The effect of introducing Al ions in cationic deposition bath on as-prepared PbS thin film through SILAR deposition method

Undoped and Al doped lead sulfide (PbS) thin films were grown on soda lime glass substrates by Successive Ionic Layer Adsorption and Reaction (SILAR) deposition method. Al content in aqueous cationic solution was varied by adding 0.5–2% of aluminum nitrate in step of 0.5. The characterization of the film was carried out using X-ray diffraction, scanning electron microscopy, and optical and electrical measurement techniques. X-ray diffraction analysis revealed that both the undoped and doped films were polycrystalline and exhibited galena type cubic structure with average crystallite size in the range of 15.5–30.9 nm. The compositional analysis results indicated that Pb, S and Al were present in the samples. Optical studies revealed prominent blue-shift in the absorption edge of as-deposited samples upon doping as compared to that of bulk PbS and this shift was due to a quantum confinement effect. The room temperature conductivity of the PbS thin films was in the range of 1.343×10−7–1.009×10−6 (Ω cm)−1for doped samples and 5.172×10−8 for undoped PbS thin film sample. The optical band gap energy has inverse relation with grain size and electrical conductivity is closely related to structural parameters like grain size, crystallinity and microstrain. The estimated lattice parameter, grain size, optical band gaps and electrical properties were correlated with Al concentration in the cationic solution.