ABSTRACT
Graphene is the basic structural element of some carbon allotropes including 0D fullerene, 1D carbon nanotube, and 3D graphite. Its 2D one-atom-thick planar network is composed of the hexagonal crystal lattice structure packed by sp2-hybridized carbon atoms with the s, px, and py atomic orbitals on each carbon atom forming three strong σ bonds with other three surrounding atoms.1,2 Overlap of the remaining pz orbital on each carbon atom with neighboring carbon atoms produces a lled band of π orbitals called the valence band and an empty band of π* orbitals known as the conduction band. The valence and conduction bands touch at the Brillouin zone corners, thus making graphene a zero-bandgap semiconductor (Figure 39.1). Graphene exhibits many outstanding properties, such as fast room-temperature mobility of charge carriers (200,000 cm2 V−1 s−1), exceptional conductivity (106 S cm−1), and large theoretical speci c surface area (2,630 m2 g−1), which promise a technological revolution.3 However, the practical application of graphene encounters massive problems, for example, lack of economical and reliable ways to produce high-quality graphene and fundamentally unsuitable zero bandgap of graphene for the on-off switching that lies at the heart of digital electronics.
