cm202947n_si_001.pdf (1.41 MB)
Interfacial Alloying in CdSe/CdS Heteronanocrystals: A Raman Spectroscopy Analysis
journal contribution
posted on 2016-02-22, 07:50 authored by Norman Tschirner, Holger Lange, Andrei Schliwa, Amelie Biermann, Christian Thomsen, Karel Lambert, Raquel Gomes, Zeger HensWe investigate the interface between core and shell in
zinc blende
CdSe-based CdSe/CdS dot-in-dot heteronanocrystals. Using X-ray diffraction
and transmission electron microscopy, we show that a CdS shell grows
coherently around the CdSe core. A comparison of the Raman spectrum
of bare CdSe nanocrystals and CdSe/CdS heteronanocrystals indicates
that the difference in lattice constant leads to compressive and tensile
strain in core and shell, respectively. Concomitant continuum mechanical
calculations follow this result, yet the calculated strain exceeds
the experimental values. Moreover, a detailed analysis of the CdSe/CdS
Raman spectra reveals the appearance of additional features upon shell
growth. A comparison with pure Cd(Se,S) alloyed nanocrystals relates
these features to alloy vibrations. We show that these observations
point toward the presence of a mixed Cd(Se,S) layer at the CdSe/CdS
interface. In this way, this work provides an experimental framework
based on Raman spectroscopy to analyze in detail interfacial alloying
in heteronanocrystals.