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Suche nach „[Mátéfi-Tempfli] [Stefan]“ hat 165 Publikationen gefunden
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    Beitrag (Sammelband oder Tagungsband)

    Stefan Mátéfi-Tempfli

    Leading Edge Nanotechnology Research Developments

    Nanotechnology Research Collection, Hauppauge, NY

    2009

    ISBN: 978-1607412939

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    Beitrag (Sammelband oder Tagungsband)

    Stefan Mátéfi-Tempfli

    Nanostructures Grown Via Electrochemical Template Methods (Chapter)

    Encyclopedia of Nanotechnology, New York

    2009

    ISBN: 978-1606920794

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    Zeitschriftenartikel

    M. Mátéfi-Tempfli, L. Piraux, A. Vlad, Stefan Mátéfi-Tempfli, V. Antohe

    Nanowires and nanostructures fabrication using template methods: A step forward to real devices combining electrochemical synthesis with lithographic techniques

    Journal of Materials Science: Materials in Electronics, vol. 20, no. 1, pp. 249-254

    2009

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    Zeitschriftenartikel

    B. Sulik, S. Biri, É. Fekete, M. Mátéfi-Tempfli, Z. Juhász, Gy. Víkor, J. Pálinkás, Stefan Mátéfi-Tempfli, K. Tőkési, I. Iván, E. Takács

    Ion Guiding in Alumina Capillaries: MCP Images of the Transmitted Ions

    Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, vol. 267, no. 2, pp. 321-325

    2009

    DOI: 10.1016/j.nimb.2008.10.017

    Abstract anzeigen

    Transmission of a few keV impact energy Ne6+ ions through capillaries in anodic alumina membranes has been studied with different ion counting methods using an energy dispersive electrostatic spectrometer, a multichannel plate (MCP) array and sensitive current-measurement. In the present work, we focus our attention to the measurements with the MCP array. The alumina capillaries were prepared by electro-chemical oxidation of aluminium foils. For the present experiments guiding of 3-6 keV Ne6+ ions has been studied in two samples with capillary diameter of about 140 nm and 260 nm and with capillary length of about 15 μm. At these energies, the ions have been efficiently guided by the capillaries up to few degrees tilt angle. In this work, we compare the results obtained by the energy dispersive spectrometer to those studied by the MCP array.

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    Zeitschriftenartikel

    V. Moshchalkov, M. Mátéfi-Tempfli, S. Michotte, J. Vanacken, X. Hallet, L. Piraux, Stefan Mátéfi-Tempfli

    Artificial pinning centers using the barrier layer of ordered nanoporous alumina templates

    Journal of Physics: Conference Series, vol. 153, no. 1

    2009

    DOI: 10.1088/1742-6596/153/1/012013

    Abstract anzeigen

    The barrier layer of self-ordered anodized aluminium oxide, which is grown from an aluminium foil, has been revealed by a selective chemical etching of the remaining aluminium. The surface obtained in this way consists of a triangular lattice of bumps with 100nm spacing, and heights of approximately 50nm. Using this surface as a template for controlling the pinning in thin superconducting films, superconducting Nb was deposited with different thicknesses and under different deposition angles. The evaporation under a 30° angle shows an asymmetric pinning potential composed of two triangular lattices having different pinning strengths. Matching effects are observed up to 1T. Matching effects are also maintained at relatively low temperature.

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    Zeitschriftenartikel

    V. Moshchalkov, M. Mátéfi-Tempfli, S. Michotte, J. Vanacken, X. Hallet, L. Piraux, Stefan Mátéfi-Tempfli

    Quasi-hexagonal vortex pinning lattice using anodized aluminum oxide nanotemplates.

    Small, vol. 5, no. 21, pp. 2413-2416

    2009

    Abstract anzeigen

    The bottom barrier layer of well‐ordered nanoporous alumina membranes reveals a previously unexploited nanostructured template surface consisting of a triangular lattice of hemispherical nanoscale bumps. Quasi‐hexagonal vortex‐pinning lattice arrays are created in superconducting Nb films deposited onto this template (see image). Matching effects are preserved at higher magnetic fields and lower temperatures when compared to holes on the top face.

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    Zeitschriftenartikel

    V. Moshchalkov, M. Mátéfi-Tempfli, S. Michotte, J. Vanacken, X. Hallet, L. Piraux, Stefan Mátéfi-Tempfli

    High field matching effects in NbN induced by a dense ferromagnetic nanowires array grown in a nanoporous alumina template

    Applied Physics Letters, vol. 95, no. 25

    2009

    DOI: 10.1063/1.3276557

    Abstract anzeigen

    Dense arrays of ordered ferromagnetic nanowires have been used to create periodic magnetic pinning centers in thin superconducting NbN films. The nanowires were electrodeposited in a highly ordered porous alumina membrane and the thin NbN film was deposited on top of the perpendicularly oriented magnetic nanowires. Matching effects have been observed up to 2.5 T (11th matching field) and are maintained at low temperature. An appreciable enhancement of the superconducting properties is observed. At low fields, a hysteretic behavior in the magnetoresistance is found, directly related to the magnetization processes of arrays of interacting single domain ferromagnetic nanowires.

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    Zeitschriftenartikel

    P. Bertrand, S. Yunus, M. Mátéfi-Tempfli, A. Radu, C. Dutu, A. Attout, A. Vlad, Piraux L., S. Melinte, Stefan Mátéfi-Tempfli, V. Antohe

    Nanowire-Templated Microelectrodes for High-Sensitivity pH Detection

    Applied Physics Letters, vol. 94, no. 7

    2009

    DOI: 10.1063/1.3089227

    Abstract anzeigen

    A highly sensitive pH capacitive sensor has been designed by confined growth of vertically aligned nanowire arrays on interdigited microelectrodes. The active surface of the device has been functionalized with an electrochemical pH transducer (polyaniline). We easily tune the device features by combining lithographic techniques with electrochemical synthesis. The reported electrical LC resonance measurements show considerable sensitivity enhancement compared to conventional capacitive pH sensors realized with microfabricated interdigited electrodes. The sensitivity can be easily improved by changing only the thickness of the functional layer.

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    Zeitschriftenartikel

    P. Bertrand, S. Yunus, M. Mátéfi-Tempfli, A. Radu, C. Dutu, A. Attout, A. Vlad, Piraux L., S. Melinte, Stefan Mátéfi-Tempfli, V. Antohe

    Nanowire-Templated Microelectrodes for High-Sensitivity pH Detection

    Virtual Journal of Nanoscale Science & Technology (NanoUnion), vol. 19, no. 9

    2009

    Abstract anzeigen

    A highly sensitive pH capacitive sensor has been designed by confined growth of vertically aligned nanowire arrays on interdigited microelectrodes. The active surface of the device has been functionalized with an electrochemical pH transducer (polyaniline). We easily tune the device features by combining lithographic techniques with electrochemical synthesis. The reported electrical LC resonance measurements show considerable sensitivity enhancement compared to conventional capacitive pH sensors realized with microfabricated interdigited electrodes. The sensitivity can be easily improved by changing only the thickness of the functional layer.

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    Zeitschriftenartikel

    A. Milosavljević, Marinković B. P., Šević D., M. Mátéfi-Tempfli, J. Jureta, Z. Pešić, Víkor Gy., Stefan Mátéfi-Tempfli

    Low-energy electron transmission through high aspect ratio Al2O3 nanocapillaries.

    EPL - A Letters Journal Exploring the Frontiers of Physics, vol. 86, no. 2

    2009

    DOI: 10.1209/0295-5075/86/23001

    Abstract anzeigen

    Electron transmission through insulating Al2O3 nanocapillaries of different diameters (40 and 270 nm) and 15 μm length has been investigated for low-energy electrons (2–120 eV). The total intensity of transmitted current weakly depends on the incident electron energy and tilt angle defined with respect to the capillary axis. On the other hand, the intensity of elastically transmitted electrons significantly varies with the alteration of electron energy and tilt angle. In addition, we measured an energy distribution of electrons transmitted both in the straightforward direction and at large tilt angle. The measured spectra show that inelastic processes dominate and, in particular, a large amount of low-energy electrons. These low-energy electrons can be either inelastically scattered projectiles or secondary electrons emitted within the capillaries. Furthermore, a change of the tilt angle appears to influence significantly only the intensity of the elastic transmission. The present results suggest a more complex nature of low-energy electron transport through insulating nanocapillaries than proposed for positive ions.

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    Zeitschriftenartikel

    Piraux, L., J., M. Mátéfi-Tempfli, Stefan Mátéfi-Tempfli

    Fabrication of nanowires and nanostructures: combining template synthesis with patterning methods

    Applied Physics A - Materials Science and Processing, vol. 96, no. 3, pp. 603-608

    2009

    DOI: 10.1007/s00339-009-5085-6

    Abstract anzeigen

    We report on different approaches that we have adopted and developed for the fabrication of nanowires and nanostructures. Methods based on template synthesis and on self organization seem to be the most promising for the fabrication of nanomaterials and nanostructures due to their easiness and low cost. The development of a supported nanoporous alumina template and the possibility of using this template to combine electrochemical synthesis with lithographic methods open new ways for the fabrication of complex nanostructures. The numerous advantages of the supported template and its compatibility with microelectronic processes make it an ideal candidate for further integration into large-scale fabrication of various nanowire-based devices.

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    Zeitschriftenartikel

    M. Mátéfi-Tempfli, Stefan Mátéfi-Tempfli

    Vertically aligned nanowires on flexible silicone using supported alumina template prepared by pulsed anodization

    Advanced Materials, vol. 21, no. 40, pp. 4005-4010

    2009

    DOI: 10.1002/adma.200900344

    Abstract anzeigen

    Carpets of vertically aligned nanowires on flexible substrates are successfully realized by a template method. Applying special pulsed anodization conditions, defect‐free nanoporous alumina structures supported on polydimethylsiloxane (PDMS), a flexible silicone elastomer, are created. By using this template with nanopores ending on a conducting underlayer, a high‐density nanowire array can be simply grown by direct DC‐electrodeposition on the top of the silicone rubber.

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    Zeitschriftenartikel

    G. Cerullo, M. Savoini, L. Duò, B. Hecht, M. Mátéfi-Tempfli, M. Finazzi, D. Brida, M. Celebrano, G. Grancini, Stefan Mátéfi-Tempfli, P. Biagioni

    Dependence of the two-photon photoluminescence yield of gold nanostructures on the laser pulse duration

    Physical Review B, vol. 80, no. 4

    2009

    DOI: 10.1103/PhysRevB.80.045411

    Abstract anzeigen

    Two-photon photoluminescence (TPPL) from gold nanostructures is becoming one of the most relevant tools for plasmon-assisted biological imaging and photothermal therapy as well as for the investigation of plasmonic devices. Here we study the yield of TPPL as a function of the temporal width δ of the excitation laser pulses for a fixed average power. In the δ>1 ps regime, the TPPL yield decreases as δ is increased, while for shorter pulse widths it becomes independent of δ and, consequently, of the laser-pulse peak power. This peculiar dynamics is understood and modeled by considering that two-photon absorption in Au is a two-step process governed by the lifetime of the metastable state populated by the first photon absorption.

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    Zeitschriftenartikel

    L. Gangloff, S. Enouz-Védrenne, E. Minoux, D. Pribat, S. Purcell, L. Hudanski, Piraux L., Stefan Mátéfi-Tempfli, E. Ferain, P. Vincent, P. Legagneux, J-Ph. Schnell, S. Xavier

    Stable field emission from arrays of vertically aligned free-standing metallic nanowires

    Nanotechnology, vol. 19, no. 21

    2008

    DOI: 10.1088/0957-4484/19/21/215601

    Abstract anzeigen

    We present a fully elaborated process to grow arrays of metallic nanowires with controlled geometry and density, based on electrochemical filling of nanopores in track-etched templates. Nanowire growth is performed at room temperature, atmospheric pressure and is compatible with low cost fabrication and large surfaces. This technique offers an excellent control of the orientation, shape and nanowires density. It is applied to fabricate field emission arrays with a good control of the emission site density. We have prepared Co, Ni, Cu and Rh nanowires with a height of 3 µm, a diameter of 80 nm and a density of ~107 cm−2. The electron field emission measurements and total energy distributions show that the as-grown nanowires exhibit a complex behaviour, first with emission activation under high field, followed by unstable emission. A model taking into account the effect of an oxide layer covering the nanowire surface is developed to explain this particular field emission behaviour. Finally, we present an in situ cleaning procedure by ion bombardment that collectively removes this oxide layer, leading to a stable and reproducible emission behaviour. After treatment, the emission current density is ~1 mA cm−2 for a 30 V µm−1 applied electric field.

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    Zeitschriftenartikel

    A. Crahay, N. Reckinger, V. Bayot, M. Mátéfi-Tempfli, B. Olbrechts, L. Piraux, A. Vlad, S. Faniel, S. Melinte, Stefan Mátéfi-Tempfli, V. Antohe

    Nanowire-decorated Microscale Metallic Electrodes

    Small, vol. 4, no. 5, pp. 557-560

    2008

    DOI: 10.1002/smll.200700724

    Abstract anzeigen

    One of the challenging aspects of science and technology on ananometer-scale is the precise three-dimensional control ofnano-objects. Scanning probe microscopy manipulation,magnetic- or electric-field alignment and lithography-basedtechniques are only a few of the techniques that have beenreported so far.[1]Nevertheless, most of these techniques arestill being developed and their integration for devicefabrication represents a real challenge for the scientificcommunity. Within this context, nanowires and nanotubesare of great interest because they lie between the macroscopicand atomic scales. The ability to fabricate and manipulate suchobjects in a reliable manner on a large scale will foster their usein electronic, photonic, and sensing applications.[2]Template-based methods have been successfully used for nanowirefabrication as they allow the realization of complex organic/inorganic nanostructures.[3]To date, nanoporous anodicalumina oxide (AAO) made by the electrochemical oxidationof aluminum has been extensively used because it provides agood platform for the development of various nanostructures.This interest originates from the fact that AAO membranes,having a high density of nanopores (up to 1012cm2), are easilyproduced over large areas with variable thicknesses.[4]More-over, a good chemical and mechanical stability combined withinteresting electrical properties make AAO membranes goodcandidates for nanowire fabrication. However, the use of suchnanostructures as passive or active components in emergingelectronic devices requires smartly engineered arrays ofnanowires with well defined position and pitch.

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    Zeitschriftenartikel

    V. Moshchalkov, M. Mátéfi-Tempfli, W. Vinckx, S. Michotte, J. Vanacken, L. Piraux, Stefan Mátéfi-Tempfli, Ye X.

    Vortex pinning in superconductors laterally modulated by nanoscale self-assembled arrays

    Physica C: Superconductivity and its Applications, vol. 468, no. 7-10, pp. 585-588

    2008

    DOI: 10.1016/j.physc.2007.11.070

    Abstract anzeigen

    Being the exponent of the so-called “bottom-up” approach, self-assembled structures are now-a-days attracting a lot of attention in the fields of science and technology. In this work, we show that nanoscale self-assembled arrays used as templates can provide periodic modulation in superconducting thin films by studying their vortex pinning properties. In this work advantage was made of the fact that self-organized assemblies of identical units such as colloidal crystals and anodic aluminum oxide provide extended periodic topographic surfaces. By directly growing Nb on top of these self-assembled arrays, the templating effect was exploited in order to achieve triangular and honeycomb arrays of pinning centers in thin superconducting films. We show experimentally that periodic matching is achieved in both systems at magnetic fields, well above those present in lithographically prepared pinning arrays (up to 1 T!). Furthermore, we demonstrate in the case of anodic aluminum oxide that the presence of porous antidots in Nb not only provides strongly increased critical currents but also conserves matching at temperatures well below the critical temperature. The studies conducted on these systems indicate that the method of template growth might be considered as a viable alternative for the incorporation of periodic pinning arrays in superconducting applications of today and the future.

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    Zeitschriftenartikel

    M. Mátéfi-Tempfli, Piraux L., Stefan Mátéfi-Tempfli

    Characterization of nanopores ordering in anodic alumina

    Thin Solid Films, vol. 516, no. 12, pp. 3735-3740

    2008

    DOI: 10.1016/j.tsf.2007.06.076

    Abstract anzeigen

    A simple characterization method of the ordering of the nanopores is described for nanoporous anodized aluminium oxides. The method starts with image analysis on scanning electron microscopy representations for the purpose to find repetitive shapes and their centres, i.e. nanopores. Then triangles defined by coordinates of the centres are identified by Delaunay tessellation. Evaluation of the ordering degrees is then performed by a two-level analysis of the triangles. We define order parameters for triangular and hexagonal organization levels and show through typical examples that they are highly sensitive on ordering.

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    Zeitschriftenartikel

    D. Magnin, M. Mátéfi-Tempfli, V. Callegari, A. Jonas, S. Demoustier-Champagne, Stefan Mátéfi-Tempfli, K. Glinel

    Functionalization of Magnetic Nanowires by Charged Biopolymers

    Biomacromolecules, vol. 9, no. 9, pp. 2517-2522

    2008

    DOI: 10.1021/bm8005402

    Abstract anzeigen

    We report on a facile method for the preparation of biocompatible and bioactive magnetic nanowires. The method consists of the direct deposition of polysaccharides by layer-by-layer (LbL) assembly onto a brush of metallic nanowires obtained by electrodeposition of the metal within the nanopores of an alumina template supported on a silicon wafer. Carboxymethylpullulan (CMP) and chitosan (CHI) multilayers were grown on brushes of Ni nanowires; subsequent grafting of an enzyme was performed by conjugating free amine side groups of chitosan with carboxylic groups of the enzyme. The nanowires are finally released by a gentle ultrasonic treatment. Transmission electron microscopy, electron energy-dispersive loss spectroscopy, and x-ray photoelectron spectroscopy indicate the formation of an homogeneous coating onto the nickel nanowires when one, two, or three CMP/CHI bilayers are deposited. This easy and efficient route to the biochemical functionalization of magnetic nanowires could find widespread use for the preparation of a broad range of nanowires with tailored surface properties.

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    Zeitschriftenartikel

    V.-A. Antohe, P. Bertrand, S. Yunus, M. Mátéfi-Tempfli, A. Radu, A. Attout, L. Piraux, Stefan Mátéfi-Tempfli

    A versatile method to grow localized arrays of nanowires for highly sensitive capacitive devices

    Journal of Optoelectronics and Advanced Materials, vol. 10, no. 11, pp. 2936-2941

    2008

    Abstract anzeigen

    We propose a new approach to increase the detection efficiency of the capacitive sensing devices, by growing vertically aligned nanowires arrays, localized and confined on small interdigited electrodes structures. The metallic tracks are made using optical lithography, and the nanowires are realized by electrochemical synthesis in nanoporous materials (i.e. supported alumina templates). By controlling the preparation conditions, both their positions and pitches can be easily tuned, as well as their geometrical design (i.e. diameters between 5 – 350 nm and lengths between 150 nm – 10 μm). Based on these considerations, a capacitive sensor structure with high active surface is sensitized with polyaniline, for pH detection. Reported data show that the sensitivity of the sensor is substantially improved by using nanowires arrays.

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    Beitrag (Sammelband oder Tagungsband)

    Stefan Mátéfi-Tempfli

    Nanostructures Grown Via Electrochemical Template Methods: Synthesis, Measurements and Applications (Chapter 10)

    Leading edge nanotechnology research developments, New York

    2007

    ISBN: 1600219004