Seventh Framework Programme
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In this page you will find the publication related to the Project, as well as the articles and the press releases.

To get in contact with us please write to the press desk office.

Redox-active radical as an effective nanoelectronic component: stability and electrochemical tunnelling spectroscopy in ionic liquids

Physical Chemistry Chemical Physics - Go to the journal web site

A. Rudnev, C. Franco, N. Crivillers, G. Seber, A. Droghetti, I. Rungger, I.V. Pobelov, J. Veciana, M. Mas-Torrent, C. Rovira

Dynamic spin filtering at the Co/Alq3 interface mediated by weakly coupled second layer molecules

Nature Communications - Go to the journal web site

Andrea Droghetti, Philip Thielen, Ivan Rungger, Norman Haag, Nicolas Großmann, Johannes Stöckl, Benjamin Stadtmüller, Martin Aeschlimann, Stefano Sanvito, Mirko Cinchetti

"Charge and spin transport in single and packed ruthenium-terpyridine molecular devices: Insight from first-principles calculations"

Scientific Reports - Go to the journal web site

C. Morari, L. Buimaga-Iarinca, I. Rungger, S. Sanvito, S. Melinte, and G.-M. Rignanese

A Diffusion Monte Carlo perspective on the spin-state energetics of [Fe (NCH) 6] 2+

Journal of Chemical Theory and Computation - Go to the journal web site

Maria Fumanal; Lucas K Wagner; Stefano Sanvito; Andrea Droghetti

Chemical control over the energy-level alignment in a two-terminal junction

Nature Communications - Go to the journal web site

L. Yuan,C. Franco, N. Crivillers, M. Mas-Torrent, C. S. S. Sangeeth, C. Rovira,J. Veciana, C. A. Nijhuis

Current-induced phonon renormalization in molecular junctions

Physical review B - Go to the journal web site

M. Bai, C. S. Cucinotta, Z. Jiang, H. Wang, Y. Wang, I. Rungger, S. Sanvito, and S. Hou

Fundamental gap of molecular crystals via constrained density functional theory

Physical review B - Go to the journal web site

A. Droghetti, I. Rungger, C. D. Pemmaraju, and S. Sanvito

Donor/Acceptor Mixed Self-Assembled Monolayers for Realising a Multi-Redox-State Surface

Chem. Phys. Chem - Go to the journal web site

J. Casado-Montenegro, E. Marchante, N. Crivillers, C. Rovira, and M. Mas-Torrent

Exchange coupling inversion in a high-spin organic triradical molecule

Nano letters - Go to the journal web site

"Rocco Gaudenzi; Enrique Burzurí; Daniel Reta; Iberio de P. R. Moreira; Stefan Bromley; Concepcio Rovira; Jaume Veciana; Herre S. J. van der Zant."

Chapter 4: Spin transfer torque: a multiscale picture

Book: Nanomagnetic and spintronic devices for energy-effcient memory and computing

Y. Xie, I. Rungger, M. Stamenova, S. Sanvito, K. Munira, and A. W. Ghosh
John Wiley & Sons

Sequential Electron Transport and Vibrational Excitations in an Organic Molecule Coupled to Few-Layer Graphene Electrodes

ACS Nano - Go to the journal web site

Enrique Burzurí; Joshua Island; Raúl Díaz Torres; Alexandra Fursina; Arántzatu González Campo; Olivier Roubeau; Simon Teat; Nuria Aliaga Alcalde; Eliseo Ruiz; Herre van der Zant

The promoting effect of water on the electroreduction of CO2 in acetonitrile

Electrochimica Acta - Go to the journal web site

A.V. Rudnev, U.E. Zhumaev, A. Kuzume, S. Vesztergom, J. Furrer, P. Broekmann, T. Wandlowski

Transmission through correlated CunCoCun heterostructures

PHYSICAL REVIEW B - Go to the journal web site

L. Chioncel, C. Morari, A. Östlin, W. H. Appelt, A. Droghetti, M. M. Radonjić, I. Rungger, L. Vitos, U. Eckern, and A. V. Postnikov
We propose a method to compute the transmission through correlated heterostructures by combining density functional and many-body dynamical mean field theories. The heart of this combination consists in porting the many-body self-energy from an all electron basis into a pseudopotential localized atomic basis set. Using this combination we study the effects of local electronic interactions and finite temperatures on the transmission across the Cu4CoCu4 metallic heterostructure. It is shown that as the electronic correlations are taken into account via a local but dynamic self-energy, the total transmission at the Fermi level gets reduced (predominantly in the minority-spin channel), whereby the spin polarization of the transmission increases. The latter is due to a more significant d-electron contribution, as compared to the noncorrelated case in which the transport is dominated by s and p electrons.

Chapter 3: Electron transport as a driver for self-interaction-corrected methods

"Advances in Atomic, Molecular and Optical Physics "

A. Pertsova, C. M. Canali, M. R. Pederson, I. Rungger and S. Sanvito

Spin-valve Effect in NiFe/MoS2/NiFe Junctions

NANO LETTERS - Go to the journal web site

W. Wang, A. Narayan, L. Tang, K. Dolui, Y. Liu, X. Yuan, Y. Jin, Y. Wu, I. Rungger, S. Sanvito, F. Xiu
Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have been recently proposed as appealing candidate materials for spintronic applications owing to their distinctive atomic crystal structure and exotic physical properties arising from the large bonding anisotropy. Here we introduce the first MoS2-based spin-valves that employ monolayer MoS2 as the nonmagnetic spacer. In contrast with what expected from the semiconducting band-structure of MoS2, the vertically sandwiched-MoS2 layers exhibit metallic behavior. This originates from their strong hybridization with the Ni and Fe atoms of the Permalloy (Py) electrode. The spin-valve effect is observed up to 240 K, with the highest magnetoresistance (MR) up to 0.73% at low temperatures. The experimental work is accompanied by the first principle electron transport calculations, which reveal an MR of ~ 9% for an ideal Py/MoS2/Py junction. Our results clearly identify TMDs as a promising spacer compound in magnetic tunnel junctions and may open a new avenue for the TMDs-based spintronic applications.

Vibron-assisted spin relaxation at a metal/organic interface

PHYSICAL REVIEW B - Go to the journal web site

A. Droghetti, I. Rungger, M. Cinchetti, and S. Sanvito
Inspired by recent experiments for hybrid organic-ferromagnet interfaces, we propose a spin-relaxation mechanism which does not depend on either the spin-orbit or the hyperfine interaction. This takes place when a molecule with initial spin imbalance is weakly coupled to a metal surface and can be excited in various vibrational states. In such a situation the electron-vibron interaction promotes the exchange of spin-polarized electrons between the molecule and the surface, serving as an energy and angular momentum reservoir. This process leads to an effective spin relaxation of the electron population in the molecule. We suggest that this nonequilibrium mechanism can be investigated through time-resolved spin-polarized scanning tunneling microscopy experiments.

DNA-Grafted Supramolecular Polymers: Helical Ribbon Structures Formed by Self-Assembly of Pyrene–DNA Chimeric Oligomers


Y. Vyborna, M. Vybornyi, A.V. Rudnev, R. Häner
The controlled arraying of DNA strands on adaptive polymeric platforms remains a challenge. Here, the noncovalent synthesis of DNA-grafted supramolecular polymers from short chimeric oligomers is presented. The oligomers are composed of an oligopyrenotide strand attached to the 5′-end of an oligodeoxynucleotide. The supramolecular polymerization of these oligomers in an aqueous medium leads to the formation of one-dimensional (1D) helical ribbon structures. Atomic force and transmission electron microscopy show rod-like polymers of several hundred nanometers in length. DNA-grafted polymers of the type described herein will serve as models for the development of structurally and functionally diverse supramolecular platforms with applications in materials science and diagnostics.

Break junction under electrochemical gating: testbed for single-molecule electronics

Chemical Society Reviews - Go to the journal web site

C. Huang, A. Rudnev, W. Hong, Th. Wandlowski
Molecular electronics aims to construct functional molecular devices at the single-molecule scale. One of the major challenges is to construct a single-molecule junction and to further manipulate the charge transport through the molecular junction. Break junction techniques, including STM break junctions and mechanically controllable break junctions are considered as testbed to investigate and control the charge transport on a single-molecule scale. Moreover, additional electrochemical gating provides a unique opportunity to manipulate the energy alignment and molecular redox processes for a single-molecule junction. In this review, we start from the technical aspects of the break junction technique, then discuss the molecular structure-conductance correlation derived from break junction studies, and, finally, emphasize electrochemical gating as a promising method for the functional molecular devices.

Kondo effect in a neutral and stable all organic radical single molecule break junction

NANO Letters - Go to the journal web site

R. Frisenda, R. Gaudenzi, C. Franco, M. Mas-Torrent, C. Rovira, J. Veciana, I. Alcon, S. T. Bromley, E. Burzuri, H.S.J. van der Zant
Organic radicals are neutral, purely organic molecules exhibiting an intrinsic magnetic moment due to the presence of an unpaired electron in the molecule in its ground state. This property, added to the low spin–orbit coupling and weak hyperfine interactions, make neutral organic radicals good candidates for molecular spintronics insofar as the radical character is stable in solid state electronic devices. Here we show that the paramagnetism of the polychlorotriphenylmethyl radical molecule in the form of a Kondo anomaly is preserved in two- and three-terminal solid-state devices, regardless of mechanical and electrostatic changes. Indeed, our results demonstrate that the Kondo anomaly is robust under electrodes displacement and changes of the electrostatic environment, pointing to a localized orbital in the radical as the source of magnetism. Strong support to this picture is provided by density functional calculations and measurements of the corresponding nonradical species. These results pave the way toward the use of all-organic neutral radical molecules in spintronics devices and open the door to further investigations into Kondo physics.

Electronic and magnetic properties of Ti4O7 predicted by self-interaction corrected density functional theory

Phys. Rev. B - Go to the journal web site

X. Zhong, I. Rungger, P. Zapol, and O. Heinonen
Understanding electronic properties of substoichiometric phases of titanium oxide such as Magnéli phase Ti4O7 is crucial in designing and modeling resistive switching devices. Here we present our study on Magnéli phase Ti4O7 together with rutile TiO2 and Ti2O3 using density functional theory methods with atomic-orbital-based self-interaction correction (ASIC). We predict a new antiferromagnetic (AF) ground state in the low temperature (LT) phase, and we explain energy difference with a competing AF state using a Heisenberg model. The predicted energy ordering of these states in the LT phase is calculated to be robust in a wide range of modeled isotropic strain. We have also investigated the dependence of the electronic structures of the Ti-O phases on stoichiometry. The splitting of titanium t2g orbitals is enhanced with increasing oxygen deficiency as Ti-O is reduced. The electronic properties of all these phases can be reasonably well described by applying ASIC with a “standard” value for transition metal oxides of the empirical parameter α of 0.5 representing the magnitude of the applied self-interaction correction.

Single-atom based coherent quantum interference device structure

NANO Letters - Go to the journal web site

B. Naydenov, I. Rungger, M. Mantega, S. Sanvito, and J. J. Boland
We describe the fabrication, operation principles, and simulation of a coherent single-atom quantum interference device (QID) structure on Si(100) controlled by the properties of single atoms. The energy and spatial distribution of the wave functions associated with the device are visualized by scanning tunneling spectroscopy and the amplitude and phase of the evanescent wave functions that couple into the quantum well states are directly measured, including the action of an electrostatic gate. Density functional theory simulations were employed to simulate the electronic structure of the device structure, which is in excellent agreement with the measurements. Simulations of device transmission demonstrate that our coherent single-atom QID can have ON-OFF ratios in excess of 103 with potentially minimal power dissipation.

Electron-vibron coupling effects on electron transport via a single-molecule magnet

Phys. Rev. B - Go to the journal web site

A. McCaskey, Y. Yamamoto, M. Warnock, E. Burzuri, H. S.J. Van der Zant, K. Park
We investigate how the electron-vibron coupling influences electron transport via an anisotropic magnetic molecule, such as a single-molecule magnet (SMM) Fe4, by using a model Hamiltonian with parameter values obtained from density-functional theory (DFT). The magnetic anisotropy parameters, vibrational energies, and electron-vibron coupling strengths of the Fe4 are computed using DFT. A giant spin model is applied to the Fe4 with only two charge states, specifically a neutral state with a total spin S=5 and a singly charged state with S=9/2, which is consistent with our DFT result and experiments on Fe4 single-molecule transistors. In sequential electron tunneling, we find that the magnetic anisotropy gives rise to new features in the conductance peaks arising from vibrational excitations. In particular, the peak height shows a strong, unusual dependence on the direction as well as magnitude of applied B field. The magnetic anisotropy also introduces vibrational satellite peaks whose position and height are modified with the direction and magnitude of applied B field. Furthermore, when multiple vibrational modes with considerable electron-vibron coupling have energies close to one another, a low-bias current is suppressed, independently of gate voltage and applied B field, although that is not the case for a single mode with a similar electron-vibron coupling. In the former case, the conductance peaks reveal a stronger B-field dependence than in the latter case. The new features appear because the magnetic anisotropy barrier is of the same order of magnitude as the energies of vibrational modes with significant electron-vibron coupling. Our findings clearly show the interesting interplay between magnetic anisotropy and electron-vibron coupling in electron transport via the Fe4. Similar behavior can be observed in transport via other anisotropic magnetic molecules.

Exploitation of desilylation chemistry in tailor-made functionalization on diverse surfaces

Nature Communications - Go to the journal web site

Yongchun Fu, Songjie Chen, Akiyoshi Kuzume, Alexander Rudnev, Cancan Huang, Veerabhadrarao Kaliginedi, Masoud Baghernejad, Wenjing Hong, Thomas Wandlowski, Silvio Decurtins, Shi-Xia Liu
Interface engineering to attain a uniform and compact self-assembled monolayer at atomically flat surfaces plays a crucial role in the bottom-up fabrication of organic molecular devices. Here we report a promising and operationally simple approach for modification/functionalization not only at ultraflat single-crystal metal surfaces, M(111) (M=​Au, ​Pt, ​Pd, ​Rh and ​Ir) but also at the highly oriented pyrolytic graphite surface, upon efficient in situ cleavage of trimethylsilyl end groups of the molecules. The obtained self-assembled monolayers are ultrastable within a wide potential window. The carbon–surface bonding on various substrates is confirmed by shell-isolated nanoparticle-enhanced Raman spectroscopy. Application of this strategy in tuning surface wettability is also demonstrated. The most valuable finding is that a combination of the desilylation with the click chemistry represents an efficient method for covalent and tailor-made functionalization of diverse surfaces.

Observing magnetic anisotropy in electronic transport through individual single-molecule magnets

J. Phys.: Condens. Matter - Go to the journal web site

E. Burzuri, R. Gaudenzi, H.S.J. van der Zant
We review different electron transport methods to probe the magnetic properties, such as the magnetic anisotropy, of an individual Fe4 SMM. The different approaches comprise first and higher order transport through the molecule. Gate spectroscopy, focusing on the charge degeneracy-point, is presented as a robust technique to quantify the longitudinal magnetic anisotropy of the SMM in different redox states. We provide statistics showing the robustness and reproducibility of the different methods. In addition, conductance measurements typically show high-energy excited states well beyond the ground spin multiplet of SMM. Some of these excitations have their origin in excited spin multiplets, others in vibrational modes of the molecule. The interplay between vibrations, charge and spin may yield a new approach for spin control.

Assembly of Extra-Large Nanosheets by Supramolecular Polymerization of Amphiphilic Pyrene Oligomers in Aqueous Solution

CHEMISTRY OF MATERIALS - Go to the journal web site

M. Vybornyi, A. Rudnev, R. Häner
The precise arraying of functional entities in a reproducible and predictable way in morphologically well-defined shapes is a key challenge in materials science. In this work, we describe the importance of kinetic effects in the two-dimensional (2D) self-assembly of a negatively charged pyrene trimer (Py3) in aqueous media. Under optimized experimental conditions the chain-folded oligomers assemble into exceptionally thin planar assemblies (∼2 nm thick) with a very high aspect ratio (area/thickness ratio ≈ 107 nm). The morphology of the nanosheets was characterized by different microscopic techniques (AFM, TEM, and optical microscopy), while UV-vis and fluorescence spectroscopy revealed details on the intramolecular folding of the oligomer strands. Temperature control was shown to be crucial for preventing the formation of kinetically trapped states, thus allowing the development of extra-large 2D assemblies.

Probing transverse magnetic anisotropy by electronic transport through a single-molecule magnet

Phys. Rev. B - Go to the journal web site

M. Misiorny, E. Burzuri, R. Gaudenzi, K. Park, M. Leijnse, M. R. Wegewijs, J. Paaske, A. Cornia, H.S.J. van der Zant
By means of electronic transport, we study the transverse magnetic anisotropy of an individual Fe4 single-molecule magnet (SMM) embedded in a three-terminal junction. In particular, we determine in situ the transverse anisotropy of the molecule from the pronounced intensity modulations of the linear conductance, which are observed as a function of applied magnetic field. The proposed technique works at temperatures exceeding the energy scale of the tunnel splittings of the SMM. We deduce that the transverse anisotropy for a single Fe4 molecule captured in a junction is substantially larger than the bulk value.

Electrochemical Control of Single-Molecule Conductance by Fermi-Level Tuning and Conjugation Switching

Journal of the American Chemical Society - Go to the journal web site

M. Baghernejad, X. Zhao, K. Baruel Ørnsø, M. Füeg, P. Moreno-García, A. Rudnev, V. Kaliginedi, S. Vesztergom, C. Huang, W. Hong, P. Broekmann, Th. Wandlowski, K.S. Thygesen, M. R. Bryce
ACS Publications
Controlling charge transport through a single molecule connected to metallic electrodes remains one of the most fundamental challenges of nanoelectronics. Here we use electrochemical gating to reversibly tune the conductance of two different organic molecules, both containing anthraquinone (AQ) centers, over >1 order of magnitude. For electrode potentials outside the redox-active region, the effect of the gate is simply to shift the molecular energy levels relative to the metal Fermi level. At the redox potential, the conductance changes abruptly as the AQ unit is oxidized/reduced with an accompanying change in the conjugation pattern between linear and cross conjugation. The most significant change in conductance is observed when the electron pathway connecting the two electrodes is via the AQ unit. This is consistent with the expected occurrence of destructive quantum interference in that case. The experimental results are supported by an excellent agreement with ab initio transport calculations.

Single-molecule transistors

CHEMICAL SOCIETY REVIEWS - Go to the journal web site

M. Perrin, E. Burzurí, H.S.J. van der Zant
The use of a gate electrode allows us to gain deeper insight into the electronic structure of molecular junctions. It is widely used for spectroscopy of the molecular levels and its excited states, for changing the charge state of the molecule and investigating higher order processes such as co-tunneling and the Kondo effect. Gate electrodes have been implemented in several types of nanoscale devices such as electromigration junctions, mechanically controllable break junctions, and devices with carbon-based electrodes. Here we review the state-of-the-art in the field of single-molecule transitors. We discuss the experimental challenges and describe the advances made for the different approaches.

Promising anchoring groups for single-molecule conductance measurements

Physical Chemistry Chemical Physics - Go to the journal web site

V. Kaliginedi, P. Moreno-García, A. Rudnev, M. Baghernejad, C. Huang, W. Hong, and Th. Wandlowski
The understanding of the charge transport through single molecule junctions is a prerequisite for the design and building of electronic circuits based on single molecule junctions. However, reliable and robust formation of such junctions is a challenging task to achieve. In this topical review, we present a systematic investigation of the anchoring group effect on single molecule junction conductance by employing two complementary techniques, namely scanning tunneling microscopy break junction (STM-BJ) and mechanically controllable break junction (MCBJ) techniques, based on the studies published in the literature and important results from our own work. We compared conductance studies for conventional anchoring groups described earlier with the molecular junctions formed through π-interactions with the electrode surface (Au, Pt, Ag) and we also summarized recent developments in the formation of highly conducting covalent Au-C σ-bonds using oligophenyleneethynylene (OPE) and an alkane molecular backbone. Specifically, we focus on the electron transport properties of diaryloligoyne, oligophenyleneethynylene (OPE) and/or alkane molecular junctions composed of several traditional anchoring groups, (dihydrobenzo[b]thiophene (BT), 5-benzothienyl analogue (BTh), thiol (SH), pyridyl (PY), amine (NH2), cyano (CN), methyl sulphide (SMe), nitro (NO2)) and other anchoring groups at the solid/liquid interface. The qualitative and quantitative comparison of the results obtained with different anchoring groups reveals structural and mechanistic details of the different types of single molecular junctions. The results reported in this prospective may serve as a guideline for the design and synthesis of molecular systems to be used in molecule-based electronic devices.

Long Distance Electron Transfer at the Metal/Alkanethiol/Ionic Liquid Interface

Journal of Physical Chemistry C - Go to the journal web site

V. Nikitina, A. Rudnev, G. Tsirlina, Th. Wandlowski 
ACS Publications
The rate constants of simple electron transfer (ET) reactions in room temperature ionic liquids (ILs) available now are rather high, typically at the edge of experimental accuracy. To consider ET phenomena in these media in view of theory developed earlier for molecular solvents, it is crucial to provide quantitative comparison of experimental kinetic data for certain reactions. We report this comparison for ferrocene/ferrocenium reaction. The ET distance is fixed by Au surface modification by alkanethiol self-assembled monolayers, which were characterized by in situ scanning tunneling microscopy. The dependence of ln kapp on barrier thickness in the range of ca. 6–20 Å is linear, with a slope typical for the same plots in aqueous media. This result confirms diabatic mode of Fc oxidation at long distance. The data for shorter ET distances point to the adiabatic regime of ET at a bare gold surface, although more detailed computational studies are required to justify this conclusion.

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