Nucleation and Growth of CdSe Layers on ZnS Quantum Crystallite Seeds, and {Vice Versa} under, in Inverse Micelle.

Approximately 45angstroms diameter semiconductor particles involving a layer of CdSe on a ZnS seed and vice versa, have been grown and ``capped'' with organic ligands in inverse micelle solutions. These quantum crystallites exhibit size dependent electronic properties, with partially developed band structure. The composite particles, as well as the ``capped'' seed particles of CdSe and ZnS, have been isolated and purified. In order to understand the structural and electronic properties of such layered particles, they all have been characterized by optical absorption, luminescence, X-ray fluorescence, powder X-ray diffraction, Auger, and transmission electron microscopy. The CdSe seed, and the composite CdSe particle grown on a ZnS seed, undergo a low temperature structural annealing at 169C to give a near single crystal cluster. The CdSe annealing is blocked if there is a monolayer of ZnS on the surface. A small 15angstroms ZnS seed inside a 45angstroms diameter CdSe particle has little effect on the lowest excited electronic state; this result is in agreement with a simple theoretical model. Growth of CdSe on ZnS seeds shows disproportionation, in that CdSe prefers to grow on composite particles having thicker CdSe surface layers. Neither composite particle exhibits epitaxial growth.