High angle annular dark field imaging of stacking faults

High angle annular dark field imaging has been extensively applied to high resolution imaging of crystalline materials. Dislocations have also been imaged using the high angle dark field detector, even when the lattice has not been directly resolved. Diffraction contrast, as employed in transmission electron microscopy analysis of defects, is a possible mechanism for dislocation contrast. Stacking faults should also show diffraction contrast and a Bloch wave theory is developed for the high angle dark field image. The results are compared with an experiment which shows, in agreement with the theory, that the strongest contrast is found when the fault is close to the surface and the objective aperture is small.