We present a short overview of surface studies on the main low-index surfaces of anatase, the technologically most interesting crystallographic form of titanium dioxide. Results are compared to the extensively investigated surfaces of TiO2 rutile. The anatase (101) surface is stable in a (1 × 1) configuration. It exhibits twofold coordinated (bridging) oxygen atoms and fivefold coordinated Ti atoms with a density comparable to the one found on rutile (110). Step edges are terminated by fourfold coordinated Ti sites. In contrast to rutile (110), anatase (101) does not show a strong tendency for losing twofold coordinated oxygen atoms upon annealing in ultrahigh vacuum. The apparent lack of point defects is also reflected in the adsorption/desorption behavior of water and methanol. The anatase (100) surface has the second-lowest surface energy and tends to from a (1 × 2) reconstruction. A model with (101)-oriented microfacets agrees with the observed features in atomically-resolved STM images. The (001) surface forms a (1 × 4) reconstruction that is well explained by an "ad-molecule" model predicted from density functional theory calculations. A (1 × 3) reconstruction was observed for the anatase (103) surface.
Corresponding author: Ulrike Diebold (diebold).
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