Controlled surface assembly and size-dependent electronic properties of large C96 nanographenes on Au(111)

Abstract

Polycyclic aromatic hydrocarbons (PAHs) provide a versatile platform for engineering electronic functionality at the molecular scale; however, achieving precise control over their surface assembly and emergent properties remains a significant challenge. Here, we investigate the growth and electronic behavior of a large nanographene molecule (C₉₆-tBu₈) on Au(111) using two complementary deposition methods: pulsed-valve injection and molecular beam epitaxy (MBE). Low-temperature scanning tunneling microscopy and spectroscopy (STM/STS) reveal that the deposition pathway governs distinct growth regimes, ranging from highly ordered extended monolayers to isolated molecules and anisotropic stripe-like nanostructures.

A clear size-dependent evolution of the electronic structure is observed: small assemblies exhibit a semiconducting gap on the order of 1 eV, whereas larger assemblies display a finite density of states near the Fermi level. Rather than indicating a fully metallic state, this behavior is more appropriately described as a transition toward a reduced-gap regime associated with increased electronic delocalization. This evolution is attributed to the interplay between quantum confinement, intermolecular electronic coupling, and molecule-substrate interactions.

Overall, these findings establish a correlation between growth dynamics, structural organization, and electronic properties, demonstrating that surface assembly provides an effective route to tune functionality within a single molecular system. This work highlights large nanographenes as promising building blocks for nanoscale electronic and quantum architectures.

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BibTeX RIS

BibTeX

@article{kari2026controlled,
  title = {{Controlled surface assembly and size-dependent electronic properties of large C96 nanographenes on Au(111)}},
  author = {Hamza El Kari and Xiao Zhang and Hanna Enriquez and Andrew Mayne and Hamid Oughaddou},
  journal = {Applied Surface Science},
  year = {2026},
  month = may,
  doi = {10.1016/j.apsusc.2026.167373},
  url = {https://hal.science/hal-05853449v1},
  note = {CC BY 4.0},
}

RIS

TY  - JOUR
TI  - Controlled surface assembly and size-dependent electronic properties of large C96 nanographenes on Au(111)
AU  - Hamza El Kari
AU  - Xiao Zhang
AU  - Hanna Enriquez
AU  - Andrew Mayne
AU  - Hamid Oughaddou
PY  - 2026
DA  - 2026/05/26
JO  - Applied Surface Science
DO  - 10.1016/j.apsusc.2026.167373
UR  - https://hal.science/hal-05853449v1
AB  - Polycyclic aromatic hydrocarbons (PAHs) provide a versatile platform for engineering electronic functionality at the molecular scale; however, achieving precise control over their surface assembly and emergent properties remains a significant challenge. Here, we investigate the growth and electronic behavior of a large nanographene molecule (C₉₆-tBu₈) on Au(111) using two complementary deposition methods: pulsed-valve injection and molecular beam epitaxy (MBE). Low-temperature scanning tunneling microscopy and spectroscopy (STM/STS) reveal that the deposition pathway governs distinct growth regimes, ranging from highly ordered extended monolayers to isolated molecules and anisotropic stripe-like nanostructures.  A clear size-dependent evolution of the electronic structure is observed: small assemblies exhibit a semiconducting gap on the order of 1 eV, whereas larger assemblies display a finite density of states near the Fermi level. Rather than indicating a fully metallic state, this behavior is more appropriately described as a transition toward a reduced-gap regime associated with increased electronic delocalization. This evolution is attributed to the interplay between quantum confinement, intermolecular electronic coupling, and molecule-substrate interactions.  Overall, these findings establish a correlation between growth dynamics, structural organization, and electronic properties, demonstrating that surface assembly provides an effective route to tune functionality within a single molecular system. This work highlights large nanographenes as promising building blocks for nanoscale electronic and quantum architectures.
SN  - 0169-4332
SN  - 1873-5584
ER  -

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