Molecular adsorbates as probes of the local properties of doped graphene

Van Dong Pham, Frédéric Joucken, Vincent Repain, Cyril Chacon, Amandine Bellec, Yann Girard, Sylvie Rousset, Robert Sporken, Maria Cristina Dos Santos, Jérôme Lagoute

Research output: Contribution to journalArticlepeer-review

Abstract

Graphene-based sensors are among the most promising of graphene's applications. The ability to signal the presence of molecular species adsorbed on this atomically thin substrate has been explored from electric measurements to light scattering. Here we show that the adsorbed molecules can be used to sense graphene properties. The interaction of porphyrin molecules with nitrogen-doped graphene has been investigated using scanning tunneling microscopy and ab initio calculations. Molecular manipulation was used to reveal the surface below the adsorbed molecules allowing to achieve an atomic-scale measure of the interaction of molecules with doped graphene. The adsorbate's frontier electronic states are downshifted in energy as the molecule approaches the doping site, with largest effect when the molecule sits over the nitrogen dopant. Theoretical calculations showed that, due to graphene's high polarizability, the adsorption of porphyrin induces a charge rearrangement on the substrate similar to the image charges on a metal. This charge polarization is enhanced around nitrogen site, leading to an increased interaction of molecules with their image charges on graphene. Consequently, the molecular states are stabilized and shift to lower energies. These findings reveal the local variation of polarizability induced by nitrogen dopant opening new routes towards the electronic tuning of graphene.

Original languageEnglish
Article number24796
JournalScientific Reports
Volume6
DOIs
Publication statusPublished - 21 Apr 2016

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