Annealing Effects on Band Tail Width, Urbach Energy and Optical Parameters of Fe₂O₃:Ni Thin Films Prepared by Chemical Spray Pyrolysis Technique

In this research, nickel doped Iron oxide (Fe₂O₃:Ni) thin films were deposited onto glass substrates by using chemical spray pyrolysis (CSP) technique. The deposited films thickness was found to be about 350 ± 30 nm. The films were annealed at two different temperatures (450 °C and 500 °C). The X-ray Diffraction spectra (XRD) results indicate that the structure of the three prepared thin films was polycrystalline in nature and has a hexagonal phase with preferred orientation along (104) plane. Temperature annealing effects on the optical properties of the deposited films was studied. It was found that, the optical parameters, such as the refractive index (n), the real (ε₁) and imaginary (ε₂) parts of dielectric constant which related to n, Urbach energy and the energy gap; all depend on the annealing temperature. The results show that there was a reduction in the optical absorbance as well as the dielectric constants. The dispersion parameters decreased with the increasing annealing temperature while the determined Urbach energy was increased. The optical energy gap decreased from 2.74 to 2.67 eV with the increasing annealing temperature, on the account that there is an inverse relation between Urbach energy and energy gap.