Electronic Structures and Optical Properties of the O Vacancy in ZnO

The electronic structures and optical properties of ZnO0.875 were calculated by the ultra-soft pseudo-potential plane wave (pp-pw) method based on density functional theory. The crystal structure of ZnO with oxygen vacancies was optimized using first-principles. The electronic-state densities in pure ZnO and ZnO0.875 were then calculated. The dielectric functions, absorption spectrum, refractive index, extinction coefficient, and reflectivity of ZnO0.875 dominated by electron inter-band transitions were analyzed in terms of the precisely calculated density of state and the polarization dependencies of the optical properties were discussed in detail. Results indicate that the ZnO0.875 crystal is a uniaxial crystal and exhibits some features in the low energy region, which are caused by the O vacancy. Our results provide new insights into the study of the luminescent behavior of ZnO and offer theoretical data for the design and application of ZnO optoelectronic materials.