Influence of substrate temperature on the physical properties of thermally evaporated nanocrystalline bismuth sulfide thin films

Nanocrystalline bismuth sulfide thin films were deposited on glass substrate by thermal evaporation technique using the solvothermally synthesized nanometer-sized bismuth sulfide powder as the source material. X-ray diffraction (XRD) analysis revealed that the films are polycrystalline in nature with orthorhombic structure. The crystallinity of the thin films improved with substrate temperature, and the estimated crystallite size are in the nanometer regime. Scanning electron microscope (SEM) analysis showed homogenous distribution of grains with well defined grain boundaries. The optical transmittance of the nanocrystalline bismuth sulfide thin films increases with the increase in substrate temperature, and the optical transition was found to be direct and allowed. The estimated optical band gap energy was found to decrease with the increase in substrate temperature. The electrical resistivity of the bismuth sulfide thin films is of the order of 10−4 Ω-cm and exhibits semiconductor nature. Experimental results demonstrate that the structural, optical and electrical properties of bismuth sulfide thin films have strong dependence on the substrate temperature.

► Nanocrystalline Bi2S3 thin films were prepared by thermal evaporation technique.
► Solvothermally synthesized Bi2S3 nanopowder was used as the source material.
► Effect of substrate temperature on the physical properties was investigated.
► The crystallinity and optical quality improved with substrate temperature.
► Grain boundary defects annihilate and electrical resistivity decreased.