Radiative Defect Varying in Aging ZnO:Ag Nanocrystals

ZnO nanocrystal (NC) films prepared by ultrasonic spray pyrolysis and doped with Ag have been studied in as-grown and aged states. Photoluminescence (PL) and x-ray photo electronic spectroscopy (XPS) have been used in this study. PL spectra of as-grown ZnO:Ag NCs include a number of PL bands peaking at: 3.18 eV, 2.85 eV, 2.70 eV, 2.50 eV and 2.10 eV. It is revealed that the 2.70 eV and 2.85 eV PL bands are connected with Ag-doping ZnO NCs. PL intensities of the first three PL bands decline at aging, but the PL intensity of the orange PL band increases. This last fact indicates that aging at 300 K is connected with increasing the concentration of oxygen interstitials in ZnO NC films. In XPS research, the variation of substitutional AgZn defects and the formation of Ag-O bounds at aging have been detected. The nature of optical transitions and radiative defects varying at aging have been analyzed and discussed.