Direct bandgap optical transitions in Si nanocrystals
A. A. Prokofiev+, A. S. Moskalenko+*, I. N. Yassievich+, W. D. A. M. de Boer∇, D. Timmerman∇, H. Zhang, W. J. Buma, T. Gregorkiewicz∇
+Ioffe Physico-Technical Institute, 194021 Saint-Petersburg, Russia *Institut für Physik, Martin-Luther-Universität, Halle-Wittenberg, Germany ∇Van der Waals-Zeeman Institute, University of Amsterdam, NL-1018 XE Amsterdam, The Netherlands Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, NL-1018 WS Amsterdam, The Netherlands
PACS: 73.22.Dj, 78.67.-n
Abstract
The effect of quantum confinement on the direct bandgap of
spherical Si nanocrystals has been modelled theoretically. We
conclude that the energy of the direct bandgap at the
Γ-point decreases with size reduction: quantum confinement
enhances radiative recombination across the direct bandgap and
introduces its "red" shift for smaller grains. We postulate to
identify the frequently reported efficient blue emission
(F-band) from Si nanocrystals with this zero-phonon
recombination. In a dedicated experiment, we confirm the "red"
shift of the F-band, supporting the proposed
identification.
|