Regensburg 2007 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 13: Poster 1
HL 13.49: Poster
Montag, 26. März 2007, 15:00–17:30, Poster A
Raman studies of surface phonons in CdSe and CdS quantum dots embedded in dielectric media — •Yuriy Azhniuk1, Volodymyr Dzhagan2, Stepan Kuchmii3, Alexandra Raevskaya3, Alexandr Stroyuk3, Mykhailo Valakh2, and Dietrich Zahn4 — 1Institute of Electron Physics, Uzhhorod, Ukraine — 2Institute of Semiconductor Physics, Kyiv, Ukraine — 3Institute of Physical Chemistry, Kyiv, Ukraine — 4Chemnitz University of Technology, Chemnitz, Germany
Contribution of surface phonons strongly affects Raman spectra of quantum dots (QDs). In spite of a number of studies for CdSe and CdS, there is still no unique opinion on the behaviour of surface phonon parameters on the QD size. Moreover, since surface phonons are localized near the QD / host matrix interface, they can be sensitive to the type of host media as well as to the shell type for capped QDs.
Here we present resonant micro-Raman studies of surface phonons of bare and capped colloidal CdSe and CdS QDs in different organic media (gelatine, polyvinyl alcohol, polyacrylamide) as well as those grown in silicate glass. Measurements were performed using a Dilor XY 800 spectrometer and different Ar laser lines for excitation.
The dependences obtained for the surface phonon frequency, halfwidth as well as surface-to-LO phonon intensity ratio on the QD size, excitation wavelength, type of host media, passivating shell are analyzed. The results are compared with the calculations in the framework of a dielectric continuum model. The differences observed can be related to the QD surface reconstruction.