Effect of annealing on structural, optical and electrical properties of nickel oxide thin films synthesized by the reactive radio frequency sputtering

In this paper, Nickel oxide (NiO) thin films were synthesized by the reactive radio frequency sputtering. NiO thin films were annealed at different temperatures (350, 400, 450 and 500 C). Structural characterizations were performed using X-Ray Diffraction, Scanning Electron Microscopy (SEM), Raman spectroscopy, Infrared spectroscopy. Ultraviolet-visible spectrophotometer were used to estimate the energy band-gap and the thickness. Electrical resistivity measurements were carried out using the four-point probe method then analyzed basing on the structural characterization. The XRD patterns showed that the crystallite size increases by increasing the annealing temperature from 6.3 to 15.8 nm. The structure is cubic with lattice parameter of 4.17 nm and the dislocation and micro strain decrease by annealing. The Thin films surfaces were observed to be homogenous and without cracks. The Raman spectra proved the presence of four peaks, related to vibration of Ni-O bands. The FTIR spectra showed the NiO stretching and bending mode. The optical analyses showed that the transmittance and energy band gap augments by increasing the annealing temperature from 3.54 to 3.68 eV. Finally, the resistivity grows by annealing from 0.33 to 1.4 x 10(4) omega cm and decreases by increasing the measuring temperature.