Fe原子吸附对单层WS_2结构和性质的影响  

Effect of Adsorption of Fe Atoms on the Structure and Properties of WS_2 Monolayer

作　　者：徐位云 汪丽莉[1] 宓一鸣[1] 赵新新[1] 

机构地区：[1]上海工程技术大学基础教学学院,上海201620 [2]上海工程技术大学材料工程学院,上海201620

出　　处：《物理化学学报》2017年第9期1765-1772,共8页Acta Physico-Chimica Sinica

基　　金：国家自然科学基金(11504228)资助项目~~

摘　　要：本文采用基于密度泛函理论(DFT)的第一性原理方法研究了Fe原子吸附对单层WS_2结构和性质的影响。研究结果表明:Fe原子吸附在W原子的顶位最稳定,相应的原子吸附能为1.84 eV。Fe与衬底间的相互作用削弱了紧邻W―S键,使其键长增大0.011 nm。由于衬底原子的影响,Fe原子d轨道的电子重新分布,形成了2μB左右的局域原子磁矩。在低覆盖度下(0.125和0.25 ML),磁性作用以超交换作用为主,铁磁序不稳定。而在高覆盖度下(0.5和1.0 ML),Fe原子间距减小,磁性作用以RKKY作用为主,铁磁序稳定。电子结构的计算结果显示,在高覆盖度下,Fe/WS_2结构在费米能级处的电子自旋极化率等于100%。自旋向上与向下通道分别为间接带隙的半导体和金属。在1.0 ML覆盖度下,自旋向上的禁带宽度约为0.94 eV。这说明Fe原子吸附可以将直接带隙的WS_2半导体转变成半金属,形成一种潜在的自旋电子器件材料。In this work, first-principles calculations were performed to study the effect of the adsorption of Fe atoms on the structure and properties of the WS2 monolayer. It was found that the most stable adsorption site for an Fe atom on WS2 at low coverage （〈 0.0625 ML） of the monolayer lies directly above the W atom and the atomic adsorption energy is ca. 1.84 eV. The interaction between the Fe and substrate atoms weakens the nearest W-S bonds which increases their bond length by ca. 0.011 nm. The orbital occupation of the adsorbed Fe atoms also undergoes redistribution. The 3d orbitals of Fe are fully occupied with the exception of the spin down channel of dyz and dxz orbitals. The magnetic interactions of Fe-Fe are mainly believed to involve super-exchange interactions which are mediated by the substrate. Thus the ferromagnetic order is unstable at low coverage. However, at high coverage, the distance between Fe-Fe decreases and the states close to the Fermi energy level induce magnetic interactions between the local magnetic moment and the itinerant electron, which are identified as RKKY interactions. In this manner, the ferromagnetic order is more stable at high coverage of the monolayer. The Density of state and band-structure calculations show that the spin polarization of Fe-WS2 near the Fermi energy level is about 100%. The spin up channel acts as an indirect band gap semiconductor, while the another one acts as a metal. These calculations indicate that the Fe-WS2 layer at high coverage could be half metallic, which can be potentially used to develop spin-based electronic materials.

关 键 词：密度泛函理论 Fe/WS_2 过渡金属硫化物 交换作用 半金属 

分 类 号：O647.3[理学—物理化学]