Production of Ultrathin and High-Quality Nanosheet Networks via Layer-by-Layer Assembly at Liquid-Liquid Interfaces.

Abstract

Solution-processable 2D materials are promising candidates for a range of printed electronics applications. Yet maximizing their potential requires solution-phase processing of nanosheets into high-quality networks with carrier mobility (μ_Net) as close as possible to that of individual nanosheets (μ_NS). In practice, the presence of internanosheet junctions generally limits electronic conduction, such that the ratio of junction resistance (<i>R</i>_J) to nanosheet resistance (<i>R</i>_NS), determines the network mobility via μ_NS/μ_Net ≈ <i>R</i>_J/<i>R</i>_NS + 1. Hence, achieving <i>R</i>_J/<i>R</i>_NS < 1 is a crucial step for implementation of 2D materials in printed electronics applications. In this work, we utilize an advanced liquid-interface deposition process to maximize nanosheet alignment and network uniformity, thus reducing <i>R</i>_J. We demonstrate the approach using graphene and MoS₂ as model materials, achieving low <i>R</i>_J/<i>R</i>_NS values of 0.5 and 0.2, respectively. The resultant graphene networks show a high conductivity of σ_Net = 5 × 10⁴ S/m while our semiconducting MoS₂ networks demonstrate record mobility of μ_Net = 30 cm²/(V s), both at extremely low network thickness (<i>t</i>_<i>Net</i> < 10 nm). Finally, we show that the deposition process is compatible with nonlayered quasi-2D materials such as silver nanosheets (AgNS), achieving network conductivity close to bulk silver for networks <100 nm-thick.