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Wet chemical synthesis and characterization of tin sulphide thin films from different host solutions

A. J. Ragina, K. C. Preetha,  K. V. Murali, K. Deepa and T. L. Remadevi

Tin sulphide thin films have been deposited on glass substrates by chemical bath deposition from various host solutions. In the present work, three different host solutions were used. One comprises of stannous chloride, thioacetamide and acetone, second bath contains stannous chloride, sodium thiosulphate and tartaric acid and the third bath contains stannous chloride, thioacetamide, and glacial acetic acid. The as grown films were smooth, well adherent and brown in color and were highly reproducible in the ambient conditions. The as prepared films were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and optical measurements. The film compositions were determined by energy dispersive X-ray analysis (EDAX). XRD patterns showed that the films developed were uniform and polycrystalline in nature with orthorhombic structure. There is a considerable difference in the nature of growth and their crystalline form. SEM images of the SnS films confirmed the formation of nanowires of diameter 57 nm, spherical grains of 151 nm and uniform nanowires having a diameter of 24 nm from the first, second and third baths respectively. Film smoothness and uniformity were confirmed from the absence of pin holes and cracks in the SEM images. Purity of the films was established by EDAX analysis and films from the third bath showed good stoichiometry. The transmittance versus wavelength measurement showed transparency of about 80% in the wavelength range 600-1000 nm for the films from first bath. The films from second and third bath showed transparency of only 50% in the range 600-1000 nm. Absorption spectra revealed medium absorption in the visible region and a decrease with higher wavelength. Films fabricated from the baths possess a direct band gap of 1.9 eV, 1.1 eV and 1.79 eV respectively. We believe that this is the first report of synthesis of uniformly dispersed tin sulphide nanowires. The properties demonstrated by the films make them potential candidates as absorber layer in the fabrication of hetero junction solar cells. Also, since the constituent elements of the films are nontoxic and abundant in nature, promotes the development of devices that are environmentally safe.