SmOBr Quasi-van der Waals Dielectric with High-κ and Ultralow Hysteresis for Two-Dimensional Electronics.

The integration of two-dimensional (2D) semiconductors into next-generation electronics critically depends on the availability of high-κ dielectrics that combine wide band gaps, strong breakdown fields, and pristine interfaces. Conventional oxides such as HfO2 suffer from interfacial incompatibility with 2D channels, while van der Waals dielectrics like h-BN offer excellent stability but limited capacitance. Here, we report the synthesis of quasi-vdW samarium oxybromide (SmOBr) nanosheets via a molten salt-assisted chemical vapor deposition method, establishing a previously unexplored member of the rare-earth oxyhalide family as a high-performance gate dielectric. SmOBr exhibits a wide band gap (4.63 eV), a high dielectric constant (ε ≈ 13.1), a breakdown field exceeding (EBD) 11.9 MV·cm-1, and ultralow leakage currents (<10-6 μA μm-2), achieving an exceptional balance between dielectric strength and capacitance. When integrated as a top-gate dielectric in MoS2 field-effect transistors, SmOBr enables outstanding device metrics, including subthreshold swings down to 79.5 mV dec-1, Ion/Ioff ratios >107, and ultralow gate hysteresis (∼4.3 mV), with excellent reproducibility and long-term ambient stability. These results position SmOBr as a compelling addition to the quasi-vdW rare-earth dielectric family, with low-power and reliable 2D nanoelectronics.