Annealing Temperature Dependence of Various Properties of ZnO Nanoparticles Investigated with Soft XAS

Abstract

In this paper, structural, optical and electronic properties of ZnO nanoparticles were investigated with the variation in the annealing temperature. X-ray diffraction, High-Resolution Transmission Electron Spectroscopy, Absorption spectroscopy, Raman Spectroscopy and Soft X-ray spectroscopy techniques were invoked to investigate and gauge the effect of annealing temperature on these properties. Intact Hexagonal Wurtzite phase of the nanoparticles with increasing crystallinity and spherical shape with particle size between 20[Formula: see text]nm and 23[Formula: see text]nm [using both X-ray Diffractometer (XRD) and High-resolution Transmission of electron microscopy (HRTEM)], blue shift of absorption peak from 372[Formula: see text]nm to 366[Formula: see text]nm and Optical Band Gap from 3.24[Formula: see text]eV to 3.17[Formula: see text]eV (UV-Vis-NIR), narrowing of [Formula: see text] mode in Raman Spectra; all indicated enhanced crystallinity with increased annealing temperature. Effects produced by the sole variable such as annealing temperature on the indicative parameters in a definite order catapult the annealing conditions as a significant candidate for customized properties. To have a deeper insight at the electronic levels, Synchrotron-based X-ray absorption spectroscopic studies of ZnO nanoparticles were undertaken. The analysis of Soft XAS spectra showed the change in number of O 2[Formula: see text] and Zn 4[Formula: see text] unoccupied states with increasing particle size and crystallinity of ZnO nanoparticles for varying annealing temperature.