Department of Applied Physics, Aalto University, Finland There has been tremendous progress in the bottom-up synthesis of graphene nanostructures. In particular, atomically well-defined armchair-terminated graphene nanoribbons (AGNRs) has been shown to provide precise control over the width and edge geometry of the ribbon. By changing the monomer design, the fabrication of a wide range of GNRs including different widths and doping can be achieved. While all the experimentally studied systems have exhibited wide band gaps, theory predicts that every third ANGR (N=3p+2) should be (nearly) metallic with a very small band gap. Here, we target the narrowest possible AGNR belonging to the metallic family that is only 5 carbon atoms wide. Scanning tunneling spectroscopy shows that N=5 ribbon can have bandgaps below 500 meV, which is much less than in the wider N=7 GNRs belonging to the N=3m+1 family. We have performed first principle calculations to support our experimental STS data and to identify fingerprints in the dI/dV maps. This allows detailed understanding of the length-dependent properties of these ultra-narrow GNRs, which is important for their potential use as interconnects in nanoelectronic circuits or in transistor structures. |
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