The rutile TiO{sub 2} (110) (1x1) surface is considered the prototypical ''well-defined'' system in the surface science of metal oxides. Its popularity results partly from two experimental advantages: bulk-reduced single crystals do not exhibit charging, and stoichiometric surfaces--as judged by electron spectroscopes--can be prepared reproducibly by sputtering and annealing in oxygen. We present results that show that this commonly-applied preparation procedure may result in a surface structure that is by far more complex than generally anticipated. Flat, (1x1) terminated surfaces are obtained by sputtering and annealing in ultrahigh vacuum. When re-annealed in oxygen at moderate temperatures (470 K to 660 K), irregular networks of partially-connected, pseudohexagonal rosettes (6.5 x 6 {angstrom} wide), one-unit cell wide strands, and small ({approximately} tens of {angstrom}) (1x1) islands appear. This new surface phase is formed through reaction of oxygen gas with interstitial Ti from the reduced bulk. Because it consists of an incomplete, kinetically-limited (1x1) layer, this phenomenon has been termed restructuring. We report a combined experimental and theoretical study that systematically explores this restructuring process. The influence of several parameters (annealing time, temperature, pressure, sample history, gas) on the surface morphology is investigated using STM. The surface coverage of the added phase as well as the kinetics of the restructuring process are quantified by LEIS and SSIMS measurements in combination with annealing in {sup 18}O-enriched gas. Atomic models of the essential structural elements are presented and are shown to be stable with first-principles density functional calculations. The effect of oxygen-induced restructuring on surface chemistry and its importance for TiO{sub 2} and other bulk-reduced oxide materials is briefly discussed.
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sandia National Lab. (SNL-CA), Livermore, CA (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 8790
- Report Number(s):
- SAND99-1730J; TRN: AH200121%%217
- Journal Information:
- Faraday Discussions #114, Surface Science of Metal Oxides, Other Information: Submitted to Faraday Discussions No.114, Surface Science of Metal Oxides; PBD: 7 Jul 1999
- Country of Publication:
- United States
- Language:
- English
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