Distortion of the zeroth-order Laue-zone pattern caused by dislocations in a silicon crystal

The effect of dislocations in a silicon single crystal on the zeroth-order Laue-zone (ZOLZ) pattern in large-angle convergent-beam electron diffraction (LACBED) has been studied experimentally. It is found that edge dislocations cause the ZOLZ pattern to be compressed or elongated and screw dislocations cause it to be dislocated. This phenomenon is the consequence of opposite shifts of the two halves of the Tanaka pattern, separated by the shadow image of the dislocation line along directions b and -b of the Burgers vector. The shift direction of each half of the pattern depends on the dislocation characteristics and the position of the incident-beam crossover. The pattern on the side, pointed to by the vector u × c (or -u × c) from the shadow image of the dislocation line is shifted along b (or -b), where u is the direction of the dislocation-line vector and c is a vector pointing to the beam crossover from the dislocation line. This phenomenon can be used to determine the Burgers vector (both its direction and sense) of a dislocation.