Electronic Structure And Characteristics Of Bent Graphene

Andre Geim and Konstantin Novoselov, who are in Physics and Astronomy Institute of Manchester University, have accessed the 2010 Nobel Prize in Physics since they discovered and characterized graphene successfully in 2004. During just six years, it has been significant progress to prepare the grapheme. At the same time, excellent physical properties of graphene have been found after studying widely, which has the potential applications. Graphene is a basic unit to compose other carbon allotrope, which can be deformed to form fullerenes (zero-dimension), carbon nanotubes (one-dimensional) and graphite (3D).As a unique two-dimensional crystal, graphene has been called as the rising "star" in the field of materials science and condensed matter physics. Many scientists will study the properties of this novel material with much enthusiasm. so far, the people has discovered that graphene have a lot of very excellent performances in the electronics, the optics and the magnetism, especially, excellent room temperature quantum Hall effect, bipolar electric field effect, ferromagnetism, superconductivity, high electron mobility have been found. In addition, it has excellent mechanical property, Young's modulus reached 1.0TPa; good thermal conductivity is 5300W·m-1·K-1, 10 times more than the thermal conductivity of the copper; It is almost completely transparent, absorbing only 2.3% of the light. Base on these excellent properties, graphene has good applications in the fields of micro-nano electronics, the new solar cells, micro-nano sensors, super-capacitor plateform, field emission, catalyst carrier and so onBut so far it has been researched on the infinite graphene more and more, few people study the graphene composed of limited hexagon benzene ring, including the deformation of graphene, and other atoms embedded in graphene. In view of this, we study the electronic structure and basic characteristics of the deformation of graphene, and other atoms embedded in graphene, which is composed of limited carbon atoms, using non-equilibrium Green function and functional theory based on the first principles. Specific contents are as follows:1. The ideal graphene has perfect two-dimensional structure, but the actual production usually isn't completely flat, with wavy folds or deformations. In the paper we firstly select four different curvature graphene with finite hexagonal ring. After optimizing the bending models we obtained four distortion configurations that are stable. For the optimized models we theoretically calculate their molecular orbits density, Milliken charge populations, dipole moment and energy levels. Finally we couple electrodes between the terminals and simulate an electronic transmission device, and study the electronic transport properties, density of state and voltage- ampere characteristics.2. It can be called gaphene which is crystal overlapped by several single-layer graphene, less than 10 layers. Their physical properties will change with the number of layers and the stacking. So in the forth chapter we select double-layer graphene with finite number of carbon atoms. With the same methods we study the relationship between Single- and bi-layer graphene and research the electronic structure and basic characteristic between the difference stacking ways of the bi-layer graphene. 3.Doping other atoms in graphene will change the physical and chemical properties obviously, which can form lots of new materials, what makes the research very meaningfully. Therefore, we can embed B atoms into graphene to replace the carbon atoms. In Chapter V we embed one B atom and two B atoms respectively into the rectangle graphene. With the same calculation method, first we optimized and found that the doped models changed. Then their electronic structure have been studied, including bond length and bond angle changes, Milliken charge population, dipole moments, molecular orbital density, the energy gap and the electronic density as well. And after coupling the electrodes we calculated the transmission spectra and the transmission path to study and analyze the changes after doping, as well as the number of doping atoms.In the last chapter we summarized the work of this paper and make a brief outlook about the development in this field.