Density-Functional Studies of Cr Adsorbed on Polar ZnO Surfaces

The atomic structure and electronic properties of Cr adsorbed on polar ZnO surfaces is studied using first-principles calculations based on density functional theory. It is found that the Cr atom at the on top of O forms a strong ionic bond, the electrons transfer from Cr to O atoms. The Cr atom is adsorbed at the hcp-hollow site on Zn-terminated surface forms metallic bonding with the surface Zn atom, shows a free-electron-like behavior. The adsorbed atoms could not effect more atoms in ZnO due to a strong screening of ZnO to the outside metal, the character of adsorption surfaces is only decided by the atoms near the surface.