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“Present state of the composition evaluation of ternary semiconductor nanostructures by lattice fringe analysis”. Rosenauer A, Gerthsen D, Van Aert S, van Dyck D, den Dekker AJ, Institute of physics conference series , 19 (2003)
Abstract: Semiconductor heterostructures are used for the fabrication of optoelectronic devices. Performance of such devices is governed by their chemical morphology. The composition distribution of quantum wells and dots is influenced by kinetic growth processes which are not understood completely at present. To obtain more information about these effects, methods for composition determination with a spatial resolution at a near atomic scale are necessary. In this paper we focus on the present state of the composition evaluation by the lattice fringe analysis (CELFA) technique and explain the basic ideas, optimum imaging conditions, precision and accuracy.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
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“MgB2 : superconductivity and pressure effects”. Ivanov VA, Betouras JJ, Peeters FM, , 35 (2003)
Abstract: We present a Ginzburg-Landau theory for a two-band superconductor with emphasis on MgB2. We propose experiments which lead to identification of the possible scenarios: whether both sigma- and pi-bands superconduct or sigma-alone. According to the second scenario a microscopic theory of superconducting MgB2 is proposed based on the strongly interacting or-electrons and non-correlated pi-electrons of boron ions. The kinematic and Coulomb interactions of sigma-electrons provide the superconducting state with an anisotropic gap of s(*)-wave symmetry. The critical temperature T-c has a non-monotonic dependence on the distance r between the centers of gravity of sigma- and pi-bands. The position of MgB2 on a bell-shaped curve T-c (r) is identified in the overdoped region. The derived superconducting density of electronic states is in agreement with available experimental and theoretical data. It is argued that the effects of pressure are crucial to identify the microscopic origin of superconductivity in MgB2. Possibilities for increase of T, are discussed.
Keywords: P1 Proceeding; Condensed Matter Theory (CMT)
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“Structural characterization of nanostructured Ni3Al processed by inert gas condensation”. Yandouzi M, Pauwels B, Schryvers D, Van Swygenhoven H, Van Tendeloo G, Diffusion and defect data : solid state data : part A : defect and diffusion forum 213, 19 (2003)
Abstract: High-resolution transmission electron microscopy was performed on compacted Ni(3)Al nanostructured material prepared by the inert gas condensation technique. From electron diffraction data an incomplete L1(2) ordering of the crystallites is observed in the free particles as well as in the room temperature compacted samples. However, a completely ordered L1(2) structure with much bigger and well-defined crystallites exhibiting several defects is observed in material compacted and annealed at 773 K. Sharp crystallite boundaries as well as amorphous material and voids are observed in between crystallites in all samples, the former being dominant in the annealed material, the latter in the as-prepared one.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
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“Optimization of the amount of catalyst and reaction time in single wall nanotube production”. Horvath ZE, Biro LP, Van Tendeloo G, Tondeur C, Bister G, Pierard N, Fonseca A, Nagy JB, Diffusion and defect data : solid state data : part B : solid state phenomena 94, 271 (2003)
Abstract: The influence of the amount of catalyst and the reaction time on the quantity and quality of catalytically grown single wall carbon nanotubes (SWNT) was investigated. The aim was to optimize some of the SWNT growth parameters using TEM and HRTEM. The thickness of catalyst layer influences the synthesis of the nanotube because the gas composition can differ between top and bottom. Microscopic investigation of the grown SWNT samples showed that the thicker the catalyst layer the lower relative nanotube content, so the deeper parts of the catalyst layer are less effective: The optimum time for the reaction was found to be 10 minutes. This may be understood assuming that nanotube growth needs an initial incubation time while the activity of the catalyst decreases steadily until the nariotube growth stops.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
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“Ginzburg-Landau theory and effects of pressure on a two-band superconductor : application to MgB2”. Betouras JJ, Ivanov VA, Peeters FM, European physical journal : B : condensed matter and complex systems 31, 349 (2003). http://doi.org/10.1140/epjb/e2003-00041-7
Abstract: We present a model of pressure effects of a two-band superconductor based on a Ginzburg-Landau free energy with two order parameters. The parameters of the theory are pressure as well as temperature dependent. New pressure effects emerge as a result of the competition between the two bands. The theory then is applied to MgB2. We identify two possible scenaria regarding the fate of the two Q subbands under pressure, depending on whether or not both subbands are above the Fermi energy at ambient pressure. The splitting of the two subbands is probably caused by the E-2g, distortion. If only one subband is above the Fermi energy at ambient pressure (scenario I), application of pressure diminishes the splitting and it is possible that the lower subband participates in the superconductivity. The corresponding crossover pressure and Gruneisen parameter are estimated. In the second scenario both bands start above the Fermi energy and they move below it, either by pressure or via the substitution of Mg by Al. In both scenaria, the possibility of electronical topological transition is emphasized. Experimental signatures of both scenaria are presented and existing experiments are discussed in the light of the different physical pictures.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.461
Times cited: 10
DOI: 10.1140/epjb/e2003-00041-7
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“Symmetry lowering at the structural phase transitions in NpO2 and UO2”. Nikolaev AV, Michel KH, Physical review : B : condensed matter and materials physics 68, 054112 (2003). http://doi.org/10.1103/PhysRevB.68.054112
Abstract: The structural phase transitions with electric-quadrupole long-range order in NpO2 (Fm (3) over barm-->Pn (3) over barm) and UO2 (Fm (3) over barm-->Pa (3) over bar) are analyzed from a group theoretical point of view. In both cases, the symmetry lowering involves three quadrupolar components belonging to the irreducible representation T-2g (Gamma(5)) of O-h and condensing in a triple-q structure at the X point of the Brillouin zone. The Pa (3) over bar structure is close to Pn (3) over barm, but allows for oxygen displacements. The Pa (3) over bar ordering leads to an effective electrostatic attraction between electronic quadrupoles while the Pn (3) over barm ordering results in a repulsion between them. It is concluded that the Pn (3) over barm structure can be stabilized only through some additional process such as strengthening of the chemical bonding between Np and O. We also derive the relevant structure-factor amplitudes for Pn (3) over barm and Pa (3) over bar, and the effect of domains on resonant x-ray scattering experiments.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 15
DOI: 10.1103/PhysRevB.68.054112
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“Ordering of tetrahedral chains in the Sr2MnGaO5 brownmillerite”. Abakumov AM, Alekseeva AM, Rozova MG, Antipov EV, Lebedev OI, Van Tendeloo G, Journal of solid state chemistry 174, 319 (2003). http://doi.org/10.1016/S0022-4596(03)00226-3
Abstract: Tetrahedral chain ordering in the Sr2MnGaO5 structure is studied using electron diffraction (ED) and high-resolution electron microscopy. The ED patterns show the presence of satellite reflections, which indicate a commensurately modulated structure with a = 5.4056(8) Angstrom b 16.171(3) Angstrom, c = 5.5592(7) Angstrom, q – 1/2c*, superspace group Immma(00gamma,)s00. The Superstructure arises due to ordering of the two types of symmetry related tetrahedral chains (L and R) according to a ... LRLR ... sequence, where L and R chains alternate along the c-axis within the same (GaO) layer. Numerous defects at different structural levels were observed, comprising interleaving L and R chains, violation of the ... LRLR ... chain sequence within one layer, different stacking modes of the ... LRLR ... ordered layers with subsequent alternation of blocks of different width along the h-axis of the brownmillerite subcell and island fragmentation of the modulated superstructure. By in situ heating ED experiments it is found that the long-range ordering of the tetrahedral chains is stable tip to 665degreesC and is completely suppressed at 905degreesC. (C) 2003 Elsevier Inc. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 34
DOI: 10.1016/S0022-4596(03)00226-3
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“Optical bistability and multistability in four-level systems”. Chen Z, Feng X, Xu Y, Yu MY, Physica scripta 68, 199 (2003). http://doi.org/10.1238/Physica.Regular.068a00199
Abstract: The optical behavior of a four-level system in a ring cavity driven by two coherent laser fields is studied. One laser field is treated as the incident field and the other the control field, respectively. It is found that there is optical transparency when the difference between the two frequency detunings of the incident and control fields from the corresponding atomic transition frequencies is zero. Optical bistability can be produced and controlled by increasing the magnitude of the frequency difference. The bistable hysteresis becomes larger when the frequency difference is increased. Further increase of the latter can lead to onset of multistability.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 1.28
Times cited: 8
DOI: 10.1238/Physica.Regular.068a00199
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“Longitudinal hollow cathode copper ion laser: optimization of excitation and geometry”. Mihailova D, Grozeva M, Bogaerts A, Gijbels R, Sabotinov N, , 49 (2003)
Keywords: P3 Proceeding; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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“Current-voltage characteristics of quasi-one-dimensional superconductors: an S-shaped curve in the constant voltage regime”. Vodolazov DY, Peeters FM, Piraux L, Mátéfi-Tempfli S, Michotte S, Physical review letters 91, 157001 (2003). http://doi.org/10.1103/PhysRevLett.91.157001
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 8.462
Times cited: 90
DOI: 10.1103/PhysRevLett.91.157001
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“Normal mode spectra of two-dimensional classical atoms confined by a Coulomb potential”. Ferreira WP, Peeters FM, Farias GA, Physical review : E : statistical physics, plasmas, fluids, and related interdisciplinary topics 68, 066405 (2003). http://doi.org/10.1103/PhysRevE.68.066405
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.366
Times cited: 9
DOI: 10.1103/PhysRevE.68.066405
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“Spin-polarized ballistic transport in diluted magnetic semiconductor quantum wire systems”. Chang K, Peeters FM, Physical review : B : condensed matter and materials physics 68, 205320 (2003). http://doi.org/10.1103/PhysRevB.68.205320
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 23
DOI: 10.1103/PhysRevB.68.205320
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“Four-electron quantum dot in a magnetic field”. Tavernier MB, Anisimovas E, Peeters FM, Szafran B, Adamowski J, Bednarek S, Physical review : B : condensed matter and materials physics 68, 205305 (2003). http://doi.org/10.1103/PhysRevB.68.205305
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 87
DOI: 10.1103/PhysRevB.68.205305
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“Intersubband plasmons in quasi-one-dimensional electron systems on a liquid helium surface”. Tavares MRS, Hai G-Q, Peeters FM, Studart N, Physical review : B : condensed matter and materials physics 68, 140504 (2003). http://doi.org/10.1103/PhysRevB.68.140504
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 3
DOI: 10.1103/PhysRevB.68.140504
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“Excitonic trions in vertically coupled quantum dots”. Anisimovas E, Peeters FM, Physical review : B : condensed matter and materials physics 68, 115310 (2003). http://doi.org/10.1103/PhysRevB.68.115310
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 19
DOI: 10.1103/PhysRevB.68.115310
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“Structural, dynamical and melting properties of two-dimensional clusters of complex plasmas”. Kong M, Partoens B, Peeters FM, New journal of physics 5, 23 (2003). http://doi.org/10.1088/1367-2630/5/1/323
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.786
Times cited: 67
DOI: 10.1088/1367-2630/5/1/323
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“Excitons in single and vertically coupled type II quantum dots in high magnetic fields”. Peeters FM, Janssens KL, Partoens B s.l., page 117 (2003).
Keywords: H1 Book chapter; Condensed Matter Theory (CMT)
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“Type II quantum dots in magnetic fields: excitonic behaviour”. Janssens KL, Partoens B, Peeters FM, Microelectronics journal 34, 347 (2003). http://doi.org/10.1016/S0026-2692(03)00023-5
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.163
Times cited: 1
DOI: 10.1016/S0026-2692(03)00023-5
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“Topological defects and nonhomogeneous melting of large two-dimensional Coulomb clusters”. Kong M, Partoens B, Peeters FM, Physical review : E : statistical physics, plasmas, fluids, and related interdisciplinary topics 67, 021608 (2003). http://doi.org/10.1103/PhysRevE.67.021608
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.366
Times cited: 45
DOI: 10.1103/PhysRevE.67.021608
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“Effect of strain on the magnetoexciton ground state in InP/GaxIn1-xP quantum disks”. Janssens KL, Partoens B, Peeters FM, Physical review : B : condensed matter and materials physics 67, 235325 (2003). http://doi.org/10.1103/PhysRevB.67.235325
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 23
DOI: 10.1103/PhysRevB.67.235325
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“Ground state configurations of two-dimensional plasma crystals under long-range attractive particle interaction force”. Chen Z, Kong M, Milošević, MV, Wu Y, Physica scripta 67, 439 (2003). http://doi.org/10.1238/Physica.Regular.067a00439
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 1.28
Times cited: 4
DOI: 10.1238/Physica.Regular.067a00439
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“Vortex-antivortex molecules near a magnetic disk on top of a superconducting film”. Milošević, MV, Peeters FM, Physicalia magazine 25, 185 (2003)
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
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“A microstructural study of the thermal stability of atomic layer deposited Al2O3 thin films”. Nistor LC, Richard O, Zhao O, Bender H, Stesmans A, Van Tendeloo G, Institute of physics conference series
T2 –, Microscopy of semiconducting materials , 397 (2003)
Abstract: The thermal stability of amorphous Al2O3 films (similar to8 and 80 nut thick) deposited by atomic layer deposition on HF-last and thin SiO2 covered (001) Si substrates is studied by transmission electron microscopy. The layers are in- and ex-situ annealed in the same temperature range.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
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“Electron diffraction and microscopy of single-walled carbon nanotube bundles”. Colomer J-F, Van Tendeloo G Kluwer, Boston, Mass., page 45 (2003).
Keywords: H3 Book chapter; Electron microscopy for materials research (EMAT)
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“Fe and Co nanowires and nanotubes synthesized by template electrodeposition: a HRTEM and EELS study”. Verbeeck J, Lebedev OI, Van Tendeloo G, Cagnon L, Bougerol C, Tourillon T, Journal of the electrochemical society 150, E468 (2003). http://doi.org/10.1149/1.1601230
Abstract: Co and Fe nanowires and/or nanotubes are electrochemically synthesized through nanoporous membranes. By combining high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), and energy filtered TEM techniques, their structural and crystallographic characteristics are precisely determined. The synthesis was shown to produce cigar-shaped single monocrystalline Co and Fe nanowires with a diameter of about 60 nm. All wires were surrounded by an epitaxial oxide layer (Co3O4 or Fe3O4) of roughly 10 nm. The Fe nanotubes were built up of Fe3O4 nanocrystals. Electron diffraction showed that all nanocrystals had a common crystallographic axis, creating a pseudomonocrystalline wall in the nanotubes. (C) 2003 The Electrochemical Society.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.259
Times cited: 41
DOI: 10.1149/1.1601230
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“Transmission electron microscopy study of polymorphism in barium gallate BaGa2O4”. Lemmens H, Amelinckx S, Van Tendeloo G, Abakumov AM, Rozova MG, Antipov EV, Phase transitions 76, 653 (2003). http://doi.org/10.1080/0141159021000051055
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.06
Times cited: 6
DOI: 10.1080/0141159021000051055
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“Structural phase transition at the percolation threshold in epitaxial (La0.7Ca0.3MnO3)1-x:(MgO)x nanocomposite films”. Moshnyaga V, Damaschke B, Shapoval O, Belenchuk A, Faupel J, Lebedev OI, Verbeeck J, Van Tendeloo G, Mücksch M, Tsurkan V, Tidecks R, Samwer K, Nature materials 2, 247 (2003). http://doi.org/10.1038/nmat859
Abstract: 'Colossal magnetoresistance' in perovskite manganites such as La0.7Ca0.3MnO3 (LCMO), is caused by the interplay of ferro-paramagnetic, metal-insulator and structural phase transitions. Moreover, different electronic phases can coexist on a very fine scale resulting in percolative electron transport. Here we report on (LCMO)(1-x):(MgO)(x) (0 < x less than or equal to 0.8) epitaxial nano-composite films in which the structure and magnetotransport properties of the manganite nanoclusters can be tuned by the tensile stress originating from the MgO second phase. With increasing x, the lattice of LCMO was found to expand, yielding a bulk tensile strain. The largest colossal magnetoresistance of 10(5)% was observed at the percolation threshold in the conductivity at x(c) approximate to 0.3, which is coupled to a structural phase transition from orthorhombic (0 < x less than or equal to 0.1) to rhombohedral R (3) over barc structure (0.33 less than or equal to x less than or equal to 0.8). An increase of the Curie temperature for the R (3) over barc phase was observed. These results may provide a general method for controlling the magnetotransport properties of manganite-based composite films by appropriate choice of the second phase.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 39.737
Times cited: 177
DOI: 10.1038/nmat859
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“Rings of double-walled carbon nanotube bundles”. Colomer J-F, Henrard L, Flahaut E, Van Tendeloo G, Lucas AA, Lambin P, Nano letters 3, 685 (2003). http://doi.org/10.1021/nl034159w
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 12.712
Times cited: 59
DOI: 10.1021/nl034159w
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“Structure and properties of artificial [(La0.7Sr0.3MnO3)m(SrTiO3)n]15 superlattices on (001)SrTiO3”. Lebedev OI, Verbeeck J, Van Tendeloo G, Dubourdieu C, Rosina M, Chaudouët P, Journal of applied physics 94, 7646 (2003). http://doi.org/10.1063/1.1628407
Abstract: Complex [(La0.7Sr0.3MnO3)(m)(SrTiO3)(n)] [(LSMO)(m)/(STO)(8)](15) superlattices with different layer thicknesses (m=5, 8, 12, 16, 32) have been prepared using pulsed liquid injection metalorganic chemical vapor deposition. Transmission electron microscopy and electron diffraction reveal a very clear and well-separated layer sequence. The remarkable microstructure, as well as the ferromagnetic transition temperature, depends on the LSMO layer thickness. Apart from a very clear layer sequence, electron microscopy shows evidence of a self-assembled nanostructure formation: SrMnO3 nanoinclusions and associated SrTiO3-SrMnO3 thin walls. A formation model and growth mechanism for the self-assembled structure is proposed, based on high resolution and energy filtered elemental imaging. (C) 2003 American Institute of Physics.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.068
Times cited: 22
DOI: 10.1063/1.1628407
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“Tiling silicalite-1 nanoslabs into 3D mosaics”. Kremer SPB, Kirschhock CEA, Aerts A, Villani K, Martens JA, Lebedev OI, Van Tendeloo G, Advanced materials 15, 1705 (2003). http://doi.org/10.1002/adma.200305266
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 19.791
Times cited: 82
DOI: 10.1002/adma.200305266
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