Resistance of Alkanethiol Molecular Wires

Kaun, Chao-Cheng; Guo, Hong

doi:10.1021/nl0346023

Cited by 158 publications

(181 citation statements)

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“…The conductance of alkanedithiol-Au junctions has been studied extensively using density functional theory (DFT)-based transport calculations [38][39][40]. By varying the alkyl chain length for a fixed molecular tilt angle a value for β was obtained in good agreement with experiment [38]. However, the calculated conductance is typically larger than the measured value [38][39][40].…”

Section: Influence Of S-au Bonding On Tunnelingmentioning

confidence: 99%

Mechanical and Charge Transport Properties of Alkanethiol Self-Assembled Monolayers on a Au(111) Surface: The Role of Molecular Tilt

Ratera

Park

et al. 2008

Langmuir

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ABSTRACT:The relationship between charge transport and mechanical properties of alkanethiol selfassembled monolayers (SAM) on Au(111) films has been investigated using an atomic force microscope with a conductive tip. Molecular tilts induced by the pressure applied by the tip cause stepwise increases in film conductivity. A decay constant β = 0.57 ± 0.03 Å -1 was found for the current passing through the film as a function of tip-substrate separation due to this molecular tilt. This is significantly smaller than the value of ~1 Å -1 found when the separation is changed by changing the length of the alkanethiol molecules. Calculations indicate that for isolated dithiol molecules S-bonded to hollow sites, the junction conductance does not vary significantly as a function of molecular tilt. The impact of S-Au bonding on SAM conductance is discussed.

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Section: Influence Of S-au Bonding On Tunnelingmentioning

confidence: 99%

Mechanical and Charge Transport Properties of Alkanethiol Self-Assembled Monolayers on a Au(111) Surface: The Role of Molecular Tilt

Ratera

Park

et al. 2008

Langmuir

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“…Alkane chains are standard molecules in which electron transport has been studied extensively. [15][16][17][18][19][20][21][22] The main result of those prior studies is that the current decays exponentially with chain length with a decay constant β ∼ 1.0 per CH 2 unit, with some variation across different experiments. [15][16][17][18][19]23 This dependence has been also successfully addressed computationally using Density Functional Theory (DFT) combined with non-equilibrium Green's function (NEGF) studies.…”

Section: Introductionmentioning

confidence: 99%

Charge Transport Across Insulating Self-Assembled Monolayers: Non-equilibrium Approaches and Modeling To Relate Current and Molecular Structure

et al. 2014

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This paper examines charge transport by tunneling across a series of electrically (insulating molecules with the structure HS(CH 2 ) 4 CONH(CH 2 ) 2 R) in the form of selfassembled monolayers (SAMs), supported on silver. The molecules examined were studied experimentally by Yoon et al. (Angew. Chem. Int. Ed., 51, 4658−4661, 2012), using junctions of the structure AgS(CH 2 ) 4 CONH(CH 2 ) 2 R//Ga 2 O 3 /EGaIn. The tail group R had approximately the same length for all molecules, but a range of different structures. Changing the R entity over a range of different structures (aliphatic to aromatic) does not influence the conductance significantly. To rationalize this surprising result, we investigate transport through these SAMs theoretically, using both full quantum methods and a generic, independent-electron tight-binding toy model. We find that the frontier orbitals HOMO, HOMO-1, HOMO-2 and HOMO-3, have similar structures for all of the different R-groups, and that the HOMO, which is largely responsible for the transport in these molecules, is always strongly localized on the thiol group. The relative insensitivity of the current density to the structure of the R group is due not only to these similar frontier orbitals but also to a combination of energy levels (ε) and tunneling amplitudes (t), which lead to similar conductance for different tail groups, i.e. the large difference between ε's in conjugated and saturated groups is compensated by tunneling amplitudes inside the tail group. In addition, the coupling of the tail group to the alkane chain is much weaker for conjugated groups than for saturated ones. Conductance change in these molecules is not influenced by the broadening of the molecular levels connected to the left and right electrodes, since in all these molecules the effective coupling to the silver substrate is the same, whereas the other effective couplings are determined by the weak connection to the oxide Ga 2 O 3 layer. All these factors combine to produce currents largely insensitive to the R group.An estimation of the attenuation constant, β, of the simplified Simmons equation obtained using these methods is β = 1.1 per CH 2 group, in good agreement with observed results. Our analysis sketches the potential landscapes across which tunneling occurs, and suggests that it will be difficult to change rates of tunneling by simple changes 2 in molecular structure. This work indicates that significant control over SAMs largely composed of nominally insulating groups may be possible when tail groups are used that are significantly larger than those used in the experiments of Yoon et al. 13

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“…Their results are in accordance with our calculation shown in Figure 5(b). In addition, Kaun's calculation suggests that transport accurs through HOMO [39] while our results show transport might accur through LUMO in alkanedithiolgold junctions. On the other hand, the conductance in gold-BDT-gold junction is larger than the one in alkanedithiol junctions.…”

Section: Analysis On Density Of States (Dos)mentioning

confidence: 40%

First-principles calculation of the transport properties of molecular wires between Au clusters under equilibrium

et al. 2005

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Resistance of Alkanethiol Molecular Wires

Cited by 158 publications

References 24 publications

Mechanical and Charge Transport Properties of Alkanethiol Self-Assembled Monolayers on a Au(111) Surface: The Role of Molecular Tilt

Mechanical and Charge Transport Properties of Alkanethiol Self-Assembled Monolayers on a Au(111) Surface: The Role of Molecular Tilt

Charge Transport Across Insulating Self-Assembled Monolayers: Non-equilibrium Approaches and Modeling To Relate Current and Molecular Structure

First-principles calculation of the transport properties of molecular wires between Au clusters under equilibrium

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