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Basics of EBSD
Pattern formation
For EBSD, a beam of electrons is directed at a point of interest on a tilted crystalline sample in the SEM (Figure 2).
The mechanism by which the diffraction patterns are formed is complex, but the following model describes the principal features. The atoms in the material inelastically scatter a fraction of the electrons with a small loss of energy to form a divergent source of electrons close to the surface of the sample. Some of these electrons are incident on atomic planes at angles which satisfy the Bragg equation:
where n is an integer, λ is the wavelength of the electrons, d is the spacing of the diffracting plane, and θ is the angle of incidence of the electrons on the diffracting plane. These electrons are diffracted to form a set of paired large angle cones corresponding to each diffracting plane. When used to form an image on the fluorescent screen the regions of enhanced electron intensity between the cones produce the characteristic Kikuchi bands of the electron backscatter diffraction pattern (Figure 3).
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