  The resonance effects on the Raman spectra from 5 to 900 cm-1 of few-layer
MoS2 thin films up to 14-layers were investigated by using six excitation
energies. For the main first-order Raman peaks, the intensity maximum occurs at
~2.8 eV for single layer and at ~2.5 eV for few-layer MoS2, which correspond to
the band-gap energy. At the excitation energy of 1.96 eV, several anomalous
behaviors are observed. Many second-order peaks are anomalously enhanced even
though the main first-order peaks are not enhanced. In the low-frequency region
(<100 cm-1), a broad peak centered at ~38 cm-1 and its second order peak at 76
cm-1 appear for the excitation energy of 1.96 eV. These anomalous resonance
effects are interpreted as being due to strong resonance with excitons or
exciton-polaritons.
