Oxygen-assisted growth of monolayer MoS2 films on graphene by chemical vapor deposition

MoS2/graphene heterojunctions have a great potential for optoelectronic applications. Here, we demonstrate the oxygen (O2) assisted growth of large-area monolayer MoS2 films on graphene using chemical vapor deposition (CVD) technique. The introduction of O2 has greatly improved the growth environment of MoS2 domains as well as increased the grain size of MoS2 from submicron to micron range. Spectroscopic results show that a monolayer of MoS2 with high crystal quality has been deposited on the graphene. Effective charge transfer is observed in MoS2/graphene heterojunctions. MoS2 is doped with different concentrations of O2 in situ by optimizing its flow rates. The photodetector prepared by MoS2/graphene film has a good response to light. Due to the effective photoresponse of synthesized heterojunctions, these would be useful in various applications in the optoelectronic thin films and devices.