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Metal irradiated with ions (in the following examples Au -ion with energies
of some 10 kV) will be heavily damaged; besides lots of Frenkel pairs, small vacancy type dislocation loops usually
form some 10 nm below the surface. |
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This kind of research was important for nuclear materials science and for ion implantation techniques in
general. |
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The loops are far too small to be seen as loops in conventional imaging; at best they appear as black dots.
However, if imaged with dynamical bright-field conditions, they give rise to so-called black-white contrasts with peculiar
geometries. |
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The following picture shows black-white contrasts of dislocation loops imaged with a {1,1,-2,0}
type of diffraction vector in a specimen with a {0001} orientation. Six distinctly different kinds of contrast are
observed. Two calculated contrast profiles for a particular set of Burgers vector and normal vector of the loop are also
included. The size of the black-white contrasts is about 20 nm. |
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Same as before, but for a {1122} type specimen orientation. The observed contrasts match closely
the calculated profiles for the types of dislocation loops assumed. |
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© H. Föll (Defects - Script)
6.3.2 Examples and Case Studies for Dislocations 
With frame