Chemical bath deposition of PbS nanocrystals: Effect of substrate

Nanocrystalline PbS layers have been deposited chemically on Si, Ge and GaAs substrates from alkaline solutions containing 0.05 mol l-1 of Pb(NO3)2, 0.04 mol l-1 of thiourea, 0.05 mol l-1 of triethanolamine, and 0.15 mol l-1 of NaOH. Rutherford backscattering spectroscopy, transmission electron and atomic force microscopy reveal that the chemical nature of the substrate has a profound influence on the structure and thickness of the deposited layers. It is found that a large lattice mismatch between the substrate and PbS results in formation of coarse-grained layers with a small effective thickness (e.g. PbS on Si). On the other hand, close matching of lattice constants leads to deposition of thicker layers with smaller grain size (e.g. PbS on Ge, GaAs)