Dislocation walls on {111} and {110} planes in vapor-grown crystals were studied by means of light-scattering tomography, cathodoluminescence scanning electron microscopy and molten KOH etching. Many Y-shaped nodes and hexagonal nets of dislocation lines, caused by reactions between the lines, were clearly observed on (111) planes by means of light-scattering tomography. Many dislocations of irregular shape, and some parallel dislocation arrangements, were also found. Slip lines on (111) planes were clearly observed as dark lines by means of cathodoluminescence scanning electron microscopy, and this permitted the determination of the dislocation glide planes. Undecorated dislocations and slip lines were difficult to observe, in these high refractive index crystals, by means of light-scattering tomography. The dislocations made up most of the dislocation walls, and Y-shaped nodes were immobile; even when the stress was sufficient to fracture the specimen. Some of the other dislocations were displaced.

M.Ma, T.Ogawa: Philosophical Magazine A, 1996, 74[2], 477-93