Solution-Processable Electronic-Grade 2D WTe₂ Enabled by Synergistic Dual Ammonium Intercalation.

Abstract

Tungsten ditelluride (WTe₂) exhibits thickness-dependent properties, including magnetoresistance, ferroelectricity, and superconductivity, positioning it as an ideal candidate for nanoelectronics and spintronics. Therefore, the scalable synthesis of WTe₂ with defined thicknesses down to the monolayer limit is crucial for unlocking these properties. Here, we introduce a universal electrolyte chemistry utilizing dual-ammonium compounds to exfoliate WTe₂, enabling precise control over the intercalation stages and flake thicknesses. This approach achieves an 86% exfoliation yield, producing high-quality flakes averaging 2.83 nm in thickness, in which approximately 10% are monolayers. A solution-processed, single-flake device (10 nm thick) exhibits a magnetoresistance (MR) of 50% at 2 K and 9 T, and piezo-response force microscopy (PFM) indicates ferroelectricity in WTe₂ flakes. Additionally, large-area WTe₂ thin films (15 × 15 mm²), fabricated using Langmuir-Schaefer deposition, exhibit metallic behavior with a high conductivity of 2.9 × 10⁴ S/m. Overall, the hybrid electrolyte approach facilitates the scalable synthesis of high-quality, solution-processable, two-dimensional (2D) WTe₂ flakes with excellent properties. This versatility of the developed method has been further exemplified through the exfoliation of other transition metal dichalcogenides (e.g., MoS₂ and MoSe₂), expanding the potential for the extensive application of exfoliated 2D materials in printable and flexible nanoelectronics.