Ab initio analysis of electron currents in thioalkanes

Seminario, Jorge M.; Yan, Liuming

doi:10.1002/qua.20384

Cited by 83 publications

(81 citation statements)

References 53 publications

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“…The 5d band region of Au (111), where we observe the occupied state A, was not considered by Zhu et al [11]. Density functional calculations of individual (standing-up) alkanethiols in contact with a gold substrate derive HOMO orbitals of the alkyl chain at about 3 eV binding energy [22,25]. However, conventional (UPS) photoemission data on alkanethiol SAMs do not yield evidence for any adsorbate induced state in this energy regime [26,27].…”

Section: Resultsmentioning

confidence: 90%

Two-photon photoemission from ex-situ prepared butanethiol SAMs on Au (111)

et al. 2011

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Section: Resultsmentioning

confidence: 90%

Two-photon photoemission from ex-situ prepared butanethiol SAMs on Au (111)

et al. 2011

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“…According to Eq. (2), this offset originates from the different end groups, -CH 3 versus -SH, yielding a different top contact contribution, r SAM PEDOT [5,6,9,[12][13][14]. The numbers imply a more transparent contact barrier, i.e.…”

Section: Discussionmentioning

confidence: 99%

Binary self-assembled monolayers: Apparent exponential dependence of resistance on average molecular length

Katsouras

Geskin

Kronemeijer

et al. 2011

Organic Electronics

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Binary self-assembled monolayers Katsouras, Ilias; Geskin, Victor; Kronemeijer, Auke J.; Blom, Paul W. M.; de Leeuw, Dago M. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. b s t r a c tWe investigate the electrical transport through mixed self-assembled monolayers of alkanemonothiols and alkanedithiols in large-area molecular junctions. To disentangle the role of the molecular length and the interfacial composition, monothiol-monothiol, dithiol-dithiol, and monothiol-dithiol binary combinations are studied. In all cases, we find that the resistance of these mixed SAMs appears to depend exponentially on the average number of carbon atoms, thus resembling monocomponent SAMs, whose resistance is known to depend exponentially on molecular length. However, in monocomponent SAMs this behavior has a single-molecule tunneling origin, which is not directly relevant for mixtures. Furthermore, in certain mixed SAMs the resistance decreases with increasing average layer thickness (the case of monothiol-dithiol systems). We suggest an explanation for the observed dependence of the resistance in the mixed SAMs on their composition within an equivalent circuit model based on a simple assumption concerning their microdomain structure. The simulated dependence is non-exponential but leads to a good agreement between calculated and measured resistances with only two fit parameters.

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“…The electrical transport through self-assembled monolayers of alkanedithiols was studied in large-area molecular junctions and described by the Simmons model [ [7][8][9] and theoretically (10)(11)(12)(13)(14)(15). Theoretical descriptions of electrical transport through molecular wires show that contacts, coupling of contacts to molecules, interface geometries, and vibrations are important in single-molecule experiments (16)(17)(18)(19)(20)(21).…”

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Electron tunneling through alkanedithiol self-assembled monolayers in large-area molecular junctions

Akkerman

Naber

Jongbloed

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

179

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The electrical transport through self-assembled monolayers of alkanedithiols was studied in large-area molecular junctions and described by the Simmons model [Simmons JG (1963) J Appl Phys 34:1793-1803 and 2581-2590] for tunneling through a practical barrier, i.e., a rectangular barrier with the image potential included. The strength of the image potential depends on the value of the dielectric constant. A value of 2.1 was determined from impedance measurements. The large and well defined areas of these molecular junctions allow for a simultaneous study of the capacitance and the tunneling current under operational conditions. Electrical transport for octanedithiol through tetradecanedithiol self-assembled monolayers up to 1 V can simultaneously be described by a single effective mass and a barrier height. There is no need for additional fit constants. The barrier heights are in the order of 4 -5 eV and vary systematically with the length of the molecules. Irrespective of the length of the molecules, an effective mass of 0.28 was determined, which is in excellent agreement with theoretical predictions. and consist of a saturated carbon backbone with one (or two) thiol end groups. Experimentally, the tunneling current through a monolayer of alkane(di)thiols was shown to be temperatureindependent and to decrease exponentially with increasing molecular length (4, 5). The transport has been interpreted in terms of the classical tunneling model through a thin insulating film as provided by Simmons (24,25). In this model the tunneling current depends on the mean value of the barrier height, allowing for a simplification of the problem of an arbitrarily shaped potential barrier to that of a rectangular barrier. This model has been applied to junctions based on SAMs (4, 26), but an extra fit parameter ␣ is needed to obtain a fit to the measured data. However, as already explained by Simmons (24, 25), for a practical tunnel junction the image potential has to be taken into account. This effect has been neglected in the literature so far.The system studied in this article is a tunnel junction with an alkanedithiol SAM as the insulating film, a bottom gold electrode, and a highly conducting polymer as a top contact. The polymeric top contact allows for the fabrication of devices with a yield of almost unity for areas up to 100 m in diameter (5). The highly conducting polymer used is PEDOT:PSS, a waterbased suspension of poly(3,4-ethylenedioxythiophene) stabilized with poly(4-styrenesulfonic acid). The polymer acts as a cushion for the thermally evaporated metal atoms to land on and prevents the metal atoms from penetration into the molecular layer. Consequently, the formation of electrical shorts is prevented (27). Simmons ModelThe tunneling current density J through a rectangular potential barrier with height 0 is given by (4, 24, 26):wherewhere ⌬s is the barrier width at the Fermi level of the electrodes, here equal to the total length s of the tunneling path between the electrodes, m e is the bare electron mass, V is th...

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Ab initio analysis of electron currents in thioalkanes

Cited by 83 publications

References 53 publications

Two-photon photoemission from ex-situ prepared butanethiol SAMs on Au (111)

Two-photon photoemission from ex-situ prepared butanethiol SAMs on Au (111)

Binary self-assembled monolayers: Apparent exponential dependence of resistance on average molecular length

Electron tunneling through alkanedithiol self-assembled monolayers in large-area molecular junctions

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