Dresden 2014 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 54: Poster Session 3

CPP 54.74: Poster

Thursday, April 3, 2014, 15:00–19:00, P2

The effect of electric fields on CdSe-nanocrystals — •Robert Niemöller, Daniel Braam, Günther M. Prinz, Martin Geller, and Axel Lorke — Experimentalphysik und CENIDE, Universität Duisburg-Essen

Using a micro-photoluminescence (µ-PL) setup, we investigate field-induced spectral changes in the emission of CdSe/ZnS nanocrystals, pumped with a Nd:YVO₃ laser. We embed the nanocrystals between two layers of polymethylmethacrylat (PMMA) and place them inside a capacitor-like structure consisting of a doped silicon substrate and thin transparent metal electrodes. Thus, we are able to subject the crystals to a tunable electric field and record their PL simultaneously. Small agglomerates of crystals show different behavior in their PL when a voltage is applied, depending on the substrates used. The samples with p-doped substrates show a shift in their peak energy, which is proportional to the square of the applied voltage, caused by the quantum-confined Stark effect. From this dependency we can extract the polarizability of the nanocrystals which is in good agreement with values measured by other groups on a different sample structure. However, the samples prepared on n-doped substrates only show a shift when a negative voltage is applied to the metal electrode, leading to an asymmetric Stark shift. When cooled down to approximately 15 K, the structures on p-doped substrates exhibit a similar asymmetric dependence of the PL energy on the applied voltage.