Stacking two dimensional tunneling heterostructures has always been an important strategy to improve the optoelectronic device performance. However, there are still many disputes about the blocking ability of monolayer (1L-) h-BN on the interlayer coupling. Graphene/h-BN/MoS2 optoelectronic devices have been reported for superior device results. In this study, starting with graphene/h-BN/MoS2 heterostructures, we report experimental evidence of 1L-h-BN barrier layer modulation effects about the electronic band structures and exciton properties. We find that 1L-h-BN insertion only partially blocks the interlayer carrier transfer. In the meantime, the 1L-h-BN barrier layer weakens the interlayer coupling effect, by decreasing the efficient dielectric screening and releasing the quantum confinement. Consequently, the optical conductivity and plasmon excitation slightly improve, and the electronic band structures remain unchanged in graphene/h-BN/MoS2, explaining their fascinating optoelectronic responses. Moreover, the excitonic binding energies of graphene/h-BN/MoS2 redshift with respect to the graphene/MoS2 counterparts. Our results, as well as the broadband optical constants, will help better understand the h-BN barrier layers, facilitating the developing progress of h-BN-based tunneling optoelectronic devices.
Keywords: electronic band structures; excitons; graphene/h-BN/MoS2 heterostructures; interlayer coupling; tunneling effect.