Anisotropic Optical Properties of 2D Silicon Telluride
Anisotropic Optical Properties of 2D Silicon Telluride
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二维碲化硅的各向异性光学性质
DOI：
10.1557/adv.2020.186
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发表时间：
2020-01-01
期刊：
影响因子：
0.8
通讯作者：
Shen, Xiao
中科院分区：
文献类型：
--
作者：
Bhattarai, Romakanta;Chen, Jiyang;Shen, Xiao
碲化硅 (Si2Te3) 是一种硅基二维硫族化物，在光电子领域具有潜在的应用前景。它具有独特的晶体结构，其中硅原子形成Si-Si二聚体以占据“金属”位点。在本文中，我们报告了使用 GW 近似和 Bethe-Salpeter 方程 (BSE) 对其光学介电特性进行的从头计算研究。发现了强的面内光学各向异性。发现平行于Si-Si二聚体方向的介电常数虚部远低于垂直于二聚体的介电常数。二维 Si2Te3 纳米片吸收光谱的光学测量显示 90 度旋转下吸收系数的调制，证实了计算结果。我们证明光学各向异性源于价带和导带中波函数的特定组成。由于它与 Si 二聚体方向相关，因此面内光学各向异性可以通过电场和应变动态控制，这可能对新器件设计有用。此外，BSE 计算将块体中的 GW 准粒子带隙降低了 0.3 eV，单层中的 GW 准粒子带隙降低了 0.6 eV，这表明 Si2Te3 中存在很大的激子效应。此外，在体计算中包括电子-空穴相互作用显着降低了面外方向介电常数的虚部，表明 Si2Te3 多层膜中存在很强的层间激子效应。
Silicon telluride (Si2Te3) is a silicon-based 2D chalcogenide with potential applications in optoelectronics. It has a unique crystal structure where Si atoms form Si-Si dimers to occupy the "metal" sites. In this paper, we report an ab initio computational study of its optical dielectric properties using the GW approximation and the Bethe-Salpeter equation (BSE). Strong in-plane optical anisotropy is discovered. The imaginary part of the dielectric constant in the direction parallel to the Si-Si dimers is found to be much lower than that perpendicular to the dimers. The optical measurement of the absorption spectra of 2D Si2Te3 nanoplates shows modulation of the absorption coefficient under 90-degree rotation, confirming the computational results. We show the optical anisotropy originates from the particular compositions of the wavefunctions in the valence and conduction bands. Because it is associated with the Si dimer orientation, the in-plane optical anisotropy can potentially be dynamically controlled by electrical field and strain, which may be useful for new device design. In addition, BSE calculations reduce GW quasiparticle band gap by 0.3 eV in bulk and 0.6 eV in monolayer, indicating a large excitonic effect in Si2Te3. Furthermore, including electron-hole interaction in bulk calculations significantly reduces the imaginary part of the dielectric constant in the out-of-plane direction, suggesting strong interlayer exciton effect in Si2Te3 multilayers.