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Phase-separation in ZnxCd1-xSe/C Core/shell nanocrystals studied with cathodoluminescence spectroscopy

Published online by Cambridge University Press:  01 February 2011

Yevgeni Estrin ,
Daniel H Rich ,
Ofer Moshe ,
Sayan Bhattacharyya  and
Aharon Gedanken
Yevgeni Estrin
Affiliation:
estriny@bgu.acw.il, Ben-Gurion University of the Negev, Department of Physics, Beer-Sheva, Israel
Daniel H Rich
Affiliation:
danrich@bgu.ac.il, Ben-Gurion University of the Negev, Department of Physics, Beer-Sheva, Israel
Ofer Moshe
Affiliation:
mosheo@bgu.ac.il, Ben-Gurion University of the Negev, Department of Physics, Beer-Sheva, Israel
Sayan Bhattacharyya
Affiliation:
sayan1001@gmail.com, Bar-Ilan University, Department of Chemistry, Ramat-Gan, Israel
Aharon Gedanken
Affiliation:
gedanken@mail.biu.ac.il, Bar-Ilan University, Department of Chemistry, Ramat-Gan, Israel
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Abstract

ZnxCd1-xSe/C core/shellnanocrystals with 31-39 nm diameter semiconductor cores and 11-25 nm-thick carbon shells were synthesized from solid state precursors. Transmission electron microscopy showed striations on a scale of ˜1 – 5 nm in the nanocrystals that are indicative of a composition modulation, and reveal a chemical phase separation and possible spinodal decomposition within the nanocrystals. Such a composition modulation within the ternary nanocrystals represents a rarely reported phenomenon that could lead to additional applications. The optical properties and carrier relaxation kinetics of the nanocrystals were examined with variable excitation cathodoluminescence (CL). As the excitation level is increased, carrier filling in two-dimensional (2D) phase-separated Cd-rich regions leads to a partial saturation of states before the onset of carrier filling in the higher bandgap homogenous Zn0.47Cd0.53Se regions. In order to model the state filling using Fermi-Dirac statistics for non-interacting carriers, a random quantum well model was used to determine the electron and hole eigensates in the Cd-rich regions of the nanocrystals.

Keywords

nanostructureoptical propertiesluminescence
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1260: Symposium T – Photovoltaics and Optoelectronics from Nanoparticles , 2010 , 1260-T10-03
Copyright
Copyright © Materials Research Society 2010

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