Atomic structure of dislocation kinks in silicon

TL;DR

This study uses a linear-scaling density-matrix technique to analyze dislocation core reconstructions and kink structures in silicon, revealing differences in stability, energies, and migration barriers between two main dislocation types.

Contribution

It provides detailed computational insights into the atomic structure and energetics of dislocation kinks and core reconstructions in silicon, including comparisons with experimental data.

Findings

Reconstructed bonds at dislocation cores reduce formation energies.

Kink migration barriers are high for reconstructed structures.

Complexes of kinks and defects show different stability in 30° and 90° dislocations.

Abstract

We investigate the physics of the core reconstruction and associated structural excitations (reconstruction defects and kinks) of dislocations in silicon, using a linear-scaling density-matrix technique. The two predominant dislocations (the 90-degree and 30-degree partials) are examined, focusing for the 90-degree case on the single-period core reconstruction. In both cases, we observe strongly reconstructed bonds at the dislocation cores, as suggested in previous studies. As a consequence, relatively low formation energies and high migration barriers are generally associated with reconstructed (dangling-bond-free) kinks. Complexes formed of a kink plus a reconstruction defect are found to be strongly bound in the 30-degree partial, while the opposite is true in the case of 90-degree partial, where such complexes are found to be only marginally stable at zero temperature with very low dissociation barriers. For the 30-degree partial, our calculated formation energies and migration barriers of kinks are seen to compare favorably with experiment. Our results for the kink energies on the 90-degree partial are consistent with a recently proposed alternative double-period structure for the core of this dislocation.