High-κ KBe₂BO₃F₂ dielectric material with wide bandgap for two-dimensional electronics

Further transistor scaling requires gate dielectric materials with both high dielectric constant and wide bandgap to improve gate control and suppress leakage current. However, these two properties typically exhibit an inverse relationship, making it challenging to simultaneously optimize both. Here, we report the exfoliation of KBe₂BO₃F₂ (KBBF) dielectric nanosheets that overcome this trade-off. The material possesses a wide band gap exceeding 8 eV and a bulk dielectric constant of 63. Such dielectric properties give rise to a low leakage current of 10^-6 A cm^-2 at an equivalent oxide thickness of 0.62 nm and a high gate voltage of 15 V, and is predicted to work stably for 10 years at 6.6 V. 2D MoS₂ transistors gated by KBBF show a subthreshold swing of 60 mV dec^-1, reaching the theoretical limit at room temperature, and an on/off ratio up to 10⁹. Moreover, the good electrostatic controllability of KBBF enables the fabrication of short-channel devices and inverter circuits. Our research broadens the scope of dielectrics and provides promising opportunities for the development of low-power 2D electronics and integrated circuits.