Influence of Fe2+/Fe3+ ions in tuning the optical band gap of SnO2 nanoparticles synthesized by TSP method: Surface morphology, structural and optical studies

Fe doped nanostructured SnO2 thin films are prepared by a thermal spray pyrolysis (TSP) method at a substrate temperature (Ts) 450 °C. In addition, an effort is made to comprehend the effect of Fe doping on the surface morphology, micro-structural and optical properties of SnO2 thin film. The result of XRD data confirms that the fabricated SnO2 films are tetragonal cassiterite structure and the lattice parameters are slightly changed with Fe2+/Fe3+ contents. The values of lattice parameters are analogous in Rietveld refinement and DFT function. The lattice strain and stresses value are ranging from 2.07 to 0.13, × 10−3 and 0.71-0.04 respectively. The films are made up of nano-sized crystals with slender and polyhedron shaped particle size ranging from 17.23 to 159.50 nm observed by field emission scanning electron microscope (FESEM), Scherrer's formula and uniform deformation model (UDM). With increasing Fe concentrations, the optical band gap of SnO2 films is decreased from 3.89 to 3.39 eV. Reduction in optical band gap is attributed to the influence of Fe ions and conduction/valence bands of SnO2 structure. Fe doped SnO2 nanostructured film addresses the suitability of the material to have a good potential application in optoelectronic devices.