Dislocation Detection by CBED and LACBED
- Practical Electron Microscopy and Database -
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Figure 1997 shows the bright-field discs of convergent electron beam patterns obtained from an Fe-3ONi-19Cr alloy, with an incident beam along <114> axis and beam diameter of ~200 Å at 100 kV. The <114> projection of conventional CBED pattern in the perfect region (shown in Figure 1997 (a)) has a {110} mirror (m) along the arrowed direction, consisting with the pattern of HOLZ deficiency. However, as shown in Figure 1997 (b) the mirror is broken at the dislocation region with the deficiency lines displaced, indicating more information. The CBED pattern is a sensitive function of the distance of the probe from the dislocation and the probe size. The LACBED pattern shown in Figure 1997 (c) was obtained by a defocussed probe covering a 1-µm area across a specimen region, containing the same dislocation. The dislocation crosses various displaced deficiency lines, split into a number of subsidiary peaks. These features can be interpreted by a standard kinematic approach. [1]

Bright-field discs of convergent electron beam patterns obtained from an Fe-3ONi-19Cr alloy

Figure 1997. Bright-field discs of convergent electron beam patterns obtained from an Fe-3ONi-19Cr alloy, with an incident beam along <114> axis and beam diameter of ~200 Å at 100 kV: (a): Conventional CBED taken from a region of perfect crystal; (b) Conventional CBED near a single dislocation; and (c) LACBED from an extended region including the same dislocation (The approximate position of the dislocation is arrowed.) Adapted from [1]

 

 

 

 

 

[1] Cherns D, and Preston A. R., Convergent beam diffraction studies of interfaces, defects, and multilayers, J Electron Microsc Tech. 1989 Oct;13(2):111-22.

 

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