二维铁电In_(2)Se_(3)/InSe垂直异质结能带的应力调控

Strain control of two-dimensional ferroelectric In_(2)Se_(3)/InSe vertical heterojunction energy band

近年来,二维铁电异质结在高密度存储及光电器件等领域展现了应用潜能,开发新颖二维铁电异质结是当前的一个重要研究方向.本论文采用第一性原理计算研究二维铁电材料α-In_(2)Se_(3)与二维单层InSe组成的In_(2)Se_(3)/InSe垂直异质结的能带结构及应力调控.计算表明,In_(2)Se_(3)/InSe异质结为间接带隙半导体,具有Ⅱ型能带匹配.当In_(2)Se_(3)的极化方向垂直表面朝外时,带隙大小为0.50 eV,价带顶和导带底分别来自于InSe和In_(2)Se_(3);当In_(2)Se_(3)的极化方向指向面内时,带隙降低0.04 eV,价带顶和导带底的来源互换.在面内拉伸下,拉伸度越大,带隙越小.当极化方向指向面外(内)时,在双轴拉伸应变达到6%(8%)及以上时会使异质结由半导体转变为导体;在双轴压缩应变为-6%(-8%)下还可使异质结由间接带隙变为直接带隙;对于单轴拉伸及压缩,定性结果与双轴应变一致.本论文的研究结果表明改变极化方向和施加应力是调控二维In_(2)Se_(3)/InSe铁电异质结的有效方式,可为设计相关铁电器件提供理论参考.

In recent years,two-dimensional ferroelectric heterojunctions have shown potential applications in the fields of high-density storage and optoelectronic devices.The development of novel two-dimensional ferroelectric heterojunctions is an important current research direction.In this work,first-principles calculations are used to study the band structure and stress control of In_(2)Se_(3)/InSe vertical heterojunction composed of two-dimensional ferroelectric material α-In_(2)Se_(3) and monolayer InSe.The calculations show that the In_(2)Se_(3)/InSe heterojunction is an indirect band gap semiconductor with type-II band matching.When the polarization direction of In_(2)Se_(3) is perpendicular to the surface facing outward,the band gap is 0.50 eV,and the top and bottom of the valence band originate from InSe and In_(2)Se_(3) respectively;when the polarization direction of In_(2)Se_(3) points inward the plane,the band gap decreases by 0.04 eV,and the sources of the top of the valence band and the bottom of the conduction band are interchanged.Under in-plane stretching,the greater the degree of stretching,the smaller the band gap is.After a certain threshold is exceeded,the heterojunction changes from a semiconductor into a conductor,which can also change the heterojunction with an indirect band gap into that with a direct band gap.The research results of this work show that changing the polarization direction and applying stress is an effective way to control the two-dimensional In_(2)Se_(3)/InSe ferroelectric heterojunction,which can provide a theoretical reference for designing the relevant ferroelectric devices.