Without a grain of salt: micropatterning clean MXene thin-film electronics

Abstract

MXenes exhibit remarkable electrical, mechanical, and thermal properties, positioning them as strong candidates for high-performance electrodes and interconnects. Deposited 2D MXene thin-films suffer from a persistent issue of crystalline salt residues that originate from dissolved intercalation salts used for the exfoliation process during synthesis. These 3D salt by-products can cause issues during further nanofabrication processing and be detrimental to integrated device performance. This study introduces a three-step approach involving spin-coating deposition, HCl spin-cleaning, and lift-off. Rigorous morphological characterization of the patterned MXene was performed, confirming that the spin-cleaning step effectively removed all halide salt residues. Transparent sub-10 nm-thick MXene thin-film electrodes, down to a width of 5 μm with ∼1.5 μm resolution, were produced. The electrical properties were probed, showcasing exceptional conductivity (∼1350 S cm⁻¹ for a 50 μm-wide electrode) with high photosensitivity at the MXene–Si junction. The proposed method yields clean patterned MXene thin films, enabling easier integration of MXene or other 2D materials into future microelectronic devices.