General Approach for Two-Dimensional Rare-Earth Oxyhalides with High Gate Dielectric Performance

Two-dimensional (2D) rare-earth oxyhalides (REOXs) with novel properties offer fascinating opportunities for fundamental research and applications. The preparation of 2D REOX nanoflakes and heterostructures is crucial for revealing their intrinsic properties and realizing high-performance devices. However, it is still a great challenge to fabricate 2D REOX using a general approach. Herein, we design a facile strategy to prepare 2D LnOCl (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy) nanoflakes using the molten salt method assisted by the substrate. A dual-driving mechanism was proposed in which the lateral growth could be guaranteed by the quasi-layered structure of LnOCl and the interaction between the nanoflakes and the substrate. Furthermore, this strategy has also been successfully applied for block-by-block epitaxial growth of diverse lateral heterostructures and superlattice. More significantly, the high performance of MoS₂ field-effect transistors with LaOCl nanoflake as the gate dielectric was demonstrated, exhibiting competitive device characteristics of high on/off ratios up to 10⁷ and low subthreshold swings down to 77.1 mV dec^-1. This work offers a deep understanding of the growth of 2D REOX and heterostructures, shedding new light on the potential applications in future electronic devices.