Fundamental and experimental aspects of diffraction for characterizing dislocations on bulk materials by electron channeling contrast imaging in scanning electron microscope
Résumé
The SEM is an easier way to use electron microscope compared to TEM essentially because of the possibility to observed centimetric bulk specimen and the larger space available in the chamber. SEM can access diffraction contrast on bulk materials with the phenomenon of electron channeling [1]. The Electron Channeling Contrast Imaging (ECCI) is a non-destructive groundbreaking technique offering the ability to provide, inside a SEM, TEM-like diffraction contrast imaging of sub-surface defects (at a depth of about one hundred of nanometers) on centimetric bulk specimen with still unsurpassed resolutions [2,3]. Electron channeling contrast is produced from electrons, that channel down the crystal planes. Strain and defects distort the crystal planes, which produce changes in backscattered electron intensity leading to a contrast on the image. Dislocations for example can be characterized by ECCI using the well-known TEM g·b=0 and g·bxu=0 extinction criteria [4] where g is the diffraction vector and b the Burgers vector. In this study, fundamental and experimental aspects of electron diffraction for characterizing dislocation by ECCI in SEM are reported [5]. The (+g,-g) method is explored on several dislocation configurations in an Interstitial-Free steel sample. Moreover, the first detailed characterization of a dislocation dipole by ECCI [4,5] is presented.
References
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[2] – H. Mansour, J. Guyon, M.A. Crimp, N. Gey, B. Beausir, N. Maloufi, Scripta. Mater. 84-85, (2014).
[3] – J. Guyon, H. Mansour, N. Gey, M.A. Crimp, S. Chalal, N. Maloufi, Ultramicroscopy 149, (2015).
[4] – H. Kriaa, A. Guitton, N. Maloufi, Scientific reports 7, (2017).
[5] – H. Kriaa, A. Guitton, N. Maloufi, Materials, 2019, 12 (10), 1587