The effects of surface stress relaxation on electron channelling contrast images of dislocations

Abstract

Profiles of the back-scattered electron intensity within electron channelling contrast images of dislocations have been calculated using a two-beam dynamical diffraction model and a simple treatment of multiple scattering. Within this diffraction model, the full displacement field was used, for a dislocation in an isotropic elastic medium, parallel to a free surface with which it interacts. The effects of the surface stress relaxation were found to be relatively small when the dislocation was close to the free surface. However, for dislocations deeper in the specimen the surface interaction was sufficient to cause the calculated contrast to be in the opposite sense from that expected if the free surface were ignored. Such free-surface effects are essential for the correct interpretation of electron channelling contrast images.