Characterization of ZnO:Ni thin films deposited by the spin coating method

ZnO:Ni thin films with Ni content of 0, 3, 5 and 7% were deposited onto ITO/glass substrates using the spin coating method. The deposited films were characterized for their structural, photoluminescence and electrical properties by respectively X ray diffraction (XRD), Raman spectroscopy, photoluminescence spectroscopy (PL) and the four points probe techniques. XRD patterns showed that the deposited films were polycrystalline with a hexagonal wurtzite structure. The absence of the Ni related diffraction peaks reflected the substitution of Zn atoms by Ni atoms in the ZnO lattice. The variation of both lattice parameters and crystallite size, as a function of Ni content, indicated that the Ni doping enhance the structural properties of the deposited films. In Raman spectra, the band at 667.9 cm−1 appeared for doped samples, was attributed to the Zn sites occupied by Ni atoms in the ZnO lattice. In PL spectra, the decrease of the UV band emission intensity, as a function of Ni content, was attributed to Ni ions doping. The concentration of deep level defect such as Zni,VZn and VO, decreased as a function of the Ni content. The electrical resistivity increase correlated with the increase of the of Ni3+-related impurity concentration which behaves as a source of free electrons for n-type conduction.