Quantitative Interpretations of Break Junction Conductance Histograms in Molecular Electron Transport

Quan, Robert; Pitler, Christopher S.; Ratner, Mark A.; Reuter, Matthew G.

doi:10.1021/acsnano.5b03183

Cited by 27 publications

(26 citation statements)

References 68 publications

(175 reference statements)

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“…Nevertheless, during the shrinking of the nanogap between two-terminal devices, tunneling leakage current is dominated by the through-space tunneling between the source and drain terminals, which increases exponentially with the terminal distance and becomes non-negligible, as described in Figure 1A. 17,18 Therefore, the determination of transition distance between the intrinsic molecular tunneling and the tunneling leakage current through single-molecule devices is of fundamental significance and will enhance…”

Section: Introductionmentioning

confidence: 99%

Transition from Tunneling Leakage Current to Molecular Tunneling in Single-Molecule Junctions

Liu

Zhao

Zheng

et al. 2019

Chem

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Tunneling leakage is a major inevitable quantum obstacle that hinders further miniaturization of electronic devices. To explore the miniaturization limits of molecular electronics, the oligo(aryleneethynylene) (OAE) molecules were employed to investigate the transition distance between through-space tunneling and molecular tunneling. For the shortest OAE molecule, the intrinsic singlemolecule charge transport can be outstripped from tunneling leakage down to 0.66 nm, suggesting the potential to push the miniaturization limit of molecular electronic devices to the angstrom scale.

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Section: Introductionmentioning

confidence: 99%

Transition from Tunneling Leakage Current to Molecular Tunneling in Single-Molecule Junctions

Liu

Zhao

Zheng

et al. 2019

Chem

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“…Zuschriften sional conductance-distanceh istograms [10a, 19] were constructed for each state without any data selection, as shown in Figures 2c and Figure 2d,w ith each of their relative displacement distributions shown as the upright insets.All the histograms showed unambiguous conductance clouds,i ndicating ah igh junction formation probability.I ti sfound that the traces of PTZ-BT start with the direct tunnelling feature before the molecular plateau, [20] while the PTZ-BT + C conductance plateau appeared immediately after the rupture of the gold-gold contact. Therelative displacement distribution enlarged very slightly from the neutral state into the radical state (1.5 nm of PTZ-BT to 1.6 nm of PTZ-BT + C), for which the statistical range was from 10 À0.3 to 10 À6.0 G 0 for PTZ-BT and from 10 À0.3 to 10 À4.5 G 0 for PTZ-BT + C,respectively.When adding the 0.5 nm snap-back distance, [10a, 21] the length of the molecular junction is 2.0 and 2.1 nm for PTZ-BT and PTZ-BT + C,r espectively,w hich are slightly less than the maximum possible values,b ased on the computed molecular lengths of 2.31 nm and 2.33 nm for PTZ-BT and PTZ-BT + C obtained from DFT simulations,respectively (see Figure S6-1 for more details).…”

Section: Angewandte Chemiementioning

confidence: 89%

Radical‐Enhanced Charge Transport in Single‐Molecule Phenothiazine Electrical Junctions

et al. 2017

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We studied the single-molecule conductance through an acid oxidant triggered phenothiazine (PTZ-) based radical junction using the mechanically controllable break junction technique.T he electrical conductance of the radical state was enhanced by up to 200 times compared to the neutral state,with high stability lasting for at least two months and high junction formation probability at room-temperature.T heoretical studies revealed that the conductance increase is due to asignificant decrease of the HOMO-LUMO gap and also the enhanced transmission close to the HOMO orbital when the radical forms.T he large conductance enhancement induced by the formation of the stable PTZ radical molecule will lead to promising applications in single-molecule electronics and spintronics.Investigations of charge transport through single molecules provide vital information for the design of materials for nextgeneration electronic devices. [1] Recently,a ll-organic radical species have raised broad interests as the unpaired electron can lead to novel quantum phenomena for tuning the electronics properties, [2] such as Kondo effects, [3] quantum interference [4] and magnetoresistive effects. [5] However, although some pioneering studies investigated the charge transport through radicals using molecular assemblies [5a, 6] or under ultrahigh vacuum and cryogenic environment, [3b,5b] the seeking of appropriate molecular radicals for the fabrication of stable and highly conductive single-molecule devices remained as amajor challenge for applying molecular radicals for future electronics devices.Thep henothiazine (PTZ) system can undergo oneelectron oxidation on the nitrogen atom to form ar adical cation (PTZ + C) [7] with accompanying significant color change in solution by adding acid oxidant such as trifluoroacetic acid (TFA) under ambient conditions.M ore interestingly,t he butterfly structure of the PTZ became more planar for the radical cation with electron density delocalized over the whole molecule including the central ring. [8] Such prominent changes in the electronic properties of the PTZ radicals have received increasing research interests in organic light-emitting diodes, [9] and also offer promising applications in the radical-based molecular electronics devices.Herein, we study the single-molecule conductance of aP TZ derivative and its corresponding radical cation using the mechanically controllable break junction (MCBJ) technique [10] in am ixed tetrahydrofuran/1,3,5-trimethylbenzene (THF/TMB,1:4 v/v)solution at room temperature,asshown in Scheme 1. Prominent conductance signals of both the PTZ derivative and its corresponding radical cation are observed with alarge conductance enhancement of up to 200 times for the radical state.T heoretical studies also reproduced the results that the radical state possesses as ignificantly higher electrical conductance compared with the neutral state because of significant electronic structural changes.ThePTZ derivative (10-Methyl-PTZ) named as PTZ-BT was designed and synthesized with...

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“…From a naïve point of view, thermoelectric transport in molecular junctions should accompany an effect of direct tunnelling through vacuum44. In order to quantify its possible influence on the measured junction properties, we analysed the conductance versus thermovoltage characteristics in detail.…”

Section: Discussionmentioning

confidence: 99%

Roles of vacuum tunnelling and contact mechanics in single-molecule thermopower

Tsutsui

Yokota

Morikawa

et al. 2017

Sci Rep

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Molecular junction is a chemically-defined nanostructure whose discrete electronic states are expected to render enhanced thermoelectric figure of merit suitable for energy-harvesting applications. Here, we report on geometrical dependence of thermoelectricity in metal-molecule-metal structures. We performed simultaneous measurements of the electrical conductance and thermovoltage of aromatic molecules having different anchoring groups at room temperature in vacuum. We elucidated the mutual contributions of vacuum tunnelling on thermoelectricity in the short molecular bridges. We also found stretching-induced thermoelectric voltage enhancement in thiol-linked single-molecule bridges along with absence of the pulling effects in diamine counterparts, thereby suggested that the electromechanical effect would be a rather universal phenomenon in Au-S anchored molecular junctions that undergo substantial metal-molecule contact elongation upon stretching. The present results provide a novel concept for molecular design to achieve high thermopower with single-molecule junctions.

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Quantitative Interpretations of Break Junction Conductance Histograms in Molecular Electron Transport

Cited by 27 publications

References 68 publications

Transition from Tunneling Leakage Current to Molecular Tunneling in Single-Molecule Junctions

Transition from Tunneling Leakage Current to Molecular Tunneling in Single-Molecule Junctions

Radical‐Enhanced Charge Transport in Single‐Molecule Phenothiazine Electrical Junctions

Roles of vacuum tunnelling and contact mechanics in single-molecule thermopower

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