Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 24: Adsorption III

O 24.9: Talk

Tuesday, March 28, 2006, 17:45–18:00, TRE Phys

Self-Organization of Au Atoms on a polar FeO film — •Emile D. L. Rienks, Niklas Nilius, Hans-Peter Rust, and Hans-Joachim Freund — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4–6, 14195 Berlin

On polar oxide surfaces, the large surface dipole can have a significant effect on the adsorption characteristics. We have explored this effect using a mono-layer thick film of FeO grown on Pt(111). In this system a surface dipole is built up between the positive Fe and the negative O layers. A lattice mismatch between the FeO film and the Pt substrate gives rise to a Moiré pattern, in which Fe atoms alternately occupy on-top, fcc and hcp positions on the Pt lattice. Modulations of the surface dipole have been observed within the Moiré unit cell that can be traced back to the structural inhomogeneity of the film. Single Au atoms, deposited at 10 K, preferentially bind to the region of the Moiré cell with the largest surface dipole. This indicates a significant role of electrostatic interaction in the binding. In addition, the Au atoms display a remarkably small tendency to form clusters upon increasing the coverage. Instead, a hexagonal network of single atoms with a lattice constant of 2.5 nm is formed. Electrostatic repulsion between polarized or partially charged Au atoms can account for this phenomenon.