Conduction and Valence Band Offsets in WSe2-Graphene Heterostructures*

We investigate the electron transport in graphene-WSe$_{2}$ heterostructures realized using a layer-by-layer transfer. Lateral electron transport shows ambipolar behavior characteristic of graphene, with a marked saturation at high positive (negative) gate bias, associated with the population of the conduction (valence) band in WSe$_{2}$. The graphene carrier density dependence on gate bias was extracted from magneto-transport measurements. Using WSe$_{2}$ as a top dielectric in dual-gate graphene field-effect transistors, we determine the WSe$_{2}$ dielectric constant along the c-axis. By combining the graphene density dependence on gate bias in back-gated graphene-WSe$_{2}$ heterostructures with the WSe$_{2}$ dielectric constant, we determine the offset between the graphene charge neutrality point and the WSe$_{2}$ conduction and valence bands.