First principles study of ZnO adsorption on stressed metal surfaces

The effect of a stressed metal surface on the structural and energetic properties of adsorbed ZnO monomers and small n-mers is investigated using the first principles density functional theory. It is found that the monomers prefer to align parallel to a Ag (111) surface and that they cause a local surface rumpling effect when the metal is subjected to compressive strain. The surface rumpling, which is not present without the monomer, acts to relieve the surface tension. ZnO dimers and trimers do not aggregate to form three-dimensional clusters but instead form linear chains of alternating Zn and O atoms also parallel to the surface. The preference for chains suggests that two-dimensional structures would form in the early stages of ZnO growth on a metal surface when more monomers are adsorbed. Cross-linking of the chains could easily create Zn3O3 hexagonal rings with the same symmetry as the (111) surface leading to the formation of graphitic (h-BN like) ZnO which has already been observed experimentally.