Excitonic exchange splitting and Stokes shift in Si nanocrystals and Si clusters

Toshihide Takagahara, Kyozaburo Takeda

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Abstract

The size dependence of the electron-hole exchange interaction in Si nanocrystals is investigated and the excitonic exchange splitting is predicted to be as large as 300 meV in extremely small Si clusters. The exciton-phonon interaction in Si nanocrystals for acoustic phonon modes is formulated to calculate the Stokes shift and the Huang-Rhys factor. It is found that the observed onset energy of photoluminescence can be interpreted mainly in terms of the excitonic exchange splitting, although the contribution from the Stokes shift is not negligible. The importance of the self-consistent determination of the effective dielectric constant of Si clusters including the excitonic effect is demonstrated in view of the possibility of resolving the large discrepancy between theories and experiments concerning the size dependence of the exciton energy.

Original languageEnglish
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume53
Issue number8
Publication statusPublished - 1996
Externally publishedYes

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Excitons
Nanocrystals
nanocrystals
excitons
shift
Exchange interactions
Beam plasma interactions
Photoluminescence
Permittivity
Acoustics
interactions
permittivity
photoluminescence
acoustics
energy
Electrons
Experiments
LDS 751

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

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AU - Takeda, Kyozaburo

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AB - The size dependence of the electron-hole exchange interaction in Si nanocrystals is investigated and the excitonic exchange splitting is predicted to be as large as 300 meV in extremely small Si clusters. The exciton-phonon interaction in Si nanocrystals for acoustic phonon modes is formulated to calculate the Stokes shift and the Huang-Rhys factor. It is found that the observed onset energy of photoluminescence can be interpreted mainly in terms of the excitonic exchange splitting, although the contribution from the Stokes shift is not negligible. The importance of the self-consistent determination of the effective dielectric constant of Si clusters including the excitonic effect is demonstrated in view of the possibility of resolving the large discrepancy between theories and experiments concerning the size dependence of the exciton energy.

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