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HL: Halbleiterphysik

HL 50: Quantenpunkte und -dr
ähte: Optische Eigenschaften III

HL 50.7: Vortrag

Freitag, 12. März 2004, 12:30–12:45, H14

How individual are individual CdSe nanocrystals? A single nanocrystal study. — •Frank Cichos¹, Abey Issac², Thomas Blaudeck¹, and Christian von Borczyskowski² — ¹Institut für Physik 123705, TU Chemnitz, 09107 Chemnitz — ²Institut für Physik 121501, TU Chemnitz, 09107 Chemnitz

The control of the emission intermittency (No-dqblinkingNo-dq) of single semiconductor nanocrystals is one of the challenging tasks to create nano-units i.e. for optoelectronic applications. Such a control has to be based on the understanding of the blinking process itself, which is currently only poorly understood. For this purpose we study the blinking process of individual ZnS capped CdSe nanocrystals over long time periods to compare the behavior of different nanocrystals. While fluorescent dye molecules commonly show a very specific blinking statistics, which differs from molecule to molecule due to the local environment of the molecule, all studied nanocrystals obey the same blinking statistics within the measurement accuracy. Further, a change of the surrounding matrix does not influence the statistics of the blinking process. Therefore, the processes behind the blinking have to be hierarchical processes. We propose that one of these processes, which is responsible for the dark periods in the emission time traces of individual nanocrystals is a charge diffusion through trap states in the direct vicinity of the nanocrystal. A more detailed analysis of the blinking further reveals that the processes which limit the emitting (on) and non-emitting (off) periods of the nanocrystal are partly decoupled, since on and off periods follow different statistical laws.