Charge injection and transport properties of large area organic junctions based on aryl thin films covalently attached to a multilayer graphene electrode

Abstract

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 2 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/ bisthienyl benzene molecules interface and by the pinning of the hybridized molecular orbitals.

Combined spin filtering actions in hybrid magnetic junctions based on organic chains covalently attached to graphene

“…The gradual decrease of the current is related to the passivation of the electrode through the grafting of NB radicals onto Gr/Ni surface. This behavior is clearly attributed to the formation of NO 2 -phenyl (NB) film over the Gr/Ni electrode as usually reported for graphene surfaces 39 or for standard metallic surfaces. 26,40 Microscopically, each monomer in its radical form is either covalently bonded to the graphene surface locally modifying its hybridization from sp 2 to sp 3 (ref.…”

“…46 This demonstrates that the proposed approach indeed allows us to probe transport properties across the organic film. We note that we observe a small rectification (I = +623pA for V = +300 mV and I = −651 pA for V = −300 mV) similar to that found at multilayer graphene/oligomer chain/Au junctions 39 and attributed to the molecule-graphene covalent contact. 55 The use of spin polarizer and analyzer electrodes in our configuration indeed allows to further probe the spin transport properties across the graphene/NB film.…”

Ion-Assisted Resonant Injection and Charge Storage in Carbon-Based Molecular Junctions

“…Molecular junctions (MJs) have been studied for their charge transport characteristics with the anticipation of realizing new electronic tasks that can enhance semiconductor technologies. − Redox-active molecules and metal oxides have been employed in MJs to modulate the charge transport features, successfully resulting in enhanced current rectification and conductance switching in solid state, − vapor, − and liquid environments. − We reported recently that redox reactions can occur in solid state MJs in the absence of electrolyte ions or a redox counter-reaction, with the oxidized or reduced molecule stabilized by the image charge on the opposing electrode . Charge storage exceeded that of a conventional parallel plate capacitor and was accompanied by redox kinetics absent in a parallel plate.…”

Organic–Inorganic Hybrid Interfaces for Spin Injection into Carbon Nanotubes and Graphene

“…A perfect compatibility in terms of chemistry with extremely stable configurations such as the covalent coverage of carbon nanotubes with diazonium‐based molecules for instance; [ 79,198,199 ]…”