Atomic Layer Deposition of High-Quality Al₂O₃ Thin Films on MoS₂ with Water Plasma Treatment

Atomic layer deposition (ALD) of ultrathin dielectric films on two-dimensional (2D) materials for electronic device applications remains one of the key challenges because of the lack of dangling bonds on the 2D material surface. In this work, a new technique to deposit uniform and high-quality Al2O3 films with thickness down to 1.5 nm on MoS2 is introduced. By treating the surface using water plasma prior to the ALD process, hydroxyl groups are introduced to the MoS2 surface, facilitating the chemisorption of trimethylaluminum in a conventional water-based ALD system. Raman and X-ray photoelectron spectroscopy measurements show that the water plasma treatment does not induce noticeable material degradation. The deposited Al2O3 films show excellent device-related electrical performance characteristics, including low interface trap density and outstanding gate controllability.