Title
Persistent misconceptions about incoherence in electron microscopy Persistent misconceptions about incoherence in electron microscopy
Author
Faculty/Department
Faculty of Sciences. Physics
Publication type
article
Publication
Amsterdam ,
Subject
Chemistry
Source (journal)
Ultramicroscopy. - Amsterdam
Volume/pages
111(2011) :7 , p. 894-900
ISSN
0304-3991
ISI
000300461000022
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
Incoherence in electron microscopic imaging occurs when during the observation the microscope and the object are subject to fluctuations. In order to speed up the computer simulation of the images, approximations are used that are considered as valid. In this paper we will question the validity of these approximations and show that in specific cases they can lead to erroneous results. It is shown in particular in the case of one single vibrating atom that the thermal diffuse scattering that causes the signal in HAADF STEM is not only dependent on Z but also on the mean square displacement of the atom so that it can even be large for light atoms in soft matter, provided the right HAADF aperture is used. In HREM imaging the diffuse scattering leaks out of the coherent (elastic) wave and is redistributed in the background. This might explain the mismatch in elastic contrast (Stobbs factor) especially for crystals with a thickness beyond the extinction distance, where also the HAADF signal saturates and the elastic (coherent) component vanishes. (C) 2011 Elsevier B.V. All rights reserved.
E-info
https://repository.uantwerpen.be/docman/iruaauth/655c18/c7d1520.pdf
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