Temperature-induced crossover between bright and dark exciton emission in silicon nanoparticlesS. 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-fielddependent 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-fielddependent 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