Functionalization The Electronic Properties Of Silicene By Halogen Atoms Unilateral Adsorption:A First-principles Study

Silicene is a new type of two-dimensional(2D)graphene-like material with buckled honeycomb lattice structure.Due to the difference with the perfect planar structure in graphene,the monolayer silicene is composed by two layers of equivalent silicon atoms with a buckling height of 0.44 A.Silicene inherites the excellent electronic properties of graphene and can be compatible well with today's silicon-based semiconductor technology.At present,monolayer silicene has been successfully synthesized on a number of substrates under ultrahigh vacuum such as Ag(111),ZrB2(0001),MoS2(0001),and Ir(111).Silicene is a semiconductor with zero band gap as graphene,the band gap including the spin orbit coupling effect is only 1.55 meV.In order to further explore the electronic properties of silicene,the question of how to open the band gap of silicene has attracted wide attention.In this paper,the structural,electronic and magnetic properties of unilateral halogenated silicene Si2X1(X=F,Cl,Br,I)are systematically studied by using the first principle calculation method based on density functional theory.The regulation mechanism of plane strain on the electronic properties of unilateral halogenated silicene was also explored.The main conclusions were obtained as following:1.After analyzing the calculation results of unilateral halogenated silicene Si2X1(X=F,Cl,Br,I),it can be found that halogen atoms can be combined with silicene to form an angle of sp3 hybridization.Halogen atoms obtain electrons from adjacent Si atoms and form strong o covalent bonds with it.The unilateral adsorptions of halogen atoms leads the honeycomb structure of silicene become more buckled.The calculation of formation energy explains that unilateral halogenated silicene Si2X1(X=F,Cl,Br,I)have better thermodynamic stability than pure silicene.Among them,the formation energy of half-fluorinated silicene Si2Fj is the lowest,indicating that it is more favourable to form new fluorine storage materials.The unilateral halogenated silicene Si2X1(X=C1,Br,I)exhibits half-metallic property and has nearly 1?B total magnetic moment per unit cell.They have important application prospects in the field of silicon based nano spintronics.2.By applying symmetrical elastic tensile strain on unilateral halogenated silicene Si2X1(X=F,Cl,Br,I),the Si2F1 configuration is converted from metallic property to half-metallic property as the symmetrical strain increases up to 12.9%.The electronic property of Si2X1(X=C1,Br,I)configurations is firstly transfered from half-metallic property to semiconductor property.Then,its electronic property can be back to half-metallic property,and finally to metallic property with the increasing of the strain.Band decomposed charge density of spin-polarized CBM and VBM explains the transition of the energy band under the symmetrical strain.The total magnetic moments of Si2F1 configuration increase monotonically from the initial zero?B to 1 ?B with the increasing of the strain.This results show the electronic and magnetic effects of the unilateral fluorinated silicene under strain modulation.It is found that the band structure transition characteristics of the unilateral brominated silicene Si2Br1 under the effect of asymmetric strain is similar to that in the case of applying symmetrical strains.The speed and amplitude of energy band dispersion induced by strain is different in two directions(parallel to zigzig edge or armchair edge).The difference of Poisson ratio in the two directions reflects the anisotropy of the band gap dispersion.