Abstract：
The optical properties of the direct-bandgap transition metal dichalcogenides (TMDCs) MoS2and WS2are heavily influenced by their atomic defect structure and substrate interaction. In this work we use low-voltage chromatic and spherical aberration (CC/CS)-corrected high-resolution transmission electron microscopy to simultaneously create and image chalcogen vacancies in TMDCs. However, correlating the defect structure, produced and analyzed using transmission electron microscopy (TEM), with optical spectroscopy often presents challenges because of very different fields of view and sample platforms involved. Here we employ a reverse transfer technique to transfer electron-irradiated single-layer MoS2and WS2from the TEM grid to various substrates for subsequent optical examination. The dynamics of defect creation are studied in atomic resolution on a separate sample, which allows to apply the derived statistics to larger irradiated areas on the other samples. The intensity of both the defect-bound exciton peak in photoluminescence (PL) and the defect-inducedLA(M) mode in Raman spectra increase with defect density. The best substrates for defect-density determination by optical spectroscopy are polystyrene for PL and SiC and Si/SiO2for Raman spectroscopy. These investigations represent an important step towards the quantification of defects using solely optical spectroscopy, paving the way for fast, reliable, and automatable optical quality control of optoelectronic devices.
摘要：
直接带隙过渡金属二硫属化合物（TMDC）MoS2和WS2的光学特性受到其原子缺陷结构和衬底相互作用的严重影响。在这项工作中，我们使用低压色差和球面像差（CC/CS）校正的高分辨率透射电子显微镜（HRTEM）同时在TMDC中创建和成像硫属元素空位。然而,关联缺陷结构，用透射电镜制作和分析，由于涉及的视野和样品平台非常不同，因此通常会带来挑战。在这里，我们采用反向转移技术将电子辐照的单层MoS2和WS2从TEM网格转移到各种基板上，以进行后续的光学检查。在单独的样本上以原子分辨率研究缺陷产生的动力学，这允许将导出的统计数据应用于其他样品上的较大辐照区域。光致发光（PL）中缺陷结合的激子峰的强度和拉曼光谱中缺陷诱导的LA（M）模式的强度都随缺陷密度的增加而增加。通过光谱学确定缺陷密度的最佳基材是用于PL的聚苯乙烯（PS）和用于拉曼光谱的SiC和Si/SiO2。这些调查代表了一个重要的一步，对缺陷的量化仅使用光学光谱学，为快速铺平道路，可靠,和光电设备的自动光学质量控制。
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