A review of the determination of dislocation parameters using strong‐ and weak‐beam electron microscopy

Abstract

SUMMARY This paper reviews the results of the investigation of dislocation image characteristics as formed using strong‐ and weak‐beam transmission electron microscopy as well as the application of these data for the determination of the basic dislocation parameters: the value, direction and sign of the Burgers vector, and the dissociation width of dislocations split into Shockley partials. The relative advantages and limitations of strong‐ and weak‐beam techniques in studies of dislocation parameters are discussed. This is exemplified by an examination of the possibility of revealing dislocation dissociation with separation Δ 10 nm using strong diffracted beams. The influence of the anisotropy of the elastic moduli on the strong‐beam images of dissociated dislocations is also discussed. The effects of the column approximation on the calculated weak‐beam images of dissociated dislocations are analysed using the results of non‐column calculations. The statistical analysis of the measured dissociation values is also described, allowing the enhancement of the precision of the weak‐beam measurements and their sensitivity in revealing small variations in dissociation width. Finally, the differences in the form of weak‐beam images of dissociated dislocations and of ordinary and faulted dipoles are discussed.

Analysis of crystal defects by scanning transmission electron microscopy (STEM) in a modern scanning electron microscope

“…Qualitative considerations and simulations show that double-line contrast is frequently observed in bright-field TEM images for dislocations under g·b = 2 conditions and single-line contrast for g·b = 1 without excitation error [1,3]. In more detail, dislocation contrast is also affected by the excitation error s g from the Bragg reflecting condition and depends on the dislocation type, TEM sample thickness, dislocation depth in the sample, and degree of crystal anisotropy which may lead to deviations from the contrast behavior described above [1,4].…”