ZnO nanocrystals with different oxygen vacancy concentrations were characterized by high-resolution electron energy loss spectroscopy. ZnO nanocrystals showed a decrease in green emission with increasing annealing temperature in an oxygen environment and which significantly quenches in a sample annealed at 400C. O K and Zn L3 pre-edge absorption structures of ZnO nanocrystals were studied by high-resolution electron energy loss spectroscopy as a function of annealing temperature. Absorption edge peak broadening and variation in pre-edge absorption edge structure of Zn L3 were observed in experimental electron energy loss spectroscopy spectra with different oxygen defect concentrations. All electron density functional theory based calculation of electronic density of states and electron energy loss near edge structure were carried out with different oxygen vacancy concentrations and compared with experimental observations. Appearance of additional peaks in pre-edge electron energy loss structure with increasing oxygen vacancy was shown to be due to the oxygen defect states in the band-gap just below the conduction band.

Electron Energy Loss Spectroscopy of ZnO Nanocrystals with Different Oxygen Vacancy Concentrations. Dileep, K., Panchakarla, L.S., Balasubramanian, K., Waghmare, U.V., Datta, R.: Journal of Applied Physics, 2011, 109[6],  063523