A theoretical investigation of the combined effect of confinement geometry, valley degeneracy, crystallographic orientations, and anisotropy of the effective mass on the intraband absorption of the conduction band of Si nanocrystals is presented. We show that the coupling between the nanocrystal shape and arbitrary orientations of the crystalline Si core plays a dramatic role in the intraband optical properties through interesting changes in the electronic structure and intra- and inter-valley degeneracy. Different orientations of the crystalline Si also affect the shape and orientation of the orbital wave functions, thereby modifying transition rules and fine structure of the intraband absorption. The anisotropy of the effective mass is also responsible for the emergence of absorption peaks that are not present in isotropic nanocrystals. Additional intraband transitions are also induced by changes in the nanocrystal shape with respect to spherical dots. Moreover, the quantum confined Stark effect blueshifts the absorption peaks and induces the appearance of peak structures as a consequence of the relaxation of selection rules caused by the displacement of the wave functions in response to external electric fields. This effect was found to be only appreciable in large nanocrystals.
|Original language||English (US)|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - Oct 15 2005|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics