title: On-Surface Synthesis and Characterization of 9-Atom Wide Armchair Graphene Nanoribbons.
abstract: The bottom-up approach to synthesize graphene nanoribbons strives not only to introduce a band gap into the electronic structure of graphene but also to accurately tune its value by designing both the width and edge structure of the ribbons with atomic precision. We report the synthesis of an armchair graphene nanoribbon with a width of nine carbon atoms on Au(111) through surface-assisted aryl-aryl coupling and subsequent cyclodehydrogenation of a properly chosen molecular precursor. By combining high-resolution atomic force microscopy, scanning tunneling microscopy, and Raman spectroscopy, we demonstrate that the atomic structure of the fabricated ribbons is exactly as designed. Angle-resolved photoemission spectroscopy and Fourier-transformed scanning tunneling spectroscopy reveal an electronic band gap of 1.4 eV and effective masses of ≈0.1 mefor both electrons and holes, constituting a substantial improvement over previous efforts toward the development of transistor applications. We use ab initio calculations to gain insight into the dependence of the Raman spectra on excitation wavelength as well as to rationalize the symmetry-dependent contribution of the ribbons' electronic states to the tunneling current. We propose a simple rule for the visibility of frontier electronic bands of armchair graphene nanoribbons in scanning tunneling spectroscopy.
authors.forename: Leopold
authors.identifier: 0000-0002-1524-5903
authors.initials: L
authors.lastname: Talirz
authors.forename: Hajo
authors.initials: H
authors.lastname: Söde
authors.affiliation: Max Planck Institute for Polymer Research , 55128 Mainz, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Dumslaff
authors.forename: Shiyong
authors.initials: S
authors.lastname: Wang
authors.forename: Juan Ramon
authors.initials: JR
authors.lastname: Sanchez-Valencia
authors.forename: Jia
authors.initials: J
authors.lastname: Liu
authors.forename: Prashant
authors.initials: P
authors.lastname: Shinde
authors.forename: Carlo A
authors.initials: CA
authors.lastname: Pignedoli
authors.affiliation: Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute , Troy, 12180 New York, United States.|Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, 37831 Tennessee, United States.
authors.forename: Liangbo
authors.identifier: 0000-0003-1199-0049
authors.initials: L
authors.lastname: Liang
authors.affiliation: Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute , Troy, 12180 New York, United States.
authors.forename: Vincent
authors.initials: V
authors.lastname: Meunier
authors.affiliation: Swiss Light Source, Paul Scherrer Institute , 5232 Villigen, Switzerland.
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Plumb
authors.affiliation: Swiss Light Source, Paul Scherrer Institute , 5232 Villigen, Switzerland.
authors.forename: Ming
authors.initials: M
authors.lastname: Shi
authors.affiliation: Center for Advancing Electronics Dresden and Department of Chemistry and Food Chemistry, Technische Universität Dresden , 01062 Dresden, Germany.
authors.forename: Xinliang
authors.initials: X
authors.lastname: Feng
authors.affiliation: Max Planck Institute for Polymer Research , 55128 Mainz, Germany.
authors.forename: Akimitsu
authors.initials: A
authors.lastname: Narita
authors.affiliation: Max Planck Institute for Polymer Research , 55128 Mainz, Germany.
authors.forename: Klaus
authors.identifier: 0000-0001-6630-8786
authors.initials: K
authors.lastname: Müllen
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern , 3012 Bern, Switzerland.
authors.forename: Roman
authors.initials: R
authors.lastname: Fasel
authors.forename: Pascal
authors.identifier: 0000-0001-5729-5354
authors.initials: P
authors.lastname: Ruffieux
keywords: Raman spectroscopy; bottom-up synthesis; graphene nanoribbons; on-surface chemistry; scanning tunneling spectroscopy