Quasi-Fano Resonance-Induced Asymmetric E2g1 Raman Mode in WS2 Nanoflakes

Abstract

In addition to their technological importance, nanomaterials also act as a physical bed for investigation for revealing new scientific insight about quantum mechanics-driven phenomena. Here, WS2 nanosheets have been chosen to investigate an interesting Fano-type excitation wavelength-dependent Raman line shape from a 2D system. The study reveals the presence of electron-phonon interaction (Fano interaction), the mixing of a discrete spectrum with a continuous spectrum, in the E2g1 Raman mode of WS2 nanoflakes. A typical Fano-type asymmetric Raman line shape has been observed while using a red excitation wavelength, and the same has been validated by theoretical Fano-Raman line shape fitting. To further validate this, excitation wavelength-dependent variation in the Raman line shape has been studied, which confirms that the asymmetry is due to Fano interaction. The experimentally observed Raman line shape shows very good agreement with the theoretically generated line shapes using the Fano-Raman line shape function. An excitation wavelength-dependent Fano coupling parameter has been calculated, and an empirical relation has also been proposed. © 2023 American Chemical Society.