Structural, Morphological, Optical, and NH3 Gas Sensing Properties of Fe-Doped NiO Nanostructured Thin Films Prepared by Chemical Spray Pyrolysis

Pure and iron doped nickel oxide (NiO) thin films at 2% and 4% Fe levels were successfully deposited onto glass substrates by chemical spray pyrolysis (CSP) technique. That which relates to the effect of iron doping on the structural, morphological, optical, and gas-sensing properties of the films was studied in a systematic way out. X ray diffraction (XRD) analysis put forth a polycrystalline cubic structure with a preferential orientation along the (111) plane. Also, we saw an increase in the average crystallite size from 15.40 nm in pure NiO to 24.38 nm in 4% Fe doped films at the same time, we noted a drop in dislocation density from 24.45 x 10 to the power of 14 to 10.53 x 10 to the power of 14 lines/m squared. Atomic force microscopy showed that iron doping reduced surface roughness and also the average particle size. Also, we reported over 77.8% in the visible region for the optical transmittance which at the same time saw the absorption coefficient go up with iron concentration. Also, we saw the optical band gap narrow from 3.70 eV in pure NiO to 3.60 eV. At 180°C we saw that the sensitivity of ammonia (NH₃) gas to be 48.1% for pure NiO, which went down to 6.7% at 270 ppm for 4% Fe-doped films, which is a result of lower sensor response as we increased doping.