Theoretical Study Of Spin-polarized Transport Properties Of Graphene Nanoribbons With Nitrogen-vacancy Defects

Molecular spintronics emerges rapidely in the past years. In this field, one of central issues is to search the promising magnetic candidates. This dissertation for the Master Degree includes the following four chapters. Here, we try to explore electronic and structures and spin-polarized transport properties of graphene nanoribbons with nitrogen-vacancy defect by performing density functional theory (DFT) calculations and non-equilibrium Green’s function (NEGF) technique.In Chaper1, we mainly introduce the basic concepts and theoretical frame of DFT including the various assumptions, the K-S equations, and several exchange-correlation functionals.In the first half part of Chapter2, we give a brief introduction of molecular electronics. Then we turn to review transport theory of molecular junction. Since fully self-consistent DFT calculations combined with NEGF technique are used in this dissertation. Therefore, the correspoding basic ideas and formula are presented in the late half of this chapter as well as the adopted computational packages.Electronic structures and spin-polarized transport properties of asymmetric zigzag edged graphene nanoribbons with nitrogen-vacancy defect (AZGNR-NVs) are presented in Chapter3. Theoretical results show that these proposed molecular junctions based on AZGNR-NV display robust negative differential resistance (NDR) effect. The width of AZGNR-NVs and the position of NV defect will not destroy the predicted NDR effect, but they give observable impact on the position of peak/valley, the value of current and PVR. Interestingly, we find that these juncions also have spin-filtering effect, and its spin filter efficiency is close to100.0%, which can be tuned by the relative position between H/H2edges and NV defect. These predictions indicate that AZGNR-NVs holds great promise in molecular electronics and spintronics applications.In Chapter4, we turn to examine electronic structures and spin-polarized transport properties of d GNR-NVs with symmetric zigzag edges. We also observe the obvious NDR effect in these examined junctions, but the spin-filtering feature becomes less significant compared with these AZGNR-NVs.