Refractive index of SnS thin nano-crystalline films

•SnS films were grown by thermal evaporation.•Films were nano-crystalline with grains having size 10–25 nm.•Nature of band-gap variation shows grains are in nano regime.•The refractive index of the films depend on the lattice ordering.•Thus refractive index was shown related to grain size.

The refractive indices of nano-crystalline thin films of Tin Sulphide (SnS) were investigated here. The experimental data conformed well with the single oscillator model for refractive indices. Based on the this, we explain the increasing trend of refractive index to the improvement in crystal ordering with increasing grain size.