  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.
