Growth of the MoSe2/MoS2 heterostructures

A two-step CVD method was used for the growth of the MoSe₂/MoS₂ lateral heterostructures. Briefly, the MoSe₂ monolayer was first grown by a CVD method in a 5.08-cm tube. A mixed Ar/H₂ flow of 80:5 sccm was used as the carrier gas, and a silicon boat containing 10 mg of MoO₃ was put in the center of the tube. The SiO₂/Si substrate was placed on the boat with surface downside. Another silicon boat containing 0.5 g of Se powder was located on the upstream. The temperature ramped up to 750°C in 15 min, where it was kept for about 10 min. The as-grown MoSe₂ was then transferred into another CVD setup for subsequent MoS₂ growth. For the growth of MoS₂, Ar flow of 60 sccm was used as the carrier gas, and a silicon boat containing 10 mg of MoO₃ was put in the center of a 2.54-cm tube. The MoSe₂/SiO₂/Si substrate was placed on the boat with surface downside. Another silicon boat containing 0.5 g of S powder was located on the upstream. The temperature was ramped up to 650°C in 13 min and was kept there for about 5 min.