Pressure-Induced Insulator–Metal Transition in Silicon Telluride from First-Principles Calculations
Pressure-Induced Insulator–Metal Transition in Silicon Telluride from First-Principles Calculations
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DOI：
10.1021/acs.jpcc.1c00636
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发表时间：
2021-01
影响因子：
3.7
通讯作者：
R. Bhattarai;X. Shen
中科院分区：
文献类型：
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作者：
R. Bhattarai;X. Shen
碲化硅(Si2Te3)是一种具有独特结构性质的二维半导体材料，这是由于Si和Te原子之间的尺寸反差造成的。最近的一项实验表明，材料在静水压力下变成了金属，而金属相的晶格结构还有待确定。本文利用演化算法和第一性原理密度泛函理论(DFT)计算，提出了Si2Te3的两个金属相：M1和M2。与半导体(SC)相中Si-Si二聚体的存在不同，M1和M2相都有单独的Si原子，这对金属丰度起着重要的作用。对其结构性质、电子性质、动力学和热稳定性进行了分析。在高达12 Gpa的静水压力下，将这些新结构的能量与Sc相进行了比较。结果表明，在高压下，M1和M2相的能量较低，从而解释了Si2Te3金属相的出现。此外，外加压力使Sc相发生间接-直接-间接带隙转变。对Sc相在不同气压下的拉曼光谱分析表明，主要的拉曼峰发生了移动，最后消失，证实了相变。计算结果与实验观测结果吻合较好。对绝缘体-金属相变的了解增加了材料体系的潜在用途。
Silicon telluride (Si2Te3) is a two-dimensional semiconductor with unique structural properties due to the size contrast between Si and Te atoms. A recent experiment shows that the material turns metallic under hydrostatic pressure, while the lattice structure of the metallic phase remains to be identified. In this paper, we propose two metallic phases, M1 and M2, of Si2Te3 using the evolution algorithm and first-principles density functional theory (DFT) calculations. Unlike the presence of Si-Si dimers in the semiconducting (SC) phase, both M1 and M2 phases have individual Si atoms, which play important roles in the metallicity. Analysis of structural properties, electronic properties, dynamical as well as thermal stability is performed. The energies of these new structures are compared with the SC phase under the subsequent hydrostatic pressure up to 12 GPa. The results show that M1 and M2 phases have lower energies under high pressure, thus elucidating the appearance of the metallic phase of Si2Te3. In addition, the external pressure causes the SC phase to have an indirect-direct-indirect bandgap transition. Analysis of Raman spectra of the SC phase at a different pressure shows the shifting of the major Raman peaks, and finally disappearing confirms the phase transition. The results are in good agreement with the experimental observations. The understanding of the insulator-metal phase transition increases the potential usefulness of the material system.