Density-functional study of tilt-angle and temperature-dependent conductance in biphenyl dithiol single-molecule junctions

Abstract

In the framework of a density-functional-based method, we study electron transport through several biphenyl-derived dithiol molecules connected to gold electrodes. The molecules differ in the degree of conjugation of the-electron system, which is controlled by the choice of the side groups. The low-temperature conductance depends on the tilt angle between the two phenyl ring units and follows closely a cos 2 law consistent with an effective-orbital coupling model. Tilting the phenyl rings from a planar conformation to one with perpendicular rings decreases the conductance by roughly 2 orders of magnitude. These findings are in agreement with experiments. We further study the temperature dependence of both the conductance and its fluctuations and find qualitative differences between the investigated molecules. The temperature dependence arises from thermal smearing in the leads and also from a thermal average over different contact configurations. Our results suggest that the variations of the conductance due to the latter effect can be reduced by an appropriate design of the molecule.

Impact of the Crosslinker’s Molecular Structure on the Aggregation of Gold Nanoparticles

“…We focused on short aromatic molecules, since they are a potential candidate for applications in molecular electronics. Compared to other, polymer-based ligands or saturated alkane-chains, they allow direct electron tunnelling from one particle to another [24,25]. Our results strongly suggests that the molecular structure of the aromatic linkers is also favourable for a controlled aggregation of (Au)NP.…”

Quantum conductance of 4,4-bipyridine molecular junctions: Role of electrode work function and localdband

“…The cosine derives from the angular dependence of the overlap of the orbitals on the two pyridine rings as was also found for similar molecules in previous studies. 30,31 Under room-temperature conditions, the thermal fluctuations of will be significant and the pyridine rings will not have a well-defined relative angle. Since we expect changes in the torsion angle to have a very similar effect on the Au and Pt junctions, and because we are mainly interested in comparing the two systems, we specialize for simplicity to the planar configuration in what follows.…”

Length-dependent conductance and thermopower in single-molecule junctions of dithiolated oligophenylene derivatives: A density functional study

“…The relaxed part is also the "central region" in the transport calculations. 29 The tilt angles ϕ and the distances d of the contacted molecules are not essentially different from those of the isolated molecules. …”

“…Further details of the procedure are described in Ref. 29. For R2 (and similarly for S2 and D2) we observe that for most tilt angles (ϕ 80 • ) the transmission is dominated by a single channel [ Fig.…”