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. Amina Kimouche is a postdoctoral researcher at Aalto University. Her current research focuses on probing the structure and electronic properties of materials at the atomic scale using low-temperature scanning tunneling microscopy (STM) and atomic force microscopy (AFM). She received her PhD in Physics (2013) from Joseph Fourier University in Grenoble where she studied the electronic properties of hybrid graphene-based systems by using complex instruments from scanning probe microscopies to synchrotron radiation facilities. Her expertise lies in fabricating and characterizing atomically well-defined nanostructures such as graphene nanoribbons and molecular networks, to study physical phenomena at the nanoscale for future molecular scale electronic circuity.