Molecular Electronic Junctions

McCreery, Richard L.

doi:10.1021/cm049517q

Cited by 523 publications

(556 citation statements)

References 225 publications

(602 reference statements)

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“…sensors and biochips, 2,3 photovoltaics, 4,5 fuel cell, 6 biomaterials, 7 and molecular electronics, 4,8,9 as well as to provide fundamental understanding of electron transfer, 10 controlling reactions at surfaces, 11 and tailoring surface properties. 12 Among the many exciting developments, a number of rather sophisticated molecular assemblies have been developed that not only involve organic and organometallic molecules, but also nanomaterials and/or biomolecules.…”

Section: Simone Ciampimentioning

confidence: 99%

The molecular level modification of surfaces: from self-assembled monolayers to complex molecular assemblies

2011

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The modification of surfaces with self-assembled monolayers (SAMs) containing multiple different molecules, or containing molecules with multiple different functional components, or both, has become increasingly popular over the last two decades. This explosion of interest is primarily related to the ability to control the modification of interfaces with something approaching molecular level control and to the ability to characterise the molecular constructs by which the surface is modified. Over this time the level of sophistication of molecular constructs, and the level of knowledge related to how to fabricate molecular constructs on surfaces have advanced enormously. This critical review aims to guide researchers interested in modifying surfaces with a high degree of control to the use of organic layers. Highlighted are some of the issues to consider when working with SAMs, as well as some of the lessons learnt (169 references). 2011 The Royal Society of Chemistry. The modification of surfaces with self-assembled monolayers (SAMs) containing multiple different molecules, or containing molecules with multiple different functional components, or both, has become increasingly popular over the last two decades. This explosion of interest is primarily related to the ability to control the modification of interfaces with something approaching molecular level control and to the ability to characterise the molecular constructs by which the surface is modified. Over this time the level of sophistication of molecular constructs, and the level of knowledge related to how to fabricate molecular constructs on surfaces have advanced enormously. This critical review aims to guide researchers interested in modifying surfaces with a high degree of control to the use of organic layers. Highlighted are some of the issues to consider when working with SAMs, as well as some of the lessons learnt (169 references).

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Section: Simone Ciampimentioning

confidence: 99%

The molecular level modification of surfaces: from self-assembled monolayers to complex molecular assemblies

2011

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“…30 Frisbie et al 37 showed that the mechanism of charge transport in junctions with conjugated molecular wires changes from tunneling to hopping as the molecular length increases. Used a conducting tip of an atomic force microscope as the top contact, they measured the conductivities of a series of oligophenyleneimines (OPI), with lengths ranging from 1.5 to 7.3 nm, immobilized on gold bottom-electrodes.…”

Section: Mechanisms Of Charge Transport Across Sams Three Different mentioning

confidence: 99%

“…i) At high voltages across the SAM (V > ~ 2.0 V) the SAM-based junctions have a mechanism of charge transport (field emission) that is different from the mechanism at low voltages (hopping and tunneling). 30 The half-wave rectifier ( Figure 1D) incorporating these molecular diodes rectifies at input voltages less than 2.4 V, but does not rectify at high input voltages in the range of 2.4 -10 V (these voltages are specific to the circuit and depend on the choice of resistor). ii) In operation, these molecular diodes have large internal resistances (~10 6 Ω), suffer limited lifetimes (here 30-40 min in operation at 50 Hz), and break down outside of a relatively small window of applied bias (-5.0 to 2.2 V).…”

Section: Introductionmentioning

confidence: 99%

A Molecular Half-Wave Rectifier

et al. 2011

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The field of molecular electronics applies the techniques and principles derived from studying inorganic electronic devices to investigating charge transport in organic molecules. While electrical engineers routinely use both alternating current (AC) and direct current (DC) to characterize traditional semiconductor devices, researchers in molecular electronics have, so far, relied mainly on DC measurements. Here, we show that using AC signals to investigate charge transport in self-assembled monolayers (SAMs) yields new information, including information that could not be obtained using DC signals alone, and provides a straightforward means of comparing the performance of molecular diodes against that of diodes based on traditional semiconductor technology.This paper describes half-wave rectification of AC (50 Hz) signals by junctions based on SAMs. These junctions comprised SAMs of 11-(ferrocenyl)-1-undecanethiol (SC 11 Fc) or 11-(biferrocenyl)-1-undecanethiol (SC 11 Fc 2 ), supported on template-stripped Ag (Ag TS ) bottom electrodes, and contacted by top electrodes of eutectic indiumÀgallium (EGaIn, 75.5% Ga and 24.5% In by weight, 15.7 °C melting point, with a superficial layer of Ga 2 O 3 ; Figure 1). 1,2 Similar junctions based on SAMs of 1-undecanethiol (SC 10 CH 3 )-SAMs lacking the ferrocenyl terminal group-did not rectify AC signals.Previous experiments conducted using a DC bias of (1.0 V, and junctions based on SAMs of SC 11 Fc 1 and SC 11 Fc 2 , 3 yielded rectification ratios, R (defined by eq 1, where J is the current density (A/cm 2 ) and V is the voltage (V)), of >10 2 . These high values of R make it possible to conduct physical-organic studies to determine the mechanism(s) of charge transport across these SAMs. We show that these systems-which are, in fact, "molecular diodes"-can substitute for conventional diodes in a simple circuit-a half-wave rectifier (Figure 1)-that converts an input AC signal into an output DC signal. 4These molecular diodes, indeed, provide the basis for halfwave rectifiers. The circuits were stable for 30À40 min of operation, at a frequency of 50 Hz; this interval corresponds to more than 10 5 cycles. At low frequencies (∼1 Hz) and at large input voltages (∼5 V for SC 11 Fc and ∼10 V for SC 11 Fc 2 , see the Results and Discussion section), the junctions broke down more

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“…(10,11) The mechanisms (e.g., tunneling, inelastic hopping, or other processes) of CT through peptides are still incompletely defined, and have been variously suggested to depend on the length of the peptide, the presence of secondary structure, and the presence of specific side chains. (1,12,13) Rates of charge tunneling across SAMs composed of n-alkanethiolates have been studied extensively (14)(15)(16)(17)(18), and most commonly characterized using the parameters of the simplified Simmons equation (eq. 1).…”

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confidence: 99%

Charge Tunneling along Short Oligoglycine Chains

et al. 2015

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This work examines charge transport (CT) through self‐assembled monolayers (SAMs) of oligoglycines having an N‐terminal cysteine group that anchors the molecule to a gold substrate, and demonstrate that CT is rapid (relative to SAMs of n‐alkanethiolates). Comparisons of rates of charge transport‐using junctions with the structure AuTS/SAM//Ga2O3/EGaIn (across these SAMs of oligoglycines, and across SAMs of a number of structurally and electronically related molecules) established that rates of charge tunneling along SAMs of oligoglycines are comparable to that along SAMs of oligophenyl groups (of comparable length). The mechanism of tunneling in oligoglycines is compatible with superexchange, and involves interactions among high‐energy occupied orbitals in multiple, consecutive amide bonds, which may by separated by one to three methylene groups. This mechanistic conclusion is supported by density functional theory (DFT).

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Molecular Electronic Junctions

Cited by 523 publications

References 225 publications

The molecular level modification of surfaces: from self-assembled monolayers to complex molecular assemblies

The molecular level modification of surfaces: from self-assembled monolayers to complex molecular assemblies

A Molecular Half-Wave Rectifier

Charge Tunneling along Short Oligoglycine Chains

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