Dense monolayer films of atomically precise graphene nanoribbons on metallic substrates enabled by direct contact transfer of molecular precursors

Abstract

Atomically precise graphene nanoribbons (GNRs) of two types, chevron GNRs and N = 7 straight armchair GNRs (7-AGNRs), have been synthesized through a direct contact transfer (DCT) of molecular precursors on Au(111) and gradual annealing. This method provides an alternative to the conventional approach for the deposition of molecules on surfaces by sublimation and simplifies preparation of dense monolayer films of GNRs. The DCT method allows deposition of molecules on a surface in their original state and then studying their gradual transformation to polymers to GNRs by scanning tunneling microscopy (STM) upon annealing. We performed STM characterization of the precursors of chevron GNRs and 7-AGNRs, and demonstrate that the assemblies of the intermediates of the GNR synthesis are stabilized by π-π interactions. This conclusion was supported by the density functional theory calculations. The resulting monolayer films of GNRs have sufficient coverage and density of nanoribbons for ex situ characterization by spectroscopic methods, such as Raman spectroscopy, and may prove useful for the future GNR device studies.

On‐Surface Synthesis and Spectroscopic Characterization of Laterally Extended Chevron Graphene Nanoribbons

“…We performed the growth at a low coverage of molecular precursors to avoid fused GNR structures and produce isolated nanoribbons for the STS characterization. STM and nc‐AFM images of a representative eGNR on Au(111) are shown in Figure .…”

Bottom-up Assembly of Nanoporous Graphene with Emergent Electronic States

“…11,12 This has been demonstrated recently through cross-dehydrogenative coupling of bottom-up synthesized graphene nanoribbons (GNRs) featuring periodic bay regions along the edges. 11,[13][14][15] A disadvantage of the few reported bottom-up synthesized NPGs fabricated in this way is that the constituent nanoribbons are wide gap semiconductors. Electronic coupling upon lateral extension results in, at most, a modest decrease in the overall band gap compared to that of the constituent one-dimensional (1D) ribbons.…”

Bottom-up synthesis of multifunctional nanoporous graphene

“…Another remarkable milestone is the long-range order achieved. To date, the observation of selective intermolecular aryl-aryl coupling has been limited to small supramolecular structures (19,(23)(24)(25)(26)(27)(28). The hierarchical strategy of our method allows us to set the long-range order in step T2, where the length of prealigned GNRs represent the size limitation of the NPG.…”