Tuning electronic transport in epitaxial graphene-based van der Waals heterostructures

Two-dimensional tungsten diselenide (WSe 2 ) has been used as a component in atomically thin photovoltaic devices, field effect transistors, and tunneling diodes in tandem with graphene. In some applications it is necessary to achieve efficient charge transport across the interface of layered WSe 2 graphene, a semiconductor to semimetal junction with a van der Waals (vdW) gap. In such cases, band alignment engineering is required to ensure a low-resistance, ohmic contact. In this work, we investigate the impact of graphene electronic properties on the transport at the WSe 2 graphene interface. Electrical transport measurements reveal a lower resistance between WSe 2 and fully hydrogenated epitaxial graphene (EG FH ) compared to WSe 2 grown on partially hydrogenated epitaxial graphene (EG PH ). Using low-energy electron microscopy and reflectivity on these samples, we extract the work function difference between the WSe 2 and graphene and employ a charge transfer model to determine the WSe 2 carrier density in both cases. The results indicate that WSe 2 EG FH displays ohmic behavior at small biases due to a large hole density in the WSe 2 , whereas WSe 2 EG PH forms a Schottky barrier junction. Tungsten diselenide (WSe 2 ) atomic crystals can be synthesized on graphene via metalorganic chemical vapor deposition. Depending on the synthesis temperatures and processing gases, the electron transport of synthetic WSe 2 graphene diodes could be tuned significantly.