Facile Synthesis of Large‐Area Ultrathin Hexagonal BN Films via Self‐Limiting Growth at the Molten B2O3 Surface

A self-limiting growth process based on the interface-controlled reaction of molten boron oxide (B2 O3 ) with ammonia (NH3 ) is demonstrated for the facile and lost-cost synthesis of ultrathin (20-30 nm) crystalline hexagonal boron nitride (h-BN) films over large areas. The as-grown h-BN films are of high quality, being densely continuous, uniform and smooth, and highly transparent over a broad wavelength range.