Abstract
Although the symmetry of the diffraction contrast of defects has received the attention of several authors already some time ago, symmetry rules are mainly based on geometrical arguments without solid proof for their validity in the general case. The symmetry of the diffraction contrast depends on the symmetry of the displacements and on the symmetry of the diffraction conditions (which of course follows from Neumann’s principle). General proofs for thee symmetry of dislocation contrast are given in this paper.The diffraction contrast of a dislocation (or any number of parallel straight dislocations) which are inclined with respect to the surface of the foil and therefore show the so called “oscillating contrast” can only exhibit one of a limited number of symmetries.(SAL): symmetry along the (projected) line of the dislocation(SAM): symmetry about midfoil(SAC): symmetry about center
Publisher
Cambridge University Press (CUP)