| AVS 60th International Symposium and Exhibition | |
| Graphene and Other 2D Materials Focus Topic | Wednesday Sessions |
| Session GR-WeM |
| Session: | 2D Materials on Metallic Substrates |
| Presenter: | E. Monazami, University of Virginia |
| Authors: | E. Monazami, University of Virginia P. Rudolf, University of Groningen, Netherlands L. Bignardi, University of Groningen, Netherlands P. Reinke, University of Virginia |
| Correspondent: | Click to Email |
The unique properties of graphene are coveted for application in electronic devices but doping and opening of a bandgap while retaining the integrity of the Dirac cone, remains a challenge. The electronic properties of graphene can be modified through the interaction with adsorbates or the substrate, which has also been exploited to achieve moderate doping of the graphene layer. In our study we present the intercalation of fullerene molecules at the interface between copper and graphene as a method to electronically decouple graphene from the metal substrate, introduce a controlled strain field and create a topographic superlattice.
Our presentation focuses on the synthesis of the intercalated fullerene layer, and the local impact of intercalated fullerenes on the strain and deformation of the graphene layer. The intercalation is achieved by depositing 10-20 ML of C60 on graphene, which was grown on a polycrystalline Cu-substrate. The C60-graphene-Cu sandwich is annealed at 400-500º C in UHV and subsequently imaged with Scanning Tunneling Microscopy (STM) and Spectroscopy (STS) conductivity maps at room temperature. The graphene-Cu system was studied separately to ascertain that the impact of Cu crystallinity and annealing on graphene's topographic and electronic structure is minimal. The role of temperature and Cu-structure on the intercalation process will be discussed in detail, and we will introduce specific indicators in the STM and STS signature to ascertain C60 intercalation. Recent experiments strongly suggest that a temperature around 400º C leads to the formation of regular, crystalline intercalated C60 layer, while higher temperatures favor an irregular, amorphous arrangement of the molecules.
The intercalation of C60 molecules leads to the modulation of the graphene topography due to the mechanical deformation and strain around a fullerene molecule. The graphene is detached from the Cu-substrate in the vicinity of C60 moleculesand the Fermi level is shifted with respect to the Dirac point indicating a local p-type doping at the graphene-fullerene contact. The local electronic properties are controlled by the intercalated molecules offering a new approach to manipulating of charge distribution in graphene. The intercalation leads to a considerable increase in the density of graphene wrinkles, which is attributed to the reduction of graphene adhesion. We will present a cohesive model, which integrates the impact of C60 intercalation on graphene strain, adhesion, and electronic structure.