Photoluminescence spectroscopy (PL), X-Ray Diffraction (XRD), Enegy dispersive spectroscopy (EDS) and Scanning Electron Microscopy (SEM) were used for the comparative characterization of ZnO and ZnO Er nanocrystals (NCs) obtained by spray pyrolysis method with different Er-doping (0, 1, 2, 3, 4 and 5at%). High temperature annealing in the range of 400-900 oC for 2 hours in nitrogen flow has been applied after the spray pyrolysis process. SEM study has confirmed the nanocrystal (NC) structure of obtained ZnO and ZnO Er films. X-Ray diffraction has detected the wurtzite crystal structure in ZnO and ZnO Er NCs.
Presented results have shown that the crystal quality of ZnO:Er NC films can be improved at a small level of Er-doping (≤ 3at%) together with intensity enlarging the near band edge (NBE) emission and PL bands related to the inner-shell optical transitions in Er ions. In contrary, at high level of Er-doping (≥3at%) the ZnO:Er crystallinity falling down, the PL intensities of NBE and Er-related PL bands decrease, but the intensity of green PL band related to native defects enlarges. The impact of temperatures at annealing and the mechanisms of mentioned emission transformations are discussed as well.