具有本征磁性的二维半导体材料在实现低功耗、小尺寸和高效率的自旋电子学器件方面具有重要应用前景.一些拥有特殊晶格结构的二维材料,如笼目晶格结构,凭借其在磁性和电学方面的新颖性质而受到研究者的青睐.最近,一种新的具有笼目晶格结构的二维磁性半导体材料Nb3Cl8单层被成功制备出来,为探索具有笼目结构的二维磁性半导体器件提供了新机会.本文通过第一性原理方法研究了 Nb3Cl8单层的电子结构、磁各向异性,构造了其p-n结二极管结构,并研究了其自旋输运性质.结果表明,Nb3Cl8单层易磁化轴在平面内,沿x轴方向,Nb原子对磁各向异性起主要贡献,且相关磁性可通过应力应变进行调控.此外,基于Nb3Cl8单层的p-n结二极管纳米器件表现出整流效应、自旋过滤效应以及负微分电阻现象.这些结果表明了 Nb3Cl8单层在下一代高性能自旋电子器件方面具有较大的应用潜力.
Two-dimensional semiconductor materials with intrinsic magnetism have great application prospects in realizing spintronic devices with low power consumption,small size and high efficiency.Some two-dimensional materials with special lattice structures,such as kagome lattice crystals,are favored by researchers because of their novel properties in magnetism and electronic properties.Recently,a new two-dimensional magnetic semiconductor material Nb3Cl8 monolayer with kagome lattice structure was successfully prepared,which provides a new platform for exploring two-dimensional magnetic semiconductor devices with kagome structure.In this work,we study the electronic structure and magnetic anisotropy of Nb3Cl8 monolayer.We also further construct its p-n junction diode and study its spin transport properties by using density functional theory combined with non-equilibrium Green's function method.The results show that the phonon spectrum of the Nb3Cl8 monolayer has no negative frequency,confirming its dynamic stability.The band gap of the spin-down state(1.157 eV)is significantly larger than that of the spin-up state(0.639 eV).The magnetic moment of the Nb3Cl8 monolayer is 0.997 μB,and its easy magnetization axis is in the plane and along the x-axis direction based on its energy of magnetic anisotropy.The Nb atoms make the main contribution to the magnetic anisotropy.When the strain is applied,the band gap of the spin-down states will decrease,while the band gap of the spin-up state monotonically decreases from the negative(compress)to positive(tensile)strain.As the strain variable goes from-6%to 6%,the contribution of Nb atoms to the total magnetic moment gradually increases.Moreover,strain causes the easy magnetization axis of the Nb3Cl8 monolayer to flip vertically from in-plane to out-plane.The designed p-n junction diode nanodevice based on Nb3Cl8 monolayer exhibits an obvious rectification effect.In addition,the current in the spin-up state is larger than that in the spin-down state,exhibiting a spin-polarized transport behavior.Moreover,a negative differential resistance(NDR)phenomenon is also observed,which could be used in the NDR devices.These results demonstrate that the Nb3Cl8 monolayer material has great potential applications in the next-generation high-performance spintronic devices,and further experimental verification and exploration of this material and related two-dimensional materials are needed.