Designing quantum dots and quantum-dot solids

To design nanocrystal nanosystems, a theory for nanocrystals is needed which can be applied to nanocrystals with atomic-scale variations in composition, structure and shape. We present an empirical tight-binding theory for nanocrystal heteronanostructures. Electronic structure and optical absorption spectra are obtained for CdS/HgS/CdS and ZnS/CdS/ZnS quantum-dot quantum-well barrier/well/barrier nanocrystals. Comparison with experiment shows that tight-binding theory provides a good description of nanosystems with monolayer variations in composition. Well/barrier and well/barrier/well nanocrystal heteronanostructures also are modeled to illustrate state and energy-level engineering in nanocrystal nanosystems.