Regensburg 2013 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 12: Poster: Nanoparticles and Composite Materials

CPP 12.9: Poster

Montag, 11. März 2013, 17:30–19:30, Poster C

Fast Spectral Analysis of Quantum Dot Blinking — •Clemens Göhler, Cornelius Krasselt, and Christian von Borczyskowski — Chemnitz University of Technology, Institute of Physics, Germany

While investigating individual semiconductor nanocrystals (quantum dots, QDs) using single molecule techniques, photoluminescence intermittency (blinking) can be observed. This means emission is temporarily suppressed under constant excitation. This behaviour can be explained by a trapping model, assuming electron and hole to be localised in trap-states in QD interfaces or the environment [1].

It has been shown that a two-level-system with on- and off-intensity does not exactly describe the blinking process since experiments imply the existence of intermediate intensities as well [2]. According to the trapping model, this may refer to a hole-trapping mechanism. Additionally, the localised charge will influence the recombination process due to the quantum-confined Stark effect, resulting in spectral shifts within the photoluminescence.

In our experiments we investigate this spectral diffusion in relation to the intermediate intensities. Confocal microscopy is used to detect photoluminescence light from single ZnS/CdSe QDs. Moreover, emission light is separated onto two individual photodiodes by passing a dichroic beam splitter and the intensity levels are determined from recorded photon arrival times using a Change-Point-Algorithm.

[1] F. Cichos, C. von Borczyskowski, M. Orrit: COCIS 12(2007), 272.

[2] R. Schmidt, C. Krasselt, C. von Borczyskowski: Chem. Phys. 406(2012), 9.