Engineering MoS2 contact with graphene electrodes under electrostatic doping

Semiconductor transition metal dichalcogenides (TMDs) are 2D semiconductors that host attractive transport properties such as unconventional quantum Hall effect and spin-valley physics. However, metal contacts typically result in a Schottky barrier, making it difficult to access fundamental properties of the intrinsic charge transport. In this report, we utilize graphene electrodes to achieve ohmic contact to MoS$_2$ monolayer and bilayer. Our devices are fully capsulated by boron-nitride, which reduces the disorders from Si/SiO$_2$ substrate, and benefit from a dual-gate geometry, which allow us to independently dope the MoS$_2$ channel and graphene contact regions. The transition from non-ohmic to ohmic contacts is studied as a function of graphene doping and the MoS$_2$ carrier density. Our results reveal the operational range of these new devices, and provide new insight into future device design.