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) 4H-SiC surfaces were computed using the Sturkey scattering matrix approach incorporating surface relaxation effects. Simulated diffraction contrast of the threading screw dislocations permitted 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 channelling contrast. The convergence of the incident electron beam was also shown to influence channelling contrast.

Simulation and Analysis of Electron Channeling Contrast Images of Threading Screw Dislocations in 4H-SiC. M.E.Twigg, Y.N.Picard: Journal of Applied Physics, 2009, 105[9], 093520