Tight-binding studies of surface effects on electronic structure of CdSe nanocrystals: the role of organic ligands, surface reconstruction, and inorganic capping shells

We utilize a tight-binding model to study the effects of surface structure on electronic properties of CdSe clusters. The model takes into account exp erimental information about structure and shape of the nanocrystals, as wel l as the nature and distribution of capping ligands. The effects of both or ganic capping ligands and inorganic capping shells on the densities of stat es (DOS) and on the single-particle absorption spectra of the clusters are calculated for various cluster shapes and sizes, and are compared to result s for clusters with truncated surfaces. For organic capping ligands, the ef fect of ligand hybridization is investigated and a simple model of surface reconstruction is developed. Both ligand hybridization and surface reconstr uction are seen to have a major influence on the band edge electronic and o ptical properties. Inorganic capping shells give rise to differential local ization of valence and conduction band edge states, with the hole primarily confined to the core region and the electron more evenly distributed over both core and shell.