  Using current-voltage (I-V) and capacitance-voltage (C-V) measurements, we
report on the unusual physics and promising technical applications associated
with the formation of Schottky barriers at the interface of a one-atom-thick
zero-gap semiconductor (graphene) and conventional semiconductors. When
chemical vapor deposited graphene is transferred onto n-type Si, GaAs, 4H-SiC
and GaN semiconductor substrates, there is a strong van der Waals attraction
that is accompanied by charge transfer across the interface and the formation
of a rectifying (Schottky) barrier. Thermionic emission theory in conjunction
with the Schottky-Mott model within the context of bond-polarization theory
provides a surprisingly good description of the electrical properties.
Applications, such as to sensors where in forward bias there is exponential
sensitivity to changes in the Schottky barrier height due to the presence of
absorbates on the graphene or to analogue devices for which Schottky barriers
are integral components are promising because of graphene's mechanical
stability, its resistance to diffusion, its robustness at high temperatures and
its demonstrated capability to embrace multiple functionalities.
