Effect of environment and heat treatment on the optical properties of RF-sputtered SnO_2 thin films

摘要

Thin films of SnO_2 were deposited by RF-magnetron sputtering on quartz substrates at room temperature in an environment of Ar and O_2. The XRD pattern shows amorphous nature of the as-deposited films. The optical properties were studied using the reflectance and transmittance spectra. The estimated optical band gap (E_g) values increase from 4.15 to 4.3 eV as the Ar gas content decreases in the process gas environment. The refractive index exhibits an oscillatory behavior that is strongly dependent on the sputtering gas environment. The Urbach energy is found to decrease with increase in band gap. The band gap is found to decrease on annealing the film. The role of oxygen defects is explored in explaining the variation of optical parameters.