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 (CaNb2O6, KNb3O8, and Na2Nb4O11) as promising candidates, where strong Nb 4d-O 2p covalent hybridization enables pronounced Nb5+ 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 CaNb2O6, KNb3O8, and Na2Nb4O11, 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, MoS2 field-effect transistors with these gate dielectrics achieve low subthreshold swings (∼60 mV dec−1), ON/OFF ratios > 107, gate leakage currents below 10−6 A cm−2, and ultralow trap densities. We show high-performance NOT and NAND gates using a CaNb2O6 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.