Low-Frequency Raman Spectroscopy of Few-Layer 2H-SnS₂

We investigated interlayer phonon modes of mechanically exfoliated few-layer 2H-SnS₂ samples by using room temperature low-frequency micro-Raman spectroscopy. Raman measurements were performed using laser wavelengths of 441.6, 514.4, 532 and 632.8 nm with power below 100 μW and inside a vacuum chamber to avoid photo-oxidation. The intralayer E_g and A_1g modes are observed at ~206 cm^-1 and 314 cm^-1, respectively, but the E_g mode is much weaker for all excitation energies. The A_1g mode exhibits strong resonant enhancement for the 532 nm (2.33 eV) laser. In the low-frequency region, interlayer vibrational modes of shear and breathing modes are observed. These modes show characteristic dependence on the number of layers. The strengths of the interlayer interactions are estimated by fitting the interlayer mode frequencies using the linear chain model and are found to be 1.64 × 10¹⁹ N · m^-3 and 5.03 × 10¹⁹ N · m^-3 for the shear and breathing modes, respectively.