Involved researchers : D. Nakabayashi, T. Michel, M. Paillet, J.-L. Sauvajol, J.-L. Bantignies, R. Parret, A. Zahab, N. Camara, B. Jabakhanji, B. Jouault, J.-R. Huntzinger, A. Tiberj, J. Camassel

Collaborations : P. Poncharal, A. Ayari (LPMCN, Lyon, France)
P. Godignon, N. Mestres, A. Caboni (CNM, Barcelona, Spain)
J.-Y. Veuillen, L. Magaud, P. Mallet, C. Naud, A. Mahmood, F. Hiebel (Institut Néel, Grenoble, France)
P. Soukiassian (SIMA CEA Saclay, France)
M. Asensio Carmen (synchroton SOLEIL, Orsay, France)
S. Sonde, F. Giannazo, V. Raineri (IMM-CNR, Catania, Italy)
R. Yakimova (IFM, Linköping University, Sweden)

Graphene is a single sheet of carbon atoms packed in a honeycomb lattice. It constitutes the 2D building block for graphitic materials of all other dimensionalities. It can be wrapped up into 0D fullerenes, rolled into 1D carbon nanotubes or stacked into 3D graphite. Graphene has oustanding electronic, optical, thermal and mechanical properties. Recently, Andre K. Geim and Konstantin S. Novoselov shared the 2010 Nobel Prize in Physics for their groundbreaking experiments. They succeed in producing, isolating, identifying and characterizing this amazing material.

Most of the electronic properties of graphene (including mass-less Dirac fermions, high carriers mobility and balistic transport properties at room temperature) come from its linear band structure with 6 doubles cones at the inequivalent K and K’ points of the Brillouin zone. This linear dispersion gives rise to an unusual quantum Hall effect that remains at room temperature. Graphene can then be used to develop new resistance standard for metrology applications. It is transparent, stronger than steel and has also a very high thermal conductivity. Therefore a wide range of potential applications has been identified : flexible electronics, gas sensors, transparent conductor for touch screens, liquid crystal displays, photovoltaic cells, and organic light-emitting diodes. Graphene can be produced by several methods :

mechanical exfoliation of graphite using scotch tape
chemical exfoliation using either redox reaction or solvent
chemical vapour deposition (CVD) on metal surfaces such as Ru, Ir, Ni and Cu
high temperature annealing (>1100°C) of SiC surfaces

In our lab, we are studying graphene and few layer graphene produced either by exfoliation or sublimation. This controlled sublimation of few Si atomic layers from a single crystalline SiC surface is considered as one of the most promising methods for microelectronic applications. For instance, selective epitaxial growth of graphene on prepatterned SiC substrates has been demonstrated in collaboration with the CNM [APL]. Since graphene is uniquely composed of surface atoms, its physical properties are drastically affected by the environment. Switching from a monolayer to two graphene layers stacked in Bernal AB configuration destroys the linear band structure to a parabolic one. The underlying substrate play also a significant role. For instance the properties of sublimated graphene (shape, size, interaction with the SiC substrate, doping, strain) depend strongly on the SiC surface orientation (on or off axis, Si or C face). In our lab, the electronic structure of graphene and stacked graphene layers can be probed by transport experiments under high magnetic fields (up to 14 T) and at low temperatures (down to 1.6 K) and also by Raman spectroscopy since some Raman active modes originate from a double resonance process.