Measurements of the internal friction on deformed Ge at frequences from 0.2 to 20 Hz at temperatures between 150 and 820 K show two maxima α and β, occuring after deformation only. Their activation enthalpy H, prefactor f0, and relaxation strength Δ are: Hα = (1.108 ± 0.01) eV, f0α = (0.14 to 15) × 109 s−1 (increasing with increasing deformation), Δα ≈︁ 10−2; Hβ = (2.07 ± 0.2) eV, f0β ≈︁ 1013 s−1, Δβ ≈︁ 3 × 10−2). Both shift to lower temperatures with increasing deformation. They are attributed to the movement of geometrical kinks (α) and to kink pair formation (β) on single partial dislocations. Doping with (2 to 4) × 1017 cm−3 Sb lowers the kink migration enthalpy Hα by 0.3 to 0.4 eV. This indicates that the lowering of the activation enthalpy of the dislocation velocity by doping is due to that of the kink migration enthalpy Hα only.
The precipitation of copper and (radioactive) cobalt at low energy grain boundaries in polycrystalline silicon and bicrystals is investigated. The metals are diffused in from a surface source between 800 - 1000 °C and the precipitation after cooling down is studied by TEM (for Cu) and Mößbauer spectroscopy (for Co). The precipitates are metal suicides. For copper it is shown that they appear in form of colonies containing hundreds of precipitates with a particle size between 5-60 nm. In the grain boundary they nucleate preferentially at dislocations and steps. The distribution and size of the precipitates depend on the cooling rate after the diffusion. In the vicinity of the grain boundary the volume is depleted from the impurities.
The precipitation of copper and nickel at grain boundaries in cast polycrystalline silicon is investigated. The metals are diffused into the specimens from a surface source between 800 – 1000 °C and the precipitation after cooling is studied by TEM. Copper precipitates in form of colonies containing hundreds of particles with a size between 5–6 nm. In the grain boundary they nucleate preferentially at dislocations and steps. The distribution and size of the precipitates depend on the cooling rate after the diffusion. Nickel forms only few large (micrometer size) plate-like or three dimensional precipitates at and near grain boundaries. The main features of the results and the differences between the two elements are explained under the assumption that the precipitation requires the transport of native point defects.
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