Molecular Self-Assembly on Graphene on SiO₂ and h-BN Substrates

Abstract

One of the suggested ways of controlling the electronic properties of graphene is to establish a periodic potential modulation on it, which could be achieved by self-assembly of ordered molecular lattices. We have studied the self-assembly of cobalt phthalocyanines (CoPc) on chemical vapor deposition (CVD) grown graphene transferred onto silicon dioxide (SiO2) and hexagonal boron nitride (h-BN) substrates. Our scanning tunneling microscopy (STM) experiments show that, on both substrates, CoPc forms a square lattice. However, on SiO2, the domain size is limited by the corrugation of graphene, whereas on h-BN, single domain extends over entire terraces of the underlying h-BN. Additionally, scanning tunneling spectroscopy (STS) measurements suggest that CoPc molecules are doped by the substrate and that the level of doping varies from molecule to molecule. This variation is larger on graphene on SiO2 than on h-BN. These results suggest that graphene on h-BN is an ideal substrate for the study of molecular self-assembly toward controlling the electronic properties of graphene by engineered potential landscapes.

Reduction of Mn19 Coordination Clusters on a Gold Surface

“…49 Interestingly, the Mn reduction is almost absent in the Mn 6 single-molecule magnet when deposited on a Au(111) surface. 50 In view of the finding that the second layer of molecules is of mixed valence kind similar to the pristine molecules, the introduction of spacer molecules 44,51 or decoupling layers such as hexagonal boron nitride or graphene 52,53 could be a viable means of protecting the Mn 19 (SMe) molecules from reduction.…”

Room temperature dry processing of patterned CVD graphene devices

“…Exposure to chemically aggressive treatments performed at significantly elevated temperatures also severely limits the choice of substrates, making the fabrication of hybrid devices involving organic materials underlayers highly challenging. Combining graphene with molecules or polymers is becoming increasingly popular, as graphene chemical functionalization is expected to offer new solutions to control graphene electronic properties, for example through the self-assembly of molecular lattice over graphene in order to impose a superperiodic potential [16,17] and to induce multifunctionality. Such studies require graphene material free of molecular residues.…”

Electronic and transport properties in geometrically disordered graphene antidot lattices

“…The validity of these conclusions relies on the crucial assumption that the antidots form a perfectly ordered superlattice. While the self-assembly on graphene could possibly be a promising route toward this [7], the effect of the deviation from the perfect periodicity is still an important question to be answered. This is especially important because according to the scaling theory of Anderson localization [8], electrons in low-dimensional systems become more easily localized than in 3D materials.…”