A Novel Liquid-Liquid Interface Deposition Method for the Production of Thin Films and van der Waals Heterostructures of Two-Dimensional Solids

TL;DR

This paper introduces a rapid, eco-friendly liquid interface deposition method for producing thin films and heterostructures of two-dimensional materials from aqueous suspensions, enabling versatile and efficient device fabrication.

Contribution

The study presents a novel, generalizable technique for fabricating 2D material films and heterostructures using liquid interface deposition, reducing complexity and environmental impact.

Findings

Produced transparent, conductive graphene films with high transmittance and conductivity.

Demonstrated fabrication of van der Waals heterostructures of MoS2, WS2, and graphene.

Applicable to various substrates and 2D materials.

Abstract

Thin films and van der Waals heterostructures derived from two-dimensional solids offer enormous potential for a broad range of novel, energy efficient devices, however, their use is currently hampered by slow, labor-intensive fabrication methods often employing hazardous chemicals. We demonstrate a novel technique for rapid, low-cost and environmentally-friendly production of ultra-thin films and van der Waals heterostructures of two-dimensional solids from aqueous surfactant-stabilized suspensions, which we term `Liquid Interface Deposition'. Films are produced by the transfer of platelets of two-dimensional materials assembled at the interface between two immiscible liquids (water and dicholoromethane), at which surfactants which stabilize the two-dimensional materials in the aqueous phase are `stripped' from the platelets due to preferential partitioning of the surfactant to the non-aqeuous phase. The approach is generic to two-dimensional materials which can be stabilized in aqueous suspension by a surfactant and the resulting films can then be transferred to an arbitrary substrate by a range of approaches. The generic applicability of this technique is demonstrated through production of thin films on a variety of substrates, deposition of transparent, highly conductive, graphene films with conductivities between $7.7 \times 10^{3} - 1.26\times 10^{5}~\textrm{S m}^{-1}$ and transmittances of 55-75%, and by the fabrication of van der Waals heterostructures of MoS$_2$, WS$_2$, and few-layer graphene.