Image Simulation of Partial Dislocation Lines Plan-viewed by High Resolution Electron Microscopy

Abstract

High resolution electron microscopic (HREM) images were simulated for dissociated dislocations in GaAs observed with an electron beam incident normal to the stacking fault (SF) plane. Model structures containing two types of Shockley partial dislocations (30° and 90°) were constructed according to the elastic strain field, and atomistically relaxed with a Keating-type potential. Systematic calculations varying the film thickness, the depth of the dislocation in the film, and the defocus values revealed that the image of SF represented by a superlattice contrast with √3x√3-R30° two-dimensional periodicity can be obtained for film thicknesses smaller than ∼ 5nm in the best contrast at a defocus value shorter than the Scherzer focus. Along the dislocation line, a superperiodic modulation arising from reconstruction of 30° partial dislocation core is discernible in weak contrast.