Nonlinear conductance in molecular devices: Molecular length dependence

Crljen, Željko; Grigoriev, Anton; Wendin, Göran; Stokbro, Kurt

doi:10.1103/physrevb.71.165316

Cited by 83 publications

(68 citation statements)

References 37 publications

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“…2 of the calculations presented in this paper clearly demonstrate the slightly asymmetric curves with respect to reversed bias voltages, as opposed to the results presented in Ref. 36, where the curves were symmetric with respect to bias direction. In addition, a part of the difference in the I-V curves arises due the combination of different pseudopotentials, basis sets, and exchangecorrelation flavors ͑LDA in Ref.…”

Section: A Wire Elongationcontrasting

confidence: 50%

“…2. It is interesting to compare it with the one previously reported for OPV3, 36 also shown in the upper panel of Fig. 2.…”

Section: A Wire Elongationmentioning

confidence: 63%

“…In addition, a part of the difference in the I-V curves arises due the combination of different pseudopotentials, basis sets, and exchangecorrelation flavors ͑LDA in Ref. 36 vs GGA here͒, and in particular due to the different partition of the system into the two leads and extended molecule.…”

Section: A Wire Elongationmentioning

confidence: 99%

“…The calculations in Ref. 36 employed symmetric electrodes with molecule adsorbed symmetrically in hollow fcc positions on both electrodes. In the present calculations due to the adopted geometry of the unit cell the molecule is adsorbed in fcc hollow position at one electrode, and in the hcp hollow position at the opposite one.…”

Section: A Wire Elongationmentioning

confidence: 99%

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Conductance of a phenylene-vinylene molecular wire: Contact gap and tilt angle dependence

et al. 2010

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Charge transport through a molecular junction comprising an oligomer of p-phenylene-vinylene between gold contacts has been investigated using density-functional theory and the nonequilibrium Green's function method. The influence of the contact gap geometry on the transport has been studied for elongated and contracted gaps, as well as various molecular conformations. The calculated current-voltage characteristics show an unusual increase in the low bias conductance with the contact separation. In contrast, for compressed junctions the conductance displays only a very weak dependence on both the separation and related molecular conformation. However, if the contraction of the gap between the electrodes is accommodated by tilting the molecule, the conductance will increase with the tilting angle, in line with experimental observations. It is demonstrated that the effect of tilting on transport can be interpreted in a similar way to the case of the stretching the junction with a molecule in an upright position. The lowest conductance was observed for the equilibrium gap geometry. With the dominant transport contribution arising from the system of the frontier junction orbitals, all the predicted increases in the conductance arise simply from the better band alignment between relevant frontier orbitals at the nonequilibrium geometries at the expense of weaker coupling with the contacts.

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Section: A Wire Elongationcontrasting

confidence: 50%

“…2. It is interesting to compare it with the one previously reported for OPV3, 36 also shown in the upper panel of Fig. 2.…”

Section: A Wire Elongationmentioning

confidence: 63%

Section: A Wire Elongationmentioning

confidence: 99%

Section: A Wire Elongationmentioning

confidence: 99%

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Conductance of a phenylene-vinylene molecular wire: Contact gap and tilt angle dependence

et al. 2010

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“…The difference between the electrochemical potentials µ L/R , of the left and right electrodes, respectively, is µ L − µ R = eV b . The computational procedure used was described extensively elsewhere 5 . The molecular electronic system considered consisted of a monolayer of molecules coupled to two semi-infinite electrodes, as depicted in Fig.1 for hexayne.…”

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confidence: 99%

Unusual Conductance of Polyyne-Based Molecular Wires

Crljen¹,

Baranović²

2007

Phys. Rev. Lett.

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We report a full self-consistent ab initio calculation of the current-voltage curve and the conductance of thiolate capped polyynes in contact with gold electrodes. We find the conductance of polyynes an order of magnitude larger compared with other conjugated oligomers. The reason lies in the position of the Fermi level deep in the HOMO related resonance. With the conductance weakly dependent on the applied bias and almost independent of the length of the molecular chain, polyynes appear as nearly perfect molecular wires. The study of transport properties of single molecules have attracted a significant attention because of their potential use in molecular electronic devices.One of the major classes of molecules considered in conductivity studies, primarily for their molecular wire behavior, 1,2,3,4,5 is conjugated oligomers. They have shown a number of useful nonlinear properties such as conductance switching and negative differential resistance.6,7 However, inspite of a number of interesting experiments 4,8 a molecule with good molecular wire properties has not yet been spotted.A useful molecular wire should provide a high and stable conductance over a wide bias region and for various lengths of the molecules. A linear chain of carbon atoms with double bonds between neighboring atoms, usually referred to as cumulene, was proposed as an ideal molecular wire 1 and the calculations of the conductance of cumulene connected to gold electrodes were reported. 9,10Lang and Avouris 9 showed that the conductance of cumulene did not stay constant in the ballistic regime, but rather oscillated between the constant values characteristics of the odd and even number of atoms in the chain.In this paper we show an entirely different behavior of polyynes, another form of the carbon atom chain. Polyynes are simple and yet most intriguing of conjugated organic oligomers. Only recently, have they been assembled up to decayne.11 Formed as a linear chain of carbon atom pairs (CC) n , with alternating single and triple bonds, they are a unique, truly one-dimensional, molecular system. Two π-electron systems of the sphybridized structure provide polyyne with approximately cylindrical electronic delocalization along the conjugated backbone. The electronic transport is therefore independent of the rotation around the single bond, which is a limitation often present in other organic oligomers. 7We have obtained the electronic structure and transport properties of a series of polyynes up to octayne, connected to gold electrodes. The stability of polyyne with respect to single-and triple-bond alternations was achieved by fixing the molecule at the ends with thiol bonds. In addition, the thiol capped polyynes make a strong chemisorption bond onto the metallic electrodes. We found that they had more than an order of magnitude higher conductance when compared with other conjugated oligomers. In contrast to the cumulenes they were not prone to oscillations in conductance with the length of the molecule. We also found that their conductance wa...

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Fermi Level Pinning and Orbital Polarization Effects in Molecular Junctions: The Role of Metal Induced Gap States

Dyck

Geskin

Cornil

2014

Adv Funct Materials

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Understanding the alignment of molecular orbitals and corresponding transmission peaks with respect to the Fermi level of the electrodes is a major challenge in the fi eld of molecular electronics. In order to design functional devices, it is of utmost importance to assess whether controlled changes in the electronic structure of isolated compounds are preserved once they are inserted in the molecular junctions. Here, light is shed on this central issue by performing density functional theory calculations on junctions including diarylethene-based molecules. It is demonstrated that the chemical potential equalization principle allows to rationalize the existence or not of a Fermi level pinning (i.e., same alignment in spite of a varying ionization potential in the isolated compounds), pointing to the essential role played by metal induced gap states (MIGS). It is further evidenced that the degree of level pinning is intimately linked to the degree of orbital polarization when a bias is applied between the two electrodes.

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Nonlinear conductance in molecular devices: Molecular length dependence

Cited by 83 publications

References 37 publications

Conductance of a phenylene-vinylene molecular wire: Contact gap and tilt angle dependence

Conductance of a phenylene-vinylene molecular wire: Contact gap and tilt angle dependence

Unusual Conductance of Polyyne-Based Molecular Wires

Fermi Level Pinning and Orbital Polarization Effects in Molecular Junctions: The Role of Metal Induced Gap States

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