  We report on the fabrication and measurement of a graphene tunnel junction
using hexagonal-boron nitride as a tunnel barrier between graphene and a metal
gate. The tunneling behavior into graphene is altered by the interactions with
phonons and the presence of disorder. We extract prop- erties of graphene and
observe multiple phonon-enhanced tunneling thresholds. Finally, differences in
the measured properties of two devices are used to shed light on
mutually-contrasting previous results of scanning tunneling microscopy in
graphene.
