Ultraviolet Luminescence Depending on Zn Interstitial in ZnO Polycrystalline Films

The ultraviolet emission line at 3.315eV 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 3.315eV 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.