Internal friction in germanium at low temperatures

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Abstract
The internal friction of germanium crystals having various dislocation densities in the range 103−107 cm−2 was measured in the low kHz frequency range from 80 to 473 °K and in the MHz frequency range at 300 °K. No evidence for a dislocation contribution to the internal friction was obtained. The internal friction in the kHz range did not depend significantly on the dislocation density and did not exhibit any internal‐friction peaks which could be associated with dislocation motion. The internal friction was amplitude independent and could be accounted for by thermoelastic damping. A small increase in attenuation in the MHz frequency range was observed on increasing the dislocation density. This increase could not be accounted for using the theories of dislocation damping but was less consistent with phonon scattering from the static dislocation dipole strain fields. These results were independent of the doping levels of the germanium crystals and of their orientations. They suggest that the activation energy for kink motion along dislocations in germanium is greater than about 17 kcal/mole. A small internal‐friction peak was observed at about 210 °K, which was shown to be caused by surface abrasion.