Water-assisted growth of large-sized single crystal hexagonal boron nitride grains

Growth control over the size and shape of two-dimensional hexagonal boron nitride domains is vital for its applications. Here we develop a rational water-assisted chemical vapor deposition method that allows fast growth of large-sized (more than 330 μm) single crystal domains, which are 3–5 times larger than those previously grown on solid Cu or Cu–Ni alloy. Further kinetic control results in the perfect evolution of the domain shape from negatively curved triangle, triangle, positively curved triangle, regular hexagon, polygon, to circle. This work addresses the existing major problems, paving a way for the synthesis of materials with better control.