Probing Interfacial Interactions Between MoS₂ and Ti₃C₂ MXene via Raman Spectroscopy

The MoS₂/Ti₃C₂ MXene heterostructures have recently emerged to be an interesting structure in electronics and as a catalyst. Compared to MoS₂, the MoS₂/Ti₃C₂ MXene stack has demonstrated improved performance in catalytic and tribological applications. In this work, we use Raman Spectroscopy to study the influence of Ti₃C₂ MXene, as a substrate, on the lattice vibrational modes of MoS₂.

We stacked atomically thin MoS₂ to a bulk Ti₃C₂ film synthesized from two different etching solutions, NaF-HCl and KF-HCl. We found that both fingerprint peaks, A_1g and E¹_2g modes, exhibit substantial shifts on the Ti₃C₂. The shifts increase with annealing time, which indicates the interfacial interaction between MoS₂ and Ti₃C₂ influences the intralayer vibrations in MoS₂. We attribute the red-shifted E¹_2g mode to the strain effect, which arises upon releasing the monolayer MoS₂ flake on the Ti₃C₂ film. The A_1g mode shows opposite shifts from the two sources: it blue-shifts on the film prepared by NaF-HCl solution and red-shifts on the film etched in the KF-HCl solution. We attribute the blue-shifted A_1g peak to the increased out-of-plane force constants due to the presence of Ti₃C₂ and the redshift to a combined effect of strain and electron-doping from the trapped ions. Our results unveil the unique substrate effect from Ti₃C₂ MXene on MoS₂.