Control of Phase, Structural and Optical Properties of Tin Sulfide Nanostructured Thin Films Grown via Chemical Bath Deposition

In this study, nanostructured tin sulfide (SnS) thin films were synthesized on glass substrates by means of low-cost chemical bath deposition using non-toxic trisodium citrate (TSC) as complexing agent. The influence of varying molar concentration of TSC (0.15–0.21 M) on the tin sulfide phases was investigated. The structural, morphological and optical properties of the films were studied using x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Raman spectroscopy and optical absorption spectroscopy. The XRD patterns confirmed an orthorhombic polycrystalline structure of the as-prepared SnS thin films. The values of average crystalline size and texture coefficient of the major XRD peak increased with increasing TSC concentration. The FESEM micrographs revealed that the synthesized thin films are characterized by a flake-stack structure. The Raman spectra of the films showed the presence of a Sn2S3 peak, which gradually declined in intensity until almost disappearing as the TSC concentration increased from 0.15 M to 0.21 M. The direct energy band gaps estimated from ultraviolet–visible–near-infrared absorption spectra also varied between 1.64 eV to 1.1 eV with increasing TSC concentration from 0.15 M to 0.21 M. The results indicate the crucial role of TSC in the synthesis of SnS nanostructured thin films.