Synthesis of multilayered h-BN film on the molten Ni–B and the influence of underneath W substrate

High-quality two-dimensional hexagonal boron nitride ( h -BN) film with tens of layers has been used as a universal substrate and capping layer for the van der Waals devices. Various approaches have been carried out for the synthesis of multilayered h -BN. Among them, the metal flux method is reliable in yielding h -BN crystals with high crystalline quality. However, this time- and energy-demanding method hinders its scale application. Herein, inspired by the metal flux method, we reported the time-effective growth of high-quality multilayered h -BN film (ca. 20 nm) on a molten Ni–B layer wetting on W substrate with chemical vapor deposition method. The film exhibits an excellent stacking sequence and a full-width at half maximum of the Raman E 2g peak narrow to 9.5 cm −1 . Cross-sectional high-resolution transmission electron microscopy and in-situ x-ray diffraction spectroscopy were carried out to investigate the crystal structure evolution of Ni–B layer wetting on W substrate. It is found that the low surface tension caused by the spreading of Ni–B alloy on the W substrate and the presence of the Ni subsurface may be responsible for the formation of multilayered h -BN with excellent crystalline quality. Meanwhile, the W diffusion in Ni–B-based melt can hinder the formation of h -BN under certain growth conditions. The approach demonstrates the feasibility of large-scale growth of multilayered h -BN, paving the way to future applications in van der Waals electronic and optoelectronic devices.