Controlled Chemical Vapor Deposition Growth of Single-Crystalline CoO Ultrathin Flakes as Dielectrics for High-Performance Two-Dimensional Electronics.

Two-dimensional (2D) crystalline dielectrics are essential for high-performance van der Waals electronics in 2D electronics; however, their scalable synthesis with sufficient dielectric performance remains challenging. Here, we report the scalable chemical vapor deposition (CVD) growth of ultrathin single-crystalline CoO nanoplates with orientationally aligned arrays over millimeter-scale regions on mica substrates. Lattice matching enables aligned nucleation and epitaxial growth, yielding atomically flat flakes with excellent thermal stability. The crystalline CoO dielectric exhibits a dielectric constant of ∼13.0, a breakdown field of 7.6 MV cm-1, and enables low-hysteresis graphene transistors. The presented method can be extended to the preparation of 2D Co3O4 flakes through thermal oxidation, as well as 2D Mn3O4 and Fe2O3 flakes via CVD-based chloride oxidation. This chloride-oxidation strategy is further extendable to other ultrathin transition-metal oxides and highlights 2D CoO as a promising crystalline dielectric platform for van der Waals electronics.