Influence of strain/stress on the nonlinear-optical properties of sprayed deposited ZnO:Al thin films

► ZnO:Al 3at.% thin films show a free strain/stress. ► The strain/stress of the films can influence the crystallinity and the THG. ► The higher third order nonlinear optical susceptibility is obtained for a lower strain/stress value. Nanocrystalline ZnO:Al thin films were deposited by reactive chemical pulverization spray pyrolysis technique on heated glass substrates at 450°C to study their crystalline structure, composition, strain, stress, roughness characteristics and nonlinear optical susceptibility as a function of Al concentration (0, 2, 3, 5at.%). The films were characterized by X-ray diffractometer (XRD), EDAX 9100 analyser, atomic force microscopy (AFM) and third harmonic generation (THG). The Al (3at.%) doped ZnO thin films exhibited the lower strain/stress than undoped films. The nonlinear properties of the ZnO:Al thin films have been found to be influenced by the films strain/stress.