Amine−Gold Linked Single-Molecule Circuits:  Experiment and Theory

Quek, Su Ying; Venkataraman, Latha; Choi, Hyoung Joon; Louie, Steven G.; Hybertsen, Mark S.; Neaton, Jeffrey B.

doi:10.1021/nl072058i

Cited by 471 publications

(792 citation statements)

References 31 publications

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“…Since we obtain the energies of the HOMO and LUMO from CDFT total energies, we can shift the DFT eigenvalues to lie at these energies by means of a SCO 59,60,[72][73][74][75] method. This has been shown to improve G when compared to experimental data.…”

Section: Scissor Operator Methodsmentioning

confidence: 99%

“…In the full Hamiltonian matrix we then replace the subblock H 0 mol with H SCO mol . 59,60,[73][74][75] The SCO procedure can be applied self-consistently, although in this work we apply it non-selfconsistently to the converged DFT Hamiltonian.…”

Section: Scissor Operator Methodsmentioning

confidence: 99%

“…This is particularly critical in the case of molecular junctions, where the system can be considerably large due to the presence of the metal electrodes. Therefore, different alternative approaches and corrections have been proposed to improve the description of the energy level alignment, for instance, corrections for self-interaction (SI) errors, 13,58 scissor operator (SCO) schemes 35,48,52,59,60 and constrained-DFT (CDFT). 61 In the present work we investigate, by means of total energy DFT and quantum transport calculations, the stability and conductivity of thiol and thiolate molecular junctions.…”

Section: Introductionmentioning

confidence: 99%

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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: Scissor Operator Methodsmentioning

confidence: 99%

Section: Scissor Operator Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2014

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“…To overcome the well-known problem of DFT to describe molecular energy levels we have used the DFT+ Sigma scheme to correct the DFT eigenvalues as described in previous studies. 40,41 In brief, the DFT Hamiltonian of the contacted molecule is first diagonalized to obtain the molecular orbitals. The energy of each orbital is then shifted by a sum of two terms, the first accounting for the self-interaction error in DFT and ensures the correct ionization potential and electron affinity is obtained for the molecule in the gas phase, and the second term accounts for the image charge formed in the electrodes which is completely missing in standard DFT.…”

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confidence: 99%

Electrochemical Control of Single-Molecule Conductance by Fermi-Level Tuning and Conjugation Switching

et al. 2014

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Controlling charge transport through a single molecule connected to metallic electrodes remains one of the most fundamental challenges of nanoelectronics. Here we use electrochemical gating to reversibly tune the conductance of two different organic molecules, both containing anthraquinone (AQ) centers, over >1 order of magnitude. For electrode potentials outside the redox-active region, the effect of the gate is simply to shift the molecular energy levels relative to the metal Fermi level. At the redox potential, the conductance changes abruptly as the AQ unit is oxidized/reduced with an accompanying change in the conjugation pattern between linear and cross conjugation. The most significant change in conductance is observed when the electron pathway connecting the two electrodes is via the AQ unit. This is consistent with the expected occurrence of destructive quantum interference in that case. The experimental results are supported by an excellent agreement with ab initio transport calculations.

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“…7 Au-pyridyl contacts, such as the Au-44BP bond, have been shown to provide reproducible junctions for which two conductance values can be distinguished due to different binding geometries. [8][9][10] However, despite significant progress investigating different chemical linker groups 9,[11][12][13][14][15][16][17][18] there have been few previous attempts to broaden the range of metal electrodes studied.…”

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confidence: 99%

Single-Molecule Electrochemical Transistor Utilizing a Nickel-Pyridyl Spinterface

et al. 2014

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Using a scanning tunnelling microscope break-junction technique, we produce 4,4'-bipyridine (44BP) single-molecule junctions with Ni and Au contacts. Electrochemical control is used to prevent Ni oxidation, and to modulate the conductance of the devices via non-redox gating -the first time this has been shown using non-Au contacts. Remarkably the conductance and gain of the resulting Ni-44BP-Ni electrochemical transistors is significantly higher than analogous Au-based devices. Ab-initio calculations reveal that this behaviour arises because charge transport is mediated by spin-polarized Ni d -electrons, which hybridize strongly with molecular orbitals to form a 'spinterface'.Our results highlight the important role of the contact material for single-molecule devices, and show that it can be varied to provide control of charge and spin transport. KeywordsSingle-molecule, Break-junction, Electrochemical gating, Spintronics, Density functional theory, Metal-molecule interface Main TextSingle-molecule transistor behaviour can be achieved using a gate electrode to control the energy levels of a molecule bridging two metallic electrodes. 1 This gate can be provided electrochemically using the double layer potential existing at the metal-electrolyte interface (Fig. 1a). An electrochemical gate avoids the complex fabrication of solid-state threeterminal molecular devices, can operate in room temperature liquid environments, and can produce high gate efficiencies thanks to the large electric fields which are achievable. There has been significant interest in redox active molecules such as viologens as candidates for electrochemical transistors, 2-4 however the gating of non-redox molecules has only recently been demonstrated using Au electrodes by Li et al. 5 with 4,4'-bipyridine (44BP) molecules,

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Amine−Gold Linked Single-Molecule Circuits: Experiment and Theory

Cited by 471 publications

References 31 publications

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

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

Electrochemical Control of Single-Molecule Conductance by Fermi-Level Tuning and Conjugation Switching

Single-Molecule Electrochemical Transistor Utilizing a Nickel-Pyridyl Spinterface

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