Regensburg 2007 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 25: Quantum dots and wires: Optical properties II
HL 25.6: Talk
Tuesday, March 27, 2007, 15:15–15:30, H17
Temperature-induced crossover between bright and dark exciton emission in silicon nanoparticles — •Cedrik Meier1, Stephan Lüttjohann1, Matthias Offer1, Axel Lorke1, and Hartmut Wiggers2 — 1Physics Department, University of Duisburg-Essen, D-47048 Duisburg, Germany — 2Combustion \& Gas Dynamics, University of Duisburg-Essen, D-47048 Duisburg, Germany
Silicon nanoparticles are attractive candidates for photovoltaic and optoelectronics applications, as they allow to combine the advantages of a semiconducting material with the ease of handling of dispersed particles. Moreover, the availability of silicon and the scalability of heterogenous gas-phase synthesis routes are promising for low-cost devices. We have studied the excitonic fine structure of silicon nanoparticles by time-resolved and magnetic-field 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. This makes it possible to thermally switch the nature of the recombination from bright-exciton-like to dark exciton-like. The validity of our model is further supported by magnetic-field dependent measurements, in which effects of state mixing are observed. We show that silicon nanoparticles offer a unique possibility to directly assess dark exciton photoluminescence.