Dislocation multiplication, exhaustion and mechanical behaviour for Ge single crystals

Abstract

Dislocation multiplication and exhaustion processes in germanium are revisited in the light of new data from mechanical test transients. They are documented by transmission electron microscope (TEM) observations and dislocation velocity measurements by the etch pit technique. The transient tests consist of stress relaxations, creep tests and stress dip tests performed along the monotonic curve. The relaxation and creep curves exhibit a non-logarithmic dependence on time, unlike in other classes of materials. Dislocation multiplication is evidenced by these transient curves before the upper yield point. In addition, after the lower yield point, dislocation exhaustion takes place at the end of the transient. Some evidence of strain localization is also provided by strain dip tests and transmission electron micrographs.