One-step exfoliation method for plasmonic activation of large-area 2D crystals

TL;DR

This paper introduces a cost-effective, one-step Ag-assisted exfoliation technique for large-area 2D crystals that enhances photoluminescence through surface plasmon interactions, offering a practical alternative to gold-based methods.

Contribution

The study presents a novel Ag-assisted exfoliation method that matches gold-based yields and enhances photoluminescence via surface plasmon coupling, reducing costs and broadening applications.

Findings

Ag films enable efficient exfoliation of large-area 2D monolayers.

Surface roughness of Ag films facilitates surface plasmon generation.

Enhanced photoluminescence observed due to strong coupling with Ag surface plasmons.

Abstract

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.