The Density Functional Theory Study About Electronic Structure Modification And Control Mechanism Of Layered Transition Metal Sulfides

Transition metal sulfides with unique electronic structure,intrinsic band gap and other properties,become the hot topic in the research of physics,chemistry,biology etc.They have a broad development prospect in the biocatalyst,electronics,energy conversion and other fields.In order to find a suitable modified structure with new characteristics to offer some proposals for the design of the new device.According to the density functional theory(DFT),we adopt the first principle calculation to study the effect on the structure and property of the monolayer WS2 and MoS2 adsorbed by the transition metal atoms.At first,we study the effect of Fe atom adsorption on single-layer WS2.The results show that the most stable adsorption site is the top of the W atom,corresponding atomic adsorption energy is 1.84 eV.The interaction between Fe and the substrate atoms weakens the W-S bonds,making the length of the corresponding bond increase.Affected by the substrate,the dyz and dxz orbitals of Fe(3d64s2)lose electrons in spin down,making local magnetic moments be about 2 ?B.Under the 0.125 and 0.25 ML low coverages,the distance is large between adatoms,magnetic effect is given priority to the exchange action,the anti-ferromagnetic sequence is more stable;Under the 0.5 and 1.0 ML high coverages,the distance is decreasing between adatoms,magnetic effect is given priority to the RKKY action,the ferromagnetic sequence is more stable.The analysis about electronic and band structure show that in the adsorption structure the electron polarizability P at Efermi is 100%The spin up channels is indirect band gap semiconductor,the other one is metal.Due to the adsorption,the structure become into magnetic half-metal,being the potential application of spin electronics materials.We further study the effects of the other 3d transition metal atoms adsorption on the structure and property of the single-layer WS2.For all atoms,studies have shown that the top site of W atom is the most stable adsorption.Affected by the substrate,the outermost electrons charge of the adatoms redistribute.Due to Ni,Cu and Zn atoms have no magnetic moment for 3d orbitals electrons forming a closed shell,so we only study the magnetic sequence stability and properties of the rest of the adatoms under the high coverages.The results show that(0.5 and 1.0 ML)V/WS2 and(0.5 ML)Cr/WS2 are anti-ferromagnetic sequence stability,the rest of the adsorbed structures are ferromagnetic sequence stability.Further analysis found that the structures(0.5 and 1.0 ML)Sc/WS2,Ti/WS2 and Mn/WS2 as well as(1.0 ML)Cr/WS2 are magnetic metals,(0.5 and 1.0 ML)Fe/WS2 and Co/WS2 are magnetic half-metals.The forbidden band widths of the spin up channels about the Fe/WS2 and Co/WS2 under the 1.0 ML coverages are 0.95 and 0.99 eV,respectively.Finally,we also study the adsorption of Fe and Co atoms on single-layer MoS2 surface.The most stable site for atoms is the top site of Mo atom,corresponding atomic adsorption energies are 2.18 and 3.27 eV,respectively.The orbital hybridization effect between atoms and substrate weakens the Mo-S bonds,make corresponding bond lengths increase by 0.11 and 0.09 A,respectively.Affected by the substrate,the dyz/Xz orbitals of Fe and Co atoms miss electrons in spin down,make the local magnetic moment be about 2 and 1 ?B.Under the high coverage,the distance is decreasing between atoms,magnetic effect is given priority to the RKKY action,the ferromagnetic sequence is more stable.The electron polarizability at the Efermi is also 100%,adsorption structures are half-metal,the forbidden band width of the semiconductor channels under 1.0 ML coverage are 0.93 and 0.95 eV,respectively.