Modelling Electron Channeling Contrast Intensity of Stacking Fault and Twin Boundary Using Crystal Thickness Effect

Abstract

In a scanning electron microscope, the backscattered electron intensity modulations are at the origin of the contrast of like-Kikuchi bands and crystalline defects. The Electron Channeling Contrast Imaging (ECCI) technique is suited for defects characterization at a mesoscale with transmission electron microscopy-like resolution. In order to achieve a better comprehension of ECCI contrasts of twin-boundary and stacking fault, an original theoretical approach based on the dynamical diffraction theory is used. The calculated backscattered electron intensity is explicitly expressed as function of physical and practical parameters controlling the ECCI experiment. Our model allows, first, the study of the specimen thickness effect on the channeling contrast on a perfect crystal, and thus its effect on the formation of like-Kikuchi bands. Then, our theoretical approach is extended to an imperfect crystal containing a planar defect such as twin-boundary and stacking fault, clarifying the intensity oscillations observed in ECC micrographs.

Defect characterization of {101¯3} GaN by electron microscopy

“…This is analogous to the well documented fringe contrast observable in TEM [57][58][59] and matches the contrast reported for stacking faults in metals. 38 This contrast behavior is caused by the change of the phase shift (2  π  g  u, with the diffraction vector g and the displacement vector u) along the inclined basal plane stacking fault 60 and depends on the inclination angle (% 32:1 ) and extinction distance in the material. It is notable, that some BSF lines show contrast inversion along the intersection line with the surface within the same diffraction condition, similar to observations made by Zakharov et al 57 We attribute this behavior to imaging two different I 1 BSFs with the opposite displacement vector u.…”

EBSD patterns simulating multilayer twins based on dynamical theory of electron diffraction

“…Defects are recognised by ECCI based on the difference of channelling contrasts. [3][4][5][6][7] The spatial resolution of ECCI is also poor (2-5 μm). 3 Even the selected area electron channelling pattern (SACP) technique can obtain resolution only to the submicron level.…”

“…XRD can obtain statistical data, but it has low spatial resolution and lacks spatial location and orientation information. Defects are recognised by ECCI based on the difference of channelling contrasts 3–7 . The spatial resolution of ECCI is also poor (2–5 μm) 3 .…”