Comparative studies on structural, optoelectronic and electrical properties of SILAR grown PbS thin films from acidic, neutral and alkaline cationic reaction bath

摘要

Thin films of Lead sulphide (PbS) were grown on soda lime glass substrate by Successive Ionic Layer Adsorption and Reaction method from acidic, neutral and alkaline cationic precursor reaction bath by keeping the pH of the anionic precursor invariant. The structural and morphological aspects of the as prepared samples were investigated using XRD and SEM results. The as-prepared samples were polycrystalline with nanometer sized grains and identified as galena type cubic structure. The values of average crystallite size were found to be in the range 22-30 nm. The SEM micrographs show variations in morphology. Optical studies revealed the existence of both direct and indirect band gap with values in the range of 1.65-1.98 and 0.61-0.90 eV respectively. The room temperature conductivity of the PbS thin films were in the range 1.19 × 10~(-8)-5.92 × 10~(-8) Ω cm~(-1). 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 micro strain. The estimated lattice parameter, grain size, optical band gaps, solid state and electrical properties were correlated with pH of the cationic solution. In this work, we establish that the pH of the cationic precursor media has colossal effect on the structural, morphological, optoelectronic, solid-state and electrical properties of PbS thin films.