Effect of gamma ray irradiation on structural and surface properties of c-axis oriented ZnO thin films

Abstract

The changes in structure and surface morphology of ZnO thin films due to gamma ray irradiation at high doses are reported. Raman spectroscopy measurements indicate improvement in wurtzite ZnO phase by a higher amount with initial dose of 66 kGy (kGy) and by a lower amount for doses of 132 kGy and 200 kGy. Improvement in c-axis orientation was confirmed by X-ray diffraction measurements. X-ray diffraction measurements also showed a decrease in average crystallite size of ZnO. This is attributed to dissociation of Zn-O bonds by gamma rays which was identified using spectroscopy measurements. Gamma ray irradiation induced surface rearrangement and change in surface roughness with dose were identified using atomic force microscopy measurements. The observed results are explained on the basis of displacement damage and partial annealing effects caused by energetic gamma rays in ZnO thin films.