Graphene
Graphene, a wonder material with unique electronic and mechanical properties was first created in 2004. It could be used in a host of device applications, even rivaling silicon which is used as the electronics material of choice. Graphene has no directional dependence property and is (almost) isotropic in the plane of the material. Graphene's outstanding properties are due to its peculiar double-cone band structure that features, where the conduction and valence bands meet in a single point at the Fermi level. As the bands approach this point in a linear fashion, the effective kinetic energies of the conduction electrons (and holes) become directly proportional to their momentum. The electrons in graphene behave as though they are relativistic particles with no rest mass, and so can whiz through the material at extremely high speeds, a property which is exploited to make transistors that are faster than any that exist today.
Graphynes
German researchers have conceptualized a new group of materials called graphynes using computer simulations. One of the main advantages that graphyne has over graphene is that it can be created in a vast number of possible arrangements. Though these materials have been investigated since the 1980s, researchers still know comparatively very little about it. Like graphene, a graphyne is a sheet of carbon just one atom thick. But while graphene can only exist with a honeycomb lattice structure, graphynes can assume several different 2D structures. Graphynes are 2D carbon allotropes similar in structure to graphene but built from doubly- and triply-bonded carbon atoms instead of just double bonds as in graphene. The presence of triple bonds means that graphynes can exists in geometries other than the hexagonal lattice of graphene.
The simulations suggest that graphynes have unusual and potentially useful electronic properties also characterized by Dirac cones. Graphyne with a rectangular lattice geometry has an effect on the Dirac cones which could prove useful in developing new types of carbon-based electronic devices.
Types
Graphynes have band structure and classified into three graphynes – α-graphene, β-graphene and 6,6,12-graphyne, the first two graphynes have hexagonal structures and the third is rectangular, but all the three possess Dirac cones with two different Dirac cones lying slightly above and below the Fermi level.
The 6, 6, 12-graphyne due to its rectangular symmetry can have electronic properties different along different directions in the plane of the material, leading to a conductance that depends on the direction of the current. This directional dependence could be put to good use in future nanoscale electronic devices.
Graphynes are 'self-doped' and naturally contain conducting charge carriers (electrons and holes). They could be used as a semiconductor in electronic devices and carbon-based electronic nanodevices without the need for external doping.