Effects of annealing temperature on optical properties of ZnO nanocrystals embedded in SiO2 matrix thin films

ZnO nanocrystals embedded in SiO2 matrix thin films were fabricated on Si (1 0 0) single crystal substrates by plasma enhanced chemical vapour deposition (PECVD) at 230 deg. C. Subsequently, the as-deposited samples were annealed at different temperatures ranging from 500 deg. C to 900 deg. C, respectively. The effects of annealing temperature on optical properties of the thin films were investigated by Raman spectra and photoluminescence spectra. The results indicate that the annealing process can promote crystallinity and optical properties of the thin films, and that the optimized annealing temperature is 800 deg. C. They also suggest that the UV band originates from free exciton recombination, and the wide emission bands located from 2.71 to 2.91 eV are originated from localized trapping levels relating to the interface between ZnO and SiO2