GENERAL SCIENTIFIC SUMMARY
Introduction and background. Defects in oxide surfaces exhibit in general larger binding energies for metal atoms and molecules than regular lattice sites. They are consequently of decisive importance for the adsorption behavior and, closely related, the chemical properties of oxide materials.

Main results. In this study, we have investigated the interaction of individual Au atoms with a defective V2O3 surface, employing low-temperature scanning tunneling microscopy and spectroscopy. The oxide is vanadyl-terminated and exhibits a small number of defects that are assigned to missing V=O groups. Surprisingly, these defects are not the preferred binding sites for the Au atoms, which adsorb on regular bridge positions of the vanadyl lattice instead. Only a few defect-bound adatoms are observed, which differ from their regular counterparts as they induce a pronounced defect state into the oxide band gap. The findings are corroborated with density functional calculations, revealing a higher Au binding energy on regular than V=O vacancy sites. The low binding potential of the vanadyl defects is rationalized by the fact that they perturb the oxide electronic structure only weakly.

Wider implications. Our study demonstrates that defects might not determine the adsorption characteristic of oxide surfaces in selected cases.

Figure. STM image of single Au atoms (bright protrusions) bound to a vanadyl-terminated V₂O₃ surface with a few numbers of lattice defects (dark holes).

68.43.Mn Adsorption kinetics

68.55.A- Nucleation and growth

68.35.Dv Composition, segregation; defects and impurities

71.15.Mb Density functional theory, local density approximation, gradient and other corrections

73.20.Hb Impurity and defect levels; energy states of adsorbed species

73.20.At Surface states, band structure, electron density of states

Condensed matter: electrical, magnetic and optical

Surfaces, interfaces and thin films

Issue 9 (September 2009)

Received 20 May 2009

Published 14 September 2009