Ultraflat single-crystal hexagonal boron nitride film grown on Cu/Ni (1 1 1) for high-performance deep ultraviolet photodetectors

Large-area single-crystal two-dimensional (2D) semiconducting layered materials have the potential to extend Moore's law by increasing the number of transistors in integrated circuits. While monolayer single-crystal hexagonal boron nitride (h-BN) has been synthesized on molten gold surfaces and bulk copper foils using chemical vapor deposition (CVD), the scalable growth of large single-crystal mutilayer h-BN remains challenging. Here we use Cu/Ni (1 1 1) alloy foil and synthesize wafer-scale trilayer h-BN film by CVD method. The h-BN film grown on the Cu/Ni (1 1 1) alloy substrate exhibits an ultraflat surface over a large area. A set of microscopies, spectroscopies and electrical characterization techniques consistently showed that the h-BN is single crystal. This effective method for producing large-area single-crystal h-BN paves the way for future nano-electronic applications.