Controlled van der Waals epitaxy of monolayer MoS₂ triangular domains on graphene

Multilayered heterostructures of two-dimensional materials have recently attracted increased interest because of their unique electronic and optical properties. Here, we present chemical vapor deposition (CVD) growth of triangular crystals of monolayer MoS₂ on single-crystalline hexagonal graphene domains which are also grown by CVD. We found that MoS₂ grows selectively on the graphene domains rather than on the bare supporting SiO₂ surface. Reflecting the heteroepitaxy of the growth process, the MoS₂ domains grown on graphene present two preferred equivalent orientations. The interaction between the MoS₂ and the graphene induced an upshift of the Raman G and 2D bands of the graphene, while significant photoluminescence quenching was observed for the monolayer MoS₂. Furthermore, photoinduced current modulation along with an optical memory effect was demonstrated for the MoS₂-graphene heterostructure. Our work highlights that heterostructures synthesized by CVD offer an effective interlayer van der Waals interaction which can be developed for large-area multilayer electronic and photonic devices.