Electrical characteristics of conjugated self-assembled monolayers in large-area molecular junctions

Kronemeijer, Auke Jisk; Huisman, E. H.; Akkerman, Hylke B.; Goossens, Albert; Katsouras, Ilias; Hal, Paul A. van; Geuns, Tom C. T.; Molen, Sense Jan van der; Blom, Paul W. M.; Leeuw, Dago M. de

doi:10.1063/1.3503607

Cited by 29 publications

(39 citation statements)

References 34 publications

(44 reference statements)

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“…16,21,37,38 RESULTS AND DISCUSSION these values agree with previous experimental reports using single-molecule and large-area junctions. 27,[38][39][40][41][42][43][44][45] These results presented here also agree with theoretical calculations by Ratner and coworkers; these authors predict (using density functional theory, DFT) a value of  = ~0.3 Å -1 for SAMs of polyphenyldithiolates by assuming a continuous conjugation of the molecules with the metal electrodes. 17 We compared the electrical properties of SAMs of SPh n to SAMs of C≡CPh n on Au TS (Figure 2b).…”

Section: Introductionsupporting

confidence: 81%

“…They form structures that are highly-ordered and densely-packed on both silver and gold substrates. [22][23][24][25][26][27][28] (The exception is thiophenol (HSPh) which has been reported to form poorly defined SAMs, possibly due to the weak intermolecular forces between the aromatic rings. 22,24,29 ) The surface structure of thiolates on metal is the same for SAMs of alkanethiolates and SAMs of aromatics ((√3 x √3)R30º on gold and (√7 ×√7)R10.9ºon silver), but the cant angle (α) for the aromatics is slightly less than that of the alkanethiolates (α = ~20º for SAMs of terphenylthiol on Au and α = ~30º for SAMs of alkanethiols on Au).…”

Section: Introductionmentioning

confidence: 99%

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Tunneling across SAMs Containing Oligophenyl Groups

et al. 2016

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This paper describes rates of charge tunneling across self-assembled monolayers (SAMs) of compounds containing oligophenyl groups, supported on gold and silver, using Ga 2 O 3 /EGaIn as the top electrode. It compares the injection current, J 0 , and the attenuation constant, β, of the simplified Simmons equation, across oligophenyl groups (R = Ph n ; n = 1, 2, 3), with three different anchoring groups (thiol, HSR; methanethiol, HSCH 2 R; and acetylene, HC≡CR) that attach R to the template-stripped gold and silver substrates. The results demonstrate that the structure of the molecules between the anchoring group (-S-or -C≡C-) and the oligophenyl moiety significantly influences charge transport. SAMs of SPh n , and C≡CPh n on gold show similar values of β and log|J 0 | (β = 0.28 ± 0.03 Å -1 and log|J 0 | = 2.7 ± 0.1 for Au/SPh n ; β = 0.30 ± 0.02 Å -1 and log|J 0 | = 3.0 ± 0.1 for Au/C≡CPh n ). The introduction of a single intervening methylene (CH 2 ) group, between the anchoring sulfur atom and the aromatic units to generate SAMs of SCH 2 Ph n , increases β to ~0.6 Å -1 on both gold and silver substrates. (For nalkanethiolates on gold the corresponding values are β = 0.76 Å -1 and log|J 0 | = 4.2). As a generalization, based on this and other work, it seems that increasing the height of the tunneling barrier in the region of the interfaces increases β, and may decrease J 0 ; by contrast, it appears that lowering the height of the barrier at these interfaces has little influence on β or J 0 .

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Section: Introductionsupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Tunneling across SAMs Containing Oligophenyl Groups

et al. 2016

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“…For this distance range, there is general agreement that the conductance scales exponentially with length, with an attenuation coefficient (β), defined as the slope of ln J vs. thickness (d), equal to 8 to 9 nm −1 for aliphatic molecules (3-6) and 2-3 nm −1 for aromatic molecules (7)(8)(9)(10)(11)(12)(13)(14). A few molecular electronic systems have been investigated beyond 5 nm (15,16), some of which exhibit a decrease in β to less than 1 nm −1 .…”

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confidence: 99%

Activationless charge transport across 4.5 to 22 nm in molecular electronic junctions

Yan

Bergren

McCreery

et al. 2013

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

150

259

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In this work, we bridge the gap between short-range tunneling in molecular junctions and activated hopping in bulk organic films, and greatly extend the distance range of charge transport in molecular electronic devices. Three distinct transport mechanisms were observed for 4.5-22-nm-thick oligo(thiophene) layers between carbon contacts, with tunneling operative when d < 8 nm, activated hopping when d > 16 nm for high temperatures and low bias, and a third mechanism consistent with field-induced ionization of highest occupied molecular orbitals or interface states to generate charge carriers when d = 8-22 nm. Transport in the 8-22-nm range is weakly temperature dependent, with a field-dependent activation barrier that becomes negligible at moderate bias. We thus report here a unique, activationless transport mechanism, operative over 8-22-nm distances without involving hopping, which severely limits carrier mobility and device lifetime in organic semiconductors. Charge transport in molecular electronic junctions can thus be effective for transport distances significantly greater than the 1-5 nm associated with quantum-mechanical tunneling.all-carbon molecular junction | attenuation coefficient | field ionization | strong electronic coupling C harge transport mechanisms in organic and molecular electronics underlie the ultimate functionality of a new generation of electronic devices. Understanding, controlling, and designing molecular devices for use as practical components requires an intimate knowledge of the system energy levels and operative transport mechanisms, and how key variables such as molecule length, identity, temperature, etc., affect device performance parameters. Especially interesting in this context is the relationship between organic electronic devices, which typically have active layer thicknesses of tens to hundreds of nanometers, and molecular electronic devices reported to date, in which at least one dimension for charge propagation is below 10 nm. Indeed, many types of functional organic electronic devices have been demonstrated, including thinfilm transistors, organic light-emitting diodes, and memory cells (1, 2). Bridging the gap between organic and molecular devices may therefore reveal pathways for improving the performance of such devices, or even lead to new types of devices based on alternative transport mechanisms.The great majority of molecular electronic devices investigated to date have transport distances of <5 nm between the contacts, where the prevalent transport mechanism is quantum-mechanical tunneling. For this distance range, there is general agreement that the conductance scales exponentially with length, with an attenuation coefficient (β), defined as the slope of ln J vs. thickness (d), equal to 8 to 9 nm −1 for aliphatic molecules (3-6) and 2-3 nm −1 for aromatic molecules (7)(8)(9)(10)(11)(12)(13)(14). A few molecular electronic systems have been investigated beyond 5 nm (15, 16), some of which exhibit a decrease in β to less than 1 nm −1 . Such small values of β ar...

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“…Published values for conjugated molecules shorter than 3 nm in single molecule and large scale self-assembled junctions range from 0.04 -0.61 Å -1 . [49] The structures of the molecules discussed in this section (2.3.2) are given on the next page (page 33). ,4'-(anthracene-2,6-diylbis(ethyne-2,1-diyl))dibenzenethiol (7), 2,6-bis((4-mercaptophenyl)ethynyl)anthracene-9,10-dione (8) and 4,4'-((9,10-dihydroanthracene-2,6-…”

Section: -Conjugated Moleculesmentioning

confidence: 99%

“…De Leeuw and co-workers performed a systematic lengthdependent study on SAMs of -conjugated oligo-para-phenylene dithiols (10) and monothiols (11), with an increasing number of phenylene rings. [30,49] The molecules investigated were 1,4-benzenedithiol (10a),…”

Section: Pedot:pss Tunneling Junctionsmentioning

confidence: 99%

Supramolecular tunneling junctions

Wimbush

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Electrical characteristics of conjugated self-assembled monolayers in large-area molecular junctions

Cited by 29 publications

References 34 publications

Tunneling across SAMs Containing Oligophenyl Groups

Tunneling across SAMs Containing Oligophenyl Groups

Activationless charge transport across 4.5 to 22 nm in molecular electronic junctions

Supramolecular tunneling junctions

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