1ST-PRINCIPLES ANALYSIS OF ELECTRONIC STATES IN SILICON NANOSCALE QUANTUM WIRES

The atomic structure of small-cross-section (almost-equal-to 10 angstr om), hydrogen-terminated silicon quantum wires is fully relaxed within the local-density approach showing bulklike coordination of the Si at oms. The electronic states near the fundamental, gap (substantially bl ueshifted from that of bulk Si) show a direct gap between bulk-Si-deri ved states. The new dipole matrix elements and the detailed level orde rings depend on the size, symmetry, and surface structure of the wire. The optical response is presented with the implications of the valley orbit splitting for radiative dynamics in light-emitting porous silic on.