Tunable as-grown graphene contacts to semiconducting transition metal dichalcogenides

Transition metal dichalcogenides (TMDs) are attractive 2D materials in the “beyond graphene” realm of materials. They provide a route to realize heterogeneous materials on demand, with properties tailored for specific applications. To utilize their unique electronic properties, it is important to develop low resistance contacts to these materials. Graphene is a promising candidate and has been shown to produce low-resistance contacts to MoS2. But this has been done by manual stacking which is not a scalable method. Various vertical combinations of 2D materials have been shown to exhibit unique optical and electronic properties,including negative differential resistance,that do not exist in the constituent layers. One avenue that is still in its infancy, yet could provide significant potential for impact in novel device properties is the realization of lateral heterostructures of graphene and 2D materials “beyond graphene”.Since graphene holds the potential of forming a good contact to the semiconducting TMDs, the combination of graphene with TMDs in the same plane allows for a lateral heterostructure with as-grown contacts, extensive scalability and “all-2D” electronics. Here, we presentas-grown heterostructures formed between epitaxial graphene and TMDs like molybdenum disulfide (MoS2), and discuss the electronic properties resulting from the lateral interface.

Using epitaxial graphene on silicon carbide (SiC) substrate, the flexibility of being able to tune the doping of the graphene exists. Upon exposure to 100% hydrogen, n-type as-grown epitaxial graphene becomes p-type. This allows us to explore the option of type-matching the graphene contact to the TMD, thus reducing the barrier for electrons and making contacts much superior to conventional metals.

S. Subramanian et al. “Properties of synthetic Epitaxial Graphene/Molybdenum Disulfide Lateral Heterostructures.” Carbon, 125, 551–556 (2017)