On the kinematical theory of diffraction contrast of electron transmission microscope images of edge dislocations

The kinematical theory developed by Hirsch et al. (1960) for the diffraction contrast of electron transmission microscope images of perfect screw dislocations parallel to the surface of the crystal foil, is extended to perfect edge dislocations with slip planes parallel to the surface.The exactly calculated line profiles for an edge dislocation are compared to the approximate ones obtained by Hirsch et al. for that case. Both types of curves are about twice as broad as those for the screw dislocation with the same Burgers vector. The exact curve rises and descends somewhat more rapidly than the one given by the approximation introduced by Hirsch et al. The exact calculation of the profiles shows that the maximum diffracted intensity is greater for an edge dislocation than for corresponding screw dislocation. This feature is not revealed if the approximation is used.The procedure may also be used to study the intensity profiles for dislocations of mixed character with slip plane parallel to the surface of the crystal.