Graphene Tunneling Heterostructures

We have fabricated tunneling heterostructures comprising graphene on boron nitride (BN) substrates and tunnel barriers constructed of exfoliated BN or MoS$_{2}$. We present measurements of the low-temperature tunneling spectrum as a function of the tunneling energy and the carrier density in the graphene, with the latter controlled by a back-gate voltage. We observe a series of tunneling resonances, reminiscent of those seen in STM and planar tunneling experiments on graphene, whose energies disperse with the back-gate voltage.