First-principles determination of the electronic structures and optical properties of one-nanometer (001) and (111) Si nanowires

Abstract

Results of precise theoretical full potential linear augmented plane wave determinations of the electronic structures and optical properties of one nm Si nanowires (SiNW) with (001) and (111) orientations are presented. The electronic states at the gaps demonstrate a strong orientation dependent parabolic character in the Brillouin zone and a clear entanglement in real space between different dimensions of the wire. The localization and local symmetry imposed in the states by quantum confinement quenches the transitions around the gap of the SiNW, yielding an optically inactive direct gap. The observed photoluminescence in the (001) wire is attributed to a transition rooted in an ${\mathrm{Si}}_8$ ring. The optical structure in the experimental range is well reproduced by the first-principles calculation that includes the screened exchange-local density approximation correction to the well-known failure of the local density approximation.