Nano-optical Imaging of In-Plane Homojunctions in Graphene and MoS2 van der Waals Heterostructures on Talc and SiO2

Understanding the impact of doping variations on the physical properties of two-dimensional materials is important for their application in electronic and optoelectronic devices. Here we report a nano-optical study on graphene and MoS2 homojunctions by placing these two materials partly on top of a layered talc substrate, partly on top of an SiO2 substrate. By analyzing the nano-Raman scattering from graphene and the nanophotoluminescense emission from MoS2, two different doping zones are evident with sub-100 nm wide charge oscillations. The oscillations occur abruptly at the homojuction and extend over longer distances away from the interface, indicating imperfect deposition of the two-dimensional layer on the substrate. These results evidence fine and unexpected details of the homojuctions, important to build better electronic and optoelectronic devices.