DISLOCATION MOBILITY AND PINNING IN HARD MATERIALS THROUGH INTERNAL FRICTION STUDIES.

Previous work has shown that the rise, with temperature, of internal friction due to dislocations in silicon may be explained by the motion of geometrical kinks with an activation energy of 1.6 eV. This report presents measurements which confirm the existence of a peak in the internal friction vs. temperature curve, followed by a further rise at higher temperatures. A theory has been developed involving mobile pinning points for the dislocations, which fits the observations very well if the points have an activation energy of motion of about 3 eV and a mean spacing of close to 0.00003 cm. The peak, believed to be analogous to the Bordoni peak in metals, will only appear in measurements made below about 1000 cs. In indium antimonide, further measurements on temperature dependence of the rate of anneal of dislocation damping indicate an activation energy of the order of the energy of motion, 0.4 eV. An internal friction peak near 80 C has been seen in electron-irradiated oxygen-doped silicon. This is believed to be related to the A-center described by Watkins, but results so far are inadequate to demonstrate its exact nature. Theoretical studies on the interaction of impurities with the dislocation core now show that impurities should broaden the core, as intuitively expected. Author