Structural and optical characterization of Mg-doped nickel ferrite thin films

This work reports the growth and deposition of pure and Mg-doped nickel ferrite thin films (Ni_1-xMg_xFe₂O₄, x = 0.0,0.1,0.2,0.3,0.4 and 0.5) using spray pyrolysis technique. The thin films were deposited on clean and ultrasonicated pre-heated glass substrate. The structural characterizations were made using X-ray diffraction technique (XRD). All the thin films possess single-phase cubic spinel structure, as evidenced from the XRD analysis. The crystallite size was evaluated using Scherrer formula and found to be vary in the range of 11 nm to 21 nm. The structural parameters like lattice constant (a), unit cell volume (V), X-ray density (d_x), micro strain (ε) and dislocation density (δ) were obtained and their variation with Mg content is discussed. Lattice constant and unit cell volume increase with Mg content x, X-ray density decreases with Mg content x, and the other structural parameters do not show any systematic trend. The surface morphological observations were carried out using Field emission scanning electron microscopy technique (FE-SEM). The spherical grains with average grain size between 26 and 41 nm were observed. The FTIR spectra recorded at room temperature show two metal oxygen absorption bands within the range 400 cm⁻¹–600 cm⁻¹. Raman spectra reveal five active modes namely T₂g (3), Eg, A₁g characterizing the spinel structure. With Mg doping, the Raman modes slightly shifted. The optical properties were studied using UV–Visible spectroscopy technique. The band gap energy values obtained from Tauc plot vary between 1.61 eV and 1.90 eV. I–V studies reveal the ohmic nature showing high values of resistivity. The obtained results are useful for photocatalytic degradation and gas sensing application.