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Fluctuation Microscopy: A New Class of Microscopy Techniques for Probing Medium Range Order in Amorphous Materials

Published online by Cambridge University Press:  02 July 2020

J. M. Gibson
Affiliation:
University of Illinois, Dept. Materials Science, 1304 W. Green Street, Urbana, IL, 61801 University of Illinois, Dept. Physics, 1110 W. Green Street, Urbana, IL, 61801
M. M. J. Treacy
Affiliation:
tNEC Research Institute, Inc., 4 Independence Way, Princeton, NJ, 08540
P. M. Voyles
Affiliation:
University of Illinois, Dept. Physics, 1110 W. Green Street, Urbana, IL, 61801
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Amorphous materials are devoid of periodic long range order, but at the nearest-neighbor level they possess a high degree of short-range order. In amorphous tetrahedral semiconductors, such as Si and Ge, this short-range order arises because each atom attempts to satisfy four bonds arranged as a regular tetrahedron. It is the rotations about each bond, from the second-nearest-neighbor outwards, that result in the loss of long-range order. It is apparent from modeling of amorphous materials, that there is considerable flexibility as to how rapidly the medium-range-order diminishes. The continuous random network (CRN) is a hypothetical tetrahedral extended structure wherein the atoms possess full four-connected coordination, but have minimal medium-range order. However, real amorphous materials infrequently exhibit true CRN-like topologies. Traditionally, diffraction has been used to study short- and medium-range order in amorphous materials. Assuming kinematical scattering, and that every atom has a similar environment, a radial distribution function (RDF) can be extracted which is sensitive only to the averaged atom pair-correlations out to ∼1 nm.

Type
Nanophase and Amorphous Materials
Copyright
Copyright © Microscopy Society of America

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References

References:

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