THE BRITTLE-TO-DUCTILE TRANSITION IN SILICON

In order to better understand the brittle-to-ductile transition in silicon, details of different experimental and numerical studies are discussed. In the concept of elastical stress intensity factors, experiments with four-point-bending bars are not directly comparable with experiments done with tapered-double-cantilever-beam samples. The internal elastic and plastic conditions of the samples are different due to large differences of the load levels applied in both cases. A smooth transition from cleavage to semi-brittle fracture with small, relatively homogeneous plastic zones precedes a sharp transition to general plasticity. The fracture toughness between both transitions is independent of temperature, yielding a plateau region. Numerical simulations qualitatively show the same results. The plateau region is a direct consequence of the shielding dynamics, the sharp transition is a consequence of the assumed emission configuration of the dislocations. The simulations do not rely on a heterogeneous distribution of dislocation sources.