Influence of S/Sn ratio on microstructural, morphological and optical properties of tin monosulfide thin films

Tin monosulfide (SnS) is promising candidate as a photovoltaic material due to its large tuneable physical properties, which can be achieved by altering the synthesis conditions. Synthesis of pure phase SnS with high crystallinity is really a challenging issue for researchers. The present work mainly focuses on synthesis SnS nanoparticles using a direct reaction approach and manipulate their properties by altering S content. The formation of orthorhombic α-SnS nanoparticles with preferential orientations along the (400) direction has been confirmed by X-ray Diffraction (XRD). Energy Dispersive X-ray analysis (EDX) is used to investigate the elemental composition of all synthesised SnS nanoparticles. SnS nanoparticles of different compositions are deposited on glass substrate using thermal evaporation. The crystal structures of deposited SnS thin films are analysed by XRD. Fourier Transform Infrared (FTIR) spectra indicate the Sn–S bond stretching around 580 - 950 cm−1 including a broad peak around 950 - 1450 cm−1. The Raman spectrum of all SnS thin films shows peaks at 136 ± 2, 190 ± 2, and 231 ± 2 cm−1 assigned as Ag mode of SnS. The presence of excess sulphur impacts on the surface morphology of the SnS thin film and is noticeable in FESEM images. UV–Vis–NIR absorbance spectrum revealed that the visible-light absorption of the SnS thin film was significantly high (α ∼105 cm−1). The calculated direct bandgaps of SnS thin films are found to increase (1.63–2.43 eV) with increasing sulphur ratio. •Attempt a new approach to the synthesis of SnS nanoparticles via a direct reaction method.•Strong influence of Sulphur (S) content is noticeable in structural, morphological and vibrational properties in thin film.•The direct optical bandgap of SnS thin films is found to blue shift with increasing S content.•All the term are neccessary to represent the property of thin film.