Berlin 2008 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 14: Heterostructures

HL 14.3: Vortrag

Montag, 25. Februar 2008, 10:00–10:15, ER 164

Anisotropic light emission of single CdSe/CdS tetrapods due to asymmetric electron localization — •Thomas Limmer¹, Christian Mauser¹, Enrico Da Como¹, Andrey Rogach¹, Dmitri V. Talapin², and Jochen Feldmann¹ — ¹Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universität München, Munich, Germany — ²Department of Chemistry, University of Chicago, Chicago, IL, USA

We have recently reported on highly luminescent CdSe/CdS tetrapod heterostructures, where wurtzite CdS arms were grown on CdSe zinc-blend nuclei [1]. Due to the peculiar energy band alignment the holes remain trapped in the CdSe core, whereas electrons in ideal tetrapods are expected to delocalize symmetrically into the four CdS arms. However, polarization dependent photoluminescence experiments on single tetrapods show asymmetric localization effects for electrons. Whereas in optical excitation nearly no polarization anisotropy is observed, high polarization degrees are present in the emission process. Calculations based on the effective mass approximation show that the electron wavefunction confinement is very sensitive to changes in the shape of the tetrapods. Breaking the symmetry by increasing the thickness of one arm gives rise to a strongly asymmetric localization of the electron and leads to high polarization degrees in emission. The related decrease in electron-hole wavefunction overlap results in a correlation between emission intensity and polarization anisotropy in agreement with our experimental findings. [1] D. V. Talapin et al., Nano Lett. 7, 2951 (2007)