Metal-assisted exfoliation of MoS₂

Interfacial modifications are probed using ultra-low-frequency (ULF) Raman spectroscopy, which, in combination with a modified linear-chain model, can quantify changes to the van der Waals coupling between layers. Across contacts with Au, Pd, Ni, Co and Ti, universal decoupling effects are observed, which weaken the MoS₂/ MoS₂ interface nearest to the metal.

The degree of decoupling increases with thickness, reaching a maximum at a few layers, which varies for different metals. This finding is corroborated by the observation of bubbles on annealed samples, which form only under thicker crystals and burst to expose monolayer, providing direct evidence of mechanical weakening. The effect does not depend on metal thickness or morphology and occurs even on atomically flat Au films, indicating that it is intrinsic to the metal/MoS₂ interaction.