Transition metal dichalcogenides (TMDs) exhibit a wide range of electronic properties due to their structural diversity. Understanding their defect-dependent properties might enable the design of efficient, bright, and long-lifetime quantum emitters. Here, we use density functional theory (DFT) calculations to investigate the 2H, 1T, and 1T′ phases of MoS₂, WS₂, MoSe₂, WSe₂ and the effect of defect densities on the electronic band structures, focusing on the influence of chalcogen vacancies. The 2H phase, which is thermodynamically stable, is a direct band gap semiconductor, while the 1T phase, despite its higher formation energy, exhibits metallic behavior. 1T phases with spin–orbit coupling show significant band inversions of 0.61, 0.77, 0.24 and 0.78 eV for MoS₂, MoSe₂, WS₂ and WSe₂, respectively. We discovered that for all four MX₂ systems, the energy difference between 2H, 1T and 1T phases decreases with increasing concentration of vacancies (from 3.13% to 21.88%). Our findings show that the 2H phase also has minimum energy values depending on vacancies. TMDs containing W were found to have a wider bandgap compared to those containing Mo. The band gap of 2H WS₂ decreased from 1.81 eV (1.54 eV with SOC included) under GGA calculations to a range of 1.37 eV to 0.79 eV, while the band gap of 2H MoSe₂ reduced from 1.43 eV (1.31 eV with SOC) under GGA to a range of 0.98 eV to 0.06 eV, depending on the concentration. Our findings provide guidelines for experimental screening of 2D TMD defects, paving the way for the development of next-generation spintronic, electronic, and optoelectronic devices.

中文翻译：

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二维过渡金属硫化物（2H、1T 和 1T′ 相）的缺陷依赖性电子特性


过渡金属硫化物 （TMD） 由于其结构多样性而表现出广泛的电子特性。了解它们的缺陷依赖性特性可能有助于设计高效、明亮且长寿命的量子发射器。在这里，我们使用密度泛函理论 （DFT） 计算来研究 MoS₂、WS₂、MoSe₂、WSe₂ 的 2H、1T 和 1T′ 相以及缺陷密度对电子能带结构的影响，重点是硫属空位的影响。热力学稳定的 2H 相是直接带隙半导体，而 1T 相尽管具有较高的形成能，但表现出金属行为。具有自旋-轨道耦合的 1T 相位显示 MoS₂、MoSe₂、WS₂ 和 WSe₂ 的显著能带反转分别为 0.61、0.77、0.24 和 0.78 eV。我们发现，对于所有四个 MX₂ 系统，2H、1T 和 1T 相之间的能量差异随着空位浓度的增加而减小（从 3.13% 增加到 21.88%）。我们的研究结果表明，2H 阶段也具有取决于空位的最小能量值。发现与含有 Mo 的 TMD 相比，含有 W 的 TMD 具有更宽的带隙。2H WS₂ 的带隙从 GGA 计算下的 1.81 eV（包括 SOC 的 1.54 eV）降低到 1.37 eV 至 0.79 eV 的范围，而 2H MoSe₂ 的带隙从 GGA 下的 1.43 eV（SOC 为 1.31 eV）降低到 0.98 eV 至 0.06 eV 的范围，具体取决于浓度。 我们的研究结果为 2D TMD 缺陷的实验筛选提供了指南，为下一代自旋电子学、电子和光电器件的开发铺平了道路。