Strain in 2D TMDCs induced by metal-assisted exfoliation from the polyvinilalcohol-covered substrate

TL;DR

This paper presents a modified metal-assisted exfoliation method for 2D TMDCs that produces large-area, minimally corrugated flakes and reveals how substrate-induced static friction can induce intrinsic strain in these materials.

Contribution

The authors introduce a new exfoliation technique involving an intermediate PVA-coated substrate and silver transfer, enabling high-yield production of deformed 2D flakes with controlled strain.

Findings

Produced large-area, low-corrugation 2D flakes with high yield.

Identified substrate-induced static friction causing intrinsic deformation.

Compared spectral properties indicating strain-related modifications.

Abstract

We have modified the metal-assisted transfer technique to obtain large-area few-layer flakes from transition metal dichalcogenides bulk crystals by introducing an initial stage - exfoliation of the bulk crystal onto an intermediate substrate, specifically a silicon wafer coated with polyvinyl alcohol. Following this, we thermally evaporate silver onto the sample and transfer the top layers of the crystal along with the silver layer to the target substrate. This technique allows the production of visually non-corrugated single- and few-layer flakes with high yield. A direct comparison of the micro-Raman and micro-photoluminescence spectra of flakes exfoliated using our method with the spectra of those exfoliated from scotch tape reveals differences in their properties. We identify signatures of deformations in the flakes exfoliated from the intermediate substrate, indicating the presence of static friction between the substrate and the flake. Our findings thus suggest a novel method to induce intrinsic deformation in 2D materials.