The role of solution composition in chemical bath deposition of epitaxial thin films of PbS on GaAs(1 0 0)

Spontaneous reaction of Pb(NO3)2 and CS(NH2)2 in aqueous NaOH solution was used for depositing PbS thin films on GaAs(1 0 0) single-crystal substrates. The effects of reagent concentrations at constant deposition time and temperature were studied. The concentrations of NaOH and CS(NH2)2 were found to be major factors which affect the film morphology and microstructure. Single-crystal film growth was induced by increasing pH, which, as in the case of increasing temperature, leads to enhanced availability of sulfide anions in solution. X-ray diffraction and transmission electron microscopy (TEM) indicated development of a 〈1 1 0〉 texture with increasing film thickness. Epitaxy was determined by cross-sectional TEM analyses, which showed a (0 1 1)PbS||(1 0 0)GaAs, [01¯1]PbS||[011¯]GaAs orientation relationship between the film and the substrate.