| AVS 59th Annual International Symposium and Exhibition | |
| Graphene and Related Materials Focus Topic | Wednesday Sessions |
| Session GR+AS+EM+NS+SS-WeA |
| Session: | Dopants and Defects in Graphene; Graphene Interfaces with Other Materials |
| Presenter: | C. Gong, The University of Texas at Dallas |
| Authors: | C. Gong, The University of Texas at Dallas R.M. Wallace, The University of Texas at Dallas K.J. Cho, The University of Texas at Dallas Y.J. Chabal, The University of Texas at Dallas |
| Correspondent: | Click to Email |
Two types of interfaces can be formed between metals and graphene depending on the strength of the metal-graphene interaction: weak (metal physisorption) and strong (metal chemisorption) interfaces. “Physisorption” interfaces (e.g., with Al, Ag, Cu, Ir, Pt and Au) are characterized by a larger metal-carbon distance (>3 Å) with some charge transfer between metal and graphene (i.e. doping of graphene) that maintains its overall π-band dispersion. “Chemisorption” interfaces (e.g. with Ni, Co, Pd, and Ti) are characterized by a smaller metal-carbon distance (<2.5 Å) and strong orbital hybridization between metal-d and carbon-pz orbitals, resulting in the destruction of the graphene’s π-band dispersion around the Dirac point. Till now, only a small fraction of all available metals has been used as electrode materials for carbon-based devices due to metal-graphene interface debonding problems. The issue therefore is to keep graphene’s intrinsic π bandstructure by using weakly interacting metals while enhancing the interface stability.
We report an enhancement of the bonding energy of weakly interacting metals by using a metal-graphene-metal sandwich geometry, without sacrificing the intrinsic π-electron dispersions of graphene that is usually undermined by strong metal-graphene interface hybridization. This sandwich structure further makes it possible to effectively tune the doping of graphene with an appropriate selection of metals. Density functional theory calculations reveal that the strengthening of the interface interaction is ascribed to an enhancement of interface dipole-dipole interactions. Raman scattering studies of metal-graphene-copper sandwiches are used to validate the theoretically predicted tuning of graphene doping through sandwich structures.