  A first principles many-body approach is employed to calculate the band
structure and optical response of nanometer sized ribbons of SiC. Many-body
effects are incorporated using the GW approximation, and excitonic effects are
included using the Bethe-Salpeter equation. Both unpassivated and hydrogen
passivated armchair SiC nanoribbons are studied. As a consequence of low
dimensionality, large quasiparticle corrections are seen to the Kohn-Sham
energy gaps. In both cases quasiparticle band gaps are increased by up to 2 eV,
as compared to their Kohn-Sham energy values. Inclusion of electron-hole
interactions modifies the absorption spectra significantly, giving rise to
strongly bound excitonic peaks in these systems.The results suggest that
hydrogen-passivated armchair SiC nanoribbons have the potential to be used in
optoelectronic devices operating in the UV-Vis region of the spectrum. We also
compute the formation energies of these nanoribbons as a function of their
widths, and conclude that hydrogen-saturated ribbons will be much more stable
as compared to the bare ones.

Materials Science;Mesoscale and Nanoscale Physics