Correlation of interfacial bonding mechanism and equilibrium conductance of molecular junctions

Abstract

We report theoretical investigations on the role of interfacial bonding mechanism and its resulting structures to quantum transport in molecular wires. Two bonding mechanisms for the Au-S bond in an Au(111)/1,4-benzenedithiol(BDT)/Au(111) junction were identified by ab initio calculation, confirmed by a recent experiment, which, we showed, critically control charge conduction. It was found, for Au/ BDT/Au junctions, the hydrogen atom, bound by a dative bond to the Sulfur, is energetically non-dissociative after the interface formation. The calculated conductance and junction breakdown forces of H-non-dissociative Au/BDT/Au devices are consistent with the experimental values, while the H-dissociated devices, with the interface governed by typical covalent bonding, give conductance more than an order of magnitude larger. By examining the scattering states that traverse the junctions, we have revealed that mechanical and electric properties of a junction have strong correlation with the bonding configuration. This work clearly demonstrates that the interfacial details, rather than previously believed many-body effects, is of vital importance for correctly predicting equilibrium conductance of molecular junctions; and manifests that the interfacial contact must be carefully understood for investigating quantum transport properties of molecular nanoelectronics.

Many-body correlations and coupling in benzene-dithiol junctions

“…1. They agree with previous calculations [25,30,46,52]. The tilt angle between the normal to the gold surface and the S-S direction of the two contact atoms measures 32 • , 31 • , and 0 • for BDT-n, BDT-p and BDTh, respectively.…”

“…Notice that E coupl should not be confused with the junction relative stabil-ity. For instance, we have calculated the relative stability of BDT-n with respect to BDT-p, E BDT-n − E BDT-p − E H2 , and found a difference of −0.23 eV, showing that BDT-n is more stable and confirming previous findings [47,48,52].…”

“…For the three junctions considered here, the calculated zero-bias conductances G(E = 0) using DFT-GGA and many-body full-COHSEX are reported in Table I. The DFT conductances of 0.305, 0.365, and 0.034 G 0 for BDT-h, BDT-p and BDT-n respectively, are in agreement with previous results from the literature [5,25,30,38,46,49,52,70]. The main results of this work are the full-COHSEX conductances.…”

Spin filtering in transition-metal phthalocyanine molecules from first principles

“…Rich phenomena such as spin-valve [1], spin filtering [2], and the Kondo effect [3] can be observed in molecular devices. A considerable amount of effort has been devoted to finding a potential single molecule that can exhibit these interesting properties [4]. For instance, Hao [5] observed spin-filtering and Kondo resonance features by using a MnCu single-molecule magnet bridged between two gold electrodes.…”

Quantum description of transport phenomena: Recent progress

“…In a mini review [7], all carbonbased molecular junctions were discussed including mechanically controlled conductance switches, negative differential resistances and electronic rectifiers. A research article [8] addresses a longstanding issue for molecular transport junction, namely whether the H atom is dissociative from the SH group in an Au-Benzenedithiol-Au structure. This article reports some compelling evidence that H remains.…”