Designing quantum dots and quantum-dot solids

To design nanocrystal nanosystems, a theory for nanocrystals is needed whic h can be applied to nanocrystals with atomic-scale variations in compositio n, structure and shape. We present an empirical tight-binding theory for na nocrystal heteronanostructures. Electronic structure and optical absorption spectra are obtained for CdS/HgS/CdS and ZnS/CdS/ZnS quantum-dot quantum-w ell barrier/well/barrier nanocrystals. Comparison with experiment shows tha t tight-binding theory provides a good description of nanosystems with mono layer variations in composition. Well/barrier and well/barrier/well nanocry stal heteronanostructures also are modeled to illustrate state and energy-l evel engineering in nanocrystal nanosystems. (C) 2001 Elsevier Science B.V. All rights reserved.