Abstract
Undoped ZnO and Zn1-xGdxO nanoparticles are made using a sono-chemical co-precipitation approach. X-ray diffraction and transmission electron microscopy investigations verified the formation of a wurtzite structure with spherical geometry. All the samples are found to be nanocrystalline by transmission electron microscopy, with crystallite diameters ranging from 14 to 22 nm. The optical constants are calculated via diffuse reflectance spectroscopy. The Urbach energy and photoluminescence spectrum both showed that all doped nanoparticle samples contained defects and disorder due to vacancies. The band structure finding suggest that the forbidden gap of ZnO may change due to the conduction band shift, Burstein-Moss shift, and shrinkage effect. The near band emission in the ultraviolet region and deep level emission of the photoluminescence spectrum are both strong and decreased with increasing Gd3+ concentration. Studies using X-ray absorption near edge spectroscopy revealed that the host nano-lattice Zn sites are substituted with Gd3+ cations to preserve the symmetry with minor distortion. Investigations into charge transfer through the oxygen bands (Gd-O-Zn) are made using O K-edge spectra. The defect emission bands identified through Gd doping indicated that these emissions may be changed for ZnO samples, which could be advantageous for applications in phosphors and light-emitting devices.