Abstract
Electron Channeling Contrast Imaging (ECCI) is becoming a powerful tool in materials science for characterizing deformation defects. Dislocations observed by ECCI in scanning electron microscope exhibit several features depending on the crystal orientation relative to the incident beam (white/black line on a dark/bright background). In order to bring new insights concerning these contrasts, we report an original theoretical approach based on the dynamical diffraction theory. Our calculations led, for the first time, to an explicit formulation of the back-scattered intensity as a function of various physical and practical parameters governing the experiment. Intensity profiles are modeled for dislocations parallel to the sample surface for different channeling conditions. All theoretical predictions are consistent with experimental results.
Highlights
The Electron Channeling Contrast Imaging (ECCI) technique is based on the fact that theBack-Scattered Electrons (BSE) signal is highly dependent on the orientation of the incident beam relative to the lattice planes [1]
For understanding the origin of the dislocation contrasts obtained by ECCI, the two-beam dynamical diffraction theory was adapted from the Transmission Electron Microscopy (TEM) [4,5]
An original theoretical model based on the Bloch wave approach of the dynamical diffraction theory was developed for modeling IBSE around dislocations without resorting to numerical methods
Summary
The Electron Channeling Contrast Imaging (ECCI) technique is based on the fact that the. Materials 2019, 12, 1587 dislocation [6,7,8,9] or a stacking fault [12] Despite their contribution to the theory of defects electron channeling contrasts [7,8,9,10,11,12], detailed calculations leading to an analytical expression of BSE signal as a function of experimental parameters are still missing. In order to determine the different coefficients of the Bloch wave function, presented in Equation (1), Reimer used the two-beam condition, i.e., only one set of lattice planes are in the channeling condition. For calculating the IBSE in the case of an imperfect crystal containing a dislocation surface, independently of the depth z, we take into account a new deviation parameter written by: Materials.
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