Van der Waals Epitaxially Grown Molecular Crystal Dielectric Sb₂O₃ for 2D Electronics

Two-dimensional (2D) semiconducting materials have attracted significant interest as promising candidates for channel materials owing to their high mobility and gate tunability at atomic-layer thickness. However, the development of 2D electronics is impeded due to the difficulty in formation of high-quality dielectrics with a clean and nondestructive interface. Here, we report the direct van der Waals epitaxial growth of a molecular crystal dielectric, Sb₂O₃, on 2D materials by physical vapor deposition. The grown Sb₂O₃ nanosheets showed epitaxial relations of 0 and 180° with the 2D template, maintaining high crystallinity and an ultrasharp vdW interface with the 2D materials. As a result, the Sb₂O₃ nanosheets exhibited a high breakdown field of 18.6 MV/cm for 2L Sb₂O₃ with a thickness of 1.3 nm and a very low leakage current of 2.47 × 10^-7 A/cm² for 3L Sb₂O₃ with a thickness of 1.96 nm. We also observed two types of grain boundaries (GBs) with misorientation angles of 0 and 60°. The 0°-GB with a well-stitched boundary showed higher electrical and thermal stabilities than those of the 60°-GB with a disordered boundary. Our work demonstrates a method to epitaxially grow molecular crystal dielectrics on 2D materials without causing any damage, a requirement for high-performance 2D electronics.