Decoherence in electron backscattering by kinked dislocations

A model is proposed that explains the origin of the bright contrast of disl ocation walls consisting of edge dislocation dipoles in electron channellin g contrast images (ECCI) of fatigued crystals, when the incident beam is pa rallel to the edge dislocations. The model is based on the assumption that the contrast arises from the dislocation segments terminating the dipoles. These are modelled as screw-type kinks which scatter electrons. Scattering by randomly distributed kinks leads to the randomization of phase of transm itted and diffracted beams and suppresses the anomalous transmission of ele ctrons. The predicted behaviour of electron-channeling contrast images agre es well with experimental observations.