Molecular Beam Epitaxy of Highly Crystalline Monolayer Molybdenum Disulfide on Hexagonal Boron Nitride

Atomically thin molybdenum disulfide (MoS₂), a direct-band-gap semiconductor, is promising for applications in electronics and optoelectronics, but the scalable synthesis of highly crystalline film remains challenging. Here we report the successful epitaxial growth of a continuous, uniform, highly crystalline monolayer MoS₂ film on hexagonal boron nitride (h-BN) by molecular beam epitaxy. Atomic force microscopy and electron microscopy studies reveal that MoS₂ grown on h-BN primarily consists of two types of nucleation grains (0° aligned and 60° antialigned domains). By adopting a high growth temperature and ultralow precursor flux, the formation of 60° antialigned grains is largely suppressed. The resulting perfectly aligned grains merge seamlessly into a highly crystalline film. Large-scale monolayer MoS₂ film can be grown on a 2 in. h-BN/sapphire wafer, for which surface morphology and Raman mapping confirm good spatial uniformity. Our study represents a significant step in the scalable synthesis of highly crystalline MoS₂ films on atomically flat surfaces and paves the way to large-scale applications.