Effect of Dislocations on the Low Temperature Thermal Conductivity in Germanium

Abstract

The thermal conductivity vs temperature relation in deformed germanium single crystals is measured in the temperature range from 1.5 to 30 K. The results are analysed on the basis of the Callaway model. Klemens' theory on the scattering of phonons due to the static strain field of dislocations accounts for the experimental results reasonably well. The dislocation densities deduced from the thermal conductivity data are greater than those counted by direct observation of dislocations by factors less than 3.7 and 2.1 in specimens deformed to stage I and stage II, respectively. Discrepancies between the theoretical curves and the experimental curves are found at temperatures around 20 K and below 2.2 K. The former is accounted for by assuming that point-defect like imperfections have been introduced into specimens during deformation, while the latter could be attributed to the scattering of phonons due to dangling electrons located at the dislocation core.