Electrical and optical properties of thin films with a SnS₂ - Bi₂S₃ alloy grown by sulphurization

In this work, thin films of SnS₂ with increased Bi content were grown by sulphurization of a thin film of Sn:Bi alloy, at temperatures around 300°C. The effect of the Bi concentration on the optical, electrical and structural properties was determined through measurements of spectral transmittance, conductivity and x-ray diffraction XRD respectively. It was found that the optical constants (refractive index n, absorption coefficient α and energy gap Eg) and the electrical conductivity are significantly affected by the Bi concentration. In particular, a variation of the energy gap between 1.44 and 1.63 eV and a change of the conductivity greater than three orders of magnitude were observed when the content of Bi in the Sn:Bi alloy varied between 0 and 100 %. The analysis of the XRD measurements allowed us to find that the SnS: Bi films grow with a mixture of the SnS₂ and Bi ₂S₃ phases, independently of the Bi content.