Adsorption and STM imaging of polycyclic aromatic hydrocarbons on graphene

Abstract

The structural characterization of polycyclic aromatic hydrocarbon molecules adsorbed on graphene is of fundamental importance in view of the use of graphene or graphene nanoribbons for electronic applications. Before reaching this point, one has to determine the structure of the adsorbed molecules. Here, we study the case of benzene, coronene, and hexabenzocoronene on a graphene layer. First, the adsorption properties of single molecules are calculated using first-principles calculations at the level of density functional theory. We benefit from a recent scheme, particularly adapted for weakly adsorbed molecules, allowing us to precisely calculate the van der Waals contribution. Then, scanning tunneling microscopy (STM) is used to produce images of self-assembled molecules comparing different theoretical approaches to experimental observations. Finally, we consider the imaging of isolated molecules, and we show how the STM tip influences the molecule position by soft mechanical interaction during the scanning process.

Is coronene better described byClar's aromatic π‐sextet model or by the AdNDP representation?

“…In summary, the outer ring of coronene is more aromatic than the inner ring and this result is in accordance with Clar's model prediction. This conclusion agrees with scanning tunnelling microscope (STM) images that show coronene as a hollow ring like structure with a circular protrusion for the outer rings of coronene and a small depression for the central “empty ring.” Finally, all indices in Table except NICS(1) zz , consider that the aromaticity of the outer ring of coronene is closer to that of the ring of naphthalene than to that of the outer ring of phenanthrene and that the aromaticity of the inner ring in coronene is similar (but somewhat lower except in the case of HOMA) to that of the central ring in phenanthrene.…”

Self-assembly and spectroscopic fingerprints of photoactive pyrenyl tectons on hBN/Cu(111)

“…This suggested that the ethynyl-functionalized pyrene cores were aligned with the high-symmetry directions of the h BN/Cu(111) support, and thus yielded only distinct orientations of the supramolecular architectures. Indeed, DFT calculations have predicted the adsorption of the pyrene with the aromatic rings centered above the N-positions of a free-standing h BN sheet [ 81 ]. Preferred alignments have also been reported for low coverages of PTCDA and MnPc on the strongly corrugated h BN/Rh(111) support [ 21 – 22 80 ], with computational modeling showing PTCDA rings positioned above the N sites of a h BN flake [ 14 ].…”

Hydrogen interaction with graphene on Ir(1 1 1): a combined intercalation and functionalization study

“…The carbon and hydrogen atoms in the tunneling junction were described by full standard 2s2p and 1s basis sets, respectively. This type of basis set has been used previously with success to model polycyclic aromatic hydrocarbons on graphene [45].…”