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Z-Contrast Stem Imaging and Eels of CdSe Nanocrystals: Towards the Analysis of Individual Nanocrystal Surfaces

Published online by Cambridge University Press:  21 February 2011

A.V. Kadavanich ,
T. Kippeny ,
M. Erwin ,
S. J. Rosenthal  and
S. J. Pennycook
A.V. Kadavanich
Affiliation:
Oak Ridge National Laboratory, Solid State Division, Oak Ridge, N 37831 Vanderbilt University, Department of Chemistry, Nashville, N 37235
T. Kippeny
Affiliation:
Oak Ridge National Laboratory, Solid State Division, Oak Ridge, N 37831
M. Erwin
Affiliation:
Oak Ridge National Laboratory, Solid State Division, Oak Ridge, N 37831
S. J. Rosenthal
Affiliation:
Oak Ridge National Laboratory, Solid State Division, Oak Ridge, N 37831
S. J. Pennycook
Affiliation:
Vanderbilt University, Department of Chemistry, Nashville, N 37235
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Abstract

We have applied Atomic Number Contrast Scanning Transmission Electron Microscopy (Z-Contrast STEM) and STEMIEELS (Electron Energy Loss Spectroscopy) towards the study of colloidal CdSe semiconductor nanocrystals embedded in MEH-PPV polymer films. Z-Contrast images are direct projections of the atomic structure. Hence they can be interpreted without the need for sophisticated image simulation and the image intensity is a direct measure of the thickness of a nanocrystal. Our thickness measurements are in agreement with the predicted faceted shape of these nanocrystals.

Our unique 1.3Å resolution STEM has successfully resolved the sublattice structure of these CdSe nanocrystals. In [010] projection (the polar axis in the image plane) we can distinguish Se atom columns from Cd columns.

EELS measurements on individual nanocrystals indicate a significant amount (equivalent to 0.5-1 surface monolayers) of oxygen on the nanocrystals, despite processing in an inert atmosphere. Spatially resolved measurements at 7Å resolution suggest a surface oxide layer.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 581: Symposium F – Nanophase & Nanocomposite Materials II , 1999 , 503
Copyright
Copyright © Materials Research Society 2000

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References

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