Raman scattering measurements of monolayer WS2 are reported as a function of the laser excitation energies from the near-infrared (1.58 eV) to the deep-ultraviolet (4.82 eV). In particular, we observed several strong Raman peaks in the range of 700∼850 cm−1 with the deep-ultraviolet laser lights (4.66 eV and 4.82 eV). Using the first-principles calculations, these peaks and other weak peaks were appropriately assigned by the double resonance Raman scattering spectra of phonons around the M and K points in the hexagonal Brillouin zone. The relative intensity of the first-order to A1g peak changes dramatically with the 1.58 eV and 2.33 eV laser excitations, while the comparable relative intensity was observed for other laser energies. The disappearance of the peak with the 1.58 eV laser light comes from the fact that valley polarization of the laser light surpasses the mode since the mode is the helicity-exchange Raman mode. On the other hand, the disappearance of the A1g peak with the 2.33 eV laser light might be due to the strain effect on the electron-phonon matrix element.
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机译:据报道,单层WS2的拉曼散射测量结果是从近红外(1.58 eV)到深紫外光(4.82 eV)的激光激发能的函数。尤其是,在深紫外激光(4.66 eV和4.82 eV)下,我们在700〜850 cm -1 sup>范围内观察到了几个很强的拉曼峰。使用第一性原理计算,这些峰和其他弱峰是由六边形布里渊区M和K点周围的声子的双共振拉曼散射光谱适当分配的。一阶展开▼