High-Fidelity Transfer of 2D Semiconductors and Electrodes for van der Waals Devices.

As traditional silicon-based materials almost reach their limits in the post-Moore era, two-dimensional (2D) transition metal dichalcogenides (TMDCs) have been regarded as next-generation semiconductors for high-performance electrical and optical devices. Chemical vapor deposition (CVD) is a widely used technique for preparing large-area and high-quality TMDCs. Yet, it suffers from the challenge of transfer due to the strong interaction between 2D materials and substrates. The traditional PMMA-assisted wet etching method tends to induce damage, wrinkles, and inevitable polymer residues. In this work, we propose an etch-free and clean transfer method via a water intercalation strategy for TMDCs, ensuring a high-fidelity, wrinkle-free, and crack-free transfer with negligible residues. Furthermore, metal electrodes can also be transferred via this method and back-gate field-effect transistors (FETs) based on CVD-grown monolayer WSe₂ with van der Waals (vdW) metal/semiconductor contacts are fabricated. Compared to the PMMA-assisted transfer method (∼1.2 cm² V^-1 s^-1 hole mobility with ∼2 × 10⁶ ON/OFF ratio), our high-fidelity transfer method significantly enhances the electrical performance of WSe₂ FET over one order of magnitude, achieving a hole mobility of ∼43 cm² V^-1 s^-1 and a high ON/OFF ratio of ∼5 × 10⁷ in air at room temperature.