Spin-polarized density functional theory calculations were performed for a Zn vacancy on the ZnO(10•0) surface. Two stable configurations of the surface Zn vacancy were found, and the activation energy barrier was estimated to be ~0.01eV. The lower energy configuration had a newly formed surface Zn-O bond to restore the bulk-like structure on the surface. Due to the newly formed bond, the vacancy state in the band gap was characterized by a complicated hybridization of neighboring surface and subsurface atoms and by a more extended electron density. Despite such a hybridization, the surface Zn vacancy was found to have a robust magnetic moment of 1μB; implying that surface Zn vacancies may be responsible for the ferromagnetism observed in ZnO thin films and nanoparticles. Simulated scanning tunnelling microscope images showed that the two structures of the surface Zn vacancy could be distinguished in the filled-state images.

Electronic Structures of a Zn Vacancy on the ZnO(1010) Surface: Density Functional Theory Calculations. Chae, K., Kim, H.: Journal of the Korean Physical Society, 2013, 62[3], 508-12