Theoretical study of kinks on screw dislocation in silicon

TL;DR

This study uses density functional theory and interatomic potentials to analyze the structure, formation, and migration of kinks on screw dislocations in silicon, revealing their energetic properties and stress effects.

Contribution

It provides a detailed theoretical analysis of kink structures and migration behaviors on screw dislocations in silicon, including the influence of stress on kink pair formation.

Findings

Kink structures have a narrow core with stretched bonds.

Kink formation energy ranges from 0.9 to 1.36 eV.

Kinks migrate freely along the dislocation line.

Abstract

Theoretical calculations of the structure, formation and migration of kinks on a non-dissociated screw dislocation in silicon have been carried out using density functional theory calculations as well as calculations based on interatomic potential functions. The results show that the structure of a single kink is characterized by a narrow core and highly stretched bonds between some of the atoms. The formation energy of a single kink ranges from 0.9 to 1.36 eV, and is of the same order as that for kinks on partial dislocations. However, the kinks migrate almost freely along the line of an undissociated dislocation unlike what is found for partial dislocations. The effect of stress has also been investigated in order to compare with previous silicon deformation experiments which have been carried out at low temperature and high stress. The energy barrier associated with the formation of a stable kink pair becomes as low as 0.65 eV for an applied stress on the order of 1 GPa, indicating that displacements of screw dislocations likely occur via thermally activated formation of kink pairs at room temperature.