Optimizing Charge Injection across Transition Metal Dichalcogenide Heterojunctions: Theory and Experiment.

In search of an improved strategy to form low-resistance contacts to semiconducting transition metal dichalcogenides, we combine ab initio density functional electronic structure calculations for an NbSe2/WSe2 interface with quantum transport measurements of the corresponding heterojunction between a few-layer WSe2 semiconductor and a metallic NbSe2 layer. Our theoretical results suggest that, besides a rigid band shift associated with charge transfer, the presence of NbSe2 does not modify the electronic structure of WSe2. Since the two transition metal dichalcogenides are structurally similar and display only a small lattice mismatch, their heterojunction can efficiently transfer charge across the interface. These findings are supported by transport measurements for WSe2 field-effect transistors with NbSe2 contacts, which exhibit nearly ohmic behavior and phonon-limited mobility in the hole channel, indicating that the contacts to WSe2 are highly transparent.