Structural and Optical Studies of Bismuth Sulphide Nanocrystalline Thin Films Prepared from Acidic Aqueous Bath

Nanocrystalline thin films of bismuth sulphide (Bi2S3) of different molarities (0.2-1.0 M) and crystallite sizes (10-19 nm) were deposited on tin chloride-treated glass substrates from an acidic aqueous solution (pH = 2.0) of bismuth nitrate and sodium thiosulfate in the presence of ethylenediamine tetraacetic acid (EDTA) at a bath temperature of 333 K. Characterization of Bi2S3 thin films were carried out using X-ray diffraction (XRD), X-ray fluorescence, scanning electron microscopy, and optical absorption. Various structural parameters were calculated from the XRD spectra. The average crystallite size and thickness of the Bi2S3 thin films have been observed to increase with the increase in molarity. The Optical band gap energy of the films obtained from the absorption spectra was found to decrease from 2.47 to 2.28 eV when the molarity was varied from 0.2 to 1.0 M.