Atomic packing characteristics and electronic structures of Si nanowires from density functional tight binding calculations

The atomic packing and electrical properties of silicon nanowires are of great significance when advancing novel optoelectrical and thermoelectric materials. Atom packing and electrical structures in silicon nanowires of the same thickness but different widths were studied by density functional tight binding (DFTB) calculations. The variations of average energy per atom, pair distribution function, bond length, bond angle, Mülliken gross population, and electronic structure were investigated. The periodic atomic rearrangements occur in the surface of these nanowires, and there are different patterns seen when decreasing the width. In rearranged surfaces, the atoms present regular arrangement in dimers along the <110> direction, whereas in the other surfaces, interval dimers and trimers appear. The surface structures affect the charge distribution and electronic structures in these nanowires with different packing patterns.