The structure and electronic properties of single Cu atoms, copper monolayersand thin copper films on the polar oxygen and zinc terminated surfaces of ZnOare studied using periodic density-functional calculations. We find that thebinding energy of Cu atoms sensitively depends on how charge neutrality of thepolar surfaces is achieved. Bonding is very strong if the surfaces arestabilized by an electronic mechanism which leads to partially filled surfacebands. As soon as the surface bands are filled (either by partial Cu coverage,by coadsorbates, or by the formation of defects), the binding energy decreasessignificantly. In this case, values very similar to those found for nonpolarsurfaces and for copper on finite ZnO clusters are obtained. Possibleimplications of these observations concerning the growth mode of copper onpolar ZnO surfaces and their importance in catalysis are discussed.
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