Volume 79, Number 3, August 2007
Article Number 37002
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 16 July 2007
EPL, 79 (2007) 37002
DOI: 10.1209/0295-5075/79/37002

Temperature-induced crossover between bright and dark exciton emission in silicon nanoparticles

S. Lüttjohann1, C. Meier1, M. Offer1, A. Lorke1 and H. Wiggers2

1  Experimental Physics and CeNIDE, University of Duisburg-Essen - Lotharstraße 1, D-47048 Duisburg, Germany
2  Combustion and Gas Dynamics, University of Duisburg-Essen - Lotharstraße 1, D-47048 Duisburg, Germany

received 8 March 2007; accepted in final form 19 June 2007; published August 2007
published online 16 July 2007

The excitonic fine structure of silicon nanoparticles is investigated by time-resolved and magnetic-field$\hbox{--} $dependent photoluminescence. The results are analyzed using the common model of an excitonic fine structure consisting of a bright and a dark exciton. We find that the radiative recombination rates of both excitons differ only by a factor of eight. Therefore, we observe a thermal crossover in the character of the emission from bright-exciton-like to dark-exciton-like. The validity of our model is further supported by magnetic-field$\hbox{--} $dependent measurements, in which effects of state mixing are observed.

78.67.Bf - Nanocrystals and nanoparticles.
78.55.-m - Photoluminescence, properties and materials.
71.35.-y - Excitons and related phenomena.

© Europhysics Letters Association 2007