Preparation of nanocrystalline Cd-doped PbS thin films and their structural and optical properties

PbS and Cd-doped PbS nanocrystalline thin films prepared by the chemical bath deposition technique was deposited onto glass substrates at 80 °C. The aqueous solution containing Cd2+ and Pb2+ precursors was used to obtain good quality film deposits at optimized preparative parameters. The characterization of these films was performed using X-ray diffraction, optical absorption, photoluminescence properties, scanning electron microscopy and energy dispersive X-ray analyses to explore the properties of the PbS and Cd-doped PbS films. The prepared films were adherent to the substrate and well crystallized according to the cubic structure, which displayed a preferred orientation. According to the X-ray diffraction analysis, the crystallite size of the films decreased from 74 nm to 64 nm with increasing Cd doping. The optical properties were determined from ultraviolet-visible spectroscopy measurements in the absorbance energy range from 300-1200 nm. The UV-visible analysis shows that the band gap value of the PbS thin films increased from 2.12 eV to 2.65 eV by doping with Cd. Morphological analysis showed that the shape of the grains over the substrate surface was changed from a regular random orientation to an irregular shape with Cd doping. The energy dispersive X-ray analysis showed that the film contains Cd, Pb and S elements without any other impurities.