Modification of the structural, linear and nonlinear optical properties of zinc oxide thin films via barium and magnesium doping

Abstract

In the current work, the structural, linear and nonlinear optical properties of zinc oxide thin films have been modified via barium/magnesium doping for modern optoelectronic applications. Ba/Mg-doped and undoped ZnO thin films were successfully prepared by the spray pyrolysis route. The surface morphology, structures' modification and structural parameters were explored using a field emission scanning electron microscope, FT-IR spectrophotometer and X-ray diffraction techniques, respectively. The XRD analysis shows that Ba/Mg-doped and undoped ZnO thin films possess a crystalline nature with a hexagonal wurtzite structure. The crystallite size of the undoped ZnO nanoparticles is 18.5 nm and varies to 21.4 nm (Ba:ZnO), 23.1 nm (Ba/Mg:ZnO) and 16.4 nm (Mg:ZnO). The optical properties (transmittance, absorbance and reflectance) were measured using a UV–visible spectrophotometer. The optical bandgap (Eg) of ZnO thin film decreases from 3.42 eV to 3.35 eV (Ba:ZnO), 3.25 eV (Ba/Mg:ZnO) and 3.31 eV (Mg:ZnO). The decrease in the Eg values of the doped ZnO films as compared with that of the undoped one is mainly attributed to the created defects and localized states in the bandgap of the host ZnO due to Ba/Mg-doping. Moreover, the major optical parameters (refractive index, distinction coefficient, dielectric constant) are also affected as a result of Ba/Mg-doping. Furthermore, a great effect of Ba/Mg-doping on the nonlinear optical constants (third-order optical susceptibility (χ(3)) and nonlinear refractive index (n2)) and first-order linear optical susceptibility (χ(1) is achieved. The obtained results show that the linear and nonlinear optical properties of ZnO film could be enhanced via Ba/Mg-doping for updated applications in multifunctional modern optoelectronics and high-speed communications.