Atomistic modeling of the dissociation of a screw dislocation in silicon

Abstract

The nature of dislocations involved in the plastic deformation of semiconductors is different in high- and low-temperature domains. Experimental investigations have not allowed to discriminate between dissociation and nucleation as the main reason behind this transition. In this work, the mechanisms leading to the dissociation of a screw dislocation in silicon, determined by means of atomistic calculations, are described. It is shown that kink pair formation, followed by successive kink migrations, leads to the formation of two 30° partial dislocations from the screw dislocation core. These mechanisms are structurally very similar to those involved in the formation and migration of kinks in the case of a single 30° partial dislocation, because of the close resemblance between the screw and 30° dislocation cores. The calculated activation energy of the whole process is 2.14 eV, thus quite comparable to the energies involved in the propagation of partial dislocations. This shows that dissociation and nucleation processes are likely to be activated at similar temperature ranges.