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The ultraviolet emission line at 3.315 eV is observed at 8K in ZnO polycrystalline films and investigated by temperature-dependent photoluminescence spectra and cathodoluminescence spatial image. The relative intensity of 3.315eV emission line depends strongly on growth and annealing conditions. The cathodoluminescence image shows that the 3.315eV emission localizes on the surface and ridge of ZnO grain. These results suggest that the 3.315 eV emission attributes to Zn interstitials at the grain surface and ridge. This emission is stable in the range from 8K to 300K and contributes to the room temperature ultraviolet band.

Nitrogen-doped ZnO (ZnO:N) films are prepared by thermal oxidation of sputtered Zn3N2 layers on Al2O3 substrates. The correlation between the structural and optical properties of ZnO:N films and annealing temperatures is investigated. X-ray diffraction result demonstrates that the as-sputtered Zn3N2 films are transformed into ZnO:N films after annealing above 600° C. X-ray photoelectron spectroscopy reveals that nitrogen has two chemical states in the ZnO:N films: the NO acceptor and the double donor (N2)O. Due to the No acceptor, the hole concentration in the film annealed at 700° C is predicted to be highest, which is also confirmed by Hall effect measurement. In addition, the temperature dependent photoluminescence spectra allow to calculate the nitrogen acceptor binding energy.

N-ZnO/p-Si heterojunctions are prepared by sputtering deposition of intrinsic ZnO films on p-Si substrates. Thicknesses of ZnO films are altered by varying the deposition time from 1 h to 3 h. The electrical properties of these structures are analysed from capacitance-voltage (C-V) and current-voltage (I-V) characteristics performed in a dark room. The results demonstrated that all the samples show strong rectifying behaviour. Photovoltaic property for the samples with different thicknesses of ZnO films are investigated by measuring open circuit voltage and short circuit current. It is found that photovoltages are kept to be almost constant of 320 mV along with the thickness while photocurrents changing a lot. The variation mechanism of the photovoltaic effect as a function of thickness of ZnO films is investigated.