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

Tharith Sriv,Kangwon Kim,Hyeonsik Cheong

doi:10.1038/s41598-018-28569-6

Tharith Sriv, Kangwon Kim + Show 1 more

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https://doi.org/10.1038/s41598-018-28569-6

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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 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 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 × 1019 N · m−3 and 5.03 × 1019 N · m−3 for the shear and breathing modes, respectively.

Highlights

SnS2 is among the most important sulfide compounds of tin[13,14] and has more than 70 polytypes[13,14,15] differing from one another by stacking sequences of the individual sandwiched layers
Raman spectroscopy is one of the most widely used characterization tools for 2D layered materials to determine the number of layers as well as polytypes or strain effects
Low-frequency shear and breathing modes are not considered, i.e., interlayer interactions of the material remains uncovered in the Raman studies of few-layer SnS2

Summary

Introduction

SnS2 is among the most important sulfide compounds of tin[13,14] and has more than 70 polytypes[13,14,15] differing from one another by stacking sequences of the individual sandwiched layers. Raman spectroscopy to study the interlayer interactions of few-layer materials by measuring the in-plane (shear) and out-of-plane (breathing) modes in the low-frequency region (

Results

Conclusion