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

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.