Raman Spectroscopy of Shear Modes in a Few-Layer MoS2

We study low frequency vibrational modes in atomically thin molybdenum disulfide (MoS2) by means of the Raman scattering spectroscopy. A shear mode related to rigid interlayer vibrations is identified. Its energy evolution with the increasing number of layers is well described using a linear chain model with only nearest neighbor interactions. The resulting force constant (K-x = 2.7 x 10(19) N/m(3)) corresponds well to the previously published data.