High‐κ Perovskite‐Like Ternary Niobium Oxide Dielectrics for 2D Electronics

ABSTRACT High‐κ dielectrics with exceptional interface quality are essential for the field‐effect control of nanoscale transistors. However, their design remains challenging due to competing atomic‐scale polarization requirements. Here, we demonstrate nonlayered perovskite‐like ternary niobium oxides (CaNb 2 O 6 , KNb 3 O 8 , and Na 2 Nb 4 O 11 ) as promising candidates, where strong Nb 4 d ‐O 2 p covalent hybridization enables pronounced Nb 5+ ionic displacements and enhanced polarization, while ionic bonding from intercalated Ca/K/Na suppresses electronic transitions, widening the bandgap and enhancing stability via configurational entropy. We successfully synthesize these high‐quality nanoflakes through a scalable molten‐salt method. Crucially, these oxides demonstrate a combination of high dielectric constants (∼16, 9, and 68 for CaNb 2 O 6 , KNb 3 O 8 , and Na 2 Nb 4 O 11 , respectively), wide bandgaps (∼4 eV), large breakdown field strengths (> 4.9 MV cm −1 ), and excellent air stability. Furthermore, due to the low‐contamination transfer via a fully dry process, MoS 2 field‐effect transistors with these gate dielectrics achieve low subthreshold swings (∼60 mV dec −1 ), ON/OFF ratios > 10 7 , gate leakage currents below 10 −6 A cm −2 , and ultralow trap densities. We show high‐performance NOT and NAND gates using a CaNb 2 O 6 dielectric layer, with the inverter achieving a static power consumption of < 0.02 µW and a gain of ∼20. This work provides new opportunities for the development of next‐generation 2D electronics devices.