The experimental diffraction parameters and contrast features associated with

electron channelling contrast imaging were determined by the study of threading

screw dislocations in 4H-SiC. The images were recorded by fore-scatter diode

detectors mounted on a commercial electron backscatter diffraction system.

Electron channelling contrast imaging of threading screw dislocations penetrating

the (00•1) surface revealed dark-to-light contrast, the direction of which depends

on the acting Bragg reflection, the deviation from the Bragg condition, and the

dislocation Burgers vector. Burgers vector identification was confirmed through

observations of the rotational direction of atomic step spirals associated with

various screw dislocations. Dark “twin-lobed” features were observed when the

incoming electron beam exactly satisfies the Bragg condition for various Bragg

reflections. The present experimentally observed behaviour of channelling contrast

features for screw dislocations was found to be consistent with transmission

electron microscopy diffraction contrast mechanisms.

Diffraction Contrast and Bragg Reflection Determination in Fore-Scattered

Electron Channeling Contrast Images of Threading Screw Dislocations in 4H-SiC.

Y.N.Picard, M.E.Twigg: Journal of Applied Physics, 2009, 104[12], 124906