Probing Spatial Phonon Correlation Length in Post-Transition Metal Monochalcogenide GaS Using Tip-Enhanced Raman Spectroscopy.
basic_science · Level V
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- Record sourced from PubMed, PMID 31469281.
- Also identified by DOI 10.1021/acs.nanolett.9b02974.
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Abstract
The knowledge of the 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 <i>L</i><sub>c</sub> of the A<sub>1g</sub><sup>1</sup> and A<sub>1g</sub><sup>2</sup> phonons of monolayer and few-layer gallium sulfide (GaS). The differences in <i>L</i><sub>c</sub> values are responsible for different enhancements of the A<sub>1g</sub> modes, with A<sub>1g</sub><sup>1</sup> always enhancing more than the A<sub>1g</sub><sup>2</sup>, independently of the number of GaS layers. For five layers, the results show an <i>L</i><sub>c</sub> of 64 and 47 nm for A<sub>1g</sub><sup>1</sup> and A<sub>1g</sub><sup>2</sup>, respectively, and the coherence lengths decrease when decreasing the number of layers, indicating that scattering with the surface roughness plays an important role.