Annealing-induced phase conversion on spray pyrolyzed cubic-SnS thin films

The cubic-tin sulfide (SnS) compound material is optimal for the absorber layer in photovoltaic technology. In this study, the role of annealing temperature on the physical properties of cubic-SnS thin film has been determined. The spray pyrolyzed SnS thin films were post-annealed, using the chemical vapor deposition system, at the temperature range between 350 and 500 °C The annealed films have been analyzed using a comprehensive range of characterization techniques i.e., X-ray diffraction (XRD), Raman spectroscopy, UV–Vis spectroscopy, Photoluminescence spectroscopy (PL), Field-emission scanning electron microscopy (FESEM), Energy dispersive spectroscopy (EDS) and Hall measurements. The XRD results discovered the phase deterioration of cubic-SnS at higher annealing temperatures i.e., > 350 °C. Further, the Raman analysis confirmed the cubic-SnS phase deterioration, along with the formation of SnS₂ and Sn₂S₃ secondary phases, at higher annealing temperatures. Besides that, a band gap in the range of 1.63–1.68 eV has been obtained for the SnS thin films. The films exhibit the near-band edge emission peak in the PL spectra. Moreover, the SEM micrographs show the needle-shaped grains, and their size and distribution were increased with respect to the enhancement in annealing temperature. A considerable amount of sulfur inclusion was observed in EDS analysis and the films annealed at 450° exhibit the near stoichiometric composition ratio of Sn/S = 1.01. The hall measurement studies showed resistivity, carrier concentration, and mobility of 29.4–376.5 Ω cm, 4.2 × 10¹⁴–3.0 × 10¹⁶ cm⁻³ and 13.1–66.1 cm²/Vs, respectively.