Dependence of Transmission and Absorption on the post deposited annealing of Zinc oxide films

Abstract

Zinc oxide films were prepared using spray pyrolysis technique at different temperatures. Attempt was made to find the effect of native defects on the optical properties such as transmission and absorption of the films. To change the concentration and type of defects, the samples were annealed in vacuum and in air separately at 500°C for 1 hour. The thickness of the films were determined from the transmission data using ‘envelop’ method. The obtained results were used to calculate refractive indices of the films for different wavelengths. The results suggested that the vacuum annealed samples showed much change in refractive index inferring the presence oxygen vacancy. From the recorded absorption spectrum, the variation in the band gap energy were noted by plotting the (αhν)2 versus photon energy. The as deposited samples and that post annealed in air showed band gap energies consistent with the theoretical suggestion. The samples annealed in vacuum showed decrease in bandgap energy due to the presence of native defects such as oxygen vacancy. The results revealed that these properties are considerably affected by annealing inferring its dependence on native defects.