The energetic, structural and electronic properties of neutral O and Zn vacancies in ZnO nanowires having different sizes was investigated using first-principles calculations and density functional theory. It was found that, for ZnO nanowire with an O vacancy on the surface, the formation energy was insensitive to the size change. The presence of the surface O vacancy resulted in the formation of metal-metal bonds. From a band structure analysis, it was predicted that the optical property related to the O vacancy could be strongly altered by decreasing the nanowire diameter. There was also a large structural deformation of the surface in the presence of a Zn vacancy. The formation of a Zn vacancy in the ZnO nanowire with diameter of 16.4Å was more favorable than in those with smaller diameters. Furthermore, the O vacancy was non-magnetic whereas the Zn vacancy was spin-polarized with a magnetic moment of 2.0µB on the surface.

Size Effects on Formation Energies and Electronic Structures of Oxygen and Zinc Vacancies in ZnO Nanowires: a First-Principles Study. Fang, D.Q., Zhang, R.Q.: Journal of Applied Physics, 2011, 109[4], 044306