Attenuation Factors in Molecular Electronics: Some Theoretical Concepts

Dappe, Yannick J.

doi:10.3390/app10186162

Cited by 6 publications

(11 citation statements)

References 49 publications

(65 reference statements)

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“…By contrast, in our present work with OPE bridges, the presence of triple carbon bonds leads to a delocalization of the electronic density, which couples strongly to the gold electrodes. This result confirms a general trend previously noted that molecular wires featuring aromatic rings linked by acetylene groups (i.e., OPEs) present a better coupling to the electrode due to a more significant electronic delocalization than oligo-phenyl molecular wires where the electronic density is more localized on the molecular rings …”

Section: Resultssupporting

confidence: 91%

“…This result confirms a general trend previously noted that molecular wires featuring aromatic rings linked by acetylene groups (i.e., OPEs) present a better coupling to the electrode due to a more significant electronic delocalization than oligo-phenyl molecular wires where the electronic density is more localized on the molecular rings. 62 Conductance of Methyl Sulfide-Terminated OPE Molecules. To further confirm the effect of asymmetric electrode contacting on the length dependence of OPE-based molecules, we replaced the amine termination with the methyl sulfide group and measured the conductance of each MJ.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Asymmetric Effect on the Length Dependence of Oligo(Phenylene ethynylene)-Based Molecular Junctions

et al. 2022

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It is well known that the electrical conductance of molecular junctions in the tunneling regime varies exponentially with the length of the molecular backbone. This behavior is strongly influenced by anchoring groups, which connect the molecular backbone to the electrodes and locate the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) resonances with respect to the Fermi level. Nevertheless, most of the studies have been performed on symmetric junctions, namely, using the same electrodes and anchoring groups at both sides of the junctions. Only recently, there have been some reports detailing the influence of introducing asymmetry into single-molecule junctions, using different contacts or different anchoring groups at either end of the molecular bridge. These studies have revealed that such junction asymmetry strongly impacts electrical characteristics. In this study, Au and graphene electrodes were used to provide asymmetry to a single-molecule junction. The conductance and length dependence of amine and methyl sulfide-terminated oligo(phenylene ethynylene) have been determined experimentally and theoretically. The impact of introducing this asymmetry has been quantified by comparing the conductance and β values of oligo(phenylene ethynylene) (OPE)-based molecules within Au/Au electrodes and Au/graphene junctions, respectively. Our results show that the introduction of a graphene electrode leads to lower conductance values and attenuation factors, similar to what has been previously observed in alkane chains. This is attributed to a shift of the electronic molecular levels toward the Fermi level, mainly driven by acetylene groups linking adjacent phenyl groups.

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Section: Resultssupporting

confidence: 91%

Section: ■ Results and Discussionmentioning

confidence: 99%

Asymmetric Effect on the Length Dependence of Oligo(Phenylene ethynylene)-Based Molecular Junctions

et al. 2022

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“…β lies between zero (for pure metallic junctions) and 25 nm −1 (for vacuum as complete attenuation occurs). 17 The area specific intrinsic conductance expression is obtained by differentiating the current density of eq for the limiting cathodic or anodic potential regime (viz., E → E 0 ′) and is obtained as…”

Section: Interfacial Conductance and Contact Resistancementioning

confidence: 99%

“…The theoretical understanding of long-range electron transfer (LRET) between a metal electrode and redox active centers separated through protein or molecular wires is important for photosynthesis, respiration, molecular rectifiers, and redox enzyme catalysis phenomena. − The LRET phenomena at the molecular self-assemble monolayer (SAM) covered metal electrode/organic–inorganic electroactive molecular interface is trending in current research to design the functional and efficient interfaces in molecular optoelectronic devices like molecular rectifiers, light-emitting diodes, organic field-effect transistors, solar cells, and electrocatalysts. − Despite the significant relevance of molecular self-assembly over metal surfaces, few theoretical results are available regarding the role of the metal, interfacial molecular dipoles, electroactive molecules, and quantitative description of the alignment of energy levels at the transition state. − The few existing computational and experimental works, highlighting the influence of molecular self-assembly and the nature of the metal on the ET process, are mostly qualitative in nature. − …”

Section: Introductionmentioning

confidence: 99%

Semi-microscopic Theory for the Current Rectification Phenomenon in Nanogap Molecular Devices

Mishra

Kant

2023

J. Phys. Chem. A

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A semi-microscopic theory is developed for heterogeneous electron transfer (HET) kinetics based on the energy level alignment approach at self-assembled monolayer (SAM) covered metal electrodes. Theory provides the electronic and molecular property-dependent equations for the HET rate constant (k 0) and the transfer coefficient (α) for potential. k 0 is formulated using the activation free energy as a product of the SAM covered metal work function (WF) and fractional electronic charge exchanged at the transition state (attained through the alignment of the frontier molecular orbital (FMO) energy level of the electroactive group with the WF of metal). k 0 is a function of the metal jellium electronic screening length and dielectric and of the molecular self-assembly (through its dipole moment, size, and packing density) and the FMO energies of electroactive groups. The operative potential at the transition state is governed by α, which is a function of molecular spacer length and characteristic electronic-dipolar coupling length. The current rectification phenomenon in nanogap molecular devices is theoretically analyzed using equations for k 0 and α for SAM covered source and drain electrodes. Theory unravels the LUMO or HOMO dichotomy for a given metal: (i) for the HOMO assisted ET, the metal with a high WF has a high current rectification ratio (RR), while (ii) for the LUMO assisted ET, the metal with a low WF has a high current RR in asymmetrical devices. Theory predicts the reversal in current rectification by altering the dipole moment of the anchoring molecule, the HOMO/LUMO energy of the electroactive groups, and the nature of the metal. Finally, theory shows qualitative and quantitative coherence with the reported experimental current–potential response of molecular device.

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“…This special issue aims at showcasing some of the many facets of research in molecular electronics and surveying the latest advances in the field. It contains seven studies, including five research papers [1][2][3][4][5] and two reviews [6,7], which span different areas of the field from both a theoretical and experimental perspective.…”

mentioning

confidence: 99%