Zigzag graphene nanoribbons with saturated edges

Zigzag graphene nanoribbons with saturated edges are investigated by first principles calculations. In these structures edge carbons have either two H or two F atoms, and are of sp(3) type. Compared to the previously studied ribbons with all carbons of sp(2) type, several similarities and differences are found. Specifically, in narrower ribbons the closed shell electronic state is the most stable one. In wider ribbons a state with antiferromagentically spin-polarized edges is the lowest in energy, similarly to the ribbons with all sp(2) type carbons. A notable feature of narrower ribbons is significant single-double carbon bond alternation across the ribbon. Calculated Raman spectra contain a distinct blue shift signature of such alternation, which perhaps can be used for the experimental identification of ribbons of this type.