Effect of Annealing and Oxygen Flow on the Optical Properties of ZnO Thin Film Grown by Using Pulsed Laser Deposition

ZnO thin films have been deposited on (001) sapphire substrates by using a pulsed laser deposition (PLD) technique with a Nd:YAG laser at a wavelength of 266 nm. The deposition of the films was performed at substrate temperatures in the range of 300 similar to 450 degrees C and at a flow rate of 100 similar to 700 sccm before annealing treatment in an oxygen ambient. In order to investigate the effect of the annealing treatment on films deposited at a fixed oxygen pressure of 350 sccm and a substrate temperature of 400 degrees C, we annealed films at various temperatures after deposition. After annealing treatment in the oxygen ambient, the structural properties of the ZnO thin films were characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The optical properties of films were also characterized by using photoluminescence (PL). The crystallinity of the ZnO thin film was improved with increased annealing temperature. As the post-annealing temperature was increased, the intensity of the UV peak broadened and decreased. In particular, the position of the visible luminescence peak shifted to a shorter wavelength, and its intensity was increased at 800 degrees C.