| As a new kind of two-dimensional Dirac nanomaterial,graphyne has become a hot material in the field of molecular electronics due to its rich carbon-carbon chemical bonds,good chemical stability and excellent charge transport properties.In addition,graphyne has a variety of allotropes and abundant controllable electronic structure and magnetic properties,which makes it of inestimable research and application value in the field of spin nanodevices.In this thesis,based on density functional theory combined with non-equilibrium Green’s function method,the effects of various strain regulation modes,such as in-plane strain,homogeneous strain and site strain,on the electronic structure and spin transport properties of graphyne nanoribbons are studied in depth.By analyzing the transmission coefficient,local state density and spin splitting characteristics of the system,the microcosmic mechanism of the multi-strain regulation of the spin transport properties of graphyne molecular devices is analyzed.The main research contents are as follows:（1）The effect of in-plane strain on the spin transport properties of zigzagγ-graphyne nanoribbons（ZγGYN）between gold electrodes is studied.The results show that the in-plane strain plays an important role in the transport properties of the device.Firstly,the in-plane strain can effectively strengthen the interface coupling between the gold electrode and the central scattering region,which widens the electron transport channel and leads to the enhancement of the current through the device.Secondly,the length of nanoribbons in the scattering region of the device can weaken the coupling between the electrode and the scattering region.Finally,after the introduction of S-shaped in-plane strain,there is an obvious spin splitting phenomenon in the corresponding device,indicating that strain can change the magnetic distribution of the system.（2）The effect of the synergistic effect of homogeneous strain and chemical anchored groups on the spin transport properties of ZγGYN between gold electrodes is studied.The results show that when different chemical molecules（pyrrole,thiophene and 1H-Phosphole）are connected,the effects of uniform strain on charge transport are different.Under uniform strain control,the spin polarization of the device is obvious and the maximum polarization is about 90%,and the negative differential resistance（NDR）effect is observed in the current-voltage（I-V）curve of the device.（3）The effect of strain sites on the electronic structure and spin transport properties of ZγGYN between two dimensional magnetic Fe3Ge Te2 electrodes is studied.It is found that the introduction of two-dimensional magnetic electrodes will bring spin injection effect to the system and change the magnetic distribution of electrons in the system,so the spin splitting phenomenon occurs in the transmission spectrum of each device.In addition,the electronic structure of ZγGYN exhibits semi-metallic properties after introducing 10%tensile strain at the carbon single bond.The NDR effect is also observed by calculating the charge transport properties of the device.（4）The effects of bilateral and unilateral fluorination on the electronic structure and spin transport properties of zigzagδgraphyne nanoribbons（ZδGYNR）is studied.Firstly,the ground state of ZδGYNR can be determined as an antiferromagnetic（AFM）state by calculating the total energy.Secondly,by analyzing the influence of fluoridation on the transmission behavior of the device under different magnetic configurations,it is found that fluoridation causes obvious negative differential resistance effect in the device.Finally,the double spin filter effect with spin polarizability approaching 100%is induced by bilateral fluorination effect,and the unilateral conductivity and spin rectification function can be realized at the same time. |
