Multiwavelength excitation Raman Scattering Analysis of bulk and 2 dimensional MoS2: Vibrational properties of atomically thin MoS2 layers

TL;DR

This study provides a comprehensive Raman scattering analysis of bulk and atomically thin MoS2 layers across multiple excitation wavelengths, revealing new vibrational peaks and demonstrating UV resonant Raman spectroscopy's potential for non-destructive layer thickness assessment.

Contribution

It presents the first systematic Raman analysis of MoS2 under UV excitation and identifies 22 previously unobserved vibrational peaks, advancing understanding of its vibrational properties.

Findings

Identified 41 Raman peaks, including 22 new ones.

Demonstrated UV resonant Raman's effectiveness for non-destructive layer thickness measurement.

Revealed different resonant conditions depending on excitation wavelength.

Abstract

In order to deepen in the knowledge of the vibrational properties of 2-dimensional MoS2 atomic layers, a complete and systematic Raman scattering analysis has been performed using both bulk single crystal MoS2 samples and atomically thin MoS2 layers. Raman spectra have been measured under non-resonant and resonant conditions using seven different excitation wavelengths from near-infrared (NIR) to ultraviolet (UV). These measurements have allowed to observe and identify 41 peaks, among which 22 have not been previously experimentally observed for this compound, characterizing the existence of different resonant excitation conditions for the different excitation wavelengths. This has also included the first analysis of resonant Raman spectra that are achieved using UV excitation conditions. In addition, the analysis of atomically thin MoS2 layers has corroborated the higher potential of UV resonant Raman scattering measurements for the non destructive assessment of 2 dimensional MoS2 samples. Analysis of the relative integral intensity of the additional first and second order peaks measured under UV resonant excitation conditions is proposed for the non destructive characterization of the thickness of the layers, complementing previous studies based on the changes of the peak frequencies.