In situ deposition of Sn-doped CdS thin films by chemical bath deposition and their characterization

In-situ Sn-doped CdS thin films have been deposited successfully by the chemical bath deposition method using tartaric acid as a complexing agent. The films have been characterized by x-ray diffraction for structure determination, and microstructural parameters like crystallite size, rms strain and dislocation density have been calculated using x-ray line profile analysis. The composition of the films has been determined by x-ray photoelectron spectroscopy and energy dispersive x-ray analysis. Optical studies show that the band gap decreases significantly for pure CdS (2.39 eV) to 3.8 mol% of Sn-doped CdS (1.84 eV). A detailed PL study of CdS when doped with varying Sn concentrations has also been discussed. Temperature variation of the electrical resistivity of Sn-doped CdS thin films confirmed their semiconducting behaviour similar to the pure CdS. It also shows that doping of Sn in CdS makes a pronounced drop in the room temperature resistivity value from 10¹⁰–10³ Ω cm for pure CdS to 3.8 mol% of Sn-doped CdS, respectively.