Effects of laser irradiation on the structure and optical properties of ZnO thin films

The effects of laser irradiation on the surface microstructure and optical properties of ZnO films deposited on glass substrates were investigated experimentally and compared with those of thermal annealing. X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements showed that the irradiation treatment with an Ar+ laser of 514 nm for 5 min improves the crystalline quality of ZnO thin films through increasing the grain size and enhancing the c-axis orientation, with the effects similar to those of the thermal annealing at 500 °C for 1 h. Laser irradiation was found to be more effective both for the relaxation of the residual compressive stress in the as-grown films and for the modification of the surface morphology. A significant increase in the UV absorption and a widening in the optical band-gap of the films were also observed after laser irradiation.