Post-heat treatment effect on the properties of indium doped zinc oxide nanocrystals produced by the sol-gel method

Abstract

Indium-doped zinc oxide (In:ZnO) nanocrystals are successfully produced by a simple refluxed sol-gel technique. The influence of post-heat treatment/ annealing temperatures on the structure, morphology, optical and luminescence properties of nanostructures was investigated using X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), energy dispersion X-ray spectroscope (EDS), UV–Vis and photoluminescence spectroscopies (PL). The XRD results revealed that the synthesized In:ZnO materials are nanocrystalline with a predominant hexagonal wurtzite structure. The average crystallite sizes and lattice constants of the In:ZnO nanoparticles increase with an increase in annealing temperature. SEM micrographs confirmed the nanostructure of the material and showed that the morphologies of In:ZnO nanoparticles varied from prism-like to spindle-like and then to disk-like structures. The reflectance band edge shifted towards longer wavelength while the band gap energy decreased with an increase in annealing temperature. In addition, the PL spectra show a sharp UV and broad yellow-orange emissions in the visible range that shifts slightly due to the influence of annealing temperature. The results illustrate that an optimum property of In:ZnO nanomaterial can be produced when the samples are annealed in the temperature range of 500 to 600 °C.