Influence of Thickness on Optical Properties of ZnO Thin Films prepared by Radio Frequency Sputtering Technique

Abstract

Zinc oxide (ZnO) thin films of 75.5nm and 130.5nm were deposited at room temperature onto chemically and ultrasonically cleaned corning glass substrate by radio frequency technique and annealed at 150°C under nitrogen atmosphere for 60 minutes. The Zinc target of purity 99.99%, diameter 40mm and thickness 6.35mm was used. The optical properties of the films were ascertained by employing UV-VIS-NIR spectrophotometer (model AVASPEC 2048 MODEL). Influence of the thickness of the films on the optical properties was studied by keeping other deposition parameters constant. The optical transmittance spectra revealed an average transmittance of 81.49% and 84.26% for the 75.5nm and 130nm respectively. The band gap of the films was found to decreases with increase in thickness of the films. The band gap energy (Eg) is in the range of 3.28eV to 3.31eV respectively. Other optical parameters such as Absorbance, Reflectance and Urbach energy were also found to be thickness dependent. These effects of thickness on optical properties of ZnO thin films are suitable for solar cell applications