The exfoliation yield is related to the interaction between the metal and 2D layers that can be directly probed by Raman spectroscopy. For instance, the MoS2 monolayer changes its crystalline symmetry from freestanding D3h to C3v group while interfaced with Au. This alters the vibrational selection rules resulting the activation of few forbidden Raman modes, which we probed in our previous study using near-field plasmonic enhancement of samples prepared under ambient conditions. We also observed that the obtained intensity varies depending on the number of layers, which is due to partial contamination of the Au surface during the fabrication process. This further limits the exfoliation yield and layer homogeneity.