Termini of Bottom-Up Fabricated\nGraphene Nanoribbons

Abstract

Atomically precise graphene nanoribbons (GNRs) can be\nobtained\nvia thermally induced polymerization of suitable precursor molecules\non a metal surface. This communication discusses the atomic structure\nfound at the termini of armchair GNRs obtained via this bottom-up\napproach. The short zigzag edge at the termini of the GNRs under study\ngives rise to a localized midgap state with a characteristic signature\nin scanning tunneling microscopy (STM). By combining STM experiments\nwith large-scale density functional theory calculations, we demonstrate\nthat the termini are passivated by hydrogen. Our results suggest that\nthe length of nanoribbons grown by this protocol may be limited by\nhydrogen passivation during the polymerization step.