Sara Sangtarash

University of Warwick

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Co-Authors

Hatef Sadeghi

University of Warwick

136

Colin J. Lambert

Lancaster University

100

Simon J. Higgins

University of Liverpool

Richard J. Nichols

University of Liverpool

Andrea Vezzoli

University of Liverpool

Nicolás Agraı̈t

Universidad Autónoma de Madrid

Abdalghani Daaoub

University of Warwick

Wenjing Hong

Collaborative Innovation Center of Chemistry for Energy Materials

Harry L. Anderson

University of Oxford

M. Teresa González

Madrid Institute for Advanced Studies

Cooperative Institutions

Xiamen University

University of Liverpool

Collaborative Innovation Center of Chemistry for Energy Materials

Lancaster University

University of Western Australia

University of Oxford

University of Bern

Durham University

Swiss Federal Laboratories for Materials Science and Technology

University of Cambridge

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Quantum Interference in Graphene Nanoconstrictions

Nano Letters (2016)

Pascal Gehring Hatef Sadeghi Sara Sangtarash Chit Siong Lau Junjie Liu

We report quantum interference effects in the electrical conductance of chemical vapor deposited graphene nanoconstrictions fabricated using feedback controlled electroburning. The observed multimode Fabry-Pérot interferences can be attributed to reflections at potential steps inside the channel. Sharp antiresonance features with a Fano line shape are observed. Theoretical modeling reveals that these Fano resonances are due to localized states inside the constriction, which couple to the delocalized states that also give rise to the Fabry-Pérot interference patterns. This study provides new insight into the interplay between two fundamental forms of quantum interference in graphene nanoconstrictions.

Quantum interference

10.1021/acs.nanolett.6b01104

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Citations (73)

Dual attenuation factor in nanographene molecular wires

arXiv (Cornell University) (2021)

Sara Sangtarash

Designing molecular nanowires with high electrical conductance that facilitate efficient charge transport over long distances is highly desirable for future molecular-scale circuitry. However, most molecular wires act as tunnel barriers, and their electrical conductance decays exponentially with increasing length. Only recently have a few studies shown increasing conductance with length. In this study, we identify a new class of molecular wires that exhibit both an increase and a decrease in room-temperature conductance with length (a dual attenuation factor), depending on their connection points to the electrodes. We show that this dual attenuation factor is an inherent property of these graphene-like nanowires, and its demonstration depends on the constructive quantum interference pattern for different connectivities to the electrodes. This is significant because a given nanographene molecular wire can show both negative and positive attenuation factors. This enables the systematic design of connectivity-dependent high/low-conductance molecular wires for future molecular-scale circuitry.

Factor (programming language)

10.48550/arxiv.2102.09936

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Inside Back Cover: Hemilabile Ligands as Mechanosensitive Electrode Contacts for Molecular Electronics (Angew. Chem. Int. Ed. 46/2019)

Angewandte Chemie International Edition (2019)

Nicolò Ferri Norah Algethami Andrea Vezzoli Sara Sangtarash Maeve McLaughlin

Single-entity junctions with conductance responsive to external stimuli are of particular interest in molecular electronics. By applying a concept from homogeneous catalysis, hemilability, molecules terminated with (2-methylthio)thiophene have conductance (green line) responding exponentially to mechanical modulations of the position of one of the electrodes (red line). These mechanically actuated switches showed high reversibility, speed and durability, offering a new, robust method to control the electrical properties of molecular devices. Read more in the Research Article by A. Vezzolli, S. Sangtarash, C. J. Lambert, S. J. Higgins, and co-workers on page 16583.

Molecular Electronics

Flexible Electronics

Molecular Communication

Line (geometry)

10.1002/anie.201913163

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Optical probes of molecules as nano-mechanical switches

Nature Communications (2020)

Dean Kos Giuliana Di Martino Alexandra Boehmke Bart de Nijs Dénes Berta

Abstract Molecular electronics promises a new generation of ultralow-energy information technologies, based around functional molecular junctions. Here, we report optical probing that exploits a gold nanoparticle in a plasmonic nanocavity geometry used as one terminal of a well-defined molecular junction, deposited as a self-assembled molecular monolayer on flat gold. A conductive transparent cantilever electrically contacts individual nanoparticles while maintaining optical access to the molecular junction. Optical readout of molecular structure in the junction reveals ultralow-energy switching of ∼50 zJ, from a nano-electromechanical torsion spring at the single molecule level. Real-time Raman measurements show these electronic device characteristics are directly affected by this molecular torsion, which can be explained using a simple circuit model based on junction capacitances, confirmed by density functional theory calculations. This nanomechanical degree of freedom is normally invisible and ignored in electrical transport measurements but is vital to the design and exploitation of molecules as quantum-coherent electronic nanodevices.

Molecular Electronics

Molecular switch

10.1038/s41467-020-19703-y

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Breakdown of Curly Arrow Rules in Anthraquinone

Angewandte Chemie International Edition (2018)

Jehan Alqahtani Hatef Sadeghi Sara Sangtarash Colin J. Lambert

Understanding and controlling quantum interference (QI) in single molecules is fundamental to the development of QI-based single-molecule electronics. Simple rules such as counting rules, curly arrow rules (CARs), circuit rules, and more recently magic ratio rules have been developed to predict QI patterns in polycyclic aromatic hydrocarbons. CARs are widely used to predict destructive QI. Here we examine the validity of CARs in fully conjugated anthracene and dihydroxyanthracene, cross-conjugated anthraquinone, and broken conjugated dihydroanthracene attached to either graphene or gold electrodes through π-π stacking or thiol and Au-C anchors. For the first time, we demonstrate that CARs break down in molecular junctions formed by cross-conjugated anthraquinone. In contrast with the destructive QI predicted by CARs for a meta-connected anthraquinone core, we demonstrate that QI is constructive. This behavior is independent of the choice of electrode material or anchor groups. This is significant, because by changing the redox state of meta-connected dihydroxyanthracene to form meta-connected anthraquinone, the conductance of the junction increases by a couple of orders of magnitude due to the crossover from constructive to destructive QI. This opens new avenues for realization of QI-based single-molecule switches.

Anthraquinones

Constructive

10.1002/anie.201807257

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Low thermal conductivity in franckeite heterostructures

Nanoscale (2022)

Jean Spièce Sara Sangtarash Marta Mucientes Aday J. Molina‐Mendoza Kunal Lulla

Layered crystals are known to be good candidates for bulk thermoelectric applications as they open new ways to realise highly efficient devices. Two dimensional materials, isolated from layered materials, and their stacking into heterostructures have attracted intense research attention for nanoscale applications due to their high Seebeck coefficient and possibilities to engineer their thermoelectric properties. However, integration to thermoelectric devices is problematic due to their usually high thermal conductivities. Reporting on thermal transport studies between 150 and 300 K, we show that franckeite, a naturally occurring 2D heterostructure, exhibits a very low thermal conductivity which combined with its previously reported high Seebeck coefficient and electrical conductance make it a promising candidate for low dimensional thermoelectric applications. We find cross- and in-plane thermal conductivity values at room temperature of 0.70 and 0.88 W m-1 K-1, respectively, which is one of the lowest values reported today for 2D-materials. Interestingly, a 1.77 nm thick layer of franckeite shows very low thermal conductivity similar to one of the most widely used thermoelectric material Bi2Te3 with the thickness of 10-20 nm. We show that this is due to the low Debye frequency of franckeite and scattering of phonon transport through van der Waals interface between different layers. This observation open new routes for high efficient ultra-thin thermoelectric applications.

Phonon scattering

10.1039/d1nr07889e

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Device Integration of Atomically precise Graphene Nanoribbons (GNRs)

Bulletin of the American Physical Society (2021)

Oliver Braun Jan Overbeck Mickael L. Perrin Gabriela Borin Barin Maria El Abbassi

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CCDC 1893619: Experimental Crystal Structure Determination

The Cambridge Structural Database (2019)

Wenjun Xu Edmund Leary Songjun Hou Sara Sangtarash M. Teresa González

10.5517/ccdc.csd.cc21kghl

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CCDC 2074551: Experimental Crystal Structure Determination

The Cambridge Structural Database (2021)

Wenjun Xu Edmund Leary Sara Sangtarash Michael Jirásek M. Teresa González

10.5517/ccdc.csd.cc27mr0n

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Thermal Transport through Single-Molecule Junctions

Nano Letters (2019)

Nico Mosso Hatef Sadeghi Andrea Gemma Sara Sangtarash Ute Drechsler

Molecular junctions exhibit a rich and tunable set of thermal transport phenomena. However, the predicted high thermoelectric efficiencies, phonon quantum interference effects, rectification, and nonlinear heat transport properties of organic molecules are yet to be verified because suitable experimental techniques have been missing. Here, by combining the break junction technique with suspended heat-flux sensors with picowatt per Kelvin sensitivity, we measured the thermal and electrical conductance of single organic molecules at room temperature simultaneously. We used this method to study the thermal transport properties of two model systems, namely, dithiol-oligo(phenylene ethynylene) and octane dithiol junctions with gold electrodes. In agreement with our density functional theory and phase-coherent transport calculations, we show that heat transport across these systems is governed by the phonon mismatch between the molecules and the metallic electrodes. This work represents the first measurement of thermal transport through single molecules and opens new opportunities for studying heat management at the nanoscale level.

10.1021/acs.nanolett.9b02089

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Citations (75)