Rapid growth of inch-sized lanthanide oxychloride single crystals.

The layered lanthanide oxychloride (LnOCl) family, featuring a low equivalent oxide thickness, high breakdown field and magnetic ordering properties, holds great promise for next-generation van der Waals devices. However, the exploitation of LnOCl materials has been hindered by a lack of reliable methods for growing their single-crystalline phases. Here we achieved the growth of inch-sized bulk LnOCl single crystals and single-crystalline thin films with thickness down to the monolayer in a few hours. The monolayer LnOCl exhibits ultralow equivalent oxide thicknesses, for instance, LaOCl and SmOCl have values of 0.25 and 0.34, respectively. Furthermore, using LnOCl as a dielectric in graphene devices, we demonstrate wafer-scale enhancement of carrier mobility and a well-developed quantum Hall effect. The induced strong magnetic proximity effect by SmOCl and DyOCl enables efficient interfacial charge transfer with magnetic exchange coupling This work provides a general strategy for synthesizing large-sized single-crystalline layered materials, enriching the library of ultralow-equivalent-oxide-thickness dielectric materials, and two-dimensional magnetic materials with induced strong magnetic proximity effect.