Forbidden-reflection lattice imaging for the determination of kink densities on partial dislocations

Abstract

High-resolution electron microscope lattice images have been obtained at the Schemer focus setting for the first time from the ′forbidden′ {422}/3 Bragg reflections which result from intrinsic stacking faults (lying normal to the beam) in thin crystals of silicon. Microdiffraction patterns have also been obtained from stacking faults normal to the beam, showing these reflections. The boundaries of the SF lattice image delineate the approximate location of partial dislocation cores running normal to the beam, and these reveal a high density of directional fluctuations, despite their appearance as straight dislocations in the corresponding weak-beam images, The effects of surface roughness on an atomic scale are discussed, and this is shown to limit the accuracy with which the partial dislocation cores can be located to within a few ángstroms.