CHEMICAL BATH DEPOSITION OF CDSE LAYERS FROM CD(II)-SELENOSULFITE SOLUTIONS

The chemical bath deposition of CdSe layers from cadmium acetate + sod ium selenosulfite solutions was studied by means of quartz crystal mic robalance (QCM) experiments, combined with electron microscopy observa tions and energy-dispersive X-ray analysis. Nanocrystalline deposits w ith the cubic blende structure are obtained showing confinement effect s. From mass vs. time measurements and modeling of the time derivative , it is established that the nucleation and growth process occurs via two steps: the first corresponds to an instantaneous nucleation of cyl indrical nuclei, with two-dimensional growth until complete coverage o f the substrate; the second consists of a three-dimensional instantane ous nucleation and growth process occurring on sites randomly distribu ted on the evolving surface. The addition of silicotungstic acid to th e deposition bath is shown to influence the growth kinetics of the CdS e deposit. From analysis of the kinetic data, and from the transmissio n and scanning electron microscope images, it is suggested that the ch emical deposition of CdSe occurs through the aggregation of colloids a nd not according to an atom-by-atom mechanism.