Dresden 2009 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 17: Oxides and insulators III

O 17.1: Vortrag

Dienstag, 24. März 2009, 10:30–10:45, SCH A01

Oxygen adatoms at SrTiO₃(001): A density-functional theory study — •Hannes Guhl¹, Wolfram Miller¹, and Karsten Reuter² — ¹Institut für Kristallzüchtung, Max-Born-Str. 2, D-12489 Berlin, Germany — ²Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany

Apart from its use in photo-catalytic and sensing applications, the SrTiO₃(001) surface is also receiving increasing attention as a suitable substrate material for thin film growth. For the latter context the numerous reported surface reconstructions, partly in sensitive dependence of the applied annealing temperature, indicate a complex surface kinetics, which needs to be understood and controlled when aiming at growth experiments tailored to the atomic-scale. As a first step in this direction we carry out density-functional theory calculations addressing the energetics and electronic properties of adsorbed oxygen atoms at both regular terminations of SrTiO₃(001). With the bonding at the SrO-termination in general stronger than at the TiO₂-termination, we find in both cases that the most stable adsorption site does not correspond to the one expected from a continuation of the perovskite lattice. Instead, the ad-atom forms a strong bond to a surface oxygen atom that is reminiscent of the oxygen-oxygen bond in SrO₂. Mapping the potential energy surface for lateral adatom motion away from the stable site, the obtained diffusion barriers are about 0.8 eV in the isolated ad-atom limit. This suggests that, at least at the studied ideal terminations, oxygen mobility is not a major bottleneck under typical growth conditions.