Effect of oxygen pressure on the structural and optical properties of ZnO/Si(100) thin films

Abstract

ZnO thin films (thickness ~ 400 nm) were prepared at different oxygen content (O2) by radio frequency (rf) sputtering method. Crystal structure and optical properties of these films were investigated by x-ray diffraction (XRD) and UV-VIS-NIR spectrophotometer, respectively. XRD measurement suggests that all films have hexagonal wurtzite structure. The transparency in the visible region of all the film is more than 90%. The optical absorption edge was described using the direct transition model proposed by Tauc and the optical band gap was calculated from the absorption coefficient by Tauc’s extrapolation procedure. The value of optical band gap was decreased with increase in the O2 content; due to Burstein-Moss shift.