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

TL;DR

This study uses low-frequency Raman spectroscopy to analyze interlayer phonon modes in few-layer 2H-SnS2, revealing layer-dependent vibrational properties and quantifying interlayer interaction strengths.

Contribution

It provides the first detailed measurement of interlayer phonon modes in 2H-SnS2 and estimates interlayer interaction strengths using a linear chain model.

Findings

Interlayer shear and breathing modes depend on layer number

Resonant enhancement of A1g mode at 532 nm laser

Quantified interlayer interaction strengths for shear and breathing modes

Abstract

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 wavelength of 441.6, 514.4, 532 and 632.8 nm with power below 100 uW and inside a vacuum chamber to avoid photo-oxidation. The intralayer Eg and A1g modes are observed at ~206 cm-1 and ~314 cm-1, respectively, but the Eg mode is much weaker for all excitation energies. The A1g 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 x10^19 N.m-3 and 5.03 x10^19 N.m-3 for the shear and breathing modes, respectively.