Successful application of two-dimensional transition metal dichalcogenides in optoelectronic, catalytic, or sensing devices heavily relies on the materials’ quality, that is, the thickness uniformity, presence of grain boundaries, and the types and concentrations of point defects. Raman spectroscopy is a powerful and nondestructive tool to probe these factors but the interpretation of the spectra, especially the separation of different contributions, is not straightforward. Comparison to simulated spectra is beneficial, but for defective systems first-principles simulations are often computationally too expensive due to the large sizes of the systems involved. Here, we present a combined first-principles and empirical potential method for simulating Raman spectra of defective materials and apply it to monolayer MoS₂ with random distributions of Mo and S vacancies. We study to what extent the types of vacancies can be distinguished and provide insight into the origin of different evolutions of Raman spectra upon increasing defect concentration. We apply to our simulated spectra the phonon confinement model used in previous experiments to assess defect concentrations, and show that the simplest form of the model is insufficient to fully capture peak shapes, but a good match is obtained when the type of phonon confinement and the full phonon dispersion relation are accounted for.

二维过渡金属二卤化物在光电，催化或传感设备中的成功应用在很大程度上取决于材料的质量，即厚度均匀性，晶界的存在以及点缺陷的类型和浓度。拉曼光谱法是探测这些因素的有力且非破坏性的工具，但是对光谱的解释，尤其是不同贡献的分离，并非易事。与模拟光谱进行比较是有益的，但是对于有缺陷的系统，由于所涉及系统的尺寸较大，因此第一性原理模拟在计算上通常过于昂贵。在这里，我们提出了模拟缺陷材料拉曼光谱的第一性原理和经验势相结合的方法，并将其应用于单层MoS ₂具有Mo和S空位的随机分布。我们研究了在何种程度上可以区分空位类型，并提供了随着缺陷浓度增加而拉曼光谱的不同演化起源的见解。我们将先前实验中使用的声子限制模型应用于模拟光谱以评估缺陷浓度，并表明该模型的最简单形式不足以完全捕获峰形，但是当声子限制的类型与完整的声子色散关系被考虑。