Spin Transport Properties In Zigzag Silicene Nanoribons

Silicene, with the similar geometry structure and excellent electrical properties of graphene and broad applications in recent nanoelectronic devices, silicene nanoribbons(Si NRs) have attracted considerable attention in recent years. In this paper, by performing density functional theory(DFT) calculations and non-equilibrium Green’s function(NEGF) technique. we study the electronic structures and transport properties of zigzag-edged silicene nanoribbons(ZSi NRs) with doping different atoms.In Chapter one, we mainly introduce the research progress of silicene and the electrical properties of silicene nanoribbons. In chapter two, we give a brief introduction of the theory methods including density functional theory and non-equilibrium Green’s function, and then the ATK software package. Chapters three and four describe in detail and summarize the work done during my studies. The main contents and results are listed as follows:(1) The effects of single and multiple dopants on the transport properties in zigzag-edged silicene nanoribbons is investigated. According to the different magnetization direction of two edges, we study the antiferromagnetic state(AFM) and ferromagnetic state(FM) ZSi NRs. The results show that in the antiferromagnetic state the presence of a single Al or P atom induces quasibound states in ZSi NRs that can be observed as new dips in the electron transmission. The Al atom acts as an acceptor whereas the P atom acts as a donor when it is placed at the center of the ribbon. This behavior is reversed when the dopant is placed on the edges. Accordingly, an acceptor-donor transition is observed in ZSi NRs upon changing the dopant’s position. When doped two impurities, because of the impurity-impurity interaction, the nature of the quasibound states will become more complex, and this will reflect in the transmission. However, if the quasibound states induced by impurities are appear at opposite sides of the Fermi level, then the transmission can be viewed as a simple superposition of the transmission function of single doped cases. As we know, pristine FM configuration 8-ZSi NRs show metallic character, in some double doping ribbons a large polarization can be obtained in a narrow region around the EF.(2) The spin-dependent transport properties of a line of carbon atom doped in ferromagnetic state ZSi NRs is investigated. When a line of C atom doped perpendicular to the nanoribbons direction, we can find that the current obviously decrease compared with pristine ZSi NRs, and in a specific region the current decreases with the increase of voltage, leading to the negative differential resistance(NDR) behavior. When a line of C atom doped along the direction of ZSi NRs, the complete spin polarization emerges around the Fermi level, and practically 100% polarization can be obtained in EF, the system tuned to be half-metallic. The research provides ideas for the design of nanoelectronics and spintronic devices based on Si NRs.