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101. Interference Controls Conductance in Phthalocyanine Molecular Junctions

Author

González, M. Teresa, primary, Ismael, Ali K., additional, García-Iglesias, Miguel, additional, Leary, Edmund, additional, Rubio-Bollinger, Gabino, additional, Grace, Iain, additional, González-Rodríguez, David, additional, Torres, Tomás, additional, Lambert, Colin J., additional, and Agraït, Nicolás, additional

Published
2021
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102. Corrigendum to:Unusual Length Dependence of the Conductance in Cumulene Molecular Wires (Angewandte Chemie International Edition, (2019), 58, 25, (8378-8382), 10.1002/anie.201901228)

Author

Xu, Wenjun, Leary, Edmund, Hou, Songjun, Sangtarash, Sara, González, M. Teresa, Rubio-Bollinger, Gabino, Wu, Qingqing, Sadeghi, Hatef, Tejerina, Lara, Christensen, Kirsten E., Agraït, Nicolás, Higgins, Simon J., Lambert, Colin J., Nichols, Richard J., Anderson, Harry L., Xu, Wenjun, Leary, Edmund, Hou, Songjun, Sangtarash, Sara, González, M. Teresa, Rubio-Bollinger, Gabino, Wu, Qingqing, Sadeghi, Hatef, Tejerina, Lara, Christensen, Kirsten E., Agraït, Nicolás, Higgins, Simon J., Lambert, Colin J., Nichols, Richard J., and Anderson, Harry L.

Abstract

The authors of this Communication have noticed a mistake in Table 1. In the second column of this table, the single-molecule conductances for compounds 3 and 5 were incorrect (but the values plotted in Figure 3 g were correct). The correct log(G/G0) values for compounds 3 and 5 are −3.70 and −3.77, respectively. No changes in analysis or conclusions result from this correction. The authors apologize for this transcription error.

Published
2021

103. Molecular Structure–(Thermo)electric Property Relationships in Single-Molecule Junctions and Comparisons with Single- and Multiple-Parameter Models

Author

Naher, Masnun, Milan, David C., Al-Owaedi, Oday A., Planje, Inco J., Bock, Sören, Hurtado-Gallego, Juan, Bastante, Pablo, Abd Dawood, Zahra Murtada, Rincón-García, Laura, Rubio-Bollinger, Gabino, Higgins, Simon J., Agraït, Nicolás, Lambert, Colin J., Nichols, Richard J., Low, Paul J., Naher, Masnun, Milan, David C., Al-Owaedi, Oday A., Planje, Inco J., Bock, Sören, Hurtado-Gallego, Juan, Bastante, Pablo, Abd Dawood, Zahra Murtada, Rincón-García, Laura, Rubio-Bollinger, Gabino, Higgins, Simon J., Agraït, Nicolás, Lambert, Colin J., Nichols, Richard J., and Low, Paul J.

Abstract

The most probable single-molecule conductance of each member of a series of 12 conjugated molecular wires, 6 of which contain either a ruthenium or platinum center centrally placed within the backbone, has been determined. The measurement of a small, positive Seebeck coefficient has established that transmission through these molecules takes place by tunneling through the tail of the HOMO resonance near the middle of the HOMO–LUMO gap in each case. Despite the general similarities in the molecular lengths and frontier-orbital compositions, experimental and computationally determined trends in molecular conductance values across this series cannot be satisfactorily explained in terms of commonly discussed “single-parameter” models of junction conductance. Rather, the trends in molecular conductance are better rationalized from consideration of the complete molecular junction, with conductance values well described by transport calculations carried out at the DFT level of theory, on the basis of the Landauer–Büttiker model.

Published
2021

104. Selective anchoring groups for molecular electronic junctions with ITO electrodes

Author

Engineering and Physical Sciences Research Council (UK), Fundação para a Ciência e a Tecnologia (Portugal), European Commission, European Research Council, Royal Society (UK), Ministerio de Economía y Competitividad (España), Leverhulme Trust, Agencia Estatal de Investigación (España), Ministerio de Ciencia, Innovación y Universidades (España), Gobierno de Aragón, Planje, Inco J., Davidson, Ross J., Vezzoli, Andrea, Daaoub, Abdalghani, Sangtarash, sara, Sadeghi, Hatef, Martín, Santiago, Cea, Pilar, Lambert, Colin J., Beeby, Andrew, Higgins, Simon J., Nichols, Richard J., Engineering and Physical Sciences Research Council (UK), Fundação para a Ciência e a Tecnologia (Portugal), European Commission, European Research Council, Royal Society (UK), Ministerio de Economía y Competitividad (España), Leverhulme Trust, Agencia Estatal de Investigación (España), Ministerio de Ciencia, Innovación y Universidades (España), Gobierno de Aragón, Planje, Inco J., Davidson, Ross J., Vezzoli, Andrea, Daaoub, Abdalghani, Sangtarash, sara, Sadeghi, Hatef, Martín, Santiago, Cea, Pilar, Lambert, Colin J., Beeby, Andrew, Higgins, Simon J., and Nichols, Richard J.

Abstract

Indium tin oxide (ITO) is an attractive substrate for single-molecule electronics since it is transparent while maintaining electrical conductivity. Although it has been used before as a contacting electrode in single-molecule electrical studies, these studies have been limited to the use of carboxylic acid terminal groups for binding molecular wires to the ITO substrates. There is thus the need to investigate other anchoring groups with potential for binding effectively to ITO. With this aim, we have investigated the single-molecule conductance of a series of eight tolane or “tolane-like” molecular wires with a variety of surface binding groups. We first used gold–molecule–gold junctions to identify promising targets for ITO selectivity. We then assessed the propensity and selectivity of carboxylic acid, cyanoacrylic acid, and pyridinium-squarate to bind to ITO and promote the formation of molecular heterojunctions. We found that pyridinium squarate zwitterions display excellent selectivity for binding to ITO over gold surfaces, with contact resistivity comparable to that of carboxylic acids. These single-molecule experiments are complemented by surface chemical characterization with X-ray photoelectron spectroscopy, quartz crystal microbalance, contact angle determination, and nanolithography using an atomic force miscroscope. Finally, we report the first density-functional theory calculations involving ITO electrodes to model charge transport through ITO–molecule–gold heterojunctions.

Published
2021

106. A one-pot synthesis of oligo(arylene–ethynylene)-molecular wires and their use in the further verification of molecular circuit laws†.

Author

Naher, Masnun, Gorenskaia, Elena, Moggach, Stephen A., Becker, Thomas, Nichols, Richard J., Lambert, Colin J., and Low, Paul J.

Abstract

A convenient two-step, one-pot synthesis of oligo(arylene–ethynylene) (OAE) type molecular wires in yields of up to 70% via in situ desilylation of protected bis(alkynes) Me3SiC≡CArC≡CSiMe3 (Ar = 2,5-thienyl, 1,4-naphthylene, 9,10-anthrylene) and subsequent Sonogashira cross-coupling with S -(4-iodophenyl) ethanethiolate, 4-iodothioanisole, or 5-bromo-3,3-dimethyl-2,3-dihydrobenzo[ b ]thiophene is described. The in situ desilylation avoids the manipulation of the sensitive terminal dialkynes (HC≡CArC≡CH), whilst the general approach presented has some advantages over alternative synthetic strategies based on coupling of aryl dihalides (XArX) by avoiding the multi-step preparation and purification of the terminal alkynes S -(4-ethynylphenyl) ethanethiolate, 4-ethynylthioanisole and 5-ethynyl 3,3-dimethyl-2,3-dihydrobenzo[ b ]thiophene. The molecular conductance of the resulting thiolate or thioether functionalised OAE molecular wires has been determined using scanning tunneling microscope break junction (STM-BJ) methods. The trends in molecular conductance do not track simply with the degree of aromaticity of the molecular core despite the rather similar molecular lengths. Rather, the STM-BJ data are better correlated with the nature of the anchor group, highlighting the important role of electrode–molecule coupling on electron transport in a molecular junction. The experimental conductance data are in good agreement with recently described quantum circuit rules, further highlighting the potential for these relationships to be used as predictive tools in molecular electronics research. A two-step, one-pot synthesis of oligo(arylene–ethynylene) molecular wires that avoids manipulation of sensitive terminal bis(alkynes) is described. Trends in molecular conductance do not track with the molecular core aromaticity, but correlate with the recently described quantum circuit rules and associated bridge and anchor parameters. [ABSTRACT FROM AUTHOR]

Published
2022
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107. Berichtigung: Unusual Length Dependence of the Conductance in Cumulene Molecular Wires

Author

Xu, Wenjun, primary, Leary, Edmund, additional, Hou, Songjun, additional, Sangtarash, Sara, additional, González, M. Teresa, additional, Rubio‐Bollinger, Gabino, additional, Wu, Qingqing, additional, Sadeghi, Hatef, additional, Tejerina, Lara, additional, Christensen, Kirsten E., additional, Agraït, Nicolás, additional, Higgins, Simon J., additional, Lambert, Colin J., additional, Nichols, Richard J., additional, and Anderson, Harry L., additional

Published
2021
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108. Corrigendum: Unusual Length Dependence of the Conductance in Cumulene Molecular Wires

Author

Xu, Wenjun, primary, Leary, Edmund, additional, Hou, Songjun, additional, Sangtarash, Sara, additional, González, M. Teresa, additional, Rubio‐Bollinger, Gabino, additional, Wu, Qingqing, additional, Sadeghi, Hatef, additional, Tejerina, Lara, additional, Christensen, Kirsten E., additional, Agraït, Nicolás, additional, Higgins, Simon J., additional, Lambert, Colin J., additional, Nichols, Richard J., additional, and Anderson, Harry L., additional

Published
2021
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109. Controlled Quantum Dot Formation in Atomically Engineered Graphene Nanoribbon Field-Effect Transistors

Author

El Abbassi, M. (author), Perrin, M.L. (author), Barin, Gabriela Borin (author), Sangtarash, Sara (author), Overbeck, Jan (author), Braun, Oliver (author), Lambert, Colin J. (author), Sun, Qiang (author), Prechtl, Thorsten (author), El Abbassi, M. (author), Perrin, M.L. (author), Barin, Gabriela Borin (author), Sangtarash, Sara (author), Overbeck, Jan (author), Braun, Oliver (author), Lambert, Colin J. (author), Sun, Qiang (author), and Prechtl, Thorsten (author)

Abstract

Graphene nanoribbons (GNRs) have attracted strong interest from researchers worldwide, as they constitute an emerging class of quantum-designed materials. The major challenges toward their exploitation in electronic applications include reliable contacting, complicated by their small size (<50 nm), and the preservation of their physical properties upon device integration. In this combined experimental and theoretical study, we report on the quantum dot behavior of atomically precise GNRs integrated in a device geometry. The devices consist of a film of aligned five-atom-wide GNRs (5-AGNRs) transferred onto graphene electrodes with a sub 5 nm nanogap. We demonstrate that these narrow-bandgap 5-AGNRs exhibit metal-like behavior at room temperature and single-electron transistor behavior for temperatures below 150 K. By performing spectroscopy of the molecular levels at 13 K, we obtain addition energies in the range of 200-300 meV. DFT calculations predict comparable addition energies and reveal the presence of two electronic states within the bandgap of infinite ribbons when the finite length of the 5-AGNR is accounted for. By demonstrating the preservation of the 5-AGNRs' molecular levels upon device integration, as demonstrated by transport spectroscopy, our study provides a critical step forward in the realization of more exotic GNR-based nanoelectronic devices., QN/van der Zant Lab

Published
2020
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110. Bottom-up Synthesis of Nitrogen-doped Porous Graphene Nanoribbons

Author

Pawlak, Rémy, Liu, Xunshan, Ninova, Silviya, d'Astolfo, Philipp, Drechsel, Carl, Sangtarash, Sara, Häner, Robert, Decurtins, Silvio, Sadeghi, Hatef, Lambert, Colin J., Aschauer, Ulrich, Liu, Shi Xia, Meyer, Ernst, Pawlak, Rémy, Liu, Xunshan, Ninova, Silviya, d'Astolfo, Philipp, Drechsel, Carl, Sangtarash, Sara, Häner, Robert, Decurtins, Silvio, Sadeghi, Hatef, Lambert, Colin J., Aschauer, Ulrich, Liu, Shi Xia, and Meyer, Ernst

Abstract

Although methods for a periodic perforation and heteroatom doping of graphene sheets have been developed, patterning closely spaced holes on the nanoscale in graphene nanoribbons is still a challenging task. In this work, nitrogen-doped porous graphene nanoribbons (N-GNRs) were synthesized on Ag(111) using a silver-assisted Ullmann polymerization of brominated tetrabenzophenazine. Insights into the hierarchical reaction pathways from single molecules towards the formation of one-dimensional organometallic complexes and N-GNRs are gained by a combination of scanning tunneling microscopy (STM), atomic force microscopy (AFM) with CO-tip, scanning tunneling spectroscopy (STS) and density functional theory (DFT).

Published
2020

112. Molecular Structure–(Thermo)electric Property Relationships in Single-Molecule Junctions and Comparisons with Single- and Multiple-Parameter Models

Author

Naher, Masnun, primary, Milan, David C., additional, Al-Owaedi, Oday A., additional, Planje, Inco J., additional, Bock, Sören, additional, Hurtado-Gallego, Juan, additional, Bastante, Pablo, additional, Abd Dawood, Zahra Murtada, additional, Rincón-García, Laura, additional, Rubio-Bollinger, Gabino, additional, Higgins, Simon J., additional, Agraït, Nicolás, additional, Lambert, Colin J., additional, Nichols, Richard J., additional, and Low, Paul J., additional

Published
2021
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113. Selective Anchoring Groups for Molecular Electronic Junctions with ITO Electrodes

Author

Planje, Inco J., primary, Davidson, Ross J., additional, Vezzoli, Andrea, additional, Daaoub, Abdalghani, additional, Sangtarash, Sara, additional, Sadeghi, Hatef, additional, Martín, Santiago, additional, Cea, Pilar, additional, Lambert, Colin J., additional, Beeby, Andrew, additional, Higgins, Simon J., additional, and Nichols, Richard J., additional

Published
2021
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115. Soft versus hard junction formation for α-terthiophene molecular wires and their charge transfer complexes.

Author

Vezzoli, Andrea, Grace, Iain M., Brooke, Carly, Nichols, Richard J., Lambert, Colin J., and Higgins, Simon J.

Subjects
ALPHA-terthienyl, NANOWIRES, CHARGE transfer, SCANNING tunneling microscopy, ELECTRIC admittance
Abstract

We used a range of scanning tunnelling microscopy (STM)-based methods to conduct a detailed study of single molecule junction conductance enhancement upon charge transfer complex formation, using bis(thiaalkyl)arene molecular wires as electron donors and tetracyanoethylene (TCNE) as an electron acceptor. Using the "hard" STM break junction (STM-BJ) method, in which a Au STM tip is pushed into a Au substrate and then withdrawn in the presence of molecules, we see a single, very broad, peak in the resulting conductance histogram when all data are used; the conductance enhancement is 25-fold for a terthiophene donor and 15-fold for a phenyl group. After rational data selection, in which only current-distance curves that contain a current plateau >0.2 nm long are used in the conductance histogram, three sharper peaks are resolved in the histograms for the charge transfer complexes; two substantially lower-conductance peaks are resolved for the uncomplexed molecules. Using the "soft" STM I(s) technique, in which initial contact between tip and substrate is avoided and the current limit is about an order of magnitude lower, we were able to resolve two peaks for the uncomplexed molecules depending upon the initial set point current (i.e., tip height), one at the same value as the lower of the two data-selected STM-BJ histogram peaks and an additional peak beyond the low-current limit for the STM-BJ experiment. For the terthiophene, the low, medium, and high conductance peaks for the TCNE complex are, respectively, ca. 70, 70, and 46 times higher in conductance than the corresponding peaks for the free molecule. [ABSTRACT FROM AUTHOR]

Published
2017
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116. Discriminating single-molecule sensing by crown-ether-based molecular junctions.

Author

Ismael, Ali K., Al-Jobory, Alaa, Grace, Iain, and Lambert, Colin J.

Subjects
MOLECULES, ALKALINE solutions, ELECTRIC conductivity, GOLD electrodes, FERMI energy
Abstract

Crown-ether molecules are well known to selectively bind alkali atoms, so by incorporating these within wires, any change in electrical conductance of the wire upon binding leads to discriminating sensing. Using a density functional theory-based approach to quantum transport, we investigate the potential sensing capabilities of single-molecule junctions formed from crown ethers attached to anthraquinone units, which are in turn attached to gold electrodes via alkyl chains. We calculate the change in electrical conductance for binding of three different alkali ions (lithium, sodium, and potassium). Depending on the nature of the ionic analyte, the conductance is enhanced by different amounts. This change in electrical conductance is due to charge transfer from the ion to molecular wire causing the molecular resonances to shift closer to the electrode Fermi energy. [ABSTRACT FROM AUTHOR]

Published
2017
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117. Athermal Energy Loss from X-rays Deposited in Thin Superconducting Films on Solid Substrates

Author

Kozorezov, Alexander G, Lambert, Colin J, Bandler, Simon R, Balvin, Manuel A, Busch, Sarah E, Sagler, Peter N, Porst, Jan-Patrick, Smith, Stephen J, Stevenson, Thomas R, and Sadleir, John E

Subjects
Electronics And Electrical Engineering
Abstract

When energy is deposited in a thin-film cryogenic detector, such as from the absorption of an X-ray, an important feature that determines the energy resolution is the amount of athermal energy that can be lost to the heat bath prior to the elementary excitation systems coming into thermal equilibrium. This form of energy loss will be position-dependent and therefore can limit the detector energy resolution. An understanding of the physical processes that occur when elementary excitations are generated in metal films on dielectric substrates is important for the design and optimization of a number of different types of low temperature detector. We have measured the total energy loss in one relatively simple geometry that allows us to study these processes and compare measurements with calculation based upon a model for the various di.erent processes. We have modeled the athermal phonon energy loss in this device by finding an evolving phonon distribution function that solves the system of kinetic equations for the interacting system of electrons and phonons. Using measurements of device parameters such as the Debye energy and the thermal di.usivity we have calculated the expected energy loss from this detector geometry, and also the position-dependent variation of this loss. We have also calculated the predicted impact on measured spectral line-shapes, and shown that they agree well with measurements. In addition, we have tested this model by using it to predict the performance of a number of other types of detector with di.erent geometries, where good agreement is also found.

Published
2013

118. Bottom-up Synthesis of Nitrogen-Doped Porous Graphene Nanoribbons

Author

Pawlak, Rémy, primary, Liu, Xunshan, additional, Ninova, Silviya, additional, D’Astolfo, Philipp, additional, Drechsel, Carl, additional, Sangtarash, Sara, additional, Häner, Robert, additional, Decurtins, Silvio, additional, Sadeghi, Hatef, additional, Lambert, Colin J., additional, Aschauer, Ulrich, additional, Liu, Shi-Xia, additional, and Meyer, Ernst, additional

Published
2020
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120. Scale-Up of Room-Temperature Constructive Quantum Interference from Single Molecules to Self-Assembled Molecular-Electronic Films

Author

Wang, Xintai, primary, Bennett, Troy L. R., additional, Ismael, Ali, additional, Wilkinson, Luke A., additional, Hamill, Joseph, additional, White, Andrew J. P., additional, Grace, Iain M., additional, Kolosov, Oleg V., additional, Albrecht, Tim, additional, Robinson, Benjamin J., additional, Long, Nicholas J., additional, Cohen, Lesley F., additional, and Lambert, Colin J., additional

Published
2020
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121. Constructive Quantum Interference in Single‐Molecule Benzodichalcogenophene Junctions

Author

Baghernejad, Masoud, primary, Yang, Yang, additional, Al‐Owaedi, Oday A., additional, Aeschi, Yves, additional, Zeng, Biao‐Feng, additional, Abd Dawood, Zahra Murtada, additional, Li, Xiaohui, additional, Liu, Junyang, additional, Shi, Jia, additional, Decurtins, Silvio, additional, Liu, Shi‐Xia, additional, Hong, Wenjing, additional, and Lambert, Colin J., additional

Published
2020
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122. Controlled Quantum Dot Formation in Atomically Engineered Graphene Nanoribbon Field-Effect Transistors

Author

El Abbassi, Maria, primary, Perrin, Mickael L., additional, Barin, Gabriela Borin, additional, Sangtarash, Sara, additional, Overbeck, Jan, additional, Braun, Oliver, additional, Lambert, Colin J., additional, Sun, Qiang, additional, Prechtl, Thorsten, additional, Narita, Akimitsu, additional, Müllen, Klaus, additional, Ruffieux, Pascal, additional, Sadeghi, Hatef, additional, Fasel, Roman, additional, and Calame, Michel, additional

Published
2020
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123. Conductance Behavior of Tetraphenyl-Aza-BODIPYs

Author

Markin, Andrei, primary, Ismael, Ali K., additional, Davidson, Ross J., additional, Milan, David C., additional, Nichols, Richard J., additional, Higgins, Simon J., additional, Lambert, Colin J., additional, Hsu, Yu-Ting, additional, Yufit, Dmitry S., additional, and Beeby, Andrew, additional

Published
2020
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124. Structure‐Independent Conductance of Thiophene‐Based Single‐Stacking Junctions

Author

Li, Xiaohui, primary, Wu, Qingqing, additional, Bai, Jie, additional, Hou, Songjun, additional, Jiang, Wenlin, additional, Tang, Chun, additional, Song, Hang, additional, Huang, Xiaojuan, additional, Zheng, Jueting, additional, Yang, Yang, additional, Liu, Junyang, additional, Hu, Yong, additional, Shi, Jia, additional, Liu, Zitong, additional, Lambert, Colin J., additional, Zhang, Deqing, additional, and Hong, Wenjing, additional

Published
2020
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128. Exploring the thermoelectric properties of oligo(phenylene-ethynylene) derivatives

Author

Chen, Hang, primary, Sangtarash, Sara, additional, Li, Guopeng, additional, Gantenbein, Markus, additional, Cao, Wenqiang, additional, Alqorashi, Afaf, additional, Liu, Junyang, additional, Zhang, Chunquan, additional, Zhang, Yulong, additional, Chen, Lijue, additional, Chen, Yaorong, additional, Olsen, Gunnar, additional, Sadeghi, Hatef, additional, Bryce, Martin R., additional, Lambert, Colin J., additional, and Hong, Wenjing, additional

Published
2020
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129. Electrochemical control of the single molecule conductance of a conjugated bis(pyrrolo)tetrathiafulvalene based molecular switch† †This paper is dedicated to the memory of Prof. Thomas Wandlowski. ‡ ‡Electronic supplementary information (ESI) available: Synthetic procedures, characterisation data, NMR spectra, MALDI mass spectra, details of CV measurements, details of break-junction measurements and data analysis, computational methods. See DOI: 10.1039/c7sc02037f Click here for additional data file

Author

O'Driscoll, Luke J., Hamill, Joseph M., Grace, Iain, Nielsen, Bodil W., Almutib, Eman, Fu, Yongchun, Hong, Wenjing, Lambert, Colin J., and Jeppesen, Jan O.

Subjects
Chemistry
Abstract

The single molecule conductance of a conjugated molecular wire is electrochemically switched upon oxidising or reducing a central bispyrrolotetrathiafulvalene unit., As the field of unimolecular electronics develops, there is growing interest in the development of functionalised molecular wires, such as switches, which will allow for more complex molecular-scale circuits. To this end, a three redox state single molecule switch, 1, based on bis(pyrrolo)tetrathiafulvalene (BPTTF) has been designed, synthesised and investigated using scanning tunnelling microscopy break junction (STM-BJ) studies and quantum transport calculations. Oxidising the BPTTF unit increases its conjugation, which was anticipated to increase the molecular conductance of 1. By changing the redox state of 1 electrochemically it was possible to vary the single molecule conductance by more than an order of magnitude (from 10–5.2 G 0 to 10–3.8 G 0). Simulations afforded a qualitatively similar trend. An additional, higher conductance feature is present in most traces at junction sizes of around 2.0 nm – further extension affords the switchable lower conductance feature at junction sizes closer to the molecular length (ca. 3.0 nm). Analysis of the conductance traces shows that these two conductance features occur sequentially in nearly all junctions. This behaviour is attributed to an alternative initial junction conformation in which one or more of the BPTTF sulfur atoms acts as an anchoring group. This hypothesis is supported by a computational study of binding conformations and STM-BJ studies on a model compound, 2, with only one thiol anchor. Our results indicate that the redox properties of BPTTF make it an excellent candidate for use in single molecule switches.

Published
2017

130. Single‐Molecule Conductance Studies of Organometallic Complexes Bearing 3‐Thienyl Contacting Groups

Author

Bock, Sören, Al‐Owaedi, Oday A., Eaves, Samantha G., Milan, David C., Lemmer, Mario, Skelton, Brian W., Osorio, Henrry M., Nichols, Richard J., Higgins, Simon J., Cea, Pilar, Long, Nicholas J., Albrecht, Tim, Martín, Santiago, Lambert, Colin J., and Low, Paul J.

Subjects
organometallic chemistry, single-molecule conductors, Full Paper, scanning tunneling microscopy, Full Papers, Molecular Electronics, density functional calculation, contacting group
Abstract

The compounds and complexes 1,4‐C6H4(C≡C‐cyclo‐3‐C4H3S)2 (2), trans‐[Pt(C≡C‐cyclo‐3‐C4H3S)2(PEt3)2] (3), trans‐[Ru(C≡C‐cyclo‐3‐C4H3S)2(dppe)2] (4; dppe=1,2‐bis(diphenylphosphino)ethane) and trans‐[Ru(C≡C‐cyclo‐3‐C4H3S)2{P(OEt)3}4] (5) featuring the 3‐thienyl moiety as a surface contacting group for gold electrodes have been prepared, crystallographically characterised in the case of 3–5 and studied in metal|molecule|metal junctions by using both scanning tunnelling microscope break‐junction (STM‐BJ) and STM‐I(s) methods (measuring the tunnelling current (I) as a function of distance (s)). The compounds exhibit similar conductance profiles, with a low conductance feature being more readily identified by STM‐I(s) methods, and a higher feature by the STM‐BJ method. The lower conductance feature was further characterised by analysis using an unsupervised, automated multi‐parameter vector classification (MPVC) of the conductance traces. The combination of similarly structured HOMOs and non‐resonant tunnelling mechanism accounts for the remarkably similar conductance values across the chemically distinct members of the family 2–5.

Published
2017

131. Hemilabile Ligands as Mechanosensitive Electrode Contacts for Molecular Electronics

Author

Ferri, Nicolò, Algethami, Norah, Vezzoli, Andrea, Sangtarash, Sara, McLaughlin, Maeve, Sadeghi, Hatef, Lambert, Colin J., Nichols, Richard J., Higgins, Simon J., Ferri, Nicolò, Algethami, Norah, Vezzoli, Andrea, Sangtarash, Sara, McLaughlin, Maeve, Sadeghi, Hatef, Lambert, Colin J., Nichols, Richard J., and Higgins, Simon J.

Abstract

Single-molecule junctions that are sensitive to compression or elongation are an emerging class of nanoelectromechanical systems (NEMS). Although the molecule–electrode interface can be engineered to impart such functionality, most studies to date rely on poorly defined interactions. We focused on this issue by synthesizing molecular wires designed to have chemically defined hemilabile contacts based on (methylthio)thiophene moieties. We measured their conductance as a function of junction size and observed conductance changes of up to two orders of magnitude as junctions were compressed and stretched. Localised interactions between weakly coordinating thienyl sulfurs and the electrodes are responsible for the observed effect and allow reversible monodentate⇄bidentate contact transitions as the junction is modulated in size. We observed an up to ≈100-fold sensitivity boost of the (methylthio)thiophene-terminated molecular wire compared with its non-hemilabile (methylthio)benzene counterpart and demonstrate a previously unexplored application of hemilabile ligands to molecular electronics.

Published
2019

133. Conductance of ‘bare-bones’ tripodal molecular wires

Author

Davidson, Ross J, Milan, David C, Al-Owaedi, Oday A, Ismael, Ali K, Nichols, Richard J, Higgins, Simon J, Lambert, Colin J, Yufit, Dmitry S, and Beeby, Andrew

Abstract

Controlling the orientation of molecular conductors on the electrode surfaces is a critical factor in the development of single-molecule conductors. In the current study, we used the scanning tunnelling microscopy-based break junction (STM-BJ) technique to explore ‘bare-bones’ tripodal molecular wires, employing different anchor groups (AGs) at the ‘top’ and ‘bottom’ of the tripod. The triarylphosphine tris(4-(methylthio)phenyl)phosphine and its corresponding phosphine sulfide showed only a single high conductance feature in the resulting 1- and 2-dimensional conductance histograms, whereas analogous molecules with fewer than three thiomethyl AGs did not show clear conductance features. Thus, by systematic molecular modifications and with the aid of supporting DFT calculations, the binding geometry, with respect to the surface, was elucidated.

Published
2018
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136. Turning the Tap: Conformational Control of Quantum Interference to Modulate Single‐Molecule Conductance

Author

Jiang, Feng, primary, Trupp, Douglas I., additional, Algethami, Norah, additional, Zheng, Haining, additional, He, Wenxiang, additional, Alqorashi, Afaf, additional, Zhu, Chenxu, additional, Tang, Chun, additional, Li, Ruihao, additional, Liu, Junyang, additional, Sadeghi, Hatef, additional, Shi, Jia, additional, Davidson, Ross, additional, Korb, Marcus, additional, Sobolev, Alexandre N., additional, Naher, Masnun, additional, Sangtarash, Sara, additional, Low, Paul J., additional, Hong, Wenjing, additional, and Lambert, Colin J., additional

Published
2019
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140. Unusual Length Dependence of the Conductance in Cumulene Molecular Wires

Author

Xu, Wenjun, primary, Leary, Edmund, additional, Hou, Songjun, additional, Sangtarash, Sara, additional, González, M. Teresa, additional, Rubio‐Bollinger, Gabino, additional, Wu, Qingqing, additional, Sadeghi, Hatef, additional, Tejerina, Lara, additional, Christensen, Kirsten E., additional, Agraït, Nicolás, additional, Higgins, Simon J., additional, Lambert, Colin J., additional, Nichols, Richard J., additional, and Anderson, Harry L., additional

Published
2019
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142. Cross-conjugation increases the conductance of meta-connected fluorenones

Author

Alanazy, Asma, primary, Leary, Edmund, additional, Kobatake, Takayuki, additional, Sangtarash, Sara, additional, González, M. Teresa, additional, Jiang, Hua-Wei, additional, Bollinger, Gabino Rubio, additional, Agräit, Nicolás, additional, Sadeghi, Hatef, additional, Grace, Iain, additional, Higgins, Simon J., additional, Anderson, Harry L., additional, Nichols, Richard J., additional, and Lambert, Colin J., additional

Published
2019
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147. Thermoelectric performance of various benzo-difuran wires.

Author

Péterfalvi, Csaba G., Grace, Iain, Manrique, Dávid Zs., and Lambert, Colin J.

Subjects
ELECTRON transport, NANOWIRES, ELECTRIC properties of nanowires, RESONANCE, ELECTRONEGATIVITY, THERMAL properties
Abstract

Using a first principles approach to electron transport, we calculate the electrical and thermoelectrical transport properties of a series of molecular wires containing benzo-difuran subunits. We demonstrate that the side groups introduce Fano resonances, the energy of which is changing with the electronegativity of selected atoms in it. We also study the relative effect of single, double, or triple bonds along the molecular backbone and find that single bonds yield the highest thermopower, approximately 22 μV/K at room temperature, which is comparable with the highest measured values for single-molecule thermopower reported to date. [ABSTRACT FROM AUTHOR]

Published
2014
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148. Electronic properties of linear carbon chains: Resolving the controversy.

Author

Al-Backri, Amaal, Zólyomi, Viktor, and Lambert, Colin J.

Subjects
ELECTRONIC structure, ELECTRIC conductivity, CARBON, ATTENUATION coefficients, BAND gaps
Abstract

Literature values for the energy gap of long one-dimensional carbon chains vary from as little as 0.2 eV to more than 4 eV. To resolve this discrepancy, we use the GW many-body approach to calculate the band gap Eg of an infinite carbon chain. We also compute the energy dependence of the attenuation coefficient β governing the decay with chain length of the electrical conductance of long chains and compare this with recent experimental measurements of the single-molecule conductance of end-capped carbon chains. For long chains, we find Eg = 2.16 eV and an upper bound for β of 0.21 Å−1. [ABSTRACT FROM AUTHOR]

Published
2014
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149. A study of planar anchor groups for graphene-based single-molecule electronics.

Author

Bailey, Steven, Visontai, David, Lambert, Colin J., Bryce, Martin R., Frampton, Harry, and Chappell, David

Subjects
GRAPHENE, ATOMS, ANTHRACENE, PARTICLES (Nuclear physics), SEPARATION (Technology)
Abstract

To identify families of stable planar anchor groups for use in single molecule electronics, we report detailed results for the binding energies of two families of anthracene and pyrene derivatives adsorbed onto graphene. We find that all the selected derivatives functionalized with either electron donating or electron accepting substituents bind more strongly to graphene than the parent non-functionalized anthracene or pyrene. The binding energy is sensitive to the detailed atomic alignment of substituent groups over the graphene substrate leading to larger than expected binding energies for -OH and -CN derivatives. Furthermore, the ordering of the binding energies within the anthracene and pyrene series does not simply follow the electron affinities of the substituents. Energy barriers to rotation or displacement on the graphene surface are much lower than binding energies for adsorption and therefore at room temperature, although the molecules are bound to the graphene, they are almost free to move along the graphene surface. Binding energies can be increased by incorporating electrically inert side chains and are sensitive to the conformation of such chains. [ABSTRACT FROM AUTHOR]

Published
2014
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150. Quantum interference mediated vertical molecular tunneling transistors.

Author

Jia, Chuancheng, Jia, Chuancheng, Famili, Marjan, Carlotti, Marco, Liu, Yuan, Wang, Peiqi, Grace, Iain M, Feng, Ziying, Wang, Yiliu, Zhao, Zipeng, Ding, Mengning, Xu, Xiang, Wang, Chen, Lee, Sung-Joon, Huang, Yu, Chiechi, Ryan C, Lambert, Colin J, Duan, Xiangfeng, Jia, Chuancheng, Jia, Chuancheng, Famili, Marjan, Carlotti, Marco, Liu, Yuan, Wang, Peiqi, Grace, Iain M, Feng, Ziying, Wang, Yiliu, Zhao, Zipeng, Ding, Mengning, Xu, Xiang, Wang, Chen, Lee, Sung-Joon, Huang, Yu, Chiechi, Ryan C, Lambert, Colin J, and Duan, Xiangfeng

Abstract

Molecular transistors operating in the quantum tunneling regime represent potential electronic building blocks for future integrated circuits. However, due to their complex fabrication processes and poor stability, traditional molecular transistors can only operate stably at cryogenic temperatures. Here, through a combined experimental and theoretical investigation, we demonstrate a new design of vertical molecular tunneling transistors, with stable switching operations up to room temperature, formed from cross-plane graphene/self-assembled monolayer (SAM)/gold heterostructures. We show that vertical molecular junctions formed from pseudo-p-bis((4-(acetylthio)phenyl)ethynyl)-p-[2,2]cyclophane (PCP) SAMs exhibit destructive quantum interference (QI) effects, which are absent in 1,4-bis(((4-acetylthio)phenyl)ethynyl)benzene (OPE3) SAMs. Consequently, the zero-bias differential conductance of the former is only about 2% of the latter, resulting in an enhanced on-off current ratio for (PCP) SAMs. Field-effect control is achieved using an ionic liquid gate, whose strong vertical electric field penetrates through the graphene layer and tunes the energy levels of the SAMs. The resulting on-off current ratio achieved in PCP SAMs can reach up to ~330, about one order of magnitude higher than that of OPE3 SAMs. The demonstration of molecular junctions with combined QI effect and gate tunability represents a critical step toward functional devices in future molecular-scale electronics.

Published
2018

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