Edge states in chiral-shaped graphene nanoribbons

Abstract

Understanding the configuration of electrons in confined graphene nanoribbons (GNRs), and the physical phenomena beneath, is still a challenging quest. Among all the graphene-like ribbons studied to date, chiral-shaped GNRs (i.e. with periodically alternating armchair and zigzag-like segments) represent the most scarcely explored ones. Here we present several routes for constructing chiral nanoribbons with different widths using on-surface synthesis techniques. Recently we reported the growth of narrow (3,1) GNRs (alternating 3 zigzag segments and 1 armchair) by deposing the 2,2'-dibromo-9,9'-bianthracene molecular precursor on different coinage metallic surfaces and annealing to relatively mild temperatures. This chiral ribbon is semiconducting, presenting a small gap of 670 mV. Here we present the (on-surface) synthesis of wider chiral GNRs (cGNRs) by using molecular precursors with additional anthracene units. Using scanning tunneling spectroscopy we demonstrate that the width strongly determines the formation and shape of electronic edges states.