  The quantum interaction between molecules and electrode s material at
molecules-electrode interfaces is a major ingredient in the electronic
transport properties of organic junctions. Driven by the coupling strength
between the two materials, it results mainly in a broadening and an energy
shift of the interacting molecular orbitals. Using new electrodes materials,
such as the recent semi-conducting two-dimensional nanomaterials, has become a
recent challenge in the field of molecular-organic electronics that opens new
possibilities for controlling the interfacial electronic properties and thus
the charge injection properties. In this article, we report the use of
atomically thin two-dimensional multilayer graphene films as base electrode in
organic junctions with a vertical architecture. The interfacial electronic
structure dominated by the covalent bonding between bis-thienyl benzene
diazonium-based molecules and the multilayer graphene electrode has been probed
by ultraviolet photoelectron spectroscopy and the results compared with those
obtained on junctions with standard Au electrodes. Room temperature injection
properties of such interfaces have been also explored by electronic transport
measurements. We find that, despite strong variations of the density of states,
the Fermi energy and the injection barriers, both organic junctions with Au
base electrodes and multilayer graphene base electrodes show similar electronic
responses. We explain this observation by the strong orbital coupling occurring
at the bottom electrode-bis(thienyl) benzene molecules interface and by the
pinning of the hybridized molecular orbitals.
