Voltage-dependent conductance of a single graphene nanoribbon

Abstract

Electronic transport in a zigzag edge graphene nanoribbon (GNR) and its modification by ad-sorbed transition metal porphyrins is studied by means of density functional theory calculations. The detachment reaction of the metal centre of the porphyrin is investigated both in the gas phase and for molecules adsorbed on the GNR. As most metal porphyrins are very stable against this reaction, it is found that these molecules bind only weakly to a perfect nanoribbon. However, interaction with a single-atom vacancy in the GNR results in chemical bonding by the transition metal centre being shared between nitrogen atoms in the porphyrin ring and the carbon atoms next to the vacancy in the GNR. For both the physisorbed and the chemisorbed geometry, the inclusion of van der Waals interaction results in a significant enlargement of the binding energy and reduction of the adsorption height. Electronic transport calculations using non-equilibrium Greens functions show that the conductivity of the GNR is altered by the chemisorbed porphyrin molecules. Since the metal centers of porphyrins carry an element-specific magnetic moment, not only the net conduc-tance, but also the spin-dependent conductance of the GNR is affected. In particular, the adsorption of Ru-porphyrin on the single-atom vacancy results in a very large spin polarization of the current of 88% at small applied source-drain voltages. Based on our results, we suggest that a spin valve constructed from a GNR with ferromagnetic contacts could be used as a sensitive detector that could discriminate between various metal porphyrins.

Suppression of electron–vibron coupling in graphene nanoribbons contacted via a single atom

“…We have carried out combined low-temperature STM/AFM experiments on atomically well-defined GNRs grown through the on-surface polymerization of 10-10 0 -dibromo-9,9 0 -bianthryl followed by thermal cyclodehydrogenation on Au(111) single crystals (Fig. 1a, see Cai et al 13 ; Ruffieux et al 16 ; Koch et al 17 and Methods for details). A typical overview STM scan is shown in Fig.…”

“…Here, we contact an atomically well-defined GNR 13,16,17 to the gold substrate by a chemical bond via only one atom. This welldefined contact is formed by removing an individual hydrogen atom from the end of a GNR.…”

Quantum Field Theory Approach to the Optical Conductivity of Strained and Deformed Graphene

“…bending graphene nanoribbons [14]. Within the formalism of the Dirac equation in a curved background geometry one can also describe strained graphene.…”

Optical conductivity of curved graphene

“…Recently, in [32] the authors were able to bend a nanoribbon, which could be associated with a metric of the type discussed here, i.e. z = h(x).…”

“…In the recent experiment in [32] a single graphene nanoribbon was bended and its voltage-dependent conductance measured. Further, the experiment accounted for the conductance dependence on the precise atomic structure and bending of the molecule in the junction.…”