  Advanced exfoliation techniques are crucial for exploring the intrinsic
properties and applications of 2D materials. Though the recently discovered
Au-enhanced exfoliation technique provides an effective strategy for
preparation of large-scale 2D crystals, the high cost of gold hinders this
method from being widely adopted in industrial applications. In addition,
direct Au contact could significantly quench photoluminescence (PL) emission in
2D semiconductors. It is therefore crucial to find alternative metals that can
replace gold to achieve efficient exfoliation of 2D materials. Here, we present
a one-step Ag-assisted method that can efficiently exfoliate many large-area 2D
monolayers, where the yield ratio is comparable to Au-enhanced exfoliation
method. Differing from Au film, however, the surface roughness of as-prepared
Ag films on SiO2/Si substrate is much higher, which facilitates the generation
of surface plasmons resulting from the nanostructures formed on the rough Ag
surface. More interestingly, the strong coupling between 2D semiconductor
crystals (e.g. MoS2, MoSe2) and Ag film leads to a unique PL enhancement that
has not been observed in other mechanical exfoliation techniques, which can be
mainly attributed to enhanced light-matter interaction as a result of extended
propagation of surface plasmonic polariton (SPP). Our work provides a
lower-cost and universal Ag-assisted exfoliation method, while at the same
offering enhanced SPP-matter interactions.
