| Autor: |
Berdonces-Layunta A; Donostia International Physics Center, 20018 San Sebastián, Spain.; Centro de Física de Materiales, 20018 San Sebastián, Spain., Schulz F; Department of Applied Physics, Aalto University, FI-00076 Aalto, Finland.; Fritz Haber Institute of the Max Planck Society, 14195 Berlin, Germany., Aguilar-Galindo F; Donostia International Physics Center, 20018 San Sebastián, Spain., Lawrence J; Donostia International Physics Center, 20018 San Sebastián, Spain.; Centro de Física de Materiales, 20018 San Sebastián, Spain., Mohammed MSG; Donostia International Physics Center, 20018 San Sebastián, Spain.; Centro de Física de Materiales, 20018 San Sebastián, Spain., Muntwiler M; Paul Scherrer Institute, 5232 Villigen, Switzerland., Lobo-Checa J; Instituto de Nanociencia y Materiales de Aragón, 50009 Zaragoza, Spain.; Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50009 Zaragoza, Spain., Liljeroth P; Department of Applied Physics, Aalto University, FI-00076 Aalto, Finland., de Oteyza DG; Donostia International Physics Center, 20018 San Sebastián, Spain.; Centro de Física de Materiales, 20018 San Sebastián, Spain.; Ikerbasque, Basque Foundation for Science, 48009 Bilbao, Spain. |
| Abstrakt: |
The advent of on-surface chemistry under vacuum has vastly increased our capabilities to synthesize carbon nanomaterials with atomic precision. Among the types of target structures that have been synthesized by these means, graphene nanoribbons (GNRs) have probably attracted the most attention. In this context, the vast majority of GNRs have been synthesized from the same chemical reaction: Ullmann coupling followed by cyclodehydrogenation. Here, we provide a detailed study of the growth process of five-atom-wide armchair GNRs starting from dibromoperylene. Combining scanning probe microscopy with temperature-dependent XPS measurements and theoretical calculations, we show that the GNR growth departs from the conventional reaction scenario. Instead, precursor molecules couple by means of a concerted mechanism whereby two covalent bonds are formed simultaneously, along with a concomitant dehydrogenation. Indeed, this alternative reaction path is responsible for the straight GNR growth in spite of the initial mixture of reactant isomers with irregular metal-organic intermediates that we find. The provided insight will not only help understanding the reaction mechanisms of other reactants but also serve as a guide for the design of other precursor molecules. |
