Nanomaterials, nanostructures and nano-devicesA
Atomic and molecular scale systems and devices
Introduction and scope:
Atomic and Molecular scale systems and devices are the ultimate limit as smallest materials. The scope of this symposium is to disclose novel phenomena in isolated atomic and molecular units and to compare cutting edge technologies for controlling and understanding systems at this scale and find viable paths for their applications.
Different systems, including multifunctional molecular units, single atoms in crystalline matrix (defects) in Si or diamond are nowadays controlled at atomic and molecular level. They constitute the bench for testing the scaling of physical lawsand for exploring novel quantum phenomena in materials down to (sub-)nanoscale. Mastering matter at the level of a single molecule or atom is also the crossing point between top-down and bottom-up preparation techniques. Investigations in these fields require the use of front edge experimental and theoretical tools such as scanning probe microscopies, advanced nano-fabrication techniques, advanced photonics, surface chemistry and multi-scale modeling. In spite of their different origin, investigating systems at molecular and atomic scale presents several common points and therefore the scope of this symposium is:
- to report, in a comparative way, on the latest achievements on the study of different atomic and molecular scale systems and devices.
- to discover and compare common fundamental quantum properties and phenomena at atomic and molecular scale. To share common practices to investigate them and for encoding qubits.
- to study and exploit interplay between multiple degrees of freedoms such as charge, spin, photons, vibrations etc. at atomic and molecular scale.
- to compare and find common strategies for scalabilities towards complex atomic/molecular architectures.
- to discuss common issues between different atomic and molecular systems and propose appropriate solutions
- to find possible paths for scalable applications.
- to evaluate energy dissipation mechanisms at atomic and molecular scale.
- to explore and compare innovative experimental and theoretical tools.
- to assess potentialities for applications in this emerging field.
During the symposium a round table discussion on Quantum Technologies (QT) with Molecular Systems and with dopants in Diamond and Siwill be organized. The aim of this discussion is to evidence societal needs and interests for QT and propose short and long term applications of atom and molecular scale quantum technologies.
Hot topics to be covered by the symposium:
- molecular electronics and logics
- molecular quantum spintronics
- molecular architectonics, hierarchical molecular assembly,hybrid molecular systems and devices
- nitrogen-vacancy centersin diamond
- single atoms in crystalline matrix: dopants in Si
- quantum technologies (QC, QIP, Q-sensors, Q-metrology) with dopants and molecular systems.
- advanced tools and techniques for addressing single molecules and atoms
List of keynote speakers:
- David Awschalom (Chicago US)
- Leo Gross (IBM, Zurich, CH)
- Marek Kolmer (Krakow, PL)
- Wolfgang Wernsdorfer (Grenoble, F)
- Jörg Wrachtrup (Stuttgart, D)
This symposium is jointly organized and supported by four FP7-FET Proactive projects: MOQUAS, SiAM, DIADEMS, PAMS.
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Joint session A+J : -
Authors : Joerg Wrachtrup
Affiliations : University of Stuttgart and Center for Integrated Quantum Science and Technology, IQST
Resume : Spin defects are versatile sensors for magnetic and electric fields as well as quantities like temperature or force. Owing to the point-like nature of the defects, these parameters can be measured with nanometre precision. While measurements with high spatial accuracy are possible, spin-based sensing is not restricted to surfaces as quantities can be detected in a three dimensional fashion over at least some ten nanometre distance. Also, spin sensors are rather broad band allowing for some ten ps time resolution. The talk will highlight recent measurements and discuss the limitations as well as prospects of the method for material and life sciences as well as the sensor industry.
Authors : Michal Gulka, Emilie Bourgeois, Jaroslav Hruby, Michael Trupke, Milos Nesladek
Affiliations : CTU in Prague, Faculty of Biomedical Engineering, Sítná sq. 3105, 272 01, Kladno, Czech Republic and Institute of Physics, AS CR, v.v.i., Na Slovance 5, 185 00, Prague 8, Czech Republic and Institute for Materials Research (IMO), Hasselt University, Wetenschapspark 1, B-3590 Diepenbeek, Belgium; Institute for Materials Research (IMO), Hasselt University, Wetenschapspark 1, B-3590 Diepenbeek, Belgium and IMOMEC division, IMEC, Wetenschapspark 1, B-3590 Diepenbeek, Belgium.; Institute for Materials Research (IMO), Hasselt University, Wetenschapspark 1, B-3590 Diepenbeek, Belgium; Vienna Center for Quantum Science and Technology, Atominstitut, TU Wien, 1020 Vienna, Austria; Institute for Materials Research (IMO), Hasselt University, Wetenschapspark 1, B-3590 Diepenbeek, Belgium and IMOMEC division, IMEC, Wetenschapspark 1, B-3590 Diepenbeek, Belgium.
Resume : The use of the negatively charged nitrogen-vacancy (NV) center for nanoscale  and ultrasensitive  magnetometry has been demonstrated. A new method for NV spin readout, by direct electric detection of charge carriers promoted to the conduction band of diamond by NV ionization, has been recently introduced by our group . Compared to the commonly used optical readout, the photoelectric detection of magnetic resonances (PDMR) could lead to improved detection efficiency, easier integration on the electronic chip and more compact device construction, as it does not require complex readout optical path. In this paper we present first results of DC magnetometry obtained using PDMR to detect the Zeeman splitting. To this end, a type-IIa single crystal diamond implanted (N4 , 1E14 per cm2, 8 keV) with ensembles of shallow NV centres and equipped with coplanar Ti-Au electrodes has been used. To remove the parasitic current resulting from the ionization of non-NV diamond defects, we referenced the signal lock-in amplification to the microwaves pulsing frequency. Also, better signal-to-noise ratio was obtained by integrating high frequency microwave and laser sequence in a low frequency envelope read by the lock-in technique. The magnetic field sensitivity and possible limitations are discussed and compared with ODMR.  P. Maletinski et al., Nature Nanotechnol. (2012)  T. Wolf et al., Phys. Rev. X (2015)  E. Bourgeois et al., Nature Comm. (2015)
Authors : Z. T. Zhang,1,2,3 D. Dmytriieva,1,4 S. Molatta,1,4 Yutian Wang,2 Shengqiang Zhou,2 Zhaorong Yang3, Manfred Helm2, 4, J. Wosnitza,1,4 and H. Kühne,1
Affiliations : 1 Hochfeld-Magnetlabor Dresden (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden, Germany 2 Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden, Germany 3 Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, People’s Republic of China 4 TU Dresden, D-01062 Dresden, Germany
Resume : It is still an open question whether a material with only s or p electrons can be magnetic. Recently, we showed that the defects in SiC, generated by neutron irradiation, introduce paramagnetism, the amplitude of which scales with the defect concentration [Phys. Rev. B 92, 174409]. Here, we report on a 13C and 29Si nuclear magnetic resonance (NMR) investigation of the defect-induced magnetism in SiC. Consistent with magnetization measurements, the temperature dependence of the NMR shift can well be described by a Curie-Weiss behavior for both nuclear isotopes, allowing for a detailed study of the electronic paramagnetism in SiC from a local probe point of view. The increasing line width of the NMR spectra upon cooling indicates a growing amplitude of the internal dipole fields stemming from the local moments. Below 20 K, a sharp decrease of the integrated signal intensity implies a pronounced increase of the nuclear spin-lattice relaxation time T1. Simulations based on a local dipole field model were performed, and are compared to the amplitude of the experimental 13C and 29Si NMR shifts and line widths. For comparison, NMR measurements were performed on a virgin sample of SiC without defects, and, as expected, no NMR signal was observed due to its gapped, non-magnetic nature. Our study provides clear indications of defect-induced magnetism in SiC. The project is supported by Helmholtz-Association (VH-PD-146). Z. T. Zhang was financially supported by the National Nature Science Foundation of China (Grant No. 11304321) and by the International Postdoctoral Exchange Fellowship Program 2013 (Grant No. 20130025).
Single atoms in Si : Xavier Jehl
Authors : Vyacheslavs Kashcheyevs
Affiliations : University of Latvia
Resume : Resonant tunnelling through an individual dopant under the gate of a field-effect transistor can be used to control clocked charging of a small metallic island. Quantized charge pumping is typically achieved by applying rf signals to the entrance and exit gates. We show that a distinctive characteristic of the resonance-controlled transport is the sign reversal of the pumping current as function of the average potential on the island. We show how to infer electrostatic and tunnelling coupling parameters of a particular device from the pumping-current maps and the co-tunnelling corrections to deterministic single-electron transfer. These principles are demonstrated on a recent realization of a hybrid metallic island/single dopant pump with fully depleted silicon-on-insulator technology.
Authors : J. Pernot1,2,3, T. T. Pham1,2,4, A. Maréchal1,2,4, N. Rouger1,4, D. Eon1,2, E, Gheeraert1,2
Affiliations : 1 Université Grenoble Alpes, Institut NÉEL, F-38000 Grenoble, France 2 CNRS, Institut NÉEL, F-38042 Grenoble, France 3 Institut Universitaire de France, 103 boulevard Saint-Michel, F-75005 Paris, France 4 Univ. Grenoble Alpes, G2ELab, F-38000 Grenoble, France
Resume : The high breakdown electric field of diamond, its large carrier mobility and its exceptional thermal conductivity make it the ultimate semiconductor for high power and high frequency electronics. These features and the important progresses that have been made recently in the fields of substrate fabrication, epilayer growth and doping control should in principle allow the development of new low loss electric switches. Different devices are under study in Europe to demonstrate the potentialities of diamond for power electronics: i) Schottky diode and ii) metal oxide semiconductor field effect transistor and iii) delta doped field effect transistor. In this presentation, we will first review the recent progresses achieved in the field of diamond devices for power electronics. Then, we will focus on our specific work on O-terminated diamond based MOSFET. More precisely, we will investigate the interface properties of the Al203 oxide deposited on O-terminated (100) p-type diamond. Using O-terminated diamond, a diamond MOS field effect transistor is expected to be able to work in inversion regime with electrons or holes as minority carriers. However, some problems are still not solved before the fabrication of an efficient diamond MOSFET for high voltage applications. The recent progresses will be summarized and the main issues for the coming years will be discussed.
Authors : P. Reynaud1,3, A.Thuaire1,3,E. Rolland1,3, A. Garnier1,3, X. Jehl2,3, S. Chéramy1,3
Affiliations : 1 CEA, LETI, MINATEC Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France. 2 CEA, DRF, MINATEC Campus, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France. 3 University Grenoble Alpes, F-38000 Grenoble France.
Resume : During the last decade, an important effort has been allocated to emergent nanotechnologies, as alternatives to current silicon-based technologies, in order to face physics issues appearing with the downscaling of electronic components (Moore’s law). One solution which is today explored in the research laboratories, relies on the use of the tip of a Scanning Tunneling Microscope (STM) for the fabrication of atomic scale devices. Typically, a 1.5 nm-wide phosphorous nanowire can be fabricated between source and drain regions by STM-assisted lithography, demonstrating both the feasibility of such fabrication and the measurement of a resistance value versus nanowire length, at the nanoscale. In this project, we propose to present the preliminary results obtained on the development of a platform structure enabling the fabrication of an atomic wire and its connection to metal lines and pads. A 200mm fabrication flow has been defined, enabling the dicing of 1cm² dies for nanowires fabrication in STM, and their further re-integration on 200mm Si substrates for the interconnections processing steps. The main technological modules will be presented, regarding both surface issues (surface reconstruction and preservation with the bonding of a temporary silicon cap, debonding step in STM) and electrical connection issues (implantation, die to wafer bonding, via processing). This innovative process flow could pave the way for the fabrication of single-atom devices at the industrial level.
Authors : T. A. Grotjohn, S. A. Zajac, N. Suwanmonka, A. Bhattacharya, S. Nad, A. Charris, S. Zhang, N. Miller, J. Albrecht, J. Asmussen, T. Hogan, C. Wang, R. Rechenberg, A. Hardy, M. Becker, T. Schuelke
Affiliations : Electrical and Computer Engineering, Michigan State University, East Lansing, MI USA; Fraunhofer Center for Coatings and Diamond Technologies, East Lansing, MI USA
Resume : Diamond as a semiconductor material for electronics has potential due to its material properties including high thermal conductivity, high electric field breakdown strength, and high carrier mobilities. In this paper we will report broadly on the diamond based power electronics work in the USA and more specifically on our work on diamond power electronics in the MSU/Fraunhofer Center for Coatings and Diamond Technologies (CCD). We will present our work to improve the quality of bulk and epitaxial mono-crystalline diamond material and its use in making vertical diamond diodes for power electronics. The desired diode characteristics in this project includes a reverse bias breakdown voltage exceeding 1000 V and a forward current exceeding 10 A. Work will be described that improves the quality of the bulk substrates by reducing the line defect (dislocation) density by growing a thick diamond layer using a microwave plasma CVD diamond deposition process on a substrate and then cutting substrates such that the new substrate’s surface is parallel to the growth direction. Boron doped epitaxial layers are then grown on the cut substrates with conditions and processes to minimize the generation of new dislocation defects. Diode architectures being studied include a Schottky vertical diode, a Schottky quasi-vertical diode and these same structures with field plates of Al2O3. To make the diamond diodes, a heavily-doped p-type layer and a lightly-doped p-type layer are deposited in microwave plasma-assisted CVD reactors using boron as the dopant. Efforts are made during the lightly boron doped deposition to minimize the unwanted nitrogen and other impurity incorporation. Diodes have been fabricated with both small Schottky contact areas of 150 micrometer diameter and larger Schottky contact areas of 2 sq. mm. Various types of Schottky contacts have been used including gold, platinum and molybdenum. Diodes with the smaller contacts have been fabricated with breakdown voltages of over 1000 V and forward current flow densities of 500 A/cm^2. Diodes with the larger contacts have been fabricated with current flows up to 18 A and a current density of 900 A/cm^2. Diode characteristics are measured in the temperature range from 300-600 K and comparisons are made to device simulations using the MEDICI and Sentaurus TCAD semiconductor device simulators. This work is supported by US Department of Energy: ARPA-E SWITCHES program.
Authors : Tomas Skeren, Nikola Pacher, Sigrun A. Koester, Andreas Fuhrer
Affiliations : IBM Research - Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
Resume : Hydrogen resist lithography is a technique capable of preparing atomic scale dopant devices. It is enabled by a large difference in chemical reactivity of a bare and hydrogen passivated Si(001): 2x1 surface. Using a scanning tunneling microscope (STM), the hydrogen layer of the H:Si(001) surface is locally desorbed with nanometer precision leaving behind exposed areas of reactive bare Si. When exposed to gaseous dopant precursor the hydrogen layer acts as a resist and the dopants stick only to the desorbed areas. Compared to conventional fabrication methods, hydrogen resist lithography enables doping with sub-nanometer lateral resolution and extremely abrupt doping profiles. Fabrication of n-type dopant devices is already quite well established and the interaction of phosphine with the Si(001) surface is well studied and understood. For p-type devices incorporation of acceptor atoms into the silicon matrix is required. We will show how this can be achieved with a diborane precursor and discuss the incorporation and activation of boron into the Si(001) surface. For the first time we also show how a bipolar dopant device (a p-n junction) can be created by hydrogen resist lithography using sequential doping with both phosphine and diborane. Preliminary electrical measurements confirm that the planar nanoscale p-n junction is electrically active. Furthermore, we find resonant inter-band tunneling signatures similar to the behavior of an Esaki diode. We discuss the results and give an outlook for possible future applications of this technique.
Addressing Planar Single Molecules : Angelika Kuehnle
Authors : Leo Gross, Bruno Schuler, Niko Pavliček, Wolfram Steurer, Shadi Fatayer, Zsolt Majzik, Nikolaj Moll, Gerhard Meyer
Affiliations : IBM Research - Zurich
Resume : The fuctionalization of tips by atomic manipulation dramatically increased the resolution of atomic force microscopy (AFM) . The combination of high-resolution AFM with atomic manipulation now offers the unprecedented possibility to custom-design individual molecules by making and breaking bonds with the tip of the microscope and directly characterizing the products on the atomic scale. We recently applied this technique to generate and study reaction intermediates  and to investigate chemical reactions trigged by atomic manipulation. We formed diradicals by dissociating halogen atoms and then reversibly triggered ring-opening and -closing reactions via atomic manipulation, allowing us to switch and control the molecule’s reactivity, magnetic and optical properties . Additional information about charge states  and charge distributions  can be obtained by Kelvin probe force spectroscopy. On multilayer insulating films we investigated single-electron attachment, detachment and transfer between individual molecules . References:  L. Gross et al. Science 325, 1110 (2009)  N. Pavliček et al. Nature Chem. 7, 623 (2015)  B. Schuler et al. Nature Chem. 8, 220 (2016)  L. Gross et al. Science 324, 1428 (2009)  F. Mohn et al. Nature Nanotech. 7, 227 (2012)  W. Steurer et al. Nature Commun. 6, 8353 (2015)
Authors : Jingyuan Zhu†, Joseph McMorrow†, Rachel Crespo-Otero†, Geyou Ao∥, Ming Zheng∥, William P. Gillin§, and Matteo Palma*†
Affiliations : †School of Biological and Chemical Sciences, Materials Research Institute, Institute of Bioengineering, and §Materials Research Institute and School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom； ∥ Materials Science and Engineering Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899-8542, United States；
Resume : Despite the substantial progress in single-molecule electronics from both fundamental and technological standpoints since 1970s, challenges remain. Principal among these are the time and cost involved in nanogap fabrication, the reliable control of the nanogap size, and the need for a facile (and scalable) technology for the establishment of electrical contact between individual molecules and metal electrodes. The use of carbon-based nano-electrodes, in particular, has emerged as a promising approach because of the intrinsic nanoscale size of CNTs and graphene, and the reduced electronic mismatch granted by having molecules and electrodes of the same material (Carbon atoms). Herein we present a facile solution based assembly method for producing molecular transport junctions (MTJs) by covalently linking single-chirality (7, 4) metallic DNA wrapped single-wall carbon nanotubes (SWCNTs) with electrically functional molecules. As a proof of principle, the single-molecule junction conductance of a series of oligophenyles was measured and found to be in line with literature values. The electrical properties of the MTJs fabricated in this study were investigated by measuring their current-voltage (I-V) characteristics as a function of the distance between a metallic AFM tip used as a mobile electrode, and a fixed macroscopic Au electrode. Our findings are of general interest for the controlled assembly of CNT junctions as a platform for molecular conductance investigations, towards the fabrication of solution-processable single-molecule devices including rectifiers and FET-based devices.
Authors : Frank Eisenhut1, Justus Krüger1, Dmitry Skidin1, Thomas Lehmann1, Anja Nickel1, Jörg Meyer1, Robin Ohmann1, Dmitry A. Ryndyk1, Christian Joachim2,3, Gianaurelio Cuniberti1,4, and Francesca Moresco1
Affiliations : Frank Eisenhut1, Justus Krüger1, Dmitry Skidin1, Thomas Lehmann1, Anja Nickel1, Jörg Meyer1, Robin Ohmann1, Dmitry A. Ryndyk1, Christian Joachim2,3, Gianaurelio Cuniberti1,4, and Francesca Moresco1
Resume : A single 4-acetylbiphenyl (ABP) molecule adsorbed along the dimer row of a Si(100)-(2×1) surface can be reversibly switched between two stable conformations using the tunneling current of a scanning tunneling microscope. The experiment combined with density functional theory calculations demonstrates that the molecule by switching selectively passivates and de-passivates a dangling-bond pair on the silicon surface. As this switch could open new routes for the logical input in dangling bond based atomic scale circuits, we studied ABP on Si(100)-(2x1):H. We will show that the molecules are forming a one-dimensional molecular line following a dangling bond initiated growing mechanism along as well as perpendicular to the silicon dimer rows. Moreover, a reversible tip-induced conformational change of the molecule at the end of the grown molecular chain has been observed.
Authors : Bulent Baris, Hassan Khoussa, Benoit Eydoux, David Martrou and Sebastien Gauthier
Affiliations : CEMES-CNRS, 29 rue J. Marvig, 31055 Toulouse Cedex, France ;
Resume : During the last decade aluminium nitride (AlN) have received a special attention because of its many interesting physical properties like a wide direct band gap (6 eV), high thermal conductivity and high thermal stability. Such features are an advantage for UV optoelectronic and high-power devices. Generally AlN is used as buffer layer in the heteroepitaxial growth during the elaboration of nitride semiconductor. But the study of metallic adsorbates on AlN surface are poorly represented in the literature . Au growth on AlN (0001) was carried out under UHV conditions in a molecular Beam epitaxy chamber and characterised in-situ by RHEED (reflexion high energy electron diffraction), NC-AFM (non contact atomic force microscopy) and KPFM (kelvin probe force microscopy). 2D isolated Au islands were observed on the surface in NC-AFM. In addition we could also distinguish two moirre pattern in NC-AFM. This new result open the way for new studies such as the control of the charge of the islands with the NC-AFM tip. References:  P. Waltereit, O. Brandt, A. Trampert, M. Ramsteiner, M. Reiche, M. Qi and K.H. Ploog, Appl. Phys. Lett., 74 (24) ,(1999), 3660.  F. Chaumeton, S. Gauthier and D. Martrou, AIP advances 5, 067108 (2015)
Authors : Gauthier CHICOT1,2, David EON3,4, Nicolas ROUGER1,2
Affiliations : 1Univ. Grenoble Alpes, G2ELab, F-38000 Grenoble, France 2CNRS, G2ELab, F-38000 Grenoble, France 3Univ. Grenoble Alpes, Institut Néel, F-38000 Grenoble, France 4CNRS, Institut Néel, F-38000 Grenoble, France
Resume : Diamond with its high critical electric field, opens the way to very high voltage power components. Diamond Schottky diodes and transistors has been demonstrated but do not show performances as high as expected. In fact, a particular attention has to be paid to the design of the drift layer to take benefit of the diamond superlative properties. The drift region thickness and doping level must be chosen to optimize the ON state resistance for any breakdown voltage (OFF state). A focus on the optimization of the Ron.S(BV) figure of merit has been carried out, while optimizing the drift layer. Based on the ionization integral calculation with impact ionization coefficients adapted to diamond, we performed an accurate analysis of the reciprocal punch through factor as function of the breakdown voltage to propose the drift layer architecture offering the best performances. We will show how performances of experimental devices from literature could have been drastically improved using this optimum design: Ron.S divided by 20 in certain cases. Nevertheless, our analysis points out that thicknesses and doping levels required to achieve the optimum drift layer are challenging for crystal growth, especially for high breakdown voltage. Thus, it is not always possible to use this optimum design for some technological reasons or due to component specificities and therefore further tradeoffs has to be done. For instance, we proposed a specific doping profile for Schottky diode that helps to maintain a low leakage current level without slashing the on state performances. An additional two dimensional cylindrical coordinate analysis was performed to quantify the radius effect on the breakdown voltage value for different drift region designs.
Planar Molecule Devices : André Gourdon
Authors : Marek Kolmer
Affiliations : Centre for Nanometer-Scale Science and Advanced Materials, NANOSAM, Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University, Lojasiewicza 11, 30-348 Krakow, Poland
Resume : Continuation of electronic circuits miniaturization would require alternative approaches as compared with modern solid state devices. Dangling bonds (DBs) on hydrogenated semiconductor surfaces are promising candidates for implementation of novel electronic devices. Atomically precise desorption of hydrogen atoms by a tip of the Scanning Tunneling Microscope (STM) allows creation of pre-designed and complex DB nanostructures [1-5], which then may serve as wires (interconnects) or even play a role of counting/logic circuits . The presentation will be devoted to the DB nanostructures on Ge(001):H and Si(001):H surfaces comprised of dangling bond dimers (DBDs), i.e. a structure of two bonded surface Ge/Si atoms with an unsaturated bond each. First, I will describe electronic properties of DB arrays obtained from Scanning Tunneling Spectroscopy (STS) experiments [1, 2, 5]. Particularly the prototypical Quantum Hamiltonian Computing (QHC) Boolean logic gate designed and constructed on the Si(001):H will be presented . Its NOR/OR gate truth table is confirmed by dI/dV STS spectra tracking how the surface states of the QHC gate structure are shifted according to the input logical status. Finally, I will show our efforts towards multiprobe planar transport measurements performed for DBD wires by the use of the new low-temperature 4-probe STM apparatus. Our STM tips preparation procedure enables planar multiprobe STM measurements on distances below 100nm. In this case the tips relative positions are exactly determined with respect to surface atomic reconstructions. References:  Kolmer M., et al., Electronic properties of STM-constructed dangling-bond dimer lines on a Ge(001)-(2×1):H surface, Physical Review B, 86, 125307 (2012);  Kolmer M., et al., Atomic scale fabrication of dangling bond structures on hydrogen passivated Si(001) wafers processed and nanopackaged in a clean room environment, Applied Surface Science, 288, 83– 89 (2014);  Kolmer M., et al., Realization of a quantum Hamiltonian Boolean logic gate on the Si(001):H surface, Nanoscale, 7, 12325–12330 (2015);  Godlewski S., et al., Dynamical behavior of a dangling bond dimer on a hydrogenated semiconductor: Ge(001):H, Physical Review B, 92, 115403 (2015);  Engelund M., et al., Tunneling spectroscopy of close-spaced dangling-bond pairs in Si(001):H, Scientific Reports, 5, 14496 (2015).
Authors : Omid Faizy Namarvar,1 Ghassen Dridi,1 and Christian Joachim1,2
Affiliations : 1 CEMES-CNRS, 29 rue J. Marvig, 31055 Toulouse Cedex, France ; 2 WPI-MANA, National Institute for Material Sciences, 1-1 Namiki, Tsukuba, Ibaraki, Japan
Resume : Belonging to the Quantum Hamiltonian Computing (QHC) branch of quantum control [1-2], atomic-scale Boolean logic gates (LGs) with two inputs - one output (OR, NOR, AND, NAND, XOR, NXOR) and - two outputs (half-adder circuit) were designed on a Si(100)-(2× 1)–H surface following the experimental realization of a QHC NOR gate  and the formal design of an half adder with 6 quantum states in the calculating block . The logical inputs are determined by two nearest neighbor crossing surface Si dangling bonds, which can be, for example, activated by adding or extracting two hydrogen atoms per input. QHC circuit design rules together with semi-empirical full valence K-ESQC transport calculations were used to determine the output current intensity of the designed LGs when interconnected to the metallic nano-pads by surface atomic-scale wires. Our calculations demonstrate that the proposed devices can reach a “0” to “1” logical output ratio up to 10 000 for a running current in the 0.2 µA range for 50 mV to 150 mV bias voltage around the nano-pads Fermi level.
Authors : R. Zuzak1, S. Godlewski1, M. Kolmer1, Marios Markoulides2, A. Gourdon2, M. Szymonski1
Affiliations : 1 Centre for Nanometer-Scale Science and Advanced Materials, NANOSAM, Faculty of Physics, Astronomy and Applied Computer Science, Lojasiewicza 11, 30-348 Krakow, Jagiellonian University in Krakow, Poland 2 Nanosciences group, CEMES CNRS-UPR 8011, Bât. PicoLab, BP 94347, 31055 Toulouse, France
Resume : In recent years we observe an increasing interest in the formation of low dimensional molecular structures on crystalline surfaces. Among them the quasi one-dimensional molecular wires attract growing attention driven by the interest in the fundamental structural and electronic properties as well as due to potential practical applications as conductive wires in nanometer-scale future electronic circuits. Bottom-up strategies basing on the self-assembly processes and on-surface chemical reactions are attractive way to form a variety of coupled molecular nanostructures on solid surfaces [1-2]. Especially the on-surface chemistry methods allow formation of defect-free polymers and graphene nanoribbons (GNRs) with a well-defined morphology , which due to their transport properties, are good candidates for future electronic applications . Moreover single atom dopants in GNRs structure could effectively tune their electronic properties. However, most often formation of molecular wires was demonstrated on metallic substrates, which do not allow electronic decoupling of the molecular structures from the substrate. Therefore for practical applications nanowires formation on semiconducting substrates would be more desired. Here we demonstrate that several tens of nanometer-long molecular quasi one-dimensional assemblies could be created by self-assembly processes on semiconducting surfaces. We demonstrate that the structures contain up-right oriented phthalocyanine molecules, which are stabilized by mutual interactions. Further we show that molecular wires on semiconducting surfaces could be formed via thermally triggered on-surface synthesis from molecular precursors. Finally we report on the fabrication of Cl doped 5-AGNR by using 3,4,9,10-tetrabromo-1,6,7,12-tetrachloro-perylene (TBTCP) precursors. We demonstrate that the doping leads to band gap shrinking resulting in almost metallic behavior already for short oligomers. All experiments are performed in a multichamber ultra high vacuum system and the detailed analysis of the structural and electronic properties of the molecular nanostrucutres is based on the low temperature scanning tunneling microscopy/spectroscopy experiments. References:  L. Grill et al., Nat. Nanotechnol. 2, 687 (2007)  J. Cai et al., Nature 466, 470 (2010)  L. Grill et al., Nat. Nanotechnol. 7, 713 – 717 (2012)
Atomic and Molecular Systems : Angelika Kuehnle
Authors : Bibek Adhikari, Ganesh Sivaraman and Maria Fyta
Affiliations : Institute for Computational Physics, University of Stuttgart, Allmandring 3, 70569 Stuttgart, Germany.
Resume : In this work, we deal with the electronic transport properties across small diamond-like nanostructures, the diamondoids, in a gold nanogap. In our diamondoid-based devices, a small diamondoid is placed in between the two gold electrodes of the nanogap. The diamondoids are covalently bonded to the gold electrodes through two different molecules, a thiol group and a N-heterocyclic carbene molecule. The transport properties of the diamondoid-based molecular device are evaluated with respect to these two binding possibilities and the size of the diamondoid. We also investigate the influence of doping the diamondoid on the properties of the molecular device. We find that using a nitrogen atom to dope the diamondoids leads to a considerable increase of the electron transmission across the device. In all cases, the efficiency of the device was manifested and is discussed in view of novel nanotechnological applications. In view of these applications, our results reveal a pathway to tune the electronic transport properties of diamondoid-based molecular devices by selectively choosing their structural characteristics.
Authors : Hai-Bing Xu
Affiliations : Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang, Sichuan, 621900, China
Resume : Fluorescent molecules are usually applied in chemical sensors, biological probes, and light-emitting devices. Traditionally, luminescent behaviors of molecules are usually demonstrated in solution, while they are used as materials in solid state, thus it is urgent to develop materials with aggregation induced emission (AIE). Since the electronic transitions of organometallic luminogens and AIE functional groups originate from the outer shells, their excitation energies are all susceptible to the external stimulations, it is challenging to achieve the AIE effect on organometallic complexes, which exhibit superior performance on thermal stability, long lifetime, large stokes shift, and visible light excitation. Thanks to the shielding effect and inner f-f’ electronic transitions in lanthanide(III) ions, the pumped excited energies induced by aggregation from the AIE functional sensitizer could be efficiently transferred to the lanthanide subunit, thus it is possible to introduce AIE effect into lanthanide complex systems. Here, a novel Eu(III) complex with two types of chromophores: hexafluoroacetylacetonate (hfac-) and 4'-(4-(1,2,2-triphenylvinyl)phenyl)-2,2':6',2''-terpyridine (TPE-TPy), which can be stepwise-activated to act as sensitizers for lanthanide luminescence in different concentrations, was reported. For example, hfac- mainly acts as the sensitizer to cause the EuIII-based emission at very low concentrations (≤ 10-5 M). When the concentrations are between 10-4 M and 10-3 M, both hfac- and TPE-TPy work, while once the concentration surpasses 10-3 M, only TPE-TPy does the job. It has been demonstrated that the quantum yields (ɸem) of EuIII change from high (3.95±0.15%) to low (0.160±0.001%), then climb up to 0.99±0.04%, when the concentrations range from 10-5 to 10-1 M. Since the bioprobes may accumulate on the surfaces of the biomacromolecules with different concentrations, smart ionic lanthanide bioprobes with strong output signals within a large scale of concentrations could be designed by such strategy. Interestingly, enhancing the aggregation effect by addition of n-hexane into the solution of 1 (10-4 M) in dichloromethane, the EuIII-based emission in 99% n-hexane is about three times as strong as that in 70% n-hexane. Thus it is successful to introduce the AIE effect into the lanthanide system. In brief, lanthanide complex equipped with both the AIE and ACQ effects of antennae has been prepared. And consistent signals of EuIII-based emission across wide range of concentrations are achieved by triggering the ACQ/AIE process. References 1. Y.Hong, J. W. Y. Lam, and B. Z. Tang. Aggregation-induced emission. Chem. Soc. Rev., 2011, 40, 5361. 2. Y. Zhang, P. Jiao, H. Xu, M. Tang, X. Yang, S. Huang, and J. Deng. Switchable sensitizers stepwise lighting up lanthanide emissions, Sci. Rep., 2015, 5, 9335.
Authors : Yu. Pogrebnyak
Affiliations : Department Electrophysics, Faculty of Radiophysics,Electronics and Computer Systems Taras Shevchenko National University of Kyiv
Resume : Hydroxyapatite (HA - Ca10(РО4)6 (OH)2) of the apatite group, hydroxyl analogue fluor apatite and hlor apatita. The analysis of the spectra of powders and polymerized ordered structures based on HA in compliance with the interoperability and building material for 3D synthesis. Established that the admixture to powdered HA may affect its polymerization processes. It is shown that the energy pumped reradiation on mode corresponding excitation respiratory oscillations HA.
Authors : Dmitry Skidin1, Frank Eisenhut1, Justus Krüger1, Renhao Dong2,3, Reinhard Berger2,3, Xinliang Feng2,3, Gianaurelio Cuniberti1,2, and Francesca Moresco1,2
Affiliations : 1Institute for Materials Science, Max Bergmann Center of Biomaterials; 2Center for Advancing Electronics Dresden; 3Department of Chemistry and Food Chemistry, TU Dresden, 01062 Dresden, Germany
Resume : Cyclic organosulfur molecules present a class of materials that gained a wide interest during the last decade. Long-awaited synthetic success enabled investigation of persulfurated arenes known for their outstanding properties. Strong electronic delocalization of thio-substituted arenes through the whole molecule together with high acceptor properties of sulfur as substituent let them serve as building blocks for several applications such as organic conductors, redox sensors, liquid crystals, organic electronics devices, etc. Moreover, affinity of sulfur to transition metal substrates may open a possibility of coordinating precursor molecules into highly-conductive two-dimensional networks on surfaces. We use low-temperature scanning tunneling microscopy (STM) to study the behavior of a number of cyclic organosulfur molecules on Au(111) surface. Particular emphasis is put on adsorption peculiarities, interaction with surface gold adatoms and electronic properties. Benzene- and coronene-based persulfurated molecules were specifically designed, synthesized and investigated by the means of STM. The findings suggest a wide range of possible applications for the cyclic organosulfur molecular materials.
Authors : Amretashis Sengupta1,2, Augusto F. Oliveira2,4, Thomas A. Niehaus3, Thomas Heine2,4
Affiliations : 1Indian Institute of Engineering Science and Technology, Shibpur, Howrah – 711 103, India; 2Department of Physics and Earth Science, Jacobs University, Bremen, Campus Ring 1, 28759 Bremen, Germany; 3Institut Lumière Matière,Université Claude Bernard Lyon 1, 10 rue Ada Byron,69622 Villeurbanne CEDEX, France; 4Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnéstr. 2, 04103 Leipzig, Germany;
Resume : Armchair nanotubes of transition metal dichalcogenides (MX2) such as MoS2, WS2 offer a sizeable band gap, with the advantage of a 1 dimensional electronic material, free from edge roughness and thermodynamic instability of nanoribbons. Use of such semiconducting MX2 ANTs in conjunction with metallic CNTs could prove useful for nanoelectronics applications. In this work we carry out atomistic simulations of CNT-MX2 (MoS2 or WS2) NT- CNT tunnel devices for their electronic properties. Density functional tight binding (DFTB) and DFTB-Non-equilibrium Green’s function (NEGF) method, with the QUASINANO DFTB parameters are employed to study the spatial distribution of carrier density, energy resolved conductance, transmission pathways and eigenstates, and the current-voltage characteristics of such 1D multi-junction devices. From our studies we find a more significant loss of coherence in the transmission eigenstates as electrons move from the MX2 region to the CNT contact, than that from the CNT into the MX2. Also the quenching of transmission eigenstates is more prominent in case of transport from MoS2 into CNT as compared to that from WS2 into CNT. Stronger elastic backscattering is observed in the case of the CNT-MoS2-CNT device. A greater transparency of states to carrier transport in CNT-WS2-CNT device, leads to a sharper increase in drive current and greater current saturation values, while also showing a higher peak transconductance in the given bias range of 0-4 V.
Authors : Gabriel Gil; Stefano Corni; Alain Delgado; Andrea Bertoni; Guido Goldoni
Affiliations : Department of Physics, Informatics and Mathematics, University of Modena and Reggio Emilia, Modena, Italy; CNR Institute of Nanosciences, Center S3; Department of Physics, University of Ottawa, Ottawa, Canada;Instituto de Cibernética, Matemática y Física, La Habana, Cuba; Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear, La Habana, Cuba.
Resume : Dye-functionalized nanoparticles (NPs) belong to a class of nanomaterials with great perspectives in a number of biological and medical applications as well as in optoelectronic devices, thanks to the possibility to tailor specific electronic and optical processes by controlling the size and composition of the synthesized NPs. One of these fundamental processes is the resonance energy transfer (RET), a radiation-less mechanism by which a photoexcited donor (here the dye) transfers its electronic excitation energy to an acceptor (here the NP). Even the simplest, well-known Förster theory, based on the transition dipole-dipole coupling, implicitly incorporates the inherent anisotropic character of RET through the nature of the involved interactions. However, this anisotropy is not exposed in typical experimental setups, which average over all possible orientations of the transition dipole moments of the donor and acceptor fragments. In this contribution, we discuss the possibility to expose and study the anisotropic nature of RET in properly designed nanocomposite (NC) architectures, such as semiconductor NPs functionalized with radially attached dye molecules. Optical excitations of the NP and of the dye are calculated using the envelope-function-based Configuration Interaction method and atomistic Time-Dependent Density Functional Theory, respectively, and incorporated into a generalization of Förster theory which includes interactions between all transition multipole moments of the NP and the transition dipole of the molecule,  making possible to study NCs with fragments of very different sizes. Complex dielectric environment effects (due to the solvent and the NP near to the dye) are included within a recently developed approach.  These carefully calculated dye-NP RET rates are then included in coupled kinetic equations with competing processes, such as diffusion of the excitation in the dye shell, fluorescence and non-radiative decay mechanisms, along with absorption. Finally, the complete NC photoluminiscence spectra (PL) are obtained from the steady-state regime for different polarization orientations of an excitation laser. Specifically, we considered a prototypical system composed by a core/shell wurtzite CdSe/ZnS NP and cyanine dye (Cy3B) molecules. We predict a strong (up to ~75%) quenching of the PL emission at the fluorescence peak of the dye for specific excitation laser polarization and a strong dependence on NP-dye distance. This strong optical anisotropy can be traced to the intrinsic anisotropy of the underlying wurtzite lattice of the NP and ensuing presence of an excitation dark axis. We also show that the predicted large PL anisotropy is robust against statistical dispersion of the number of dyes per NP. Therefore, we propose that the study of anisotropic PL could add to the toolbox for RET spectroscopy. References:  G. Gil, S. Corni, A. Delgado, A. Bertoni, G. Goldoni, J. Chem. Phys. 144, 074101 (2016).  A. Delgado, S. Corni, G. Goldoni, J. Chem. Phys. 139, 024105 (2013).
Authors : Imtisal Akhtar, Yongho Seo
Affiliations : Scanning Probe Microscopy Laboratory, Sejong University Faculty of Nanotechnology and Advance Material Engineering and Graphene Research Institute
Resume : 3-Dimensional imaging of semiconductor devices plays an imperative role especially for those semiconductor devices in which the layers of devices are stacked together and connected through via holes (TSV) with high aspect ratio more than 10. The diameter of such via holes can be few hundreds nanometers and depth up to micron scale. In order to take 3-D image of through silicon vias (TSVs), high aspect ratio probe, sensitive quart tuning fork sensor with high Q-factor (after attaching the tungsten tip and CNT) is required. For this purpose, tungsten tip and multiwalled CNTs are considered best candidate for 3-D imaging. A sensor using quartz tuning fork is used for 3D imaging of the holes on which tungsten tip is attached to one end of prong including CNT at the apex of tungsten tip. The tuning fork sensor is fixed on the head of the AFM and sample is moved by using piezoelectric tube scanner. For the side wall imaging of the holes, we have used single pass anodized aluminum axide (AAO) -which has deep holes. The position of the holes can be estimated by raster scan. An algorithm is implemented in Labview software to generate the 3-D image of holes. In order to test the algorithm, anodized aluminum oxide (AAO) sample is used with the 400nm diameter, 300nm depth and 400nm inter-pore distance. The sample has long cylindrical holes structure which is the suitable specimen for 3D scanning of hole. In order to measure the depth of the hole, click at the center of the hole is required after completing the 2-D scanning and force-distance (F-D) - curve can be computed at center of hole by pushing the tip inside the hole. The F-D curve not only gives the information about the depth of the hole but also tells about the strength of CNT attached to tungsten tip. Once the F-D curve is completed, 3-D scan can be initiated which includes real time line profile as well as 3D topography of each scan. The results obtained from experiments are quite satisfactory and still optimizations are required to get better 3-D image.
Authors : Aaron Z. Thong, Andrei P. Mihai, Steven Schofield, Milo S. P. Shaffer, Andrew P. Horsfield
Affiliations : Imperial College London, London SW7 2AZ, United Kingdom; University College London, London WC1E 6BT, UK
Resume : Molecular rectifiers which work at low-bias typically have low rectification ratios or low conductivities, primarily due to the large energy barrier across the sigma-bonds which bridge the donor and acceptor groups in these rectifying devices. In contrast, we present an easy synthetic route for fabricating bridgeless, unimolecular donor-acceptor rectifiers. These molecular rectifiers have a rectification ratio of 3.2 ± 1.0 in ambient scanning tunnelling spectroscopy experiments of the double-barrier-tunnel-junction. Simulations of the molecular break-junction further predict a theoretical rectification ratio of 13.9 at 0.5V, with a zero bias conductance of 0.021 G0. Analysis of the density of states within the junction reveals that the rectification is a result of bias-direction dependent coupling between donor and acceptor states. The bridgeless nature of the device allows large HOMO-LUMO coupling in the forward bias direction (from donor to acceptor), while maintaining a small coupling in the reverse bias direction. This follows from simple chemical intuition: electrons flow in the direction from donor (amine) to acceptor (C60) but face a greater barrier in the opposite direction, due to the poor accepting (donating) properties of the amine (fullerene) group. The proposed mechanism opens up new avenues for designing molecular devices which may benefit from both high conductance as well as rectification at low-bias.
Authors : Benoit EYDOUX 1, Bulent BARIS 1, Florian CHAUMETON 1, Roberto ROBLES 2, Miguel PRUNEDA 2, Nicolás LORENTE 2,3, Sébastien GAUTHIER 1, Xavier BOUJU 1, David MARTROU 1
Affiliations : 1 NanoSciences Group, CEMES, CNRS UPR 8011, 29 rue J. Marvig, F-31055 Toulouse, France 2 ICN2 – Institut Catala de Nanosciencia i Nanotecnologia, Campus UAB, 08193 Bellatera (Barcelona), Spain 3 Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU), Paseo Manuel de Lardizabal 5, 20018 Donostia-San Sebastiá́n, Spain, and Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián, Spain
Resume : Group-III nitride semiconductors are ideal candidates for high-power electronic applications. Among these materials, aluminium nitride (AlN) has the largest band gap. It also has unique properties such as small density, large stiffness, large piezoelectric constant, large fracture resistivity and chemical inertness. Unfortunately, defects and interface states seriously compromise devices based on these materials and there is an urgent need for high-quality interfaces and surfaces. For these reasons, its surface reconstructions have received a lot of attention theoretically. Furthermore, due to its high ionicity, AlN crystallizes in the wurtzite structure and its (0001) growth surface is polar, like other zinc blende (001) semiconductor surfaces. The consequence of this polarity is that the crystal should be stabilized by the apparition of surface charges that can be generated by different mechanisms like surface reconstructions. Experimentally, due to the large gap of AlN (6.2 eV) it is not possible to observe its surface by scanning tunneling microscopy (STM) except for the Al rich phase. One effective way to get information at the atomic scale is to use atomic-force microscopy in the non-contact mode (NC-AFM) under UHV. The growth of AlN samples was carried out in a MBE chamber equipped with a RHEED gun working at 15 keV. The AlN layer is grown on a 4H-SiC(0001) substrate following a recipe described previously (Chaumeton, F.; Gauthier, S.; Martrou, D. AIP Advances 2015, 5, 067108.). With the help of density functional studies, we determine new protocols for growing the technologically interesting N-rich AlN surfaces. This is achieved by dosing the precursor gases at unusually low rates. The measured surface reconstructions are in good agreement with our calculated structures. Our protocols permit us to access the surface based on one additional N atom in a (2×2) cell. These N-rich AlN surfaces could open new routes to dope AlN layers with important implications in high- power and temperature technological applications. Additionally, we have studied the adsorption of metallic components with the perspective of fabrication of planar atomic nanopads on AlN. Examples with Mg, Ag, and Au metallic deposition will be shown both experimentally and theoretically.
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Molecular Quantum Spintronics : Marco Affronte
Authors : Wolfgang Wernsdorfer
Affiliations : Institut Néel, CNRS, GRENOBLE, France PHI & INT, Karlsruher Institut für Technologie (KIT), Germany
Resume : The endeavour of quantum electronics is driven by one of the most ambitious technological goals of today’s scientists: the realization of an operational quantum computer. People start to address this goal by the new research field of molecular quantum spintronics, which combines the concepts of spintronics, molecular electronics and quantum computing . The building blocks are magnetic molecules, i.e. well-defined spin qubits. Various research groups are currently developing low-temperature scanning tunnelling microscopes to manipulate spins in single molecules, while others are working on molecular devices (such as molecular spin-transistors, spin valves and filters, and carbon-nanotubebased devices) to read and manipulate the spin state and perform basic quantum operations. We will first discuss this - still largely unexplored - field and then summarize our first results [2-5]. Finally, we will discuss the new challenges of the field and the requirements to achieve them.  L. Bogani, W. Wernsdorfer, Nature Mater., 2008, 7, 179.  M. Urdampilleta, S. Klyatskaya, M.-P. Cleuziou, M. Ruben, W. Wernsdorfer, Nature Mater., 2011, 10, 502.  A. Candini, S. Klyatskaya, M. Ruben, W. Wernsdorfer and M. Affronte, Nano Lett., 2011, 11, 2634.  S. Thiele, F. Balestro, R. Ballou, S. Klyatskaya, M. Ruben, W. Wernsdorfer, Science, 2014, 344, 1135; Nature, 2012, 488, 357.  M. Ganzhorn, S. Klyatskaya, M. Ruben, W. Wernsdorfer, Nature Nanotechnol., 2013, 8, 165; Nature Comm., 2016.
Authors : Godfrin C.1,2, Ferhat K.1,2, Ballou R.1,2, Klyatskaya S.3, Ruben M.3,4, Wernsdorfer W.1,2 and Balestro F.1,2,5
Affiliations : 1 Univ. Grenoble Alpes, Inst. Néel, F-38042 Grenoble, France. 2 CNRS, Institut Néel, F-38042 Grenoble, France. 3 Inst. of Nanotechnoogy, KIT, 76344 Eggenstein-Leopoldshafen, Germany. 4 Inst. de Phys. et Chim. des Mat. de Strasbourg, CNRS, 67034 Strasbourg, France. 5 Inst. Univ. de France, 103 Blvd Saint-Michel, 75005 Paris, France.
Resume : Manipulating a single 3/2 nuclear-spin embedded in a molecular magnet spin-transistor is of great interest to explore fundamental law of quantum physics. Since we showed the coherent manipulation of a single nuclear spin using electric fields only , we are now able to coherently manipulate the four nuclear spin states by performing on the 3 different transitions: - Rabi oscillations with frequency range from one to ten MHz, - Ramsey fringes leading to coherence time T2* of the order of 0.3 ms, - Spin-echo exhibiting coherence time T2 of the order of 0.7 ms. These measurements enlighten the strong potential of using single molecular magnet as building blocks for quantum computing as the figure of merit is of the order of 3000. More than a model system to explore quantum properties, it was shown that a 4-level system can be used to implement the Grover’s research algorithm . The idea of this quantum algorithm is to use the quantum parallelism to get a square root speed up of the research of an element in a database. In a recent experiment we pointed our ability to implement this algorithm : creating a 3 or 4 quantum states Hadamard gate, then, applying an unitary evolution to find out one of this quantum state.  Thiele et al.Science 344, 1135 (2014)  Leuenberger et al. PRL 89, 207601
Authors : S. J. van der Molen, B. Doudin, Mario Ruben
Affiliations : a Institute of Physics, Leiden University (The Netherlands). b IPCMS, Université de Strasbourg, Strasbourg (France). c Institute of Nanotechnology (INT), KIT, Karlsruhe (Germany).
Resume : Magnetic molecules have recently attracted considerable interest in view of their potential to design of (quantum) spintronic devices as there are spin valves,[1,2] spin transistors[3,4] and spin resonators by a combination of bottom-up self-assembly and top-down lithography techniques. We report herein on the self-assembly of iron (II) spin transition (ST) compounds with gold-nanoparticles to percolated networks. These hybrid materials were contacted by additional gold electrodes and the transport through has been measured in trench devices. The observed reversible minimum in the temperature dependence of the resistivity of the device reveals the fingerprint of the S=0 --> S=2 spin transition. This presence of ST in the hybrid material was additionally confirmed by Raman and SQUID experiments and also by blind measurements of the transport in networks formed from non-switching compounds.  S. Kyatskaya et. al. J. Am. Chem. Soc. 131, 15143-15151 (2009)  M. Urdampilleta et al. Nature Mater. 10, 502-506 (2011)  R. Vincent et al. Nature 488, 357-360 (2012)  S. Thiele et al. Science 344, 1135-38 (2014).  M. Ganzhorn et al. Nature Nano. 8, 165–169 (2013)  E. J. Devid et. al. ACS Nano 9, 4496–507 (2015).  E. J. Devid et. al. Beilstein J. Nano. 5, 1664–74 (2014).
Molecular Quantum Spintronics : Marco Affronte
Authors : Andrea Candini
Affiliations : Istituto Nanoscienze – CNR, Centro S3 via Campi 213/a 41125 Modena, Italy
Resume : Spins in molecular materials are a promising resource for the realization of devices, with possible applications from nano-spintronics to quantum computing. The key challenge is how to address and exploit them in scalable devices architectures. We present our approach that is to use graphene as a suitable template for embed and read out molecular spins in electronic circuits. In this emerging field, few basic results have already been demonstrated, including the realization of hybrid graphene - magnetic molecules nanodevices where the electrical current is sensitive to the molecules magnetization reversal, with sensitivity down to the single molecule level . Here we will report our most recent advances, exploring two main directions. Firstly, we develop graphene based electrodes which we employ to contact molecular units. By engineering the gap between the graphene electrodes in the nanometer range, we demonstrate charge transport through individual magnetic molecules, in a single-molecule transistor geometry. Alternatively, we used the graphene electrodes to contact atomically precise graphene nanoribbons, which represent the ultimate miniaturization of graphene devices with controllable edge properties and functionalities. The resulting all-graphene based devices show great potentialities for optoelectronic applications, including ultra-sensitive photo-detection in the UV-Vis range. References  A. Candini et al. Nano Letters 11, 2634-2639 (2011)
Authors : Nils RICHTER (a, b), Zongping CHEN (c), Akimitsu NARITA (c), Xinliang FENG (d), Mathias KLÄUI (a, b), Klaus MÜLLEN (b, c)
Affiliations : (a) Institut für Physik, Johannes Gutenberg Universität, Staudinger Weg 7, 55128 Mainz, Germany, (b) Graduate School of Excellence Materials Science in Mainz, Staudinger Weg 9, 55128, Germany, (c) Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, (d) Center for Advancing Electronics Dresden (cfaed) & Department of Chemistry and Food Chemistry, Technische Universität Dresden, Mommsenstrasse 4, 01062 Dresden, Germany
Resume : Graphene nanoribbons (GNRs) are few atoms wide nanostructures of graphene and attract particular attention due to the physical phenomena that result from their geometrical confinement. We have shown that in our chemically synthesized GNRs the edge structure is perfect on the atomic level . They are synthesized on gold surfaces employing chemical vapor deposition . Using specially tailored precursor molecules it is possible to obtain a variety of different GNRs. By evaluating their electric field dependence in standard FET devices, we determine the conductivity and mobility of chevron edged structures with 9 carbon atoms across the ribbon (N=9). At room temperature the resistivity of such devices lies in the regime of approximately 1 GOhm and the mobility is with 10^-4 cm²/Vs typical for conducting thin films of polymers. We compare their properties with armchair edged ribbons with N=9 to test the influence of the edge structure. Secondly, armchair ribbons with N=7 and N=9 are studied to test for the influence of the ribbon width. By modifying the precursors hetero-atomic doping with nitrogen and co-doping with nitrogen and sulfur is obtained for which a reduction of the charge carrier mobility is observed. Here, possible mid-gap states can be identified by performing temperature dependent measurements .  A. Narita et al., Nature Chem. 6, 126 (2014).  Z. Chen et al., (under Revision 2016).  N. Richter et al., (manuscript in preparation 2016).
Authors : Keigo MINODE*, Ken ALBRECHT**, Mariko YAMAGUCHI*, Shunpei NOBUSUE*, Tatsuhiko OHTO*, Ryo YAMADA*, Kimihisa YAMAMOTO**, Hirokazu TADA*
Affiliations : *Graduate School of Engineering Science, Osaka University **Institute of Innovative Research, Tokyo Institute of Technology
Resume : Rapid progress has been made in studies of carrier transport in single molecular junctions. It has been demonstrated that the electronic coupling between the molecule and the electrode governs the current-voltage (I-V) characteristics of the junction. The studies have implied that the configuration of the molecule on the metal electrodes causes the fluctuation of electrical conductance values. We have installed a mechanically controllable break junction (MCBJ) device in a loe-temperature cryostat, which enables us to trace the I-V characteristics of the molecular junctions as a function of the gap spacing between electrodes with the resolution of 0.01 nm. It was found that the reproducible I-V characteristics were mostly observed for the junctions with the molecule elongated just before losing the contact. In the present work, we have investigated the I-V characteristics of molecules having a permanent dipole moment. The low-temperature MCBJ measurements revealed that the molecules showed clear rectification behaviors. The rectification ratio became larger with an increase of the molecular length by the sequential stacking of the dipole unit from a monomer to a trimer. The first-principles transport calculations indicated that the electric field between the electrodes during the I-V measurements induces the deformation of the highest occupied molecular orbital, which causes the asymmetric electronic coupling between the molecule and the electrode. The guiding principle for preparation of molecular rectifiers will be given.
Graphene : Andrea Candini
Authors : Akimitsu Narita, Yunbin Hu, Bo Yang, Uliana Beser, Tim Dumslaff, Matthias Georg Schwab, Xinliang Feng, Klaus Müllen
Affiliations : Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany, Center for Advancing Electronics Dresden (CFAED), Department of Chemistry and Food Chemistry, TechnischeUniversitaet Dresden, 01062 Dresden, Germany
Resume : In contrast to the zero-bandgap graphene, structurally confined nanographenes, namely graphene nanoribbons (GNRs) and nanographene molecules, possess open bandgaps, which render them highly interesting for the nanoelectronic and optoelectronic applications. The properties of the nanographenes are critically defined by their structures such as the width, length, and the edge configuration, and thus the precise structural control is essential to reproducibly achieve desired optical and electronic properties. Nevertheless, the required precision cannot be obtained with the predominant “top-down” fabrication methods, such as “cutting” of graphene sheets and “unzipping” of carbon nanotubes. To this end, we employ “bottom-up” approaches for the synthesis of structurally defined GNRs and nanographene molecules, which can be performed “in solution” by the synthetic chemistry as well as “on surface” using metal substrates. The GNRs are characterized by a combination of different spectroscopic and microscopic methods. By changing the monomer design, GNRs can be synthesized with varying widths and edge structures, allowing for the tuning of their bandgaps. Narrow (~1 nm) and dispersible GNRs with the optical bandgap of ~1.9 eV could be obtained with the length over 600 nm, which enabled fabrication of transistor devices with films as well as isolated strands of GNRs. Moreover, lateral extension of the GNR to the width of ~2 nm lowered optical bandgap down to ~1.2 eV. Such narrow GNRs with strong absorption in the visible to near-infrared region also displayed interesting photophysical properties such as exciton-exciton annihilation and stimulated emission, marking their potential for applications in optoelectronic and photonic devices. Moreover, we have recently achieved unprecedented nanographene molecules with unique structures, such as hexa-peri-hexabenzocoronene with four extra K-regions and large nanographene disk with an internal cavity, showing modulated properties, which further enriches the chemistry of nanographenes as well as paves the way toward their applications in (opto)electronic devices.
Authors : Qiang Chen, Akimitsu Narita, Xinliang Feng, Klaus Müllen
Affiliations : Max Planck Institute for Polymer Research; Technische Universitaet Dresden
Resume : Graphene has attracted increasing interests since its discovery in 2004 owning to the potential application in electronics. Cutting infinite graphene into nano-sized structures, such as graphene nanoribbons and nanographene molecules, can open the band gap and bring new properties as a result of quantum confinement effect. This also opens an opportunity to alter specific properties by edge structure engineering, such as optical and electronic properties in the zigzag edges. In recent years, the bottom up synthesis method using small molecule have proved to be effective in controlling the edge structure with atomically precision. Here, we demonstrated the application of this strategy toward the synthesis of novel nanographene molecule with a combination of armchair and zigzag edges. First, intermediate 2 was prepared using a reported method by our group. After treatment with excess amount of 2-mesitylmagnesium bromide and BF3•OEt2, compound 1 was obtained as a blue solid. Compared with cove-edged precursor, filling the cove region with two sp2 hybridized carbons caused obvious bathochromic shift, thus leading to a narrowed HOMO-LUMO band gap. High stability in air and strong fluorescence emission make it potential applicable as OLED or Laser materials.
Authors : Gabriela Borin Barin1, Andrew Fairbrother1, Juan Pablo Llinas2, Xinliang Feng3, Klaus Müllen4, Pascal Ruffieux1, Jeffrey Bokor2, Roman Fasel1
Affiliations : 1. nanotech@surfaces Laboratory, Empa – Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland 2.Dept. of Electrical Engineering and Computer Sciences, UC Berkeley, Berkeley, CA, USA 3.Center for Advancing Electronics Dresden, TU Dresden, Dresden, DE 4.Max Planck Institute for Polymer Research, 55124 Mainz, Germany
Resume : Atomically precise graphene nanoribbons (GNRs) are excellent candidates to further stretch the upcoming scaling limit of integrated circuits technology. GNRs exhibit a sizeable bandgap, which is inversely proportional to their width, and are thus excellent candidates to overcome some of the major limitations of their parent material graphene. A bottom-up approach based on surface-assisted covalent coupling of molecular precursors1 allows for the synthesis of ultra-narrow GNRs with defined edge topologies and uniform width2. Production is, however, just the starting point of a GNR technology - in order to evaluate and exploit their properties GNRs must be transferred to semiconducting or insulating substrates. Here, we focus on 9-atom wide armchair GNRs (9-AGNR) grown under high to ultrahigh vacuum conditions on 200 nm Au(111)/mica substrates. The GNRs were transferred from the Au growth surface to SiO2/Si using a membrane-free method that avoids residual contamination. Raman spectra indicated no significant degradation of GNR quality and revealed a homogeneous GNR distribution on the target surface. Detailed characterization including multi-wavelength Raman spectroscopy and GNR stability under ambient conditions will be discussed. The overall GNR film morphology was characterized by optical and atomic force microcopy, which showed transferred films with very few tears and wrinkles. Finally, we report the fabrication of GNR field-effect transistors using 9-AGNRs (predicted band gap of 2.1eV) that show on-off ratios in the range of 10^2 to 10^5 and on-currents up to 100 nA3 1J.Cai et al. Nature 466 (2010) 470 2L.Talirz et al. Adv. Mater.(2016) DOI:10.1002/adma.201505738 3J.P. Llinas et al. http://arxiv.org/abs/1605.06730
Authors : Zongping Chen1, Bilu Liu3, Chongwu Zhou3, Andrea Candini4, Marco Affronte4, Valentina De Renzi4, Akimitsu Narita1, Xinliang Feng2* and Klaus Müllen1*
Affiliations : 1Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany 2Center for Advancing Electronics Dresden (cfaed) & Department of Chemistry and Food Chemistry, Technische Universität Dresden, 01062 Dresden, Germany 3Department of Electrical Engineering and Department of Chemistry, University of Southern California, Los Angeles, California, 90089, United States 4CNR-NANO, Istituto Nanoscienze, Centro S3, I-41125 Modena, Italy *e-mail: email@example.com; firstname.lastname@example.org
Resume : Graphene nanoribbons (GNRs), quasi-one-dimensional narrow strips of graphene, have shown great promise for use as advanced semiconductors in electronics. Compared with the lack of structural control in GNRs fabricated by “top-down” approaches, atomically precise GNRs can be “bottom-up” synthesized by surface-assisted assembly of molecular building blocks under ultrahigh vacuum (UHV) conditions. Such “bottom-up” synthesized ultranarrow (~1-2 nm) GNRs have demonstrated large bandgaps of ~1 to 2 eV with visible to near-infrared absorption, rendering them highly interesting for a broad range of applications in next-generation transistors, as well as optoelectronic and photonic devices. However, a large-scale synthesis of uniformly narrow GNRs at low cost and their transfer to insulating substrates remain significant challenges, and the device applications of the “bottom-up” synthesized GNRs are still elusive. Moreover, structural characterizations of GNRs have been limited to microscopic and spectroscopic methods, hindering the direct elucidation of the exact chemical composition, especially for heteroatom-doped GNRs. To further exploring the structural information of GNRs and make them applicable for real device applications, we demonstrate an efﬁcient CVD process for inexpensive and high-throughput growth of structurally defined GNRs over large areas under ambient-pressure conditions. The CVD-grown GNRs exhibit similar structures and properties with those synthesized under UHV conditions, as supported by Raman spectroscopy, high-resolution electron energy loss spectroscopy, and STM characterizations. Homogenous GNR films over areas of centimetres have been successfully transferred to non-conducting wafers and exhibited a large current on/off ratio of up to 6,000 in field-effect transistor devices, which is significantly larger than values reported so far for other GNR thin film transistors. Moreover, by using graphene electrodes, the contact resistance can be drastically reduced while preserving the high current on/off ratio. This “bottom-up” CVD method further allows the growth of N-doped GNRs as well as their heterojunctions, demonstrating the versatility and scalability of this process, which provides access to a broad class of GNRs with engineered structures and properties based on molecular-scale design. These results pave the way toward the scalable and controllable growth of GNRs, and provide practical solutions to the current challenges in graphene-based nanoelectronic, optoelectronic and photonic devices.
Molecular Spins : Mario Ruben
Authors : A. Ghirri, D. Komijani, C. Bonizzoni, S. Klyatskaya, E. Moreno Pineda, M. Ruben, S. Hill
Affiliations : Alberto Ghirri, Claudio Bonizzoni, CNR-Istituto Nanoscienze, Modena, Italy S. Klyatskaya, E. Moreno Pineda, M. Ruben, KIT Karlsruhe (D) D. Komijani, S. Hill NHMFL Tallahassee (FL, USA)
Resume : Bis(phtalocyaninato) lanthanide double-decker complexes (LnPc2, Pc=phtalocyanine) are among the most promising candidates for the implementation of molecular quantum technologies. In their neutral form, LnPc2 complexes show an additional radical spin ½ delocalized onto the Pc molecules, which influences the low temperature magnetic properties and plays an important role when the molecule is coupled to a spintronic device or deposited on a magnetic surface. Although neutral LnPc2 have been widely investigated with different experimental techniques, a clear understanding of the radical-lanthanide interaction in different double-decker complexes is still lacking. This motivated us to carry out a systematic study by means of Electron Paramagnetic Resonance (EPR) spectroscopy on the LnPc2 series, where Ln=Tb, Dy, Ho and Er. EPR spectra taken at different frequencies in the range 9-400 GHz show that the radical transition is influenced by the presence of different Ln ions. In particular, respect to a single doublet transition with g=2.01 measured in the analogous YPc2 compound, powder samples of LnPc2 show multiple resonances with different g-factors. We discuss these results on the basis of theoretical models comprising the Ln-radical exchange interaction.
Authors : L. Persichetti1, F. Donati2, S. Rusponi2, S. Stepanow1, C. Wackerlin2, A. Singha2, R. Baltic2, K. Diller2, E. Fernandes2, F. Patthey2, J. Dreiser2-3, Z. Sljivancanin4-5, K. Kummer6, C.Nistor1, P. Gambardella1, H. Brune2
Affiliations : 1Department of Materials, ETH Zurich, Honggerbergring 64, CH-8093 Zurich, Switzerland; 2Institute of Condensed Matter Physics, Ecole Polytechnique Federale de Lausanne (EPFL), Station 3, CH-1015 Lausanne, Switzerland; 3Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland; 4Vinca Institute of Nuclear Sciences (020), P.O. Box 522, 11001 Belgrade, Serbia; 5Texas A&M University at Qatar, Doha, Qatar; 6European Synchrotron Radiation Facility (ESRF), F-38043 Grenoble, France
Resume : For decades, the smallest known systems showing slow relaxation behavior have been polynuclear  and mononuclear  metal-organic complexes, so-called single-molecule magnets (SMM). Beyond SMM, the ultimate limit of magnet size shrinkage is an isolated magnetic atom on a nonmagnetic substrate. However, since the report of giant magnetic anisotropy in individual magnetic atoms on surfaces , the observation of magnetic remanence in single adatoms has remained an elusive goal, since the coupling- i.e. energy and angular momentum exchange, of the magnetic moment to the environment occurred on a timescale in the pico- to microsecond range, i.e. much faster compared to magnetization loop measurements. The key to stabilize the single magnetic moment of an adatom is therefore to develop a viable route for minimizing the coupling with the surrounding electronic/crystalline environment. We have recently achieved this goal for Ho atoms adsorbed on thin MgO(100) films on Ag(100), for which we measured a magnetic lifetime of 1500 s at 10 K and an open hysteresis loop with a coercive field of 3.7 T . Magnetic remanence is observed up to 30 K, a temperature higher than typical SMM. The extraordinary magnetic bistability of the Ho/MgO system is attributed to the effect of (i) the mixing of odd Jz states in the ground state of Ho due to the C4v symmetry of ligand field of MgO(100), which protects the magnetization from the reversal by quantum tunneling as well as by first-order electron scattering at zero and finite fields; (ii) the weak coupling to the electronic and (iii) vibrational degrees of freedom of the substrate ensured by the insulating and stiff MgO film.  R. Sessoli, et al., Nature 365, 141 (1993).  N. Ishikawa, et al., Angewandte Chemie International Edition 44, 2931 (2005).  P. Gambardella, et al. Science 300, 1130 (2003).  F. Donati, et al. Science 352, 318 (2016).
Authors : Simone Marocchi, Andrea Candini, Valerio Bellini
Affiliations : Simone Marocchi Centro S3, Istituto Nanoscienze, CNR, Modena, Italy; Andrea Candini Centro S3, Istituto Nanoscienze, CNR, Modena, Italy; Valerio Bellini Centro S3, Istituto Nanoscienze, CNR, Modena, Italy
Resume : We present a combined theoretical density-functional and experimental study of the electronic and magnetic properties of Terbium double deckers (TbPc2) adsorbed on Ni(111) substrates [1,2]. The calculations have been carried out by state-of-the-art density-functional theory methods, as implemented in the Quantum Espresso simulation packages. The neutral TbPc2 molecule in the gas phase is characterized, in addition to the Tb magnetic moment, by having a spin radical S=1/2 delocalized on the Pc organic planes. We have focussed on the role of the radical in mediating the magnetic coupling between the Tb magnetic moment and the Ni magnetization, considering in particular the case where a graphene layer is interposed between the molecules and the substrate. If, on one hand, graphene acts as an electronic decoupling layer, preserving the integrity of the magnetic properties of the molecule, on the other hand it allows an efficient transfer across it of the spin information leading to a measurable molecule-surface exchange coupling, as demonstrated by XMCD experiments. We observe that the spin radical is only partially suppressed on the graphene decorated Ni(111) substrate, and we explicitly consider its existence in a spin-model Hamiltonian, which is able to fit the magnetization curves extracted by the XMCD experiments. When the molecule is deposited directly on the highly-interacting Ni(111) surface, the spin radical is fully quenched and the lower Pc planes becomes spin-polarized only in virtue of a magnetic proximity mechanism. We also investigated the role of the Tb d-orbitals in allowing the localized f electronic spins to communicate with the external world. Overall, the magnetic interaction between the Tb spin and the Ni magnetization becomes possible in virtue of a Tb(f)-Tb(d)-spin polarized Pc-graphene-Ni relay-like exchange mechanism, which is able to sustain the spin communication over a distance of around 7 Angstrom.  Scientific Report, 2016, 6, 21740.  S. Marocchi et al., to be submitted, 2016.
Molecuar systems : Mario Ruben
Authors : Dr Cedric Weber
Affiliations : King's College London
Resume : Phenomena that are connected to quantum mechanics, such as magnetism, transport, and the effect of impurity atoms and disorder, and their relation to material design and energy needs are important for almost every branch of the industry. Density functional theory (DFT) was successful at making accurate predictions for many materials,in particular compounds which have a metallic behaviour. DFT combines high accuracy and moderate computational cost, but the computational effort of performing calculations with conventional DFT approaches is still non negligible and scales with the cube of the number of atoms. A recent optimised implementation of DFT was however shown to scale linearly with the number of atoms (ONETEP), and opened the route to large scale DFT calculations for molecules and nano-structures. Nonetheless, one bottleneck of DFT and ONETEP, is that it fails at describing well some of the compounds where strong correlations are present, in particular because the computational scheme has to capture boththe band-like character of the uncorrelated part of the compound and the Mott-like features emerging from the local strongly correlated centres. A recent progress has been made in this direction by the dynamical mean-field theory (DMFT), that allows to describe the two limits (metal and insulator) in a remarkable precise way when combined with DFT. The ONETEP+DMFT implementation and strategies to overcome the main bottlenecks of this type of calculations will be discussed, and its applications illustrated by a few case of studies, such as the role of quantum entanglement in Myoglobin and heme systems. References : PRL 108, 256402 ‘ 12 PRL 110, 106402 ' 13 PNAS 111, 5790 '14
Authors : Weiping Gong1, Zhaohui Guo1, S. Sydorenko2, S. Konorev2, S. Voloshko2
Affiliations : 1. Laboratory of Electronic Functional Materials, Huizhou University 2. Metal Physics Department, National Technical University of Ukraine “Kyiv Polytechnic Institute”
Resume : Creation of a new generation of solar cells involves coating the Graphene on the free surface of transition metals. Therefore, the research of the multilayer relaxation Fe surface induced by coating of Graphene is interesting. Such a task was solved by us using molecular dynamics method. Relaxation of the top five atomic layers of Fe has been simulated, taking into account the crystallographic surface orientation (001), (011), (111) before and after the Graphene coating. The conjugation angle of the Fe and Graphene crystal lattice has been also varied. Calculations of system energy and stresses have been performed for two temperatures: 300K and 400K. There was analyzed the change of interplanar distances along a normal to the surface compared to the undisturbed state (volume) depending on the packing density of different Fe verges. There was a comparison of the obtained results with literature data for pure Fe and confirmed the oscillating nature of the multilayer relaxation in particular. We have established the regularities of Graphene influence on the structural parameters of the Fe surface and discussed the conditions of practical application of the Fe/Graphene system in the solar energy.
Authors : Paolo Fantuzzi, Leonardo Martini, Andrea Candini, Valdis Corradini, Umberto del Pennino, Yunbin Hu, Xinliang Feng, Klaus Müllen, Akimitsu Narita, Marco Affronte
Affiliations : Dipartimento di Scienze Fisiche, Informatiche e Matematiche, Università di Modena e Reggio Emilia, Via G.Campi 213/a, 41125 Modena, Italy; Centro S3 - Istituto di Nanoscienze - CNR, Via G. Campi 213/a, 41125 Modena, Italy; Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany; Center for Advancing Electronics Dresden (CFAED), Department of Chemistry and Food Chemistry, Technische Universitat Dresden, 01062 Dresden, Germany;
Resume : The use of graphene in electronic devices requires the presence of an energy gap. One viable strategy to achieve this goal is the reduction of the lateral size of the graphene layers down to graphene nanoribbons (GNRs) with nm-sized width. However, as long as the GNRs are obtained by conventional top-down approaches, the resulting structure is not controllable. High-quality GNRs are grown in ultra high vacuum on metallic surfaces, whereas a non-conducting substrate is mandatory for applications in electronics. Alternatively, GNRs can be synthesized in liquid-phase. Given their huge mass, they cannot be evaporated and the deposition is usually performed by drop casting. Electrospray deposition (ESD) is an alternative technique that allows to softly land large and heavy molecules from liquid suspension. In this work Electrospray deposition (ESD) in ambient conditions has been used to deposit graphene nanoribbons (GNRs) dispersed in liquid phase on different types of substrates, including ones suitable for electrical transport. The deposition process was controlled and optimized by using Raman spectroscopy, Scanning Probe Microscopy and Scanning Electron Microscopy. When deposited on graphitic electrodes, GNRs were used as semi-conducting channel in three terminal devices showing gate tunability of the electrical current. These results suggest that ESD technique can be used as an effective tool to deposit chemically synthesized GNRs onto substrates of interest for technological applications.
Authors : Leonardo Martini, Zongping Chen, Neeraj Mishra, Domenica Convertino, Camilla Coletti, Akimitsu Narita, Xinliang Feng, Klaus Müllen, Marco Affronte, Andrea Candini
Affiliations : Dipartimento di Scienze Fisiche, Matematiche e Informatiche, Università di Modena e Reggio Emilia via G. Campi 213/A , 41125/A Modena. Italy; Centro S3, Istituto Nanoscienze - CNR, via G. Campi 213/A , 41125 Modena Italy; Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany; Center for NanotechnologyInnovation @ NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy; Center for Advancing Electronics Dresden (cfaed) & Department of Chemistry and Food Chemistry, TechnischeUniversität Dresden, 01062 Dresden, Germany
Resume : The high carrier mobility of graphene offers the possibility to build high-performance graphene-based electronic, photonic and optoelectronic devices. Graphene layers can be efficiently employed as a transparent electrode and to contact other low-dimensional materials, such as molecule or carbon based nano-structure. Starting from a pristine graphene flake a thin gap can be opened via electro-burning procedure or via EBL patterning and RIE of oxygen plasma, according to the dimension of the gap to achieve: RIE technique allow to realize a gap of around 100 nm, while a controlled electro-burning allow to realize gaps of few nanometres. To use the exceptional optical and electrical performance of graphene in applications the presence of a bandgap is fundamental. Lateral confinement of graphene in almost monodimensional(few nanometres) structure produce a band gap, due to quantum confinement and edge effects. Although various techniques allow the realization of Graphene nano-ribbons(GNR) like top-down approaches(unzipping of carbon nano-tubes or via electron beam lithography of graphene flakes), the only way to have precisely defined in size and shape GNRs is a bottom-up grown. Here we used GNRs grown from chemical synthesized monomers by chemical vapour deposition method. Large area of GNR are grown on a 200 nm of Au(111) epitaxially grown on mica substrate. As grown the GNR/Au?mica compound is put in hydroﬂuoric acid for etching away the mica; after washing with ultra-pure water the Au film was etched away by gold etchant; finally the GNR film is transfer on a pre-patterned graphene-based contacts. To avoid the broken of the thin film when transferring large area of GNR films, spin-coated PMMA thin film was used as a mechanical support before etching with HF. The PMMA was washed away by hot acetone in the last step. The devices realized as described are electrically characterized at room temperature in vacuum condition in a LakeShore probe-station. Annealing up to 400 K could be performed during the electric characterization. Here we present the realization and characterization of a field-effect transistor(FET) device, totally made of graphene, in which we combine the electrical of graphene with the band-gap of the GNRs. The conductive channel consists in a layer of chemically precise GNRs attached to multilayer graphene working as electrical contacts. GNRs are grown from chemically synthesized monomers by a chemical vapour deposition (CVD) method and are transferred on the prefabricated graphene electrodes. The devices show a current on/off ratio as high as 104 and photoresponsivity of 6 × 105 A/W in the visible-UV range. The light sensitivity is orders of magnitude higher than the ones reported for pristine graphene sheets and other photo-transistors based on two dimensional materials. Our results show the potentialities of all-graphene devices for the development of novel applications in nano-optoelectronics and sensing.
Authors : Xiao-Ye Wang,† Akimitsu Narita,† Wen Zhang,† Xinliang Feng,*‡ Klaus Müllen*†
Affiliations : † Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany; ‡ Center for Advancing Electronics Dresden (cfaed) & Department of Chemistry and Food Chemistry, Technische Universität Dresden, 01062 Dresden, Germany
Resume : A tandem demethylation-aryl borylation strategy was developed to synthesize OBO-doped tetrabenzo[a,f,j,o]perylenes (namely “bistetracenes”) and tetrabenzo[bc,ef,kl,no]coronenes (namely “peritetracenes”). The OBO-doped bistetracene analogues exhibited excellent stability and strong fluorescence, in contrast to the unstable all-carbon bistetracene. Single-crystal X-ray analysis for OBO-doped bistetracene revealed a twisted double helicene structure, indicating that this synthesis is applicable to new heterohelicenes. Importantly, cyclodehydrogenation of the bistetracene analogues successfully produced the unprecedented heteroatom-doped peritetracenes, which opened up a new avenue to periacene-type nanographenes with stable zigzag edges.
Authors : Simone Ierinò (1,2), Filippo Troiani (2)
Affiliations : Università di Modena e Reggio Emilia, via Campi 213/a, 41125, Modena, Italy. 2. S3 Istituto Nanoscience, Consiglio Nazionale delle Ricerche, 41124, Modena, Italy.
Resume : Molecular spin systems are promising candidates for the implementation of future quantum devices. In fact, they can be synthesized in large ensembles of identical systems, and their physical properties can be tailored at the chemical level. In recent years, most attention has been devoted to the ensembles of s=1/2 spins, coherently coupled with one mode of the quantized electromagnetic field and in the low-excitation regime [1-3]. Molecular spin clusters provide a variety of spin systems, with larger spin lengths and diverse level schemes. Here we provide a theoretical investigation of these cases, in the regime where the photon number is at least comparable to that of the spins in the ensemble. In particular, we consider the case of multiple ensemble of s=1/2 spins and of ensemble of spins s>1/2, characterized by different level schemes and coherently coupled with one mode of the field. When the number excitations is much larger than that of the spins, the energy spectrum can be approximated by treating the field classically. On the other hand, the presence in the system ground state of spin-photon and spin-spin entanglement provides evidence of clear quantum-mechanical features in such supposed “classical limit”. References:  M. Jenkins, T. Hümmer, M. J. Martínez-Pérez, J. García_Ripoli, D. Zueco, and F. Luis, New J. Phys. 15(9), 095007 (2013).  A. Ghirri, C. Bonizzoni, D. Gerace, S. Sanna, A. Cassinese, and M. Affronte. App. Phys. Lett. 106(16), 184101 (2015).  A. Ghirri, C. Bonizzoni, F. Troiani, N. Buccheri, L. Beverina, A. Cassinese, and M. Affronte, arXiv:1605.02879.
Authors : Stefano Lumetti (1,2), Franck Balestro (3,4,5), Clément Godfrin (3,4), Wolfgang Wernsdorfer (3,4), Svetlana Klyatskaya (6), Mario Ruben (6,7), Marco Affronte (1,2), Andrea Candini (1)
Affiliations : (1) Istituto Nanoscienze - CNR, Centro S3 Modena, via G. Campi 213A, 41124 Modena, Italy; (2) Dipartimento di Scienze Fisiche, Informatiche e Matematiche, Università degli Studi di Modena e Reggio Emilia, via G. Campi 213A, 41124 Modena, Italy; (3) Université Grenoble Alpes, Institut Néel, F-38042 Grenoble, France; (4) CNRS, Institut Néel, F-38042 Grenoble, France; (5) Institut Universitaire de France, 103 boulevard Saint-Michel, 75005 Paris, France; (6) Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), D-76344 Eggenstein-Leopoldshafen, Germany; (7) Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 UdS-CNRS, 67034 Strasbourg Cedex 2, France
Resume : Graphene is considered an appealing material for the replacement of the traditionally used metal electrodes in single-molecule devices, as its covalent bond structure assures a high mechanical stability even above room temperature and its planar geometry (with a thickness comparable to the molecular size) allows for the anchoring of diverse molecules, which strongly couple to the graphene electrodes via carbon bonds and/or pi-pi stacking. Here, we shall present the realization and functional characterization of three-terminal molecular devices in which a single-molecule magnet (the bis(phthalocyanine) terbium (III), TbPc2) is embedded between two nanometer-spaced electrodes made of few-layer graphene grown on the C-face of SiC. Nanogaps in graphene are opened via a feedback-controlled electroburning (EB) procedure, whose fast response avoids the abrupt breaking of the graphene junction and allows for a high-yield precise control on its final molecular-sized structure. Our devices work as molecular spin transistors allowing to detect the Tb3+ electronic spin flip during the sweeping of an external magnetic field. Moreover, the magnetic exchange coupling between the current passing through the molecular system in the Coulomb blockade regime and the Tb3+ electronic spin can be characterized. Our results suggest that the use of graphene is a promising and viable route for contacting single molecules and realizing complex electronic architectures at the molecular scale.
Authors : Malik Abdul Rehman, Yongho Seo
Affiliations : Scanning probe microscopy lab, Sejong University, Seoul 143-747, Republic of Korea Faculty of Nanotechnology & Advanced Materials Engineering and Graphene Research Institute,Sejong University, Seoul 143-747, Republic of Korea
Resume : In the field of nanotechnology, characterization of thin films, nanostructures, interfaces and critical dimensions (CD) are very important in order to see morphology and topology of grown materials. Usually, different techniques are used i.e. transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD) to analyze the surface. All these techniques could be used to see the morphological study but in order to observe surface topology with critical dimensions high quality 3D atomic force microscope (AFM) imaging is desirable. Carbon nanotubes (CNT) are suitable candidate for 3D AFM probes due to their exceptional strength, elastic modulus and high level of aspect ratio. Unfortunately, due to strong sp2 hybridization of CNT's the bond breaking or attachment of any host molecule is quite crucial. However, another major issue includes homogeneous dispersion of highly agglomerated CNTs and their attachment. A lot of work is being done to deal with the said attachment and dispersion problems. In the field of microscopy, atomic force microscopy (AFM) is a handy tool to observe the 2D surface topology of grown surfaces. The quality of the images is dependent on the applied force and aspect ratio of the cantilevers and tuning fork based sensor. Combination of multiwall carbon nanotubes with silicon cantilever were previously used to address these issues. Furthermore, it was impossible to get high resolution images of undercut side wall structures by using flared tips. By using this approach to attach CNTs on tungsten probes, high quality imaging and surface investigation of deep and trench structures was possible. In current work we focused on the fabrication of nanoneedle shaped long probes for 3D topography. Firstly, these probes were fabricated by electrochemical etching process and secondly, MWCNTs were attached by using dielectrophoresis method. Although, these probes are cost effective and having high Q value but its scanning speed was comparatively slow than normally used silicon cantilevers. For comparison, we did surface scanning of readable compact disk (CD-R) at ambient condition with tungsten tip and MWCNT attached tungsten probe.The topographic images confirm that the quality of our fabricated CNTs based probe was good compared with the bare tungsten tip. However, MWCNT attached tungsten probe quality factor was little decrease from 6600 to 6000 but still it is comparatively too high with commercially used cantilever's. Degradation of quality factor could be due to mass attachment with tip. To overcome most challenging issue Through Silicon Via (TSV), we believe that our fabricated MWCNT based AFM probes could be an efficient tool to get high quality topography.
Authors : G. A. Nemnes (1,2) , Camelia Visan (1)
Affiliations : (1) Horia Hulubei National Institute for Physics and Nuclear Engineering, Str. Atomistilor nr. 409, PO Box MG-6, Magurele-Ilfov, Romania ; (2) University of Bucharest, Faculty of Physics, MDEO Research Center, 077125 Magurele-Ilfov, Romania
Resume : In recent years hybrid graphene – hexagonal boron nitride (hBN) materials with highly defined patterns have been produced. Although graphene and hBN are very similar materials from the structural point of view, with a lattice mismatch of only 2%, the electronic properties are quite different: while graphene is zero-overlap semimetal with very high electrical conductivity, hBN is a wide band gap semiconductor. Based on these properties, graphene-hBN binary composites are ideal candidates for tunable electronic materials. Here we investigate the influence of the halogen passivation on the electronic and mechanical properties of zig-zag graphene nanoribbons with embedded hBN domains by ab initio density functional theory (DFT) calculations. Passivating halogen atoms of different electronegativity, present at the extremities of zig-zag terminated nanoribbons, introduce different antiferromagnetic spin couplings between the two edges. Molecular dynamics (MD) calculations performed in the framework of DFT reveal the mechanical properties of the nanoribbons, which depend on the specific shape of the graphene-hBN domains and also on the mass of the halogen atoms. In particular, the stiffness of the nanoribbon may be gradually changed by adjusting the ratio between graphene and hBN domains, which has consequences in the phonon spectrum and further in the thermal transport. Using MD simulations we make a statistical analysis of the nanoribbon buckling and establish the low noise conditions for the charge and spin transport. Our analysis is focused on attaining highly electrically conductive elements based on halogenated graphene-hBN nanostructures, with low thermal conductance and low noise suitable for thermoelectric applications.
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Quantum Spintronics with Semiconductors : Xavier Jehl
Authors : Brian B. Zhou, David D. Awschalom
Affiliations : Institute for Molecular Engineering, University of Chicago, Chicago, IL 60637 USA
Resume : Our technological preference for perfection can only lead us so far: as traditional transistor-based electronics rapidly approach the atomic scale, small amounts of disorder begin to have outsized negative effects. Surprisingly, a promising pathway out of this conundrum may emerge from embracing the quantum nature of atomic-scale defects to construct 'quantum machines’ that enable new information processing and sensing technologies. Recently, individual defects in diamond , silicon carbide [2-4], and other wide-gap semiconductors  have attracted interest as they possess electronic and nuclear spin states that can be employed as solid-state quantum bits. These systems provide a built-in optical interface in the visible and telecom bands, retain their coherence over millisecond timescales, and can be polarized, manipulated, and read out using a combination of light and microwaves [1-4]. Here, we focus on recent progress in quantum-optical techniques for qubit control compatible with an all-photonic quantum network. Utilizing a nitrogen-vacancy center lambda system, we achieve robust qubit rotations based on the quantum geometric, or Berry, phase  and accelerate the preparation and transfer of coherent superposition states via ‘shortcuts to adiabaticity’ . These results advance defect-based qubits as platforms for novel science and scalable photonic implementations of spintronic technologies.  D.D. Awschalom, L.C. Bassett, A.S. Dzurak, E.L. Hu and J.R. Petta, Science 339, 1174 (2013).  W. F. Koehl, B. B. Buckley, F. J. Heremans, G. Calusine, and D. D. Awschalom, Nature 479, 84 (2011).  D. J. Christle, A. L. Falk, P. Andrich, P. V. Klimov, J. Hassan, N. T. Son, E. Janzén, T. Ohshima, and D. D. Awschalom, Nature Materials 14, 160 (2015).  P. V. Klimov, A. L. Falk, D. J. Christle, V. V. Dobrovitski, and D. D. Awschalom, Science Advances 1, e1501015 (2015).  J. R. Weber, W. F. Koehl, J. B. Varley, A. Janotti, B. B. Buckley, C. G. Van de Walle, and D. D. Awschalom, Proc. Natl. Acad. Sci. 107, 8513 (2010).  C. G. Yale, F. J. Heremans, B. B. Zhou, A. Auer, G. Burkard, and D. D. Awschalom, Nature Photonics 10, 184 (2016).  B. B. Zhou, A. Baksic, H. Ribeiro, C. G. Yale, F. J. Heremans, P. C. Jerger, A. Auer, G. Burkard, A. A. Clerk, and D. D. Awschalom. arXiv:1607.06503 (2016).
Authors : Marco Fanciulli (1,2), Matteo Belli (2), Stefano Paleari (1)
Affiliations : 1) Università degli Studi di Milano-Bicocca, Dipartimento di Scienza dei Materiali, Milano (Italy) 2) Laboratorio MDM, IMM-CNR, Agrate Brianza (Italy)
Resume : Spin of donors or double donors in silicon are the heart of several schemes for qubits. In the last decade there has been a revival of the pioneering continuous wave electron paramagnetic resonance (CW-EPR) investigations, started in the late 50s, of these class of impurities in silicon taking advantage of pulse-EPR techniques. In addition the availability of isotopically purified silicon-28 allowed a detailed investigation of the main relaxation mechanisms and of the coherence time when super-hyperfine interactions are mostly eliminated and spin diffusion processes suppressed. We will review the main results related to the pulse-EPR investigation of conventional donors (P, As) [1, 2], other group V impurities (Bi and N) [3, 4] and double donors (S, Se) [5, 6] focusing on spin-lattice and spin-spin relaxation processes in bulk silicon. In any silicon based, CMOS compatible, nano-electronic device a major role is played by the Si/SiO2 interface and by the well-known defects, the Pb center family, there localized. Due to sensitivity issues the investigation of the spin dynamics of these centers has not been reported so far. Taking advantage of silicon nanowires fabrication and surface/interface preparation and modification we have been able to investigate the spin relaxation mechanisms of the Pb-centers and also their interaction with the donor spin dynamics . These results will be reported and discussed. 1. M. Fanciulli, P. Höfer, and A. Ponti, Physica B 340-342, 895 (2003) 2. A. Ferretti, M. Fanciulli, A. Ponti, and A. Schweiger, Phys. Rev. B 72, 235201 (2005) 3. M. Belli, M. Fanciulli, N. V. Abrosimov , Phys. Rev. B 83, 235204 (2011) 4. M. Belli, M. Fanciulli, D. Batani, Phys. Rev. B 89, 115207 (2014) 5. S. Paleari, M. Belli, M. Fanciulli, Yu. A. Astrov, ICDS 2013 6. R. Lo Nardo, et al. Phys. Rev. B 92, 165201 (2015) 7. M. Fanciulli, APS March Meeting, Baltimore, USA (2016)
Round Table discussion on Quantum Technologies : Marco Affronte, Thierry Debuisschert, André Gourdon, Angelika Kuehnle, Xavier Jehl
Authors : konrad banaszek
Affiliations : fuw edu pl
Resume : QuantERA
Authors : Jean-Charles Barbé
Affiliations : CEA Leti
Resume : CEA Leti
Authors : Thomas SKOTNICKI
Affiliations : STMicro
Resume : STMicro
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