ABSTRACT
Graphene, a one-atom-thick carbon crystal in a honeycomb lattice, possesses many fascinating properties originating from the manifold potential for interactions at electronic, atomic, or molecular levels (Novoselov et al. 2004, 2005; Zhang et al. 2005; Geim & Novoselov 2007; Schedin et al. 2007; Bolotin et al. 2009; Geim 2009; Neto et al. 2009; Kotov et al. 2012). Graphene is remarkably strong for its atomic thinness and conducts heat and electricity with great efficiency. Electron motion in graphene is essentially governed by Dirac’s relativistic equation. The charge carriers in graphene behave like relativistic particles with zero rest mass and have an effective “speed of light” of ~106 m s−1. For a perfect graphene sheet free from impurities and disorder, the Fermi level lies at the so-called Dirac point, where the density of electronic states vanishes. Unlike the two-dimensional (2D) electron system in conventional semiconductors, where the charge carriers become immobile at low densities, the carrier mobility in graphene can remain very high, even with vanishing density of states at Dirac point (Du et al. 2008; Morozov et al. 2008).
