Guo Wenyu, Ge Xun, Sun Shoutian, Xie Yiqun, Ye Xiang
Department of Physics, Shanghai Normal University, Shanghai 200234, P. R. China.
Phys Chem Chem Phys. 2020 Mar 4;22(9):4946-4956. doi: 10.1039/d0cp00403k.
The structural, mechanical and electronic properties of the MoSSe/WSSe van der Waals (vdW) heterostructure under various degrees of horizontal and vertical strain are systematically investigated based on first-principles methods. It is found that the MoSSe/WSSe vdW heterostructure of the most stable AB stacking is a direct band gap semiconductor and exhibits a type-II band alignment, which demonstrates an effective separation of photogenerated electron-hole pairs and increases their lifetime accordingly. The high angle-dependent Young's modulus and normal Poisson's ratios show the mechanical stability and anisotropy. It is found that the band gap of the heterostructure can be modulated effectively by applying strain, exhibiting a decreasing trend with increasing strain, and even lead to an intriguing semiconductor-metal transition under a certain large tensile strain. In particular, a negative correlation between the band gap and structure pressure provides a theoretical basis for experimentally regulating the electronic properties. Moreover, different strains can induce two different conditions of direct-indirect transition or can maintain the characteristics of the direct-band-gap. All these interesting results provide a detailed understanding of the MoSSe/WSSe vdW heterostructure under strain and indicate that it is a good candidate for low-dimensional electronic, nano-electronic and optoelectronic devices.
基于第一性原理方法，系统地研究了不同程度的水平和垂直应变下MoSSe/WSSe范德华（vdW）异质结构的结构、力学和电学性质。发现最稳定的AB堆积的MoSSe/WSSe vdW异质结构是一种直接带隙半导体，呈现II型能带排列，这表明光生电子-空穴对能有效分离，并相应地增加了它们的寿命。高角度依赖的杨氏模量和法向泊松比显示出力学稳定性和各向异性。研究发现，施加应变可有效调制异质结构的带隙，带隙随应变增加呈下降趋势，甚至在一定大的拉伸应变下会导致有趣的半导体-金属转变。特别地，带隙与结构压力之间的负相关为实验调控电学性质提供了理论依据。此外，不同的应变可诱导直接-间接跃迁的两种不同情况，或可保持直接带隙的特性。所有这些有趣的结果为应变下的MoSSe/WSSe vdW异质结构提供了详细的理解，并表明它是低维电子、纳米电子和光电器件的良好候选材料。
