Raman spectrum of Janus transition metal dichalcogenide monolayers WSSe and MoSSe
Raman spectrum of Janus transition metal dichalcogenide monolayers WSSe and MoSSe
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DOI：
10.1103/physrevb.103.035414
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发表时间：
2021-01-15
影响因子：
3.7
通讯作者：
Mueller, Kai
中科院分区：
文献类型：
--
作者：
Petric, Marko M.;Kremser, Malte;Mueller, Kai
Janus过渡金属二硫属化物（TMDs）失去了普通TMDs的水平镜像对称性，导致出现额外的特征，例如天然压电性、Rashba效应和增强的催化活性。虽然拉曼光谱是一个重要的非破坏性的，相位和组成敏感的工具，以监测合成的材料，全面的研究的拉曼光谱的Janus单层仍然是失踪。在这里，我们讨论的拉曼光谱的WSSe和MoSSe在室温和低温下测量，近共振和关闭。通过结合偏振分辨的拉曼数据与声子色散的计算，并使用对称性的考虑，我们确定了四个一阶拉曼模式和更高阶的双声子模式。此外，我们观察到缺陷激活的声子过程，这提供了定量评估缺陷浓度以及材料晶体质量的途径。我们的工作为未来Janus TMD单层材料合成、研究和应用的研究奠定了坚实的背景。
Janus transition metal dichalcogenides (TMDs) lose the horizontal mirror symmetry of ordinary TMDs, leading to the emergence of additional features, such as native piezoelectricity, Rashba effect, and enhanced catalytic activity. While Raman spectroscopy is an essential nondestructive, phase- and composition-sensitive tool to monitor the synthesis of materials, a comprehensive study of the Raman spectrum of Janus monolayers is still missing. Here, we discuss the Raman spectra of WSSe and MoSSe measured at room and cryogenic temperatures, near and off resonance. By combining polarization-resolved Raman data with calculations of the phonon dispersion and using symmetry considerations, we identify the four first-order Raman modes and higher-order two-phonon modes. Moreover, we observe defect-activated phonon processes, which provide a route toward a quantitative assessment of the defect concentration and, thus, the crystal quality of the materials. Our work establishes a solid background for future research on material synthesis, study, and application of Janus TMD monolayers.