Resonance Raman studies on phonon softening, phonon lifetime, Fano resonance, and multipeak analysis of MoS2 nanoflakes

Abstract

In this study, the resonance Raman spectra of hydrothermally produced 2H-MoS₂ nanoflakes excited by a 633-nm laser were examined. Spectral observations include both fundamental MoS₂ modes and additional Raman lines, which arise from alterations in the energy states of the semiconductor owing to the incidence of laser radiation. Phonon softening and alterations in the phonon lifetime were computed for different laser powers. The Fano resonance, which causes asymmetry in the Raman spectral lines, was analyzed at different laser powers. The Fano line-shape function is used to fit the asymmetry in the in-plane vibrational mode whereas multi-peak fitting using the Fano-Lorentzian function is used to fit the out-of-the-plane fundamental mode, which is coupled with “b” mode. A direct study of the electron–phonon interaction was carried out with the “b” mode. The shift in laser wavenumber was then investigated using the 2LA(M) modes observed in the resonance Raman spectra. These findings provide new optoelectronic device designers with an understanding of the intricate electron–phonon interactions in transition metal dichalcogenides.