Layer-Dependent Valley Depolarization and Raman Phonon Softening of SnS2/MoS2 Vertical van der Waals Heterostructures Layer-Dependent Valley Depolarization and Raman Phonon Softening of SnS2/MoS2 Vertical van der Waals Heterostructures AITranslate

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DOI：https://doi.org/10.1021/acsaelm.3c00529

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Two-dimensional van der Waals heterostructures (vdWhs) have aroused tremendous attention due to valley polarization and the interlayer coupling effect, providing a promising platform for valleytronics. However, the correlation between electron–phonon coupling (EPC) and valley depolarization is still less studied for vdWhs. In this work, heterobilayered and heteromultilayered SnS2/MoS2 vdWhs were prepared for the study of EPC and valley polarization by a two-step chemical vapor deposition method. The SnS2 layer has a good epitaxial relationship with the underneath MoS2 monolayer. Raman red shifts of 0.3 and 1.0 cm–1 were found for the E2g1 mode of MoS2 in the heterobilayer and heterotrilayer, respectively, concurrently with an isotropic-to-anisotropic transition of the E2g1 vibration intensity for the latter. By a helicity-resolved photoluminescence study, layer-dependent valley depolarization was revealed with the helicity of the A exciton of MoS2 decreasing from 57 to 9% for the heterobilayer and close to zero for the heterotrilayer. Strong EPC was confirmed by low-temperature resonant Raman scattering coexisting with helicity-resolved PL, and the layer-dependent evolution demonstrates the intensive relation of valley depolarization with charge transfer and localized EPC with non-zone-center phonons. Based on the layer-dependent band structure calculated by density functional theory, intervalley charge transfer and phonon-assisted intervalley scattering were proposed for layer-dependent valley depolarization. The strong EPC effect also results in layer-dependent Raman shifts.