Optical identification of interlayer coupling of graphene/MoS₂ van der Waals heterostructures

The interlayer coupling in van der Waals (vdW) heterostructures (vdWHs) is at the frontier of the fundamental research, underlying many optical behaviors. The graphene/MoS₂ vdWHs provide an ideal platform to reveal the good interfacial coupling between graphene and MoS₂ constituents. Here, three groups of graphene/MoS₂ vdWHs were prepared by transferring 1-3 layers of graphene onto monolayer MoS₂. The interlayer coupling within graphene/MoS₂ vdWHs were characterized and analyzed by Raman spectroscopy, photoluminescence (PL) spectroscopy and optical contrast (OC) spectroscopy. The upshift of the A_1g peak of MoS₂ and the upshift of the D and 2D peaks of SLG show that the electrons move from MoS₂ to graphene accompanied by the dielectric shielding effect on graphene. The weakened PL intensities and the slight red shift of A peak prove that the electrons move from MoS₂ to graphene meanwhile the recombination of hole and electron pairs is blocked in vdWHs. Our results deepen the understanding of the interlayer coupling of graphene/MoS₂ vdWHs and therefore provide guidelines for the practical design and application of optoelectronic devices based on graphene/MoS₂ vdWHs.