Exfoliation and transfer of millimetre-sized MoS2 flakes on arbitrary substrates

Abstract

Two-dimensional (2D) materials have the potential to strongly and sustainably influence technological development in the fields of optoelectronics, energy production and management, catalysis and more. One limiting factor that presently prevents the full exploitation of these materials is, however, the difficulty of obtaining large-scale, high-quality 2D samples on arbitrary substrates. In this work, we introduce a significant generalization of previously reported gold-assisted exfoliation techniques of TMDCs, marking a step forward towards the fabrication of macroscopic 2D materials samples on arbitrary substrates. We achieved the successful production of millimetre-sized monolayer MoS₂ onto silica, PDMS, and both thermal and native oxidized silicon wafers. Moreover, our method simplifies previously reported gold-assisted exfoliation methods by removing substrate functionalization procedures and complex steps to achieve a reliable and reproducible procedure. The crystal quality of the monolayers was probed using XPS, Raman and photoluminescence revealing a negligible presence of contaminants and defects in the samples. Furthermore, using imaging ellipsometry, we could investigate, on the millimetre scale, the samples morphology and the selectivity of the exfoliation process to produce single layer MoS₂ flakes. Finally, we further extended the capability of our exfoliation method by enabling the seamless transfer of large-area samples from PDMS to advanced substrates, unlocking new possibilities for large-scale 2D devices fabrication.