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O: Fachverband Oberflächenphysik

O 33: Methods: Electronic structure theory II

O 33.5: Vortrag

Mittwoch, 25. März 2009, 11:30–11:45, SCH A316

Subsurface Confinement of Oxygen Vacancies in Anatase TiO2 — •Annabella Selloni and Hongzhi Chen — Department of Chemistry, Princeton University, Princeton, NJ-08540, USA.

First principles Density Functional Theory calculations are carried out to study the relative stabilities of oxygen vacancies at surface and subsurface sites of anatase TiO2(101) and TiO2(001) and, for comparison, of the prototypical rutile TiO2(110) surface. Our results show that these defects are substantially more stable at subsurface than at surface sites in the case of anatase surfaces, whereas bridging oxygen sites are favored for O-vacancies at rutile TiO2(110). Also, calculations of vacancy diffusion pathways for anatase (101) show that the energy barrier to diffuse from surface to subsurface sites is sufficiently low to ensure a rapid equilibration of the vacancy distribution at typical surface annealing temperatures. These results can explain why experimentally anatase surfaces are found to have a significantly lower defect concentration and/or to be more difficult to reduce than those of rutile.