Internal friction in deformed germanium crystals at low temperatures

The internal friction in deformed germanium single crystals is investigated in the temperature range from 4.2 to 150 K at resonance frequencies about 70 kHz. Two relaxation peaks, denoted by P3 and P4, with activation energies of (0.08 ± 0.01) and (0.13 ± 0.01) eV, respectively, are observed to develop upon deformation. Peaks P3 and P4 are interpreted to be associated with the stress-induced motion of geometrical kinks on screw dislocations and 60° dislocations, respectively, passing over the Peierls potential barrier of the second kind. The results are discussed on the basis of the kink–chain model of abrupt kinks. It is shown that the kink–chain model leads to expressions for the relaxation strength and the relaxation time which are similar to those derived on the extensible string model by Southgate and Attard.