Characteristic properties of spin coated ZnO thin films: the effect of Ni doping

Pure and Ni doped ZnO thin films have been grown on a glass substrate with the sol-gel spin coating technique. The structural, morphological and optical features of ZnO thin films were examined as a function of Ni doping concentration. According to the x-ray diffraction (XRD) patterns, all films exhibited hexagonal wurtzite crystal structure. It was observed that the (002) peak position shifted the Bragg angle slightly higher with increasing Ni doping concentration. The scanning electron microscope (SEM) images indicated that the surface morphology of the ZnO thin films depended on the Ni doping content. Additionally, the presence of the Ni contribution was proved by energy-dispersive x-ray spectroscopy (EDX) measurements. The optical properties, such as transmittance, band-gap and Urbach energy, were evaluated by UV-VIS measurement. Moreover, all films have an optical transmission of higher than 80% and the optical band-gap values decreased from 3.27 eV to 3.19 eV depending on Ni content. The Urbach energy and steepness parameters were also studied and all results were discussed, taking Ni doping concentrations into account.