Raman spectroscopy of 2D MoS on TiC MXene: the substrate effect.

We use Raman spectroscopy to study the substrate effect of TiC MXene on the lattice vibrational modes of MoS. We observed redshifts in the fingerprint peaks of MoS, and explained the shifts based on their vibrational nature. The shift in the in-plane E mode is attributed to the strain effect, and the softened A mode associated with the out-of-plane vibration is caused by electron doping. In addition to monolayer MoS, we show that the modulation from TiC MXene is also present in few-layer and bulk MoS. Furthermore, we demonstrate that the laser-induced shift occurs even at low excitation power. Our results indicate that a detailed power-dependent measurement is indispensable for extracting the pure substrate effect from Raman spectroscopy.