Tin Sulfide Films By Spray Pyrolysis Technique Using L-Cysteine As A Novel Sulfur Source

Tin sulfide films were deposited by spray pyrolysis method using aqueous solutions containing tin chloride (SnCl2) and L-cysteine (HO2CCH(NH2)CH2SH) as a novel source of sulfur instead of commonly used thiourea. L-cysteine prevents SnCl2 from hydrolysis due to a complex formation as confirmed by Fourier Transformed Infrared Spectroscopy studies. The solution that contained SnCl2 (Sn) and L-cysteine (S) at molar ratios of Sn: S=1: 1, 1: 2 and 1: 4 was sprayed onto glass substrates at varied temperatures between 200 degrees C and 370 degrees C. Films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and UV-Vis spectroscopy. According to XRD, spray of the 1: 1 solution results in films that are composed of SnS as a main crystalline phase. An unidentified crystalline phase was present independent of the growth temperature. Single phase SnS films with bandgap value of 1.7 eV could be grown using the 1: 2 solution at deposition temperature of 370 degrees C. Films grown from 1: 4 solutions are amorphous using deposition temperatures below 370 degrees C, and composed of a mixture of SnS and Sn2S3 phases when grown at 370 degrees C. EDX study shows that SnS films contain high amount of carbon and oxygen containing residues independent of the deposition temperature and precursors' molar ratio in the spray solution. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim