Sulfide precursor concentration and lead source effect on PbS thin flms properties

Lead sul?de (PbS) thin ?lms were synthesized using chemical bath deposition (CBD). Bath solutions are formed of various concentrations of thiourea, sul?de source, ranged from 0.6 to 1.2 M and two different salts as Pb source (lead acetate and lead nitrate). From the growth mechanism, we inferred that PbS is formed through the ion by ion process when using acetate lead source, while, using nitrate source yields to ?lms growth through the complex decomposition process. Due to the difference in the involved growth process, lead acetate produces ?lms with larger crystallite size (from 4 to 16 nm), smooth and dense ?lms. However, lead nitrate produces rough ?lms with smaller crystallite size (from 1 to 4 nm).Increasing the thiourea concentration results in crystallinity improvement when using lead acetate and, oppositely, in crystallinity degradation when using lead nitrate. Due to the quantum effect caused by the small crystallite sizes, the ?lms optical gap is varied from 0.5 to 0.9 eV.