Large-area synthesis of high-quality and uniform monolayer WS2 on reusable Au foils

TLDR

Large‑area monolayer WS₂ is desirable for next‑generation electronics and optoelectronics, yet conventional CVD on rigid substrates yields non‑uniform layers, small domains, and defects, limiting flexible device fabrication. The study aims to develop a self‑limited catalytic surface growth method for uniform monolayer WS₂ on Au foils. The authors use ambient‑pressure CVD on Au, exploiting the weak WS₂–Au interaction to transfer intact monolayers by electrochemical bubbling and to roll‑to‑roll produce large‑area flexible films, heterostructures, and transistor arrays. The resulting WS₂ shows high crystal quality and optical and electrical properties comparable or superior to mechanically exfoliated samples.

Abstract

Abstract Large-area monolayer WS 2 is a desirable material for applications in next-generation electronics and optoelectronics. However, the chemical vapour deposition (CVD) with rigid and inert substrates for large-area sample growth suffers from a non-uniform number of layers, small domain size and many defects, and is not compatible with the fabrication process of flexible devices. Here we report the self-limited catalytic surface growth of uniform monolayer WS 2 single crystals of millimetre size and large-area films by ambient-pressure CVD on Au. The weak interaction between the WS 2 and Au enables the intact transfer of the monolayers to arbitrary substrates using the electrochemical bubbling method without sacrificing Au. The WS 2 shows high crystal quality and optical and electrical properties comparable or superior to mechanically exfoliated samples. We also demonstrate the roll-to-roll/bubbling production of large-area flexible films of uniform monolayer, double-layer WS 2 and WS 2 /graphene heterostructures, and batch fabrication of large-area flexible monolayer WS 2 film transistor arrays.