Thermoelectric properties of oligoglycine molecular wires

Hou, Songjun; Wu, Qingqing; Sadeghi, Hatef; Lambert, Colin J.

doi:10.1039/c8nr08878k

Cited by 15 publications

(11 citation statements)

References 49 publications

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“…To address the problem of increasing the thermoelectric performance of organic molecules, Finch et al 10 demonstrated theoretically that large values of the Seebeck coefficient could be obtained by creating transport resonances and anti-resonances within the HOMO-LUMO gap and tuning their energetic location relative to the Fermi energy. Following these pioneering works, several experimental [11][12][13][14][15][16][17][18][19][20] and theoretical studies [21][22][23][24][25][26][27][28][29][30][31][32][33][34] have attempted to probe and improve the thermoelectric performance of single molecules. However, progress has been hampered by the additional complexity of thermoelectric measurement set-ups, because unlike measurements of single-molecule conductance, Seebeck measurements require additional control and determination of temperature gradients at a molecular scale.…”

Section: Introductionmentioning

confidence: 99%

Molecular-scale thermoelectricity: as simple as ‘ABC’

et al. 2020

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Section: Introductionmentioning

confidence: 99%

Molecular-scale thermoelectricity: as simple as ‘ABC’

et al. 2020

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“…In sharp contrast, Venkataraman and co-workers reported much higher β values of 0.97 and 0.93 Å −1 in break junctions with oligoglycine and oligoglyalanine, respectively; 33 Lambert and co-workers reported high β values of 1.57 and 1.22 Å −1 for single molecules of oligoglycine with one or two Cys anchoring groups, respectively. 34 Off-resonant coherent tunneling was concluded to be the dominant charge transport mechanism in these break junctions; however, the molecules are forcefully stretched and therefore such experiments do not represent conduction across the molecules in their natural conformational state. Frisbie and co-workers found that substitution of the −CH 2 − units in alkanedithiol-based molecular junctions with −O− using conductive nanoprobes as top contacts increased the resistance of the junction but with small changes , respectively.…”

Section: ■ Introductionmentioning

confidence: 99%

Large Increase in the Dielectric Constant and Partial Loss of Coherence Increases Tunneling Rates across Molecular Wires

Chen

Salim

Zhang

et al. 2020

ACS Appl. Mater. Interfaces

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Although the dielectric behavior of monolayers is important in a large range of applications, its role in charge transport studies involving molecular junctions is largely ignored. This paper describes a large increase in the relative static dielectric constant (ε r ) by simply increasing the thickness of well-organized monolayers of oligoglycine and oligo(ethylene glycol) from 7 up to 14. The resulting large capacitance of 3.5−5.1 μF/cm 2 is thicknessindependent, which is highly attractive for field-effect transistor applications. This increase of ε r results in a linear increase of the thermal activation energy by a factor of 6, which suggests that the mechanism of charge transport gradually changes from coherent to (partially) incoherent tunneling. The comparisons of oligoglycine (which readily forms hydrogen bonds with neighboring molecules) and methyl terminated oligo(ethylene glycol) (which lacks hydrogen bond donors) monolayers, kinetic isotope effects, and relative humidity-dependent measurements all indicate the importance of strong hydrogen bonds involving ionic species and strongly bonded water in the unusual dielectric behavior and the incoherent tunneling mechanism. This partial loss of coherence of the charge carriers can explain the unusually small tunneling decay coefficients across long molecular wires, and the length-dependent increase of ε r of monolayers opens up interesting new applications.

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“…

Z T

can be thus considerably high only when

κ_{ph} \leq κ_{el}

. [ 45 ] Here we find that

κ_{ph} > κ_{el}

for σ‐saturated HDT junctions that are coupled to Au(100)NW, Au(5,3)NT and Au(7,3)NW, while

κ_{ph} ≪ κ_{el}

for π‐conjugated BDT based SMJs (see Figure 5c–f). In SMJs, the molecular states near the Fermi level influence the transmission function while the phonon vibrations can contribute to the thermal conductance.…”

Section: Resultsmentioning

confidence: 65%

“…In order to obtain the phononic part of the thermal conductance (

κ_{ph}

), the concept of dynamical matrix was exploited to compute the transmission probability of phonons,

τ_{ph} false(ω false)

, as implemented in the Gollum tool [ 43–45 ] so that

κ_{ph} = \frac{1}{2 π} \int_{0}^{\infty} d ω ℏ ω τ_{ph} false(ω false) [\frac{\partial f_{BE} (ω, T)}{\partial T}]

with

τ_{ph} false(ω false) = T r false[G_{C}^{r} (ω) Γ_{L} (ω) G_{C}^{a} (ω) Γ_{R} (ω) false]

, and

f_{BE}

{false[exp (\frac{ℏ ω}{k_{B} T}) - 1 false]}^{- 1}

being the Bose–Einstein distribution function.…”

Section: Methodsmentioning

confidence: 99%

Inelastic Tunnel Transport and Nanoscale Junction Thermoelectricity with Varying Electrode Topology

Roy

Sen

2021

Advcd Theory and Sims

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Intricacies in the charge transport behavior of single‐molecule junctions often revolve around the complex nature of orbital hybridization stemming from diversified metal‐molecule coupling at interfaces. It will hence be pertinent to fathom the myriad aspect of inelastic charge transport and nanoscale thermoelectricity in single‐molecule junctions. It is examined from first‐principles, achiral and chiral quasi‐1D electrodes to understand the role of junction heterogeneity in overall thermoelectric behavior during charge transport. This calculated inelastic electron tunneling spectra exhibit intense peaks in the low‐frequency regime (< 25 meV) with characteristic bending and rocking modes, which auger well with the available measured data. It is subsequently found that the thermopower can be as high as 212 µV K−1 for σ‐saturated molecular moieties, depending strongly on the configuration of electrodes. Besides, a majority of such single‐molecule junctions turn out to deviate from the Wiedemann–Franz law, leading to anomalies in the electronic thermal conductance. The authors' analysis suggests that as nanoscale electrodes, Au(111) nanowires are likely to render a relatively high thermoelectric figure of merit (ZT > 1) for a small molecular junction at room temperature. Discerning the diversity as driven exigently by the electrode topology may thus augment the device performance in terms of thermal stability at molecular scale.

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Thermoelectric properties of oligoglycine molecular wires

Abstract: We have investigated the electrical and thermoelectrical properties of glycine chains with and without cysteine terminal groups.

Cited by 15 publications

References 49 publications

Molecular-scale thermoelectricity: as simple as ‘ABC’

Molecular-scale thermoelectricity: as simple as ‘ABC’

Large Increase in the Dielectric Constant and Partial Loss of Coherence Increases Tunneling Rates across Molecular Wires

Inelastic Tunnel Transport and Nanoscale Junction Thermoelectricity with Varying Electrode Topology

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