Impact of Trivalent Metal Ion Doping on Structural, Photoluminescence and Electric Properties of NiFe2O4 Thin Films

Nickel aluminum ferrite thin films of chemical formula NiFe2-xAlxO4 (0.0x1.0 in the step 0.2) were deposited on glass substrate using the spray pyrolysis deposition technique. The x-ray diffraction patterns exhibited single phase cubic spinel structure with space group Fd-3m. The Fourier-transform infrared spectroscopy (FTIR) spectra shows fundamental absorption bands related to octahedral and tetrahedral sites. The average surface roughness of all the thin films was estimated from AFM study, and is found on the order of 13-52nm. The grain size is in nanosize dimensions and distributed homogeneously over the surface of the thin film to analyze by the FE-SEM. The PL spectra obtained at room temperature showed the characteristic near-band-edge emission at around 680nm and 780nm. The DC electrical resistivity ((dc)) as the function of temperature was studied for various Al3+ substitutions that indicated the decreasing trend with the increasing temperature, which exhibited a semiconducting nature of thin film. The dielectric properties decreased with increase in the Al3+ ions. The dielectric behavior of Al3+ substituted nickel ferrite thin films was explained by using Koop's phenomenological model. The dielectric parameters, such as the dielectric constant (epsilon), dielectric loss (epsilon) and loss tangent (tan ) decreased with increase in the Al3+ ions substitution as well as showing normal behavior with frequency.