DISLOCATION CONTRAST IN LARGE-ANGLE CONVERGENT-BEAM ELECTRON-DIFFRACTION PATTERNS

The rules which govern the dislocation contrast in large angle convergent-beam electron diffraction (LACBED) patterns have been discussed in detail. A generalized many-beam dynamical computation method has been described for dislocation contrast simulation in LACBED patterns. Effects of systematic and non-systematic many-beam interactions on dislocation contrast in LACBED patterns have been assessed. For cases with strong diffraction potentials, the contrast is complicated by the many-beam interactions and image simulation is needed. The observed long-range sideways shift of a rocking curve contour either side of a dislocation is caused by bending of the thin foil specimen introduced by the edge component of the dislocation. The origin of the dislocation contrast in LACBED has been presented using amplitude-phase diagrams based on the kinematical theory.