Self-organization of gold atoms on a polar FeO(111) surface

The spatial distribution of single Au atoms on a thin FeO film has been investigated by low-temperature scanning tunneling microscopy and spectroscopy. The adatoms preferentially adsorb on distinct sites of the Moire cell formed by the oxide layer and the Pt(111) support and arrange into a well-ordered hexagonal superlattice with 25 A lattice constant. The self-organization is the consequence of an inhomogeneous surface potential within the FeO Moire cell and substantial electrostatic repulsion between the adatoms.