Extended Si |P[311|P] defects

We perform total-energy calculations based on the tight-binding Hamiltonian scheme (i) to study the structural properties and energetics of the extended {311} defects depending upon their dimensions and interstitial concentrations and (ii) to find possible mechanisms of interstitial capture by and release from the {311} defects. The generalized orbital-based linear-scaling method implemented on the Cray T3D is used for supercell calculations of large-scale systems containing more than 1000 Si atoms. We investigate the {311} defects systematically from few-interstitial clusters to planar defects. For a given defect configuration, constant-temperature molecular-dynamics simulations are performed at 300–600 K for about 1 psec to avoid trapping in the local minima of the atomic structures with small energy barriers. We find that interstitial chain structures along the 〈011〉 direction are stable interstitial defects with respect to isolated interstitials. The interstitial chains provide basic building blocks of the extended {311} defects, i.e., the extended {311} defects are formed by condensation of the interstitial chains side by side in the 〈233〉 direction. We find that successive rotations of pairs of atoms in the {011} plane are mechanisms with a relatively small energy barrier for propagation of interstitial chains. These mechanisms, together with the interstitial chain structure, can explain the growth of the {311} defects and related structures such as V-shape bend structures and atomic steps observed in transmission electron microscopy images.