Energy gap modulation of graphene nanoribbons by F termination

► The electronic properties of graphene nanoribbons are studied for the F-terminated instead of the H-terminated by using the first-principles. ► F-terminated armchair graphene nanoribbons have lower band gaps than those of H-terminated ones when they have the same band width. ► C-F bond is an ionic bond, while, C-C bond displays a typical non-polar covalent bonding feature.