Effect Of Molecular Torsion On Spin Transport Properties Of Molecular Devices

Molecular electronics has more advantages than traditional solid-state electronics.Generally speaking,molecular electronics is a branch of nanotechnology,and one of the goals of researchers is to find smaller devices to replace large scale ones.A lot of work has been done on molecular devices.The development of theoretical work contributes to the understanding of the basic principles of molecular devices.The phenomenon of negative differential resistance in molecular devices has attracted wide attention because of its negative differential resistance effect.In addition,many molecular devices with different functions have been designed by scientists.In this paper,based on the density functional theory(DFT)and non-equilibrium Green's function(NEGF),the transport properties of the diphenyl ring molecular devices,and binuclear ferric phthalocyanine molecular devices,and the influence of torsion on the transport properties of the above two molecular devices are studied.The main contents are:1.This paper introduces the research progress and significance of molecular electronics,and briefly introduces the principles and mainstream software of studying transport properties.2.The DFT-NEGF method is used to calculate the spin polarization transport properties of diphenyl ring molecular devices.It is found that the device has different transport properties when the lead' magnetization is PC setup and APC setup.When the leads' magnetization is PC setup,perfect spin filtering and obvious negative differential resistance effect occur.There is a very large magnetoresistance(MR)phenomenon in the device.The MR of the molecular device is the largest at equilibrium,about 600.3.The effect of torsion on the spin transport properties of diphenyl ring molecular devices is studied by DFT-NEGF.Through I-V curves at different torsion angles,it can be found that the coplanar model has the largest current,and it is contributed by spin up state.The vertical model has the smallest current,the spin up current and spin down current are almost zero,and there is a large switch ratio.The effect of torsion on transport properties is analyzed by using the curves of current and SFE with different angles at 0.3 V.4.The effect of torsion on the transport properties of binuclear ferric phthalocyanine molecular devices is studied by DFT-NEGF.It is found that the torsion angle in a certain range can inhibit the current,and the current is the maximum when the torsion is not reversed.The current is minimum when the torsion angle is 45°,and there is a large switch ratio.The mechanism of switch effect in the structure is analyzed by using PDOS and transmission coefficient at equilibrium with different torsion angles.