Post-deposition thermal treatment of sprayed SnS films

SnS films were grown in air by chemical spray pyrolysis method using aqueous solutions containing SnCl2 and SC(NH2)2 at molar ratios of 1:1 and 1:8 and a substrate temperature of 200 °C. As-deposited films were thermally treated at 450 °C in nitrogen or vacuum atmospheres. All samples were studied using X-ray diffractometry, Raman spectroscopy, energy-dispersive X-ray analysis, and ultraviolet-visible spectroscopy. The as-grown films consisted of cubic SnS as the only crystalline phase regardless of the molar ratio of the precursors in the spray solution. Annealing of the 1:1 films (derived from the 1:1 solution) in vacuum yielded metallic Sn, whereas annealing in N2 produced films composed of a mixture of cubic SnS and SnO2 phases, indicating the presence of oxygen-containing non-crystalline phases in the as-grown films. Thermal treatment of the 1:8 films in nitrogen yielded films composed of Sn2S3, whereas vacuum annealing produced films consisting of orthorhombic SnS with a bandgap energy of 1.4 eV.