Structural Properties of Graphene - Report Example

Structural Properties of Graphene Structural Properties of Graphene Graphene refers to a flat monolayer of carbon atoms that aretightly packed to form a two-dimensional (2-D) honey-comb lattice. It is a common building block for graphitic materials as well as other dimensionalities. The structure of graphene means that it can be folded into 0-D fullerenes or rolled to form 1-D nanotubes (Huang et al 2006). It can also be stacked to form 3-D graphite. On a theoretical level, graphene has been used widely to describe the various properties of different carbon-based materials. Only recently, graphene has been identified to be an excellent source for condensed matter dimensional quantum electrodynamics. It is this physical characteristic that has propelled graphene into a potential model for a theoretical toy. Initial studies had indicated that graphene cannot exist in a free state as it was unstable for the formation of structural curvatures. However, recent evidence has thrust graphene into the limelight within the field of structural physics. This was precipitated by the discovery of free-standing structural graphene. In fact, many follow-up experiments confirmed that this new type of graphene had mass-less Dirac fermions as its charge carriers. Basically speaking, graphene is a single atomic layer of graphite. It is a carbon allotrope that is composed of tightly bonded carbon atoms that are organized to form a hexagonal lattice. With a sp2 hybridization coupled with its very thin atomic thickness (0.345Nm), graphene surpasses many other carbon structures in terms of strength, heat and electrical conduction (Meyer et al, 2007). The diagram below shows how graphene basically looks like A 2-D sheet of graphene is made up of a hexagonal structure where each atom forms three distinct bonds with each one of its nearest neighbors. The bonds are known as the σ bonds and they are oriented towards the neighboring atoms since they are formed by the three of the valence electrons. The covalent carbon-carbon bonds that are exhibited by graphene closely resemble the bonds that hold carbon atoms in diamond. This gives graphene some physical characteristics that are similar to those of diamond. In graphene, the fourth valence electron does not take part in the covalence bonding. The atom remains in the 2pz state where it is oriented perpendicularly to the graphite sheet this forming a conduction π-band. The remarkable electric conduction properties of the carbon nanotubes results from the peculiar band structure exhibited by graphene. These include the zero-band-gap semiconductor and the two linearly dispersing bands that contact each other at the corners of the first brillouin zone (Kelly 1981). A B A). The figure illustrates how the conduction band of graphene interacts with the Fermion level along the edges of the Brillouin zone.  After successful studies of graphene were conducted using transmission electron microscope, many physics scholars believed that the reason was due to slight rippling within the graphene structure. However, successive research later found that the carbon-carbon bonds in graphene are so minute and excessively strong that they effectively prevent destabilization of the structure by thermal fluctuations. Graphene is now a promising structural component in the realms of condensed matter physics and material science. Its strict 2-D material structure exhibits precisely high crystal and electronic quality. Due to its unique electronic spectrum, graphene has introduced a new paradigm in terms of ‘relativistic’ material physics. Quantum relativistic features which are usually unobservable in high energy condensed matter physics can now be easily tested and mimicked in table-top experiments. Generally, graphene presents a conceptually new kind of materials that are essentially one atom thick and hence providing new breakthroughs in low-dimensional physics that has continued to present new opportunities for the development of more applications (Poot et al, 2008). Before the invention of graphene, there had been many contentions among scholars in physics and material science regarding the number of crystal that are needed to compose a 3-dimensional structure. It is plausible that any single atomic plane is considered as a 2-D crystal. Consequently, a hundred of such layers make up a structure that can only be termed as a 3-D material. The starting of a 3-dimensional structure is quite obscured. The introduction of graphene has resolved this scientific quagmire. It is now clear that the electronic structure undergoes rapid evolution in tandem with the number of layers, and eventually approaches the 3-D limit of graphite which is conventionally at 10 layers. The melting temperature for these thin films show considerable decreases as the thickness is reduced. Finally, they become unstable and disintegrate into as the thickness reaches a few dozens of atomic layers. Atomic monolayer have for long been known as an integral part of large 3-D structures (Delhaes 2001). These include the structures that are anchored epitaxial over other monocrystals by use of matching lattices. In the absence of such a 3-D structural base, the existence of 2-D structures was unknown until the discovery of graphene. Graphene and other free-standing 2-D atomic crystals are easily obtained on top of some non-crystalline substrates. They are also obtained as suspended membranes or in liquid suspensions. The crystalline form of graphite is composed of many graphene sheets stacked together The 2-D crystals in graphene exhibit high crystal structure apart from being continuous in their formation. This structure means that charge carriers in graphene can travel many miles of inter-atomic distances without undergoing any form of scattering. The existence of such kind of crystals can be comprehended fully by reconciling this idea with other theoretical approaches. It can be argued that these 2-dimensuional crystalline structures are quenched within a meta-stable state since they have been obtained from 3-dimensional materials. On the other hand, their small size which is approximately Read More