Graphene

Fig. 1: Simulated structure and topography of a graphene sheet [1].

Graphene is the thinnest material known. It consists of just one atomic layer of carbon atoms arranged in a honeycomb lattice and can be regarded as perfect two-dimensional system. Several layers of graphene stacked up in a sandwich form the well-known graphite. Until the year 2004 graphene was considered to be unstable when it was finally obtained, stabilized on Silicon oxide substrates and characterized by Andre Geim and Konstantin Novoselov at Manchester University / UK. For this achievement Geim and Novoselov have received the Nobel Prize in Physics 2010 [2].

Graphene is a zero bandgap semiconductor, in which charge carriers exhibit a linear dispersion in the electronic structure in the vicinity of the Fermi energy (Dirac point). Charge carriers in graphene are confined to a layer which is only one atom thick and exhibit very high velocities at high fields of ~ 4x10⁷ cm/s and very high mobilities of ~120,000 cm² /Vs (at 240K), the highest ever reported for any semiconductor [3]. The density of states (DOS) at the Dirac point is zero and increases linearly for higher and lower energies allowing for carrier modulation. These unique features make graphene a very attractive material for high speed electronics [3].

Fig. 2: Sketch of the electronic structure of graphene, cone-shape linear electronic dispersion and density of states.

At IHP graphene-related research is conducted in two main branches: direct graphene growth on insulating substrates (Graphene Synthesis) and novel graphene-based high frequency devices

(Graphene Devices).