Probing Spatial Phonon Correlation Length in Post-Transition Metal Monochalcogenide GaS Using Tip-Enhanced Raman Spectroscopy (original) (raw)

Nano Letters, 2019

Abstract

The knowledge of phonon coherence length is of great importance for two-dimensional-based materials since phonons can limit the lifetime of charge carriers and heat dissipation. Here we use tip-enhanced Raman spectroscopy (TERS) to measure the spatial correlation length Lc of the A11g and A21g phonons of mono and few-layers gallium sulfide (GaS). The differences in Lc values are responsible for different enhancements of the A1g modes, with A11g always enhancing more than the A21g, independently of the number of GaS layers. For 5-layers, the results show an Lc of 64 nm and 47 nm for A11g and A21g, respectively, and the coherence lengths decrease when decreasing the number of layers, indicating that scattering with the surface roughness plays an important role.

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