Using methods developed for modelling diffraction contrast of extended defects in

thin foils, electron intensity profiles were simulated and found to qualitatively

match channelling contrast of threading screw dislocations experimentally recorded

by electron channelling contrast imaging using scanning electron microscopy.

Plan-view images of threading screw dislocations axially penetrating (00•1) 4HSiC

surfaces were computed using the Sturkey scattering matrix approach

incorporating surface relaxation effects. Simulated diffraction contrast of the

threading screw dislocation allows identification of these threading defects as well

as facilitates the determination of the dislocation Burgers vector. The directionality

of threading screw dislocation contrast features, simulated for various Bragg

reflections and deviation parameters, was consistent with both electron channelling

contrast imaging and diffraction contrast imaging by transmission electron

microscopy. Topographically enhanced imaging of atomic step spirals, generated

by the threading screw dislocations, provides a direct determination of the

threading screw dislocation Burgers vector, which was shown to agree with the

simulated electron channeling contrast imaging contrast. The convergence of the

incident electron beam was also shown to influence channeling contrast.

Simulation and Analysis of Electron Channelling Contrast Images of Threading

Screw Dislocations in 4H-SiC. M.E.Twigg, Y.N.Picard: Journal of Applied

Physics, 2009, 105[9], 093520