The Average Conductivity Problem In Graphene Nano-ribbons

Carbon is the most common element in nature. In recent years,the discover of C60 and successful preparation of carbon nanotubes exploited the new configuration of carbon, and the findings of magnetism and superconductivity for carbon compound have attracted much interests for this common element and even some people give so-called"carbon electronics". Scientists are still investigating the new configuration of carbon, so that much more new phenomena can be finding. However, conventional configuration of carbon is often ignored. Graphene, which is one of carbon configuration and belong to carbon electronics field, is layer structure and interlayer each carbon atom is sp2,hybridized orbital and neighboring three carbon atoms form three equivalent distanceσbond, and therefore conform carbon atomic infinite planar layer, and every carbon atom is vertical with this pz orbital of planar and they overlapped each other to form delocalization double bond. Electron presents metallic conductivity property in innerplanar, whereas, high resistance when it is vertical with the planar. Thus, graphene is considered planar conductor and it belongs to conventional semi-metallic materials whose transportation character is intervenient of metal and semiconductor.Nano grapheme layer may be a new generation electrics basal materials based on design and preparation of graphene nanoribbons. These basic functional apparatus consists of rectifier, PN junctions, field effect transistor and so on. We must make a systemic study for each kind of grapheme so that much most valuable physical phenomena was observed in order to realize the application of graphene on nano apparatus. The theory investigation which is not restricted by laboratorial techniques, provided some instructional information for experimental study. It can afford credible physical law for establishing and enriching principle of relativity condensed matter physics basal theory system. It provided valuable theory information for apparatus design of orgin from granpene nano electrics. Graphene open a wide filed for future application of electrical apparatus, such as ballistic transistor. Planar graphene material can become basal material of nanoelectrics since electron of graphene keep high mobility at room temperature and high carrier concentration and its structure can be cut into diversified nanostructures.Different from other semiconductor system, description of graphene crystal structure is adopted Dirac equation which described relativistic particles, not Schrodinger equation which described non- relativism. Equations in this system consists of two kinds of non- equivalent A atom and B atom, form two energy band and intersect in Brillouin zone boundary neighborhood and come into being conical type energy spectroscopy. Thus the quasiparticle of graphene existed a linear dispersive connection. Its just this linear spectrum that we may think that quasiparticle character of graphene is different from our familiar particle properties of metallic and semiconductor.Transport properties of electrons are usually calculated by density functional theory (DFT) and nonequilibrium Green function. We simulate nanostructure system and electrical perproties of nano-apparatus and transport properties of quanta. Based on electronic calculations such as pseudopotential method and linear combination of atomic orbital, electronic transport properties of nano-device under external voltage and graphene under external magnetic field were disposed by using nonequilibrium Green's function method and transport theory method. We will discuss that the effect of size of boundary and device zone on conductivity.In this paper, we first use of tight-binding approximation and the Dirac equation calculated the energy bands of graphite, at the same time with Dirac equation of the wave function strip. Finally, only the impurity transport theory in the case of the electron transport situation. We use transfer matrix method discussed different boundary strip of graphite in the spectra of impurities under the influence of changes in conductivity. Through theoretical and numerical calculation to the graphite strip on the transport properties have a deeper understanding of and, more importantly, our theoretical research results of some qualitative piece of graphite for the realization of devices in the application of the provision of guidance significance.