Regensburg 2007 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 31: Quantum dots and wires: Optical properties III
HL 31.11: Vortrag
Mittwoch, 28. März 2007, 17:30–17:45, H17
Room-temperature storage of excitons in elongated semiconductor nanocrystals — •Robert Kraus1, Pavlos Lagoudakis1, Andrey Rogach1, John Lupton2, Jochen Feldmann1, Dmitriy Talapin3, and Horst Weller3 — 1Lehrstuhl für Photonik und Optoelektronik, Ludwig-Maximilians-Universität München — 2Department of Physics, University of Utah, Salt Lake City, USA — 3Institut für Physikalische Chemie, Universität Hamburg
The excited state of colloidal nanostructures consisting of a spherical CdSe core overgrown with a rod-like CdS shell can be perturbed effectively by electric fields.[1-3] Field-induced fluorescence quenching coincides with a suppression of radiative rate without increasing ionization. After turning off the electric field, a significant fraction of quenched - and therefore stored - excitons recombines radiatively, even for a duration of the electric field pulse of up to 100 μs. Application of an electric field not only promotes the separation of electron and hole wave function but also influences the depopulation dynamics of localised states on the surface of the nanocrystal. This leads to a significant change in the exponent of the characteristic power law decay of the delayed luminescence. Furthermore, exciton storage selects the most polarisable particles, therefore a significant quantum confined Stark shift of ~15 meV along with a correlated broadening of the spectrum is visible in the time-resolved emission of the ensemble at room temperature.
[1] J. Müller et al., Phys. Rev. Lett. 93, 167402 (2004)
[2] R. Kraus et al., Phys. Rev. Lett. in press (2006)
[3] J. Müller et al., NanoLett. 5, 2044 (2005)