Tuning of structure, surface morphology and optical properties of spray-coated nickel tin oxide thin films by heat treatment

In this work, nickel tin oxide (NiSnO3) in a 1:1 ratio was synthesized using a simple spray pyrolysis technique followed by annealing at 450 °C for different time durations. The X-ray diffraction (XRD) revealed the polycrystalline nature with perovskite structure of NiSnO3 without the formation of any secondary phases. Annealing improved the crystallinity of the films. The annealed films exhibited a preference for orientation along the (310) plane. The largest crystallite size was obtained for 4 h of annealed film. The scanning electron microscopy (SEM) images of the films distinctly illustrate enhanced crystallinity following the annealing process. Energy-dispersive X-ray spectroscopy (EDS or EDX) indicates that the film possesses a near-stoichiometric composition. All the films resulted in more than 70 % transmittance in the visible region except for 8 h annealed. The gradual reduction of energy bandgap was observed for the sample. The four peaks at 358 nm, 415 nm, 436 nm, and 460 nm were observed in photoluminescence (PL) spectra corresponding to near band emission and defects related emissions respectively. The determined optical parameters from the present study indicate that the 4-h annealed film holds promise as a favourable option for optoelectronic and photonic devices.