Dresden 2009 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 9: Nanoparticles II

CPP 9.2: Vortrag

Montag, 23. März 2009, 14:15–14:30, ZEU 114

Investigations to the Influences of Charges on the Fluorescence of Single CdSe/ZnS Quantum Dots Dependent on Crystal Size — •Nicole Amecke-Mönnighoff and Frank Cichos — Molecular Nanophotonics Group, Institute of Experimental Physics I, University Leipzig, Linnéstraße 5, 04103 Leipzig

The fluorescence properties of semiconductor nanocrystals (quantum dots) are intensively studied due to many potential applications, which want to make use of their tunable emission wavelength, high quantum yield and photon statistics. Considering their fluorescence in more detail many peculiarities can be found. Along those are antibunching, power-law blinking, lifetime-fluctuations and spectral diffusion. Most of those can be explained by charges close to or in the dot center leading to Auger processes (non-radiative energy transfer to those charges) and the quantum confined stark effect. Those charges can arise from ejection of electron or hole via tunneling leaving behind the counterpart and additionally changing the matrix charge constellation. We study all those characteristics on Qdot CdSe/ZnS crystals by time-resolved spectroscopy in particular as a function of crystal size. We find strong indications of fluctuating radiative and non-radiative rates for all sizes, however suggesting that the closer vicinity of the interface in smaller crystals is more stringent in switching the crystal either on or off.