The Conduction Characteristic Of The Single Wall Carbon Nanotubes Ulterated With A Li Atom

Carbon nanotubes(CNT) have a great important influence of the world's new researches. It is expected to have more excellent properties in the electronic, materials and energy storage fields. As we know, electronic devices incline to be smaller, faster and energy saving. But the dimension of the electronic devices can't become small unlimitedly because the Moore law will abate, then the limit of quantum mechanics must be considered. It means that new electronic devices will come out. In these devices Carbon nanotubes is very important. So some researches about its conductance and electronic properties are necessary.This thesis is organized as below:Chapter 1 reviews the discovery, structure, properties and application foreground of the single walled carbon nanotubes (SWNT). The electronic devices come smaller, traditional semiconductor technologies are facing a great challenge. This needs people to find some new means to describe the electrons carrying in the electronic devices. The bottle-neck of the micro-electronics technology is to bring out the rising of the nano and molecule technology. At the end of this chapter, the electronic properties of SWNT are introduced in a simple length.Chapter 2 introduces the main methods which are used in this work including the Lundauer-Büttiker formalism, tight-binding approximation and the Green's function and nonequilibrium Green's function (NEGF). NEGF is the most important one. Some important concepts of NEGF such as self-energy matrix and scatting matrix are stated with great emphasis. At the last, the computation flow path which is used in this paper is list out.Chapter 3 gives the method to construct a CNT. It focus on the structure of the zig-zag CNT and gives out the program to build it. The constructing work contains the probes constructing, the CNT conductor constructing, the conductance systems constructing, the cut-off CNT molecule constructing and coordinate computing.Chapter 4 exhibits the results of the compution. The cut-off CNT molecules get some results such as the highest occupied molecule orbit(HOMO), the lowest unoccupied molecule orbit(LUMO) , the Femi-energy, the total energy and electron kinetic energy. Through these, analyses are done that indicate the characteristic of the electron transmission. Then the (7,0)(8,0)(9,0) CNT doped with a Lithium atom are computed , the transmission rate and the density of states(DOS) are given out then. Base on these results, we guess the relations between the transmission rate and electron energies, DOS, voltage. Some results like Open-up effect, revival of quantum steps effect are found out. At the end, the relationship between current and voltage of three kinds carbon nanotube doped by atom is displayed. It is a important relationship for molecular device designing.Chapter 5 Summarize the main works of this paper.