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Dissociated dislocations in (111) foils of silicon have been imaged in the forbidden reflection of type ⅓(422). Largo contrast effects are observed at stacking faults, and thickness fringes corresponding to changes of thickness of a repeat unit (3d111) are revealed. The partial dislocations bounding the fault are observed as very narrow images. The contrast effects are explained in terms of kinematical theory, and the potential applications of this technique are discussed.

The structure of the NiSi2/(111)Si interface is investigated by the lattice imaging of (110) cross-sectional specimens in a JEOL 200CX transmission electron microscope with 2·4 Å point-to-point resolution. NiSi2 is epitaxial and doubly-positioned on (111)Si; lattice images indicate that both silicon-silicide interfaces are atomically abrupt, smooth and well-characterized. It is shown that, although interface images are critically dependent on film thickness and defocus, careful experimental determination of these parameters and comparison with computed images enables atomic models of both interfaces to be derived.

A detailed analysis of the cross-slip and annihilation of screw dislocations in B2 ordered alloys is carried out using anisotropic elasticity. The paths of the partial dislocations are calculated and it is shown that antiphase-domain boundary tubes with complex structures may be formed by the cross-slip and annihilation of screw dislocation dipoles with a suitable range of heights (e.g. for Fe-30 at.% A1 alloy from 70 to 200 Å). APB tubes thus formed usually have a height of a few multiples of the elementary jog height, and widths of 7-50Å in agreement with experiment. Image calculations (including the effects of the limited aperture, defocus and the lens aberration) for APB tubes with a complex cross-section give a good match with experimental results. The analysis also explains why APB tubes of such small heights are generally connected to edge dislocation dipoles of much larger heights.