Intercalation is a powerful means to create sandwich structures, in which either the properties of graphene, the properties of the intercalant, or both, can be engineered.
One system which we study is graphene prepared on an Ir(111) substrate, intercalated by an ultra thin iridium oxide film. Exposure to air of freshly, UHV-prepared graphene/Ir(111) results in the spontaneous intercalation of molecular species through the open end of wrinkles, a ubiquitous defect in graphene. As a result oxide ribbons intercalate along the wrinkles. These ribbons, which are a few 100 nm in width, several microns in length and 1-2 nm in height, are weakly conductive, substantially modify the electronic charge density in graphene, and accordingly modify the inelastic optical (Raman) response of graphene. Besides, molecular species intercalated in a dilute phase between graphene and Ir(111) yield truly free-standing graphene onto a metal, as signaled by a Dirac-fermion-like signature of charge carriers.
(Left) Cartoon of the intercalation process for species along graphene wrinkles, leading to intercalated oxide ribbons. (Right) Two-dimensional mapping of the position of the 2D Raman mode, with the position of the wrinkles (doted line) highlighted.
A. Kimouche et al. Modulating charge density and inelastic optical response in graphene by atmospheric pressure localized intercalation through wrinkles. Carbon (2014)
S. C. Martin et al. Disorder and screening in decoupled graphene on a metallic substrate. Phys. Rev. (2015)
We also study graphene systems intercalated with magnetic materials, especially cobalt. We identified various intercalation pathways in this system (curved graphene regions, edges, point defects) depending on the quality of graphene, which can be activated at different temperatures. The intercalated Co films are protected from oxidation to air by the graphene membrane. We found that the Co films maintain a perpendicular magnetization up to a thickness of 2.6 nm, which is much larger than without graphene, and the sign of a strong interface magnetic anisotropy at the graphene/Co interface, only surpassed in very few other systems to date.
(Top) Cartoon showing the intercalation process. (Bottom) Two SPLEEM images, one obtained with electron spins polarized perpendicular to the surface, the other with electron spins polarized in the plane of the surface, for 8 atomic layers of Co intercalated between graphene and Ir(111), revealing a perpendicular magnetization in Co.
J. Coraux et al. Air-Protected Epitaxial Graphene/Ferromagnet Hybrids Prepared by Chemical Vapor Deposition and Intercalation. J. Phys. Chem. Lett. (2012)
N. Rougemaille et al. Perpendicular magnetic anisotropy of cobalt films intercalated under graphene. Appl. Phys. Lett. (2012)
S. Vlaic et al. Cobalt intercalation at the graphene/iridium(111) interface : influence of rotational domains, wrinkles, and atomic steps. Appl. Phys. Lett. (2014)