The effect of graphene grain boundaries on MoS 2 /graphene heterostructures

The grain boundaries of graphene are disordered topological defects, which would strongly affect the physical and chemical properties of graphene. In this paper, the spectral characteristics and photoresponse of MoS2/graphene heterostructures are studied. It is found that the blueshift of G and 2D peaks of graphene in Raman spectrum is due to doping. The lattice mismatch at the graphene boundaries results in a blueshift of MoS2 features in the photoluminescence spectra, comparing to the MoS2 grown on SiO2. In addition, the photocurrent signal in MoS2/hexagonal single-crystal graphene heterostructures is successfully captured without bias, but not in MoS2/polycrystalline graphene heterostructures. The electron scattering at graphene grain boundaries affects the optical response of MoS2/graphene heterostructures. The photoresponse of the device is attributed to the optical absorption and response of MoS2 and the high carrier mobility of graphene. These findings offer a new approach to develop optoelectronic devices based on two-dimensional material heterostructures.