General Chemical Vapor Deposition Approach for Synthesizing Two-Dimensional Alkali and Alkaline Earth Niobates and...

A flux-assisted chemical vapor deposition (CVD) strategy is developed to synthesize two-dimensional (2D) alkali and alkaline-earth niobates, exemplified by quaternary RbCa₂Nb₃O₁₀ and ternary Rb₄Nb₁₁O₃₀ that were previously unattainable in ultrathin crystalline form as well as CaNb₂O₆ and KNb₃O₈. The flux-mediated process enables the controlled growth of high-quality layered crystals with atomically flat surfaces, well-defined lattice structures, and outstanding dielectric performance, including high permittivity, large breakdown fields, and seamless integration with 2D channel materials. Furthermore, the method is extended to the synthesis of high-entropy analogues, producing multication 2D niobates with uniform elemental distribution across the flake. This work establishes flux-assisted CVD as a versatile and scalable platform for the synthesis of complex 2D oxides and highlights the promise of these materials as high-performance dielectrics in future 2D nanoelectronics.