Dislocation relaxation in germanium single crystals

High purity single crystals of [213] and [111] orientations were plastically deformed in tension at approximately 900 °K to various strain levels. Internal friction measurements at 50 kHz were made on the deformed specimens over the temperature range 10 to 1120 °K. Almost no strain amplitude dependence of the internal friction up to ϵ = 2 × 10−5 was observed over this whole temperature range. A small relaxation peak was found near 150 °K in all easy glide specimens but disappeared in the deformed [111] specimens. Another small peak was found at about 220 °K in deformed specimens of both orientations. These peaks, as well as the internal friction plateau above room temperature, are interpreted in terms of kink diffusion on screw and edge-type dislocations. At temperatures above ≈︁ 550 °K an exponential-like rise in internal friction occurs, which is interpreted in terms of thermally activated nucleation of kinks followed by other dislocation glide processes. A second exponential-like rise which occurs at about 1050 °K is thought to be due to non-conservative dislocation motion.