On-surface synthesis of heteroatom-doped graphene nanoribbons*

The bottom-up approaches have been demonstrated to be very efficient for preparing atomically precise GNRs with tailor-made physical properties. The bottom-up on-surface synthesis enables incorporation of various heteroatoms, such as boron, nitrogen, sulfur and oxygen, into the GNR structure. Heteroatom doping can be a powerful tool for tuning the electronic properties of GNRs. The on-surface growth and characterization of heteroatom-doped GNRs is still largely unexplored and the development of new methods for their synthesis remains highly desirable. Here we describe facile on-surface methods for preparing several new heteroatom-doped GNRs that were modified with nitrogen, sulfur or boron atoms. The structures of these GNRs were identified by scanning tunneling microscopy (STM) in combination with noncontact atomic force microscopy (nc-AFM). The electronic structure of GNRs was investigated by scanning tunneling spectroscopy (STS) measurements in combination with DFT and GW calculations, showing good agreement between the experimental and theoretical results. These new heteroatom doped GNRs may find applications in a variety of electronic and optoelectronic devices.