Influence of precursor concentration and annealing treatment on the structural and optical properties of sol gel ZnO thin films.

Abstract

In this work, ZnO thin films were fabricated using the sol-gel spin coating process and their structural and optical characteristics were investigated for various precursor concentrations and annealing temperatures. Nanocrystalline ZnO thin films were successfully deposited on glass and silicon substrates using Zinc acetate dihydrate as the precursor material. X-ray diffraction (XRD) results show that the obtained ZnO films have a (002) preferential orientation, which depends strongly on precursor concentration and substrate nature. The Scherer formula reveals that the crystallites have a nanometric character and their average size varies between 10 and 40 nm. Scanning electron microscopy (SEM) exam showed granular surface with a relatively dense structure.

Using spectrophotometry, the measured transmittance of the ZnO thin film ranged from 75 to 95% in the visible light region. The variation of the direct band gap energy with the concentration of precursor and the annealing temperature is not very significant. The prepared ZnO thin films show an average band gap energy value evaluated at 3.31 ev.