Raman spectral studies on phonon softening, surface temperature, fano resonance, and phase change in MoS2 nanoflakes

A laser power-dependent Raman spectroscopic study has been done to explore the phonon shift, electron–phonon coupling, phase change, and surface temperature in hydrothermally prepared bulk 2H-MoS 2 nanoflakes with two different laser excitation wavelengths, i.e., 532 nm and 488 nm. The phonon softening and asymmetry in the vibrational modes are attributed to the laser-induced heating and Fano resonance, respectively. Fano resonance happens due to electron–phonon coupling and appears as an asymmetry in the Raman line shape. The fundamental vibrational phonon modes which show asymmetry are fitted using the Fano line shape function, and the laser power-dependent electron–phonon coupling changes are systematically studied. The asymmetry factor for E 2 g 1 and A 1 g modes gave negative and positive values, respectively. The laser-induced surface temperature of the material is calculated using Stokes/anti-Stokes method.