title: On-surface synthesis of graphene nanoribbons with zigzag edge topology.
abstract: Graphene-based nanostructures exhibit electronic properties that are not present in extended graphene. For example, quantum confinement in carbon nanotubes and armchair graphene nanoribbons leads to the opening of substantial electronic bandgaps that are directly linked to their structural boundary conditions. Nanostructures with zigzag edges are expected to host spin-polarized electronic edge states and can thus serve as key elements for graphene-based spintronics. The edge states of zigzag graphene nanoribbons (ZGNRs) are predicted to couple ferromagnetically along the edge and antiferromagnetically between the edges, but direct observation of spin-polarized edge states for zigzag edge topologies--including ZGNRs--has not yet been achieved owing to the limited precision of current top-down approaches. Here we describe the bottom-up synthesis of ZGNRs through surface-assisted polymerization and cyclodehydrogenation of specifically designed precursor monomers to yield atomically precise zigzag edges. Using scanning tunnelling spectroscopy we show the existence of edge-localized states with large energy splittings. We expect that the availability of ZGNRs will enable the characterization of their predicted spin-related properties, such as spin confinement and filtering, and will ultimately add the spin degree of freedom to graphene-based circuitry.
authors.affiliation: Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
authors.forename: Pascal
authors.initials: P
authors.lastname: Ruffieux
authors.affiliation: Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
authors.forename: Shiyong
authors.initials: S
authors.lastname: Wang
authors.affiliation: Max Planck Institute for Polymer Research, 55128 Mainz, Germany.
authors.forename: Bo
authors.initials: B
authors.lastname: Yang
authors.affiliation: Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
authors.forename: Carlos
authors.initials: C
authors.lastname: Sánchez-Sánchez
authors.affiliation: Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
authors.forename: Jia
authors.initials: J
authors.lastname: Liu
authors.affiliation: Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Dienel
authors.affiliation: Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
authors.forename: Leopold
authors.initials: L
authors.lastname: Talirz
authors.affiliation: Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
authors.forename: Prashant
authors.initials: P
authors.lastname: Shinde
authors.affiliation: Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.|NCCR MARVEL, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
authors.forename: Carlo A
authors.initials: CA
authors.lastname: Pignedoli
authors.affiliation: Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
authors.forename: Daniele
authors.initials: D
authors.lastname: Passerone
authors.affiliation: Max Planck Institute for Polymer Research, 55128 Mainz, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Dumslaff
authors.affiliation: Center for Advancing Electronics Dresden &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: Klaus
authors.initials: K
authors.lastname: Müllen
authors.affiliation: Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.|Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland.
authors.forename: Roman
authors.initials: R
authors.lastname: Fasel