TEM imaging of dislocation kinks, their motion and pinning

HREM lattice images have been obtained using "forbidden" reflections generated by (111) stacking faults in silicon lying normal to the beam at temperatures up to 600 °C. Stationary and video images of 30°/90° partial dislocations relaxing toward equilibrium are studied. The lattice images formed from these forbidden reflections show directional fluctuations which are believed to be kinks, since, as expected from mobility measurements, a higher density is observed on 90° partials than on 30° partials, whereas artifacts contribute equally. Video difference images are used to obtain direct estimates of kink velocity. Observations of kink delay at obstacles, thought to be oxygen atoms at the dislocation core, yield unpinning energies and the parameters of the obstacle theory of kink motion. The kink formation energy is obtained from the distribution of kink pair separations in low-dose images. The kink migration rather than formation energy barrier is thus found to control the velocity of unobstructed dislocations in silicon under these experimental conditions.