Walther, T. (2014) What environmental transmission electron microscopy measures and how this links to diffusivity: thermodynamics versus kinetics. Journal of Microscopy, 257 (2). pp. 87-91. ISSN 0022-2720
Abstract
Environmental or in situ electron microscopy means the observation of material in its native environment, which can be gaseous or liquid, as compared to more traditional post-mortem electron microscopy carried out under (ultra) high vacuum conditions. Experiments can be performed on bulk samples in scanning electron microscopes or on thinned samples in transmission (scanning) electron microscopes. In the latter, the movement, in real time and in situ, of nanoparticles, clusters or even single atoms on the surfaces of thinned material or within a liquid can be observed.
It is argued here that due to the changes that a specimen typically undergoes during in situ observation, electron irradiation effects are difficult to evaluate and so thermodynamic parameters, such as activation energies for diffusion and segregation, which are governed by movements of only a minority of atoms in the specimen, cannot be reliably determined because of the potentially high energy transfer by the irradiating electron beam to some atoms in the sample. In order to measure diffusivities reliably, radiation effects and surface diffusion need to be excluded or kept minimal so as not to disturb the measurements, which can be checked by repeating experiments and comparing results as function of time and dose for the same position, at different positions or for different specimen thicknesses.
Kinetic measurements of nucleation and growth phenomena, such as Ostwald ripening, are possibly influenced to a far lesser degree by irradiation effects, as a majority of atoms actively participate in these processes and if a small fraction of them will get extra energy from the irradiation process then their influence on the overall kinetics may be rather minor.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Editors: |
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Copyright, Publisher and Additional Information: | © 2014 The Authors Journal of Microscopy © 2014 Royal Microscopical Society. This is an author produced version of a paper subsequently published in Journal of Microscopy. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Environmental TEM; growth; in situ TEM; interdiffusion; nucleation; segregation |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Electronic and Electrical Engineering (Sheffield) |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 20 Jan 2016 15:31 |
Last Modified: | 05 Nov 2017 10:39 |
Published Version: | http://dx.doi.org/10.1111/jmi.12193 |
Status: | Published |
Publisher: | Wiley |
Refereed: | Yes |
Identification Number: | 10.1111/jmi.12193 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:91476 |