平面应变对二维单层MoSi_(2)N_(4)能带结构和光电性质的影响

Plane Strain on Band Structures and Photoelectric Properties of 2D Monolayer MoSi_(2)N_(4)

二维单层MoSi_(2)N_(4)具有优异的载流子输运能力与出色的化学稳定性,受到了广泛关注,但其光电性质与外加平面应变间的内在关系尚未展开深入探讨。本研究采用平面波超软赝势方法探索了平面应变对二维单层MoSi_(2)N_(4)能带结构和光电性质的影响,发现单层MoSi_(2)N_(4)为间接带隙半导体,其价带顶由Mo4d轨道和部分N2p轨道杂化而成,导带底则均由Mo4d轨道组成。在拉应变作用下,单层MoSi_(2)N_(4)的带隙逐渐变窄且光生载流子的有效质量不断减小;在压应变作用下,其带隙逐渐变宽,光生载流子的有效质量缓慢增大。值得注意的是,当压应变ε=-2.8%时,体系由间接带隙转变为直接带隙。单层MoSi_(2)N_(4)的光学吸收表现出明显的各向异性,且在平面应变作用下光吸收带边发生了不同程度的移动,有效地拓展了体系的光谱响应范围,有利于提升光电特性。这可为进一步研究二维单层MoSi_(2)N_(4)在新型可调谐纳米光电器件领域的应用提供理论指导。

Two-dimensional(2D)monolayer MoSi_(2)N_(4)has attracted wide attention due to its excellent carrier transport capacity and chemical stability.However,the relationship between its photoelectric properties and applied plane strain has not been thoroughly explored.The effect of plane strain on band structures and photoelectric properties of 2D monolayer MoSi2N4 is revealed by the plane-wave ultrasoft pseudopotentials.The results show that the monolayer MoSi_(2)N_(4)is an indirect band gap semiconductor.Its top of valance band is dominated by Mo4d orbitals and partly contributed by N2p orbitals,while its bottom of conduction band is mainly contributed by Mo4d orbitals.Under tensile strain,band gap of monolayer MoSi_(2)N_(4)narrows gradually and effective mass of photogenerated carriers decreases continuously.Under compressive strain,the band gap widens gradually and the effective mass increases slowly.It is worth noting that a compressive strain(ε=–2.8%)results in transition form indirect to direct band gap.Optical absorption of monolayer MoSi_(2)N_(4)exhibits obvious anisotropy,which edge shifts in different degree under the plane strain,effectively expanding the spectral response range of the system and beneficial to the photoelectric properties.These results provide a theoretical guidance for further research on the application of 2D monolayer MoSi_(2)N_(4)in the field of new tunable nano optoelectronic devices.