Influence of silver dopant on the morphology and ultraviolet emission in aligned ZnO nanostructures

Silver-doped ZnO nanostructures were prepared by a chemical vapor deposition (CVD) method. Compared with pure ZnO, the doped samples have a lower crystallinity and a shift of the (002) diffraction peak to lower angle. X-ray photoelectron spectroscopy (XPS) results testify the incorporation of silver (Ag) into the ZnO nanostructures with the ratio of Ag/Zn - 1.22%. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs show that the introduction of Ag leads to morphological changes, and that the prepared nanostructures are single crystalline and grow along the (0002) direction. The detailed growth mechanism of the nanostructures is proposed and discussed. The room-temperature photoluminescence (PL) spectra indicate that the introduction of Ag can improve the intensity of ultraviolet (UV) emission, suggesting the great application prospect in UV optoelectronic devices. The temperature-dependent PL spectra reveal that the nature of UV emission in Ag-doped ZnO nanostructures should be related with the free-exciton (FX) longitudinal optical (LO) phonon replicas, and the enhanced UV emission could be attributed to the increasing concentration of excitons caused by Ag doping. (c) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim