Surface reconstruction and core distortion of silicon and germanium nanowires

Abstract

We report the results of molecular dynamics simulations for structures of pristine siliconnanowires and germanium nanowires with bulk cores oriented along the [110]direction and bounded by the (100) and (110) surfaces in the lateral direction. Wefound that the (100) surfaces for both silicon and germanium nanowires undergo2 × 1 dimerization while their (110) surfaces do not show reconstruction. The direction of the dimerrows is either parallel or perpendicular to the wire axis depending on the orientation of thesurface dangling bonds. The dimer length for Si is in good agreement with the result obtainedby first-principles calculations. However, the geometry of Si dimers belongs to the symmetrical2 × 1 reconstruction rather than the asymmetrical buckled dimers. We also show that surfacereconstruction of a small nanowire induces significant change in the lattice spacing for theatoms not on the (100) surface, resulting in severe structural distortion of the core of thenanowire.