High-Temperature Dislocation Damping in Covalent Crystals

Abstract

Dislocation damping in deformed single‐crystal silicon has been measured in the frequency range from 400 cps to 70 kc/sec and at temperatures between 500° and 1200°C. At low temperatures the logarithmic decrement shows a thermally activated rise with temperature, of activation energy 1.6 eV, varying approximately inversely with frequency. Deviation from this behavior is seen at the lower frequencies, where a peak appears near 800°C, followed by a second rise with temperature which is significantly faster than the initial rise. The results are interpreted in terms of an extensible string model, in which it is assumed that the dislocation is pinned by point defects which may diffuse with the dislocation. Agreement is obtained between theory and experiment for very reasonable values of mean dislocation length, and values of dislocation damping constant consistent with a geometrical kink diffusion model. The activation energy of motion for the pinning points is about 3.1 eV. Measurements on indium antimonide yield similar results, and it is supposed that a similar interpretation applies, although the data is not complete. The ratio of activation energies in the two materials is approximately the same as that for bond‐breaking, which is believed to be the major energy barrier to kink diffusion in covalent materials.