A liquid copper strategy for wafer-scale single-crystalline hexagonal boron nitride with tunable thickness

Wafer-scale single-crystalline hexagonal boron nitride (h-BN) films can act as an excellent interface dielectric, and are highly desirable as an ideal platform for electronic devices. However, those practical applications require the controllable synthesis of single-crystalline h-BN multilayers over large area. Here, we demonstrate a wafer-scale growth approach that can realize precise thickness-tunable single-crystalline h-BN multilayer by using liquid copper as the catalytic substrate. The production of wafer-scale thickness-tunable single-crystalline h-BN multilayer is clearly evidenced by Transmission Electron Microscopy (TEM) and centimetre-scale characterization techniques of Low Energy Electron Diffraction (LEED). All evidences show that the h-BN films are produced via a self-collimation of circular grains combined with the process that subsequently created circular h-BN domains can be further nucleated, grown and finally coalesced into a new single crystalline layer on the surface of the previously formed h-BN layer. This liquid metal approach provides a feasible way to grow wafer-scale single-crystal directly, which facilitate the wide application of two-dimensional (2D) devices and synthesize of other vdW materials.