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Exercising direct control over the unusual electronic structures arising from quantum confinement effects in graphene nanorib-bons (GNRs) is intimately linked to geometric boundary conditions imposed by the structure of the ribbon. Besides composition and position of substitutional dopant atoms, the symmetry of the unit cell, width, length, and termination of a GNR govern its electronic structure. Here we present a rational design that integrates each of these interdependent variables within a modular bottom-up syn-thesis. Our hybrid chemical approach relies on a catalyst transfer polymerization (CTP) that establishes excellent control over length, width, and end-groups. Complemented by a surface-assisted cy-clodehydrogenation step, uniquely enabled by matrix-assisted di-rect (MAD) transfer protocols, geometry and functional handles encoded in a polymer template are faithfully mapped onto the structure of the corresponding GNR. Bond-resolved scanning tun-nelling microscopy (BRSTM) and spectroscopy (STS) validate the robust correlation between polymer template design and GNR electronic structure.
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Coupling of Nondegenerate Topological Modes in Nitrogen Core-Doped Graphene Nanoribbons
Nitrogen core-doping of graphene nanoribbons (GNRs) allows trigonal planar carbon atoms along the backbone of GNRs to be substituted by higher-valency nitrogen atoms. The excess valence electrons are injected into the π-orbital system of the GNR, thereby changing not only its electronic occupation but also its topological properties. We have observed this topological change by synthesizing dilute nitrogen core-doped armchair GNRs with a width of five atoms (N2-5-AGNRs). The incorporation of pairs of trigonal planar nitrogen atoms results in the emergence of topological boundary states at the interface between doped and undoped segments of the GNR. These topological boundary states are offset in energy by approximately ΔE = 300 meV relative to the topological end states at the termini of finite 5-AGNRs. Scanning tunneling microscopy (STM) and spectroscopy (STS) reveal that for finite GNRs the two types of topological states can interact through a linear combination of orbitals, resulting in a pair of asymmetric hybridized states. This behavior is captured by an effective Hamiltonian of nondegenerate diatomic molecules, where the analogous interatomic hybridization interaction strength is tuned by the distance between GNR topological modes.
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- Award ID(s):
- 2235143
- PAR ID:
- 10631564
- Publisher / Repository:
- ACS Nano, ACS
- Date Published:
- Journal Name:
- ACS Nano
- Volume:
- 19
- Issue:
- 13
- ISSN:
- 1936-0851
- Page Range / eLocation ID:
- 13029 to 13036
- Subject(s) / Keyword(s):
- Graphene nanoribbons
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1021/acsnano.4c17602
