METAL CHALCOGENIDE SEMICONDUCTORS GROWTH FROM AQUEOUS SOLUTIONS

The chemical bath deposition of CdSe layers has been studied by means of quartz crystal microbalance (QCM) experiments, combined with TEM, HREM observations and EXAFS measurements. From mass vs time measurements and the modelling of the time derivative, it is established that the nucleation/growth process occurs via two steps : the first one corresponds to an instantaneous nucleation of cylindrical nuclei, with a 2D-growth until a complete coverage of the substrate ; the second one consists of a 3D-instantaneous nucleation and growth process occuring on sites randomly distributed on the evolving surface. The addition of silicotungstic acid to the deposition bath is shown to influence the growth kinetics of the CdSe deposit. Nanocrystalline deposits with the cubic blende structure are obtained showing confinement effects. After thermal treatment CdSe shows an hexagonal wurtzite structure with a large density of defects and the grain size is increased.