Research On The Thermoelectric Effect Of Low-dimensional Spintronic Devices Based On Carbon/Silicon

With the rapid development of nanotechnology,spintronic devices gradually occupy an important position in the information field.The theoretical research on the thermoelectric effect of spintronic components materials provides a theoretical basis for the practical application of spintronic devices.Since graphene was successfully prepared,low-dimensional materials represented by graphene and silicene have become ideal candidates for spin thermoelectric device materials due to their excellent optical and electrical properties.However,due to their zero band gap structure,their application in spin thermoelectric devices is seriously hindered.Therefore,this paper uses the density functional theory combination with non-equilibrium Green's function(NEGF-DFT)to study the electronic structure and thermoelectric transport effects of graphene and silicene nanoribbons under the introduction of nanoporous and hydrogenation are studied.The main research content of this paper is divided into the following three parts:(1)Based on the successful synthesis of bottom-up nanoporous graphene,this paper designs a perfect magnetic carbon-based organic chain spin thermoelectric device,which is tailoring this nanoporous graphene.The NEGF-DFT method was used to study the thermoelectric transport properties of porous nanoribbons.Starting from the edge localized state,porous nanoribbons have spin-semiconductor properties,and the appearance of spin-dependent transport energy gaps leads to larger spin Seebeck coefficients.Under the temperature difference,adjusting the chemical potential will produce a pure spin current or a fully spin-polarized current,and the transport direction will also change.At the same time,the thermoelectric effects of organic chains of different lengths are studied,and it is found that the narrowest device has the smallest phonon thermal conductivity and the highest Seebeck coefficient,which is beneficial to the use of spin thermoelectric devices.(2)This paper systematically studied the magnetic properties and thermoelectric transport effects of zigzag silicene nanoribbons(ZSi NRs)under hydrogen adsorption.As the adsorption site changes,the spin band gap changes,and the ground state of ZSi NRs changes from an antiferromagnetic state to a ferromagnetic state.Meanwhile,a spin-degenerate semiconductor evolves into a spin semiconductor,and hydrogen adsorption significantly enhances the thermoelectric figure of merit of the device.(3)In order to explore the influence of the magnetic coupling between edges on the transport properties of ZSi NRs under the action of hydrogen adsorption,this paper studied the thermoelectric transport properties of ZSi NRs with different widths under hydrogen adsorption.With the gradual increase of the bandwidth,the spin band gap decreases,and the maximum thermoelectric figure of merit is obtained under the narrowest bandwidth.Meanwhile,using the temperature difference in the two-probe system,a thermally induced pure spin current is obtained at the Fermi level,and its size increases as the width of the device increases.