Atomic structure of dislocation kinks in silicon

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 $90\ifmmode^\circ\else\textdegree\fi{}$ and $30\ifmmode^\circ\else\textdegree\fi{}$ partials) are examined, focusing for the $90\ifmmode^\circ\else\textdegree\fi{}$ 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 $30\ifmmode^\circ\else\textdegree\fi{}$ partial, while the opposite is true in the case of $90\ifmmode^\circ\else\textdegree\fi{}$ partial, where such complexes are found to be only marginally stable at zero temperature with very low dissociation barriers. For the $30\ifmmode^\circ\else\textdegree\fi{}$ 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 $90\ifmmode^\circ\else\textdegree\fi{}$ partial are consistent with a recently proposed alternative double-period structure for the core of this dislocation.