Conductance of Single Alkanedithiols:  Conduction Mechanism and Effect of Molecule−Electrode Contacts

Li, Xiulan; He, Jin; Hihath, Joshua; Xu, Bingqian; Lindsay, Stuart; Tao, Nongjian

doi:10.1021/ja057316x

Cited by 493 publications

(782 citation statements)

References 45 publications

(76 reference statements)

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“…A similar study for an octanedithiol-Au junction has also been reported, 89 and for an asymmetric junction they found the breaking force of the Au-thiol bond to be 0.4-0.8 nN. Other experiments using the same molecule 84,85 reported a breaking force of 1.5 nN, which is very similar to the breaking force of a Au-Au bond, therefore, leading to the conclusion that the junction might break at the Au-Au bond and also indicating the presence of Au-thiolate instead of Au-thiol junctions. In summary, we find that the dissociative reaction of methanethiol and BDT2H on Au(111) is energetically unfavorable.…”

Section: Stability Study Of Thiol-terminated Molecules On a Au(111) Fsupporting

confidence: 65%

Stretching of BDT-gold molecular junctions: thiol or thiolate termination?

et al. 2014

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It is often assumed that the hydrogen atoms in the thiol groups of a benzene-1,4-dithiol dissociate when Au-benzene-1,4-dithiol-Au junctions are formed. We demonstrate, by stability and transport property calculations, that this assumption cannot be made. We show that the dissociative adsorption of methanethiol and benzene-1,4-dithiol molecules on a flat Au(111) surface is energetically unfavorable and that the activation barrier for this reaction is as high as 1 eV. For the molecule in the junction, our results show, for all electrode geometries studied, that the thiol junctions are energetically more stable than their thiolate counterparts. Due to the fact that density functional theory (DFT) within the local density approximation (LDA) underestimates the energy difference between the lowest unoccupied molecular orbital and the highest occupied molecular orbital by several electron-volts, and that it does not capture the renormalization of the energy levels due to the image charge effect, the conductance of the Au-benzene-1,4-dithiol-Au junctions is overestimated. After taking into account corrections due to image charge effects by means of constrained-DFT calculations and electrostatic classical models, we apply a scissor operator to correct the DFT energy level positions, and calculate the transport properties of the thiol and thiolate molecular junctions as a function of the electrode separation. For the thiol junctions, we show that the conductance decreases as the electrode separation increases, whereas the opposite trend is found for the thiolate junctions. Both behaviors have been observed in experiments, therefore pointing to the possible coexistence of both thiol and thiolate junctions. Moreover, the corrected conductance values, for both thiol and thiolate, are up to two orders of magnitude smaller than those calculated with DFT-LDA.This brings the theoretical results in quantitatively good agreement with experimental data.

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Section: Stability Study Of Thiol-terminated Molecules On a Au(111) Fsupporting

confidence: 65%

Stretching of BDT-gold molecular junctions: thiol or thiolate termination?

et al. 2014

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“…7,25,26 We consider two possibilities: (1) the connection is straight with an optimized Au-S bond length, as shown in Fig. 5 (a) for a BDT molecule, which is possible to occur when the STM tip is pulled from the gold surface, as suggested in Refs.…”

Section: Resultsmentioning

confidence: 99%

“…7,25,26,27,28,29,30,31,32,33,34 We also consider two different molecule-lead contacts, through a flat Au surface or through an apex Au atom, both of which are also possible to occur in experiments. 7,25,26,27,28,33,34 We adopt a single-particle Green function method 35,36 combining a Landauer formula with ab initio DFT 37 electronic structure calculation to investigate the electron transport through the junctions. 35,36,38 In practice, we divide an infinitely long Au-molecule-Au system into three parts: left lead, right lead, and device region which contains the molecule and large parts of the Au leads (see, for instance, Fig.…”

Section: Computationmentioning

confidence: 99%

Electron transport through single conjugated organic molecules: Basis set effects in ab initio calculations

Baranger

Yang

2007

The Journal of Chemical Physics

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We investigate electron transport through single conjugated molecules -including benzenedithiol, oligophenylene-ethynylenes of different lengths, and a ferrocene-containing molecule sandwiched between two gold electrodes with different contact structures -by using a single-particle Green function method combined with density functional theory calculation. We focus on the effect of the basis set in the ab initio calculation. It is shown that the position of the Fermi energy in the transport gap is sensitive to the molecule-lead charge transfer which is affected by the size of basis set. This can dramatically change, by orders of magnitude, the conductance for long molecules, though the effect is only minor for short ones. A resonance around the Fermi energy tends to pin the position of the Fermi energy and suppress this effect. The result is discussed in comparison with experimental data.

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“…[18][19][20][21][22][23][24] A thiol group is most commonly used to build a strong chemical link between the single molecules and the Au electrodes in molecular junctions. The conductance of such single-molecule junctions is typically several orders of magnitude smaller than G 0 =2e 2 / h ͑the conduc-tance quantum͒.…”

Section: Introductionmentioning

confidence: 99%

“…20,[22][23][24]27,28 Thus, in transport experiments, for a given bonding type, several binding sites are plausible, and hundreds of fabricated samples of the bonding type give rise to a histogram of conductance for given gate voltage or a series of current-voltage curves. In the present study, we take into account five different bonding types between an Mn 12 and Au electrodes, and for each bonding type, some representative interface geometries are examined.…”

Section: Introductionmentioning

confidence: 99%

Effects of bonding type and interface geometry on coherent transport through the single-molecule magnetMn12

et al. 2010

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We examine theoretically coherent electron transport through the single-molecule magnet Mn 12 , bridged between Au͑111͒ electrodes, using the nonequilibrium Green's function method and the density-functional theory. We analyze the effects of bonding type, molecular orientation, and geometry relaxation on the electronic properties and charge and spin transport across the single-molecule junction. We consider nine interface geometries leading to five bonding mechanisms and two molecular orientations: ͑i͒ Au-C bonding, ͑ii͒ Au-Au bonding, ͑iii͒ Au-S bonding, ͑iv͒ Au-H bonding, and ͑v͒ physisorption via van der Waals forces. The two molecular orientations of Mn 12 correspond to the magnetic easy axis of the molecule aligned perpendicular ͓hereafter denoted as orientation ͑1͔͒ or parallel ͓orientation ͑2͔͒ to the direction of electron transport. We find that the electron transport is carried by the lowest unoccupied molecular orbital ͑LUMO͒ level in all the cases that we have simulated. Relaxation of the junction geometries mainly shifts the relevant occupied molecular levels toward the Fermi energy as well as slightly reduces the broadening of the LUMO level. As a result, the current slightly decreases at low bias voltage. Our calculations also show that placing the molecule in the orientation ͑1͒ broadens the LUMO level much more than in the orientation ͑2͒ due to the internal structure of the Mn 12 . Consequently, junctions with the former orientation yield a higher current than those with the latter. Among all of the bonding types considered, the Au-C bonding gives rise to the highest current ͑about one order of magnitude higher than the Au-S bonding͒, for a given distance between the electrodes. The current through the junction with other bonding types decreases in the order of Au-Au, Au-S, and Au-H. Importantly, the spin-filtering effect in all the nine geometries stays robust and their ratios of the majority-spin to the minorityspin transmission coefficients are in the range of 10 3 -10 8 . The general trend in transport among the different bonding types and molecular orientations obtained from this study may be applicable to other single-molecule magnets.

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Conductance of Single Alkanedithiols: Conduction Mechanism and Effect of Molecule−Electrode Contacts

Cited by 493 publications

References 45 publications

Stretching of BDT-gold molecular junctions: thiol or thiolate termination?

Stretching of BDT-gold molecular junctions: thiol or thiolate termination?

Electron transport through single conjugated organic molecules: Basis set effects in ab initio calculations

Effects of bonding type and interface geometry on coherent transport through the single-molecule magnetMn12

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