论文标题
应变引起的对2H和1T $^{\ prime} $单层MOS $ _ {2} $的电子和语音属性的影响
Strain induced effects on the electronic and phononic properties of 2H and 1T$^{\prime}$ monolayer MoS$_{2}$
论文作者
论文摘要
在密度函数理论的框架内，第一原理计算已在经过良好研究的2H上执行，并且较少探索的1T $^{\ prime} $单层MOS $ _ {2} $的相位。我们已经解决了两个相的电子和语音性能的应变诱导的可调性，并将其稳定性与所施加应变进行了比较。通过考虑张应力和压缩应力的大量应变曲线，我们发现2H和1T $^{\ prime} $阶段的电子性能都对所施加的应变方向敏感，并且可以以受控的方式调整。对于2H相，在大多数情况下，观察到在较低应变处直接向间接带隙转变，并且在较高应变下向金属转变的半导体转变。所应用的应变破坏了1T $^{\ prime} $相位的半金属性质，通过与拓扑保护的边缘状态的散装状态重叠。观察到声子分支的频率以及分散曲线的性质中的声音特性的显着应变诱导的变化。对于两个阶段，都可以看到区域中心的光学声子模式的系统变化。随着应变的增加，面外声学模式（ZA）变成虚构，表明晶体结构的相变或不稳定性的可能性。与1T $^{\ prime} $相比，2H相似乎承受了更大的应变，因此具有更好的稳定性，因为假想分支在后一种情况下开始以低得多的应变值出现。我们强调了应变工程在调整电子和语音性能的重要性，以及在单层MOS $ _ {2} $的不同多晶型物中应变应用的安全限制。
First-principles calculations, within the framework of density functional theory, have been performed on the well-studied 2H and the less explored 1T$^{\prime}$ phase of single-layer MoS$_{2}$. We have addressed the strain-induced tunability of the electronic and phononic properties of both phases, and compared their stability against the applied strain. By considering a large number of strain profiles for both tensile and compressive stress, we have found that the electronic properties of both 2H and 1T$^{\prime}$ phases are sensitive to the direction of the applied strain and can be tuned in a controlled way. For the 2H phase, in most cases, a direct to indirect band gap transition at lower strain and a semiconductor to metal transition at higher strain is observed. The applied strain destroys the semimetallic nature of the 1T$^{\prime}$ phase via the overlapping of the bulk states with the topologically protected edge states. Significant strain-induced changes in the phononic properties, in the frequency of the phonon branches, as well as in the nature of the dispersion curves, are observed. A systematic change in the frequency of the optical phonon modes at the zone centre is seen for both phases. With increasing strain, the out-of-plane acoustic mode (ZA) turns imaginary, indicating a possibility of phase transition or instability of the crystal structure. The 2H phase appears to withstand a larger amount of strain and therefore possesses better stability compared to the 1T$^{\prime}$ phase since the imaginary branch starts to appear at much lower values of strain in the latter case. We highlight the significance of strain engineering in tuning the electronic and phononic properties and the safe limit of the strain application in different polymorphs of single-layer MoS$_{2}$.
