Electron Transport Of Several New Two-dimensional Materials With Hexagonal Honeycomb Structure

In recent years,two-dimensional materials represented by graphene have received more and more attention.Among them,the two-dimensional materials with hexagonal honeycomb structure have rich and excellent electrical,optical,force,and magnetic properties due to its unique geometric structure.Based on this,we use the density functional theory combined with the non-equilibrium Green’s function to study the electronic transport characteristics of several new two-dimensional nanomaterials with hexagonal honeycomb structures in this paper.First of all,this paper introduces the structural characteristics of low-dimensional nanomaterials and basic content of nanoelectronics,and then introduces the methods and theories used in the research.Based on the first-principles,systematically studied the electronic structure and transport properties of the three two-dimensional materials with hexagonal honeycomb structures.Firstly,based on experiments,we construct several transition-metal dichalcogenides with atomically flat zigzag edge,such as Sc S₂,VS₂,Cr S₂,Fe S₂,Ni S₂,Mo S₂ and WS₂.One finds,at the Fermi level（0 e V）,all the transmission coefficients are finite,which indicates that they are all metallic.However,in the Sc S₂nanoribbons,the vacancy in the flat zigzag edge could open a transmission gap,and induce a metal-semiconductor transition,showing that this kind of vacancy can be used to regulate the electronic properties of ttransition-metal dichalcogenides.Secondly,we designed nanoporous graphene nanoribbons with different pore distributions.Based on verifying their stable existence,we studied the effects of different pore distributions on the electron transport properties.It was found that all these nanoribbons,under the control of the gate voltage,will also produce a a metal-semiconductor transition,and have good spin filtering properties.In a single row of holes,increasing the number of holes will change the maximum value of the up and down spin transmission coefficients at Fermi level.Further expanding the single-row holes to double-row can make the hole-type graphene appear a natural（without gate voltage）spin filtering phenomenon.But with the increase of the number of holes in each row,the transmission coefficient gradually decreases.In addition,the specific gate voltage can enable nanoribbons to filter out a certain spin current,which has far-reaching significance for the future development of spin nanoelectronic devices.Finally,we investigated the electron transport properties of borophene nanoribbons with different edge combinations in ferromagnetic and antiferromagnetic states.It is found that in the ferromagnetic state,some edge-assembled borophene nanoribbons will have spin non-polarization due to the edges,while some edge-assembled nanoribbons appear to be spin-polarized.Further research shows that the magnetic moment is distributed only on the side of a specific edge,which causes it to exhibit the characteristics of spin polarization.When the top and bottom edges are the same,the magnetic moments will be distributed on both sides,and the transport properties of the electrons will appear as spin non-polarization.The spin polarization caused by different edges of the borophene nanoribbons will have guiding significance for the practical use of borophene nanoribbons in the future.