Wu Ke, He Wenyingdi, Zhong Hongxia, Wu Shutong, Zhou Hongzhi, Yuan Shengjun, Zhang Shunping, Xu Hongxing
School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China.
School of Sciences, Hangzhou Dianzi University, Hangzhou 310018, China.
ACS Appl Mater Interfaces. 2024 Aug 21;16(33):44186-44192. doi: 10.1021/acsami.4c06488. Epub 2024 Aug 7.
Helicity-resolved Raman spectra can provide an intricate view into lattice structural details. Through the analysis of peak positions, intensities, and circular polarized Raman signals, a wealth of information about chiral structure arrangement within the moiré superlattice, interlayer interaction strength, polarizability change in chemical bond, and beyond can be unveiled. However, the relationship between the circular polarization of high-frequency Raman and twist angle is still not clear. Here, we utilize helicity-resolved Raman spectroscopy to explore the interlayer interactions and the effect of the moiré superlattice in WS/WSe heterostructures. For the out-of-plane Raman mode A of WS (A and E of WSe), its intensity is significantly enhanced (suppressed) in WS/WSe heterostructures when θ is less than 10° or greater than 50°. This observation could be attributed to the large polarizability changes in both W-S and W-Se covalent bonds. The circular polarization of 2LA(M) in WSe of the WS/WSe heterostructure (θ < 10° or θ > 50°) is significantly enhanced compared to that of 2LA(M) in the monolayer WSe. We deduce that the circular polarization of the Raman mode correlates with the proportion of high-symmetry area within a supercell of the moiré lattice. Our findings improve the understanding of twist-angle-modulated Raman modes in TMD heterostructures.
螺旋度分辨拉曼光谱可以提供对晶格结构细节的复杂视图。通过对峰位、强度和圆偏振拉曼信号的分析，可以揭示有关莫尔超晶格内手性结构排列、层间相互作用强度、化学键中极化率变化等丰富信息。然而，高频拉曼的圆偏振与扭转角之间的关系仍不明确。在此，我们利用螺旋度分辨拉曼光谱来探索WS/WSe异质结构中的层间相互作用和莫尔超晶格的影响。对于WS的面外拉曼模式A（WSe的A和E模式），当θ小于10°或大于50°时，其强度在WS/WSe异质结构中显著增强（抑制）。这一观察结果可归因于W-S和W-Se共价键中极化率的大幅变化。与单层WSe中2LA(M)的圆偏振相比，WS/WSe异质结构（θ < 10°或θ > 50°）中WSe的2LA(M)的圆偏振显著增强。我们推断拉曼模式的圆偏振与莫尔晶格超胞内高对称区域的比例相关。我们的发现增进了对TMD异质结构中扭转角调制拉曼模式的理解。
