Effect of post deposited annealing ambience and temperature on the longer visible absorption of zinc oxide films

Zinc oxide films were deposited on heated glass substrates at different substrate temperature 450°C and 500°C. After the deposition, some samples were heat treated at 500°C for one hour in air and some samples in vacuum for one hour at the same temperature. Absorbance analysis revealed that as deposited samples and post heat treated samples are showing intense absorption near 1.5eV apart from that corresponding to band gap of ZnO. The absorption coefficient variation with incident energy for the samples annealed in vacuum after deposition at 450° suggested the presence of oxygen vacancy as the native defect for the absorption near 1.5eV. The absorption energy for the samples obtained from (αhν)2 vs energy plot suggested that same kind of defect may be present in all the samples and is around 1.53eV. (paper)