Optical properties of ZnO thin films prepared by automatic sol-gel method

In this work, ZnO thin films were deposited on glass substrate using automatic sol-gel process, rather than conventional sol-gel process, and the optical properties of the prepared films were also measured. Using zinc acetate, ethanol, diethanolamine and de-ionized water, ZnO films were prepared by varying the number of coatings (2-5 dipping iterations) for zinc acetate concentrations of 1.0 mol/L. The films were decomposed at 300°C for 1 h and, after giving final coating, were annealed at 500°C for 2 h. Optical transmittance measurements of the deposited films have been carried out with UV/Visible spectrometer at 200-900 wavelengths. The prepared ZnO films have been found to be highly transparent in the visible range. The average transmittance of ZnO films for 2 coatings has been found to be of 92% in the visible range with high absorbance in the UV-region and the direct and indirect allowed band gap has been found to be of 3.21 eV and 3.08 eV respectively.