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Resonance Raman scattering and ab initio calculation of electron energy loss spectra of MoS2 nanosheets

The presence of electron energy loss (EELS) peak is proposed theoretically in molybdenum disulfide (MoS2) nanosheets. Using density functional theory simulations and calculations, one EELS peak is identified in the visible energy range, for MoS2 nanosheets with molybdenum vacancy. Experimentally, four different laser sources are used for the Raman scattering study of MoS2 nanosheets, which show two distinct Raman peaks, one at 385 cm-1 (E12g) and the other at 408 cm-1 (A1g). In the cases of three laser sources with wavelengths 405 nm (3.06 eV), 632 nm (1.96 eV) and 785 nm (1.58 eV), respectively, the intensity of E12g Raman peak is more than the A1g Raman peak, while in the case of excitation source of 532 nm (2.33 eV), the intensity profile is reversed and A1g peak is the most intense. Thus a resonance Raman scattering phenomenon is observed for 532 nm laser source.