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1 pages, 156 KiB

Open AccessEditorial

Molecular Electronics

by Linda A. Zotti

Appl. Sci. 2021, 11(11), 4828; https://doi.org/10.3390/app11114828 - 25 May 2021

Cited by 3 | Viewed by 1873

Abstract

The field of molecular electronics is currently experiencing a renaissance [...] Full article

(This article belongs to the Special Issue Molecular Electronics)

Research

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12 pages, 1583 KiB

Open AccessArticle

The Role of Metal Ions in the Electron Transport through Azurin-Based Junctions

by Carlos Romero-Muñiz, María Ortega, Jose Guilherme Vilhena, Rubén Pérez, Juan Carlos Cuevas and Linda A. Zotti

Appl. Sci. 2021, 11(9), 3732; https://doi.org/10.3390/app11093732 - 21 Apr 2021

Cited by 7 | Viewed by 3145

Abstract

We studied the coherent electron transport through metal–protein–metal junctions based on a blue copper azurin, in which the copper ion was replaced by three different metal ions (Co, Ni and Zn). Our results show that neither the protein structure nor the transmission at [...] Read more.

We studied the coherent electron transport through metal–protein–metal junctions based on a blue copper azurin, in which the copper ion was replaced by three different metal ions (Co, Ni and Zn). Our results show that neither the protein structure nor the transmission at the Fermi level change significantly upon metal replacement. The discrepancy with previous experimental observations suggests that the transport mechanism taking place in these types of junctions is probably not fully coherent. Full article

(This article belongs to the Special Issue Molecular Electronics)

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18 pages, 6110 KiB

Open AccessArticle

Tuning Single-Molecule Conductance by Controlled Electric Field-Induced trans-to-cis Isomerisation

by C.S. Quintans, Denis Andrienko, Katrin F. Domke, Daniel Aravena, Sangho Koo, Ismael Díez-Pérez and Albert C. Aragonès

Appl. Sci. 2021, 11(8), 3317; https://doi.org/10.3390/app11083317 - 7 Apr 2021

Cited by 13 | Viewed by 4035

Abstract

External electric fields (EEFs) have proven to be very efficient in catalysing chemical reactions, even those inaccessible via wet-chemical synthesis. At the single-molecule level, oriented EEFs have been successfully used to promote in situ single-molecule reactions in the absence of chemical catalysts. Here, [...] Read more.

External electric fields (EEFs) have proven to be very efficient in catalysing chemical reactions, even those inaccessible via wet-chemical synthesis. At the single-molecule level, oriented EEFs have been successfully used to promote in situ single-molecule reactions in the absence of chemical catalysts. Here, we elucidate the effect of an EEFs on the structure and conductance of a molecular junction. Employing scanning tunnelling microscopy break junction (STM-BJ) experiments, we form and electrically characterize single-molecule junctions of two tetramethyl carotene isomers. Two discrete conductance signatures show up more prominently at low and high applied voltages which are univocally ascribed to the trans and cis isomers of the carotenoid, respectively. The difference in conductance between both cis-/trans- isomers is in concordance with previous predictions considering π-quantum interference due to the presence of a single gauche defect in the trans isomer. Electronic structure calculations suggest that the electric field polarizes the molecule and mixes the excited states. The mixed states have a (spectroscopically) allowed transition and, therefore, can both promote the cis-isomerization of the molecule and participate in electron transport. Our work opens new routes for the in situ control of isomerisation reactions in single-molecule contacts. Full article

(This article belongs to the Special Issue Molecular Electronics)

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13 pages, 10023 KiB

Open AccessArticle

Spin Dependent Transport through Driven Magnetic System with Aubry-Andre-Harper Modulation

by Arpita Koley, Santanu K. Maiti, Judith Helena Ojeda Silva and David Laroze

Appl. Sci. 2021, 11(5), 2309; https://doi.org/10.3390/app11052309 - 5 Mar 2021

Cited by 7 | Viewed by 2019

Abstract

In this work, we put forward a prescription of achieving spin selective electron transfer by means of light irradiation through a tight-binding (TB) magnetic chain whose site energies are modulated in the form of well known Aubry–Andre–Harper (AAH) model. The interaction of itinerant [...] Read more.

In this work, we put forward a prescription of achieving spin selective electron transfer by means of light irradiation through a tight-binding (TB) magnetic chain whose site energies are modulated in the form of well known Aubry–Andre–Harper (AAH) model. The interaction of itinerant electrons with local magnetic moments in the magnetic system provides a misalignment between up and down spin channels which leads to a finite spin polarization (SP) upon locating the Fermi energy in a suitable energy zone. Both the energy channels are significantly affected by the irradiation which is directly reflected in degree of spin polarization as well as in its phase. We include the irradiation effect through Floquet ansatz and compute spin polarization coefficient by evaluating transmission probabilities using Green’s function prescription. Our analysis can be utilized to investigate spin dependent transport phenomena in any driven magnetic system with quasiperiodic modulations. Full article

(This article belongs to the Special Issue Molecular Electronics)

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8 pages, 1049 KiB

Open AccessCommunication

The Effect of Anchor Group on the Phonon Thermal Conductance of Single Molecule Junctions

by Mohammed D. Noori, Sara Sangtarash and Hatef Sadeghi

Appl. Sci. 2021, 11(3), 1066; https://doi.org/10.3390/app11031066 - 25 Jan 2021

Cited by 11 | Viewed by 2715

Abstract

There is a worldwide race to convert waste heat to useful energy using thermoelectric materials. Molecules are attractive candidates for thermoelectricity because they can be synthesised with the atomic precision, and intriguing properties due to quantum effects such as quantum interference can be [...] Read more.

There is a worldwide race to convert waste heat to useful energy using thermoelectric materials. Molecules are attractive candidates for thermoelectricity because they can be synthesised with the atomic precision, and intriguing properties due to quantum effects such as quantum interference can be induced at room temperature. Molecules are also expected to show a low thermal conductance that is needed to enhance the performance of thermoelectric materials. Recently, the technological challenge of measuring the thermal conductance of single molecules was overcome. Therefore, it is timely to develop strategies to reduce their thermal conductance for high performance thermoelectricity. In this paper and for the first time, we exploit systematically the effect of anchor groups on the phonon thermal conductance of oligo (phenylene ethynylene) (OPE3) molecules connected to gold electrodes via pyridyl, thiol, methyl sulphide and carbodithioate anchor groups. We show that thermal conductance is affected significantly by the choice of anchor group. The lowest and highest thermal conductances were obtained in the OPE3 with methyl sulphide and carbodithioate anchor groups, respectively. The thermal conductance of OPE3 with thiol anchor was higher than that with methyl sulphide but lower than the OPE3 with pyridyl anchor group. Full article

(This article belongs to the Special Issue Molecular Electronics)

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12 pages, 1696 KiB

Open AccessFeature PaperArticle

Role of the Binding Motifs in the Energy Level Alignment and Conductance of Amine-Gold Linked Molecular Junctions within DFT and DFT + Σ

by Enrique Montes and Héctor Vázquez

Appl. Sci. 2021, 11(2), 802; https://doi.org/10.3390/app11020802 - 15 Jan 2021

Cited by 7 | Viewed by 2255

Abstract

We investigate, using density functional theory (DFT), the electronic and conducting properties of benzenediamine connected to gold electrodes via different tip structures. We examine a series of binding motifs to the electrodes and calculate the junction spectral properties. We consider corrections to the [...] Read more.

We investigate, using density functional theory (DFT), the electronic and conducting properties of benzenediamine connected to gold electrodes via different tip structures. We examine a series of binding motifs to the electrodes and calculate the junction spectral properties. We consider corrections to the position of molecular resonances at the junction and discuss different approaches to the calculation of these shifts. We relate the magnitude of these corrections to resonance energies to the atomistic structure of the tip. Benzenediamine DFT-based transmission spectra can be well approximated by a Lorentzian model involving only the highest occupied molecular orbital (HOMO). We show how benzenediamine calculated conductance values in quantitative agreement with previous experiments can be achieved from the combination of DFT-based spectra and corrections to the DFT-based HOMO energy and an accessible Lorentzian model. Full article

(This article belongs to the Special Issue Molecular Electronics)

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Review

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18 pages, 2357 KiB

Open AccessReview

Attenuation Factors in Molecular Electronics: Some Theoretical Concepts

by Yannick J. Dappe

Appl. Sci. 2020, 10(18), 6162; https://doi.org/10.3390/app10186162 - 4 Sep 2020

Cited by 6 | Viewed by 3076

Abstract

Understanding the electronic transport mechanisms in molecular junctions is of paramount importance to design molecular devices and circuits. In particular, the role of the different junction components contributing to the current decay—namely the attenuation factor—is yet to be clarified. In this short review, [...] Read more.

Understanding the electronic transport mechanisms in molecular junctions is of paramount importance to design molecular devices and circuits. In particular, the role of the different junction components contributing to the current decay—namely the attenuation factor—is yet to be clarified. In this short review, we discuss the main theoretical approaches to tackle this question in the non-resonant tunneling regime. We illustrate our purpose through standard symmetric junctions and through recent studies on hybrid molecular junctions using graphene electrodes. In each case, we highlight the contribution from the anchoring groups, the molecular backbone and the electrodes, respectively. In this respect, we consider different anchoring groups and asymmetric junctions. In light of these results, we discuss some perspectives to describe accurately the attenuation factors in molecular electronics. Full article

(This article belongs to the Special Issue Molecular Electronics)

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41 pages, 6430 KiB

Open AccessReview

Nanofabrication Techniques in Large-Area Molecular Electronic Devices

by Lucía Herrer, Santiago Martín and Pilar Cea

Appl. Sci. 2020, 10(17), 6064; https://doi.org/10.3390/app10176064 - 1 Sep 2020

Cited by 21 | Viewed by 6837

Abstract

The societal impact of the electronics industry is enormous—not to mention how this industry impinges on the global economy. The foreseen limits of the current technology—technical, economic, and sustainability issues—open the door to the search for successor technologies. In this context, molecular electronics [...] Read more.

The societal impact of the electronics industry is enormous—not to mention how this industry impinges on the global economy. The foreseen limits of the current technology—technical, economic, and sustainability issues—open the door to the search for successor technologies. In this context, molecular electronics has emerged as a promising candidate that, at least in the short-term, will not likely replace our silicon-based electronics, but improve its performance through a nascent hybrid technology. Such technology will take advantage of both the small dimensions of the molecules and new functionalities resulting from the quantum effects that govern the properties at the molecular scale. An optimization of interface engineering and integration of molecules to form densely integrated individually addressable arrays of molecules are two crucial aspects in the molecular electronics field. These challenges should be met to establish the bridge between organic functional materials and hard electronics required for the incorporation of such hybrid technology in the market. In this review, the most advanced methods for fabricating large-area molecular electronic devices are presented, highlighting their advantages and limitations. Special emphasis is focused on bottom-up methodologies for the fabrication of well-ordered and tightly-packed monolayers onto the bottom electrode, followed by a description of the top-contact deposition methods so far used. Full article

(This article belongs to the Special Issue Molecular Electronics)

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