Effect of Surface Roughness on Laser Induced Nonlinear Optical Properties of Annealed ZnO Thin Films

Variation of nonlinear optical properties with surface roughness of ZnO thin films deposited on corning glass substrates at different annealing temperature (TA) was reported. The films were characterized by X-ray diffraction (XRD), UV-Vis-NIR transmission and single beam z-scan technique using second harmonics of Nd: YAG laser. Surface morphology of the samples was investigated by atomic force microscopy (AFM). Surface roughness was found minimum (8.4 nm) for ZnO sample annealed at 450 °C. The nonlinear optical properties (NLO) were found to be dependent on surface roughness and the highest value of third order nonlinear susceptibility (χ(3)=4.3×10−7 esu) was obtained for ZnO at TA 450 °C.