Atomically thin molybdenum disulfide (MoS), 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 MoS film on hexagonal boron nitride (h-BN) by molecular beam epitaxy. Atomic force microscopy and electron microscopy studies reveal that MoS 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 MoS 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 MoS films on atomically flat surfaces and paves the way to large-scale applications.

Large‐sized MoS2 crystals can be grown on SiO2/Si substrates via a two‐stage chemical vapor deposition method. The maximum size of MoS2 crystals can be up to about 305 μm. The growth method can be used to grow other transition metal dichalcogenide crystals and lateral heterojunctions. The electron mobility of the MoS2 crystals can reach ≈30 cm2 V−1 s−1, which is comparable to those of exfoliated flakes.

There are strong interests in constructing nanolasers using two-dimensional transition metal dichalcogenides (TMDs) due to their strong light–matter interactions and high optical gain. However, most cavity designs based on transfer of exfoliated TMDs on silicon oxide are not optimized since monolayer emitters are located far from where the photonic mode reaches maximum intensity. By taking advantage of the excellent dielectric properties of hexagonal boron nitride (h-BN), we design a new microdisk optical cavity fabricated from a van der Waals (VdW) stacked h-BN/WS2/h-BN. The heterostructure is patterned into microdisk cavities characterized by whispering gallery modes (WGMs). The emission intensity of the WS2 trion is enhanced by 2.9 times that of exciton in the heterostructure, giving rise to whisper gallery modes with resonance intensities that show nonlinear power dependence. A Rayleigh scatterer directs the cavity emission to vertical collection. Such VdW heterostructure provides an atomically smooth interface that is ideal for low loss photon propagation, giving a Q factor of 1200.

Owing to the rapid development of data communication, there is a high demand for the large-scale integration of photonic devices into broadband communication networks. For practical integration, integrated photonic circuits are ideally fabricated on silicon platforms using processes compatible with complementary metal–oxide–semiconductor technology. Two-dimensional transition metal dichalcogenides are attractive candidates as on-chip emitters and absorbers due to their direct bandgaps, compatibility with miniaturization, large exciton binding energies, anisotropic polarizations, and strong light-matter interactions. Herein, a review of the current progress in the applications of two-dimensional materials as on-chip semiconductor devices is presented, as well as their prospects of integration on the silicon photonic platform. On-chip integrated photonic circuits are proposed based on heterostructures of hexagonal boron nitride and two-dimensional materials with functions of light sources, optical modulators, and photodetectors toward high-bandwidth optical interconnects.

The discovery of graphene heralded an era of intense research on two dimensional (2D) materials 1 . 2D transiton metal dichalcogenides TX 2 (T=Mo, W, Nb, Ti; X=S, Se, Te) provide an ideal system for studying many-body interactions, which manifest strongly in 2D systems due to the enhancement of Coulomb interactions and reduced screening 2 . Since 2D materials exhibit very large surface area and low carrier density,