Cumulene molecular wire conductance from first principles

Abstract

We present first principles calculations of current-voltage characteristics ͑IVC͒ and conductance of Au͑111͒ :S 2 -cumulene-S 2 :Au͑111͒ molecular wire junctions with realistic contacts. The transport properties are calculated using full self-consistent ab initio nonequilibrium Green's function density-functional theory methods under external bias. The conductance of the cumulene wires shows oscillatory behavior depending on the number of carbon atoms ͑double bonds͒. Among all conjugated oligomers, we find that cumulene wires with odd number of carbon atoms yield the highest conductance with metalliclike ballistic transport behavior. The reason is the high density of states in broad lowest unoccupied molecular orbital levels spanning the Fermi level of the electrodes. The transmission spectrum and the conductance depend only weakly on applied bias, and the IVC is nearly linear over a bias region of Ϯ1 V. Cumulene wires are therefore potential candidates for metallic connections in nanoelectronic applications.

Interference effects in phtalocyanine controlled by H-H tautomerization: Potential two-terminal unimolecular electronic switch

“…Both cumulene 27 and gold leads are highly conductive; however, matching of the gold s states to the H 2 Pc conjugated π orbital introduces additional backscattering, yielding 1/4 the current at comparable voltages. In addition, the IVCs of junctions with gold leads exhibit pronounced NDR at high bias voltage, as well as examples of weak NDR at intermediate bias.…”

Mechano-switching devices from carbon wire-carbon nanotube junctions

“…We find that the conductance of the odd-wire is higher than that of even-wire by ∼ 60 %. The conductance values do not show any pronounced dependence on the wire length when its length increased from four to nine atoms, resulting from the ballistic transport character of electrons through the short wire 23 . To compare our findings for small radii CNTs to the large ones, we note that the latter have low curvatures and are well represented by flat graphene electrodes.…”

“…We observe that the alignment of PDOS is determined by bridging sites and bonding at the junction. As we have already known that the cumulene wire has two π orbitals around the Fermi level resulting from p x and p y orbitals 19,23 , the PDOS of the wire is decomposed into p x and p y components, as demonstrated in Fig. 8.…”

“…Note that we selected (4,0)@C n -II(C) in studying the oscillating conductance of the cumulene wire because that structure is the straight cumulene wire providing the highest conductance. Similar to the cumulene wire connected to metal leads 23,25 , we ob- serve the oscillatory characteristics in conductance of the cumulene wire-CNT junction, resulting from the difference in the electronic properties between even-and oddcumulene wires 8,23 . We find that the conductance of the odd-wire is higher than that of even-wire by ∼ 60 %.…”

“…Recently, the carbon wire connected to graphene sheets 18,19 (representing infinite radii of CNT) have been theoretically studied, revealing different electronic functions such as molecular switches 20 , molecular rectifiers 21 , and molecular spintronics devices 22 . Carbon wires connected to gold 23,24 , lithium 25 and fullerene 26 electrodes have also been investigated.…”