Deep-ultraviolet Raman scattering spectroscopy of monolayer WS2

Abstract
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 [Formula: see text] 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 [Formula: see text] peak with the 1.58 eV laser light comes from the fact that valley polarization of the laser light surpasses the [Formula: see text] mode since the [Formula: see text] 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.

Citation
Liu H-L, Yang T, Tatsumi Y, Zhang Y, Dong B, et al. (2018) Deep-ultraviolet Raman scattering spectroscopy of monolayer WS2. Scientific Reports 8. Available: http://dx.doi.org/10.1038/s41598-018-29587-0.

Acknowledgements
H.L.L. thanks financial support from the Ministry of Science and Technology of Republic of China under Grants No. MOST 105-2112-M-003-013-MY3 and Academia Sinica under thematic project Grant No. AS-105-TP-A03. T.Y. and Z.D.Z. acknowledge the National Key R&D Program of China (No. 2017YFA0206301) and the Major Program of Aerospace Advanced Manufacturing Technology Research Foundation NSFC and CASC, China (No. U1537204). H.G. acknowledges NSFC Grant No. 51702146 and Liaoning Province Doctor Startup Fund (No. 201601325). L.J.L. thanks the support from Taiwan Consortium of Emergent Crystalline Materials (TCECM), Ministry of Science and Technology, and USA AFOSR BRI (FA238615100015). R.S. acknowledges MEXT-Japan Grants Nos. JP25107005, JP15K21722, and JP18H01810. Y.K. and S.K. acknowledge JSPS-Japan Grants No. JP21226003. Y.T. acknowledges World Premier International Research Center Initiative (WPI), MEXT, Japan.

Publisher
Springer Nature

Journal
Scientific Reports

DOI
10.1038/s41598-018-29587-0

Additional Links
https://www.nature.com/articles/s41598-018-29587-0

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