Citrate-controlled chemical solution deposition of PbSe thin films

Trisodium citrate (citrate) is a commonly used co-complexing agent, yet its effect on the deposition of PbSe on GaAs from solution has not been systematically studied. This study focuses on the kinetics affecting the deposition of PbSe in the presence of citrate, which are shown to be particularly important for cases in which the bath composition is limited to relatively low pH values (<13). The film microstructure and optical properties were studied as a function of citrate concentration. The optical band gap presented a strong dependence on citrate concentration due to quantum confinement. Two distinct morphologies were found in the film, a nanocrystalline layer followed by columnar grains. Photoluminescence showed two different peaks that were correlated with the different morphologies. The results are in good agreement with simple particle-in-a-box quantum confinement models, with a weaker confinement observed for the 2D columnar region.