Activation of Raman modes in monolayer transition metal dichalcogenides through strong interaction with gold
2022
Abstract
Raman spectroscopy has become one of the most utilized methods for the characterization of transition metal dichalcogenides (TMDCs); however, the interpretation of the Raman spectra of TMDC-based heterostructures has been the subject of recent debate. Using a comprehensive combination of micro-Raman and tip-enhanced Raman spectroscopy, accompanied by ab initio simulations of both Raman frequencies and intensities, we show that the activation of the otherwise geometry-forbidden E mode and symmetry-forbidden A1 mode is the fingerprint of the strong interaction between the monolayer MX2 (M is Mo/W, X is S/Se) and the gold substrate, in contrast to the weakly interacting or freestanding MX2.