Tuning Electronic Transport in WSe2-Graphene
In many atomically thin photovoltaic devices, field effect transistors, and tunneling diodes, 2D TMDC have been used as a semiconducting layer in tandem with graphene and many other substrates. It is necessary to achieve efficient charge transport across WSe2-graphene, which creates a semiconductor to semimetal junction. In such cases, the band alignment engineering is required to ensure a low-resistance, ohmic contact. In previous chapter, we cover preparation and fundamental properties of WSe2-graphene. In this chapter, we investigate the impact of graphene properties on the transport at the interface of WSe2-graphene. Electrical transport measurements reveal a change in resistance between WSe2 and fully hydrogenated epitaxial graphene (EGFH) compared to WSe2 grown on partially hydrogenated epitaxial graphene (EGPH). Using low-energy electron microscopy and reflectivity (LEEM/LEER) on these samples, we extract the work function difference between the WSe2 and graphene and employ a charge transfer model to determine the WSe2 carrier density in both cases. The results here indicate that WSe2-EGFH displays nearly ohmic behavior at small biases due to a large hole density in the WSe2, whereas WSe2-EGPH forms a Schottky barrier junction.
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