Manipulation Of Spin Transport Graphene Nanoribbons By Atomic Chains Adsorption

Due to the novel and peculiar electronic and spin transport properties, graphene are considered as the most promising materials for non-silicon electronics and spintronics. Spin transport in quasi-one dimension graphene nanoribbons is one of hot topics of spintronics. In this thesis, we study spin transport in Fe atomic chain adsorbed on zigzag graphene nanoribbons based on the density functional theory in combination with the nonequilibrium Green's function method. The effect of different adsorption-site and adsorption of different atomic chain species on spin -polarization transports are discussed in our work. The results indicate that the adsorption of atomic chain is an effective and efficient way to control electron spin, and we hope to supply physical model and theoretical validity in designing spintronics devices with excellent properties.The paper is organized as follow. In chapter one, the research progress of graphene as well as the graphene nanoribbon are introduced. Due to the superior quantum properties, graphene and graphene nanoribbon are considered the promising materials for non-silicon electronics and spintronics.The theory research methods are introduced in chapter two. The ATK software package which based on density functional theory in combination with the nonequilibrium Green's function method can be used to deal with the electronic structure and transport properties of two-electrode system with different geometry.In chapter three, we study spin-polarized transport properties of magnetic Fe atomic chain adsorbed on zigzag graphene nanoribbons. It is found that the Fe chain has drastic effects on spin-polarized transport properties of ZGNRs compared to a single Fe atom adsorbed on the ZGNRs. Different adsorption-site of the Fe chain have different influence on the edge states of the nanoribbon, and the degree of spin-polarization are different. When the Fe chain is adsorbed on the center of the ZGNR, the original semiconductor transforms into metal, showing a very wide range of spin-polarized transport. Particularly, the spin polarization around the Fermi level is up to 100%. When the Fe chain is adsorbed on the edge of ZGNR, the original semiconductor transforms into metal and it produces a wider rang of complete spin polarization.The spin-polarized transport of nonmagnetic atomic chain adsorbed on graphene nanoribbon is studied in chapter four. The results show that no matter nonmagnetic C or Al atomic chain is adsorbed on the edge of ZGNR, the edge state of one edge can be destroyed by the additional chain. The spin electrons are transported by way of the opposite edge of the ribbon, hence, a large range of complete spin-polarization generate around the Fermi level. Due to the effects on the magnetic moment and the edge states of the nanoribbon are different, and the adsorption of different atomic chain can engender different polarization. In addition, the adsorption of different nonmagnetic atomic chains can control the bandgap of the graphene nanoribbon effective. When adsorbing a magnetic nonmetal C atomic chain, the graphene nanoribbon keeps the semiconductor behavior, whereas adsorbing magnetic metal Al atomic chain, the semiconductor can transforms into metal.In summary, a final conclusion is drawn for all the results obtained and the conception of future investigation is explicitly described.