“Direct-synthesis method towards copper-containing periodic mesoporous organosilicas : detailed investigation of the copper distribution in the material”. Lin F, Meng, Kukueva E, Altantzis T, Mertens M, Bals S, Cool P, Van Doorslaer S, Journal of the Chemical Society : Dalton transactions 44, 9970 (2015). http://doi.org/10.1039/c4dt03719g
Abstract: Three-dimensional cubic Fm (3) over barm mesoporous copper-containing ethane-bridged PMO materials have been prepared through a direct-synthesis method at room temperature in the presence of cetyltrimethylammonium bromide as surfactant. The obtained materials have been unambiguously characterized in detail by several sophisticated techniques, including XRD, UV-Vis-Dr, TEM, elemental mapping, continuous- wave and pulsed EPR spectroscopy. The results show that at lower copper loading, the Cu2+ species are well dispersed in the Cu-PMO materials, and mainly exist as mononuclear Cu2+ species. At higher copper loading amount, Cu2+ clusters are observed in the materials, but the distribution of the Cu2+ species is still much better in the Cu-PMO materials prepared through the direct-synthesis method than in a Cu-containing PMO material prepared through an impregnation method. Moreover, the evolution of the copper incorporation during the PMO synthesis has been followed by EPR. The results show that the immobilization of the Cu2+ ion/complex and the formation of the PMO materials are taking place simultaneously. The copper ions are found to be situated on the inner surface of the mesopores of the materials and are accessible, which will be beneficial for the catalytic applications.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 4.029
Times cited: 11
DOI: 10.1039/c4dt03719g
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“Dislocation-mediated relaxation in nanograined columnar palladium films revealed by on-chip time-resolved HRTEM testing”. Colla M-S, Amin-Ahmadi B, Idrissi H, Malet L, Godet S, Raskin J-P, Schryvers D, Pardoen T, Nature communications 6, 5922 (2015). http://doi.org/10.1038/ncomms6922
Abstract: The high-rate sensitivity of nanostructured metallic materials demonstrated in the recent literature is related to the predominance of thermally activated deformation mechanisms favoured by a large density of internal interfaces. Here we report time-resolved high-resolution electron transmission microscopy creep tests on thin nanograined films using on-chip nanomechanical testing. Tests are performed on palladium, which exhibited unexpectedly large creep rates at room temperature. Despite the small 30-nm grain size, relaxation is found to be mediated by dislocation mechanisms. The dislocations interact with the growth nanotwins present in the grains, leading to a loss of coherency of twin boundaries. The density of stored dislocations first increases with applied deformation, and then decreases with time to drive additional deformation while no grain boundary mechanism is observed. This fast relaxation constitutes a key issue in the development of various micro- and nanotechnologies such as palladium membranes for hydrogen applications.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 12.124
Times cited: 34
DOI: 10.1038/ncomms6922
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“Do you believe that atoms stay in place when you observe them in HREM?”.van Dyck D, Lobato I, Chen F-R, Kisielowski C, Micron 68, 158 (2015). http://doi.org/10.1016/j.micron.2014.09.003
Abstract: Recent advancements in aberration-corrected electron microscopy allow for an evaluation of unexpectedly large atom displacements beyond a resolution limit of similar to 0.5 angstrom, which are found to be dose-rate dependent in high resolution images. In this paper we outline a consistent description of the electron scattering process, which explains these unexpected phenomena. Our approach links thermal diffuse scattering to electron beam-induced object excitation and relaxation processes, which strongly contribute to the image formation process. The effect can provide an explanation for the well-known contrast mismatch (“Stobbs factor”) between image calculations and experiments. (C) 2014 Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 1.98
Times cited: 11
DOI: 10.1016/j.micron.2014.09.003
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“Dose limited reliability of quantitative annular dark field scanning transmission electron microscopy for nano-particle atom-counting”. de Backer A, Martinez GT, MacArthur KE, Jones L, Béché, A, Nellist PD, Van Aert S, Ultramicroscopy 151, 56 (2015). http://doi.org/10.1016/j.ultramic.2014.11.028
Abstract: Quantitative annular dark field scanning transmission electron microscopy (ADF STEM) has become a powerful technique to characterise nano-particles on an atomic scale. Because of their limited size and beam sensitivity, the atomic structure of such particles may become extremely challenging to determine. Therefore keeping the incoming electron dose to a minimum is important. However, this may reduce the reliability of quantitative ADF STEM which will here be demonstrated for nano-particle atom-counting. Based on experimental ADF STEM images of a real industrial catalyst, we discuss the limits for counting the number of atoms in a projected atomic column with single atom sensitivity. We diagnose these limits by combining a thorough statistical method and detailed image simulations.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 29
DOI: 10.1016/j.ultramic.2014.11.028
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“Effect of argon or helium on the CO2 conversion in a dielectric barrier discharge”. Ramakers M, Michielsen I, Aerts R, Meynen V, Bogaerts A, Plasma processes and polymers 12, 755 (2015). http://doi.org/10.1002/ppap.201400213
Abstract: This paper demonstrates that the CO2 conversion in a dielectric barrier discharge rises drastically upon addition of Ar or He, and the effect is more pronounced for Ar than for He. The effective CO2 conversion, on the other hand, drops upon addition of Ar or He, which is logical due to the lower CO2 content in the gas mixture, and the same is true for the energy efficiency, because a considerable fraction of the energy is then consumed into ionization/excitation of Ar or He atoms. The higher absolute CO2 conversion upon addition of Ar or He can be explained by studying in detail the Lissajous plots and the current profiles. The breakdown voltage is lower in the CO2/Ar and CO2/He mixtures, and the discharge gap is more filled with plasma, which enhances the possibility for CO2 conversion. The rates of electron impact excitationdissociation of CO2, estimated from the electron densities and mean electron energies, are indeed higher in the CO2/Ar and (to a lower extent) in the CO2/He mixtures, compared to the pure CO2 plasma. Moreover, charge transfer between Ar+ or Ar2+ ions and CO2, followed by electron-ion dissociative recombination of the CO2+ ions, might also contribute to, or even be dominant for the CO2 dissociation. All these effects can explain the higher CO2 conversion, especially upon addition of Ar, but also upon addition of He.
Keywords: A1 Journal article; Laboratory of adsorption and catalysis (LADCA); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.846
Times cited: 63
DOI: 10.1002/ppap.201400213
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“Effect of clay modification on structureproperty relationships and thermal degradation kinetics of \beta-polypropylene/clay composite materials”. Papageorgiou DG, Filippousi M, Pavlidou E, Chrissafis K, Van Tendeloo G, Bikiaris D, Journal of thermal analysis and calorimetry 122, 393 (2015). http://doi.org/10.1007/s10973-015-4705-y
Abstract: The influence of neat and organically modified montmorillonite on the structureproperty relationships of a β-nucleated polypropylene matrix has been thoroughly investigated. High-angle annular dark field scanning transmission electron microscopy revealed that the organic modification of clay facilitated the dispersion of the clay, while X-ray diffractograms showed the α-nucleating effect of the clays on the β-nucleated matrix. The results from tensile tests showed that the organic modification of MMT affected profoundly only the tensile strength at yield and at break. The effect of the organic modification of the clay on the thermal stability of the composites was finally evaluated by thermogravimetric analysis, where the samples filled with oMMT decomposed faster than the ones filled with neat MMT, due to the decomposition of the organic salts that were initially used for the modification of MMT. A kinetics study of the thermal degradation of the composites was also performed, in order to export additional conclusions on the activation energy of the samples.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.953
Times cited: 7
DOI: 10.1007/s10973-015-4705-y
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“Effect of interface evolution on thermal conductivity of vacuum hot pressed SiC/Al composites”. Chen Z, Tan Z, Ji G, Schryvers D, Ouyang Q, Li Z, Advanced engineering materials 17, 1076 (2015). http://doi.org/10.1002/adem.201400412
Abstract: The SiC/Al composites have been fabricated by a vacuum hot pressing (VHP) process in order to study the effect of interface evolution on the global thermal conductivity (TC). By optimizing the VHP parameters of sintering temperature and time, the three different kinds of SiC/Al interface configurations, that is, non-bonded, diffusion-bonded, and reaction-bonded interfaces, are formed and identified by measurement of relative density, X-ray diffraction, scanning and (high-resolution) transmission electron microscopy. The VHPed composite sintered at 655 °C for 60 min is fully dense and presents a tightly-adhered and clean SiC/Al interface at the nanoscale, the ideal diffusion-bonded interface being the most favorable for minimizing interfacial thermal resistance, which in turn results in the highest TC of around 270 W/mK.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.319
Times cited: 9
DOI: 10.1002/adem.201400412
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“Effect of nanoprecipitates on the transformation behavior and functional properties of a Ti50.8 at.% Ni alloy with micron-sized grains”. Wang X, Kustov S, Li K, Schryvers D, Verlinden B, Van Humbeeck J, Acta materialia 82, 224 (2015). http://doi.org/10.1016/j.actamat.2014.09.018
Abstract: In order to take advantage of both grain refinement and precipitation hardening effects, nanoscaled Ni4Ti3 precipitates are introduced in a Ti50.8 at.% Ni alloy with micron-sized grains (average grain size of 1.7 μm). Calorimetry, electrical resistance studies and thermomechanical tests were employed to study the transformation behavior and functional properties in relation to the obtained microstructure. A significant suppression of martensite transformation by the obtained microstructure is observed. The thermomechanical tests show that the advantageous properties of both grain refinement and precipitation hardening are combined in the developed materials, resulting in superior shape memory characteristics and stability of pseudoelasticity. It is concluded that introducing nanoscaled Ni4Ti3 precipitates into small grains is a new approach to improve the functional properties of NiTi shape memory alloys.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 5.301
Times cited: 51
DOI: 10.1016/j.actamat.2014.09.018
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“Effect of pinning on the response of superconducting strips to an external pulsed current”. Berdiyorov G, Harrabi K, Maneval JP, Peeters FM, Superconductor science and technology 28, 025004 (2015). http://doi.org/10.1088/0953-2048/28/2/025004
Abstract: Using the anisotropic time-dependent Ginzburg-Landau theory we study the effect of ordered and disordered pinning on the time response of superconducting strips to an external current that switched on abruptly. The pinning centers result in a considerable delay of the response time of the system to such abrupt switching on of the current, whereas the output voltage is always larger when pinning is present. The resistive state in both cases are characterized either by dynamically stable phase-slip centers/lines or expanding in-time hot-spots, which are the main mechanisms for dissipation in current-carrying superconductors. We find that hot-spots are always initiated by the phase-slip state. However, the range of the applied current for the phase-slip state increases significantly when pinning is introduced. Qualitative changes are observed in the dynamics of the superconducting condensate in the presence of pinning.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.878
Times cited: 19
DOI: 10.1088/0953-2048/28/2/025004
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“Effect of structural defects on the hydriding kinetics of nanocrystalline Pd thin films”. Delmelle R, Amin-Ahmadi B, Sinnaeve M, Idrissi H, Pardoen T, Schryvers D, Proost J, International journal of hydrogen energy 40, 7335 (2015). http://doi.org/10.1016/j.ijhydene.2015.04.017
Abstract: While the microstructure of a metal is well-known to affect its equilibrium hydrogen uptake and therefore the hydriding thermodynamics, microstructural effects on the hydriding kinetics are much less documented. Moreover, for thin film systems, such microstructural effects are difficult to separate from the internal stress effect, since most defects generate internal stresses. Such a decoupling has been achieved in this paper for nanocrystalline Pd thin film model systems through the use of a high-resolution, in-situ curvature measurement set-up during Pd deposition, annealing and hydriding. This set-up allowed producing Pd thin films with similar internal stress levels but significantly different microstructures. This was evidenced from detailed defect statistics obtained by transmission electron microscopy, which showed that the densities of grain boundaries, dislocations and twin boundaries have all been lowered by annealing. The same set-up was then used to study the hydriding equilibrium and kinetic behaviour of the resulting films at room temperature. A full quantitative analysis of their hydriding cycles showed that the rate constants of both the adsorption- and absorption-limited kinetic regimes were strongly affected by microstructure. Defect engineering was thereby shown to increase the rate constants for hydrogen adsorption and absorption in Pd by a factor 40 and 30, respectively. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.582
Times cited: 13
DOI: 10.1016/j.ijhydene.2015.04.017
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“Effect of the burn-out step on the microstructure of the solution-processed Cu(In,Ga)Se2 solar cells”. Batuk M, Buffiere M, Zaghi AE, Lenaers N, Verbist C, Khelifi S, Vleugels J, Meuris M, Hadermann J, Thin solid films : an international journal on the science and technology of thin and thick films 583, 142 (2015). http://doi.org/10.1016/j.tsf.2015.03.063
Abstract: For the development of the photovoltaic industry cheap methods for the synthesis of Cu(In,Ga)Se-2 (CIGSe) based solar cells are required. In this work, CIGSe thin films were obtained by a solution-based method using oxygen-bearing derivatives. With the aimof improving the morphology of the printed CIGSe layers, we investigated two different annealing conditions of the precursor layer, consisting of (1) a direct selenization step (reference process), and (2) a pre-treatment thermal step prior to the selenization. We showed that the use of an Air/H2S burn-out step prior to the selenization step increases the CIGSe grain size and reduces the carbon content. However, it leads to the reduction of the solar cell efficiency from 4.5% in the reference sample down to 0.5% in the annealed sample. Detailed transmission electron microscopy analysis, including high angle annular dark field scanning transmission electron microscopy and energy dispersive X-ray mapping, was applied to characterize the microstructure of the film and to determine the relationship between microstructure and the solar cell performance. We demonstrated that the relatively low efficiency of the reference solar cells is related not only to the nanosize of the CIGSe grains and presence of the pores in the CIGSe layer, but also to the high amount of secondary phases, namely, In/Ga oxide (or hydroxide) amorphous matter, residuals of organicmatter (carbon), and copper sulfide that is formed at the CIGSe/MoSe2 interface. The annealing in H2S during the burn-out step leads to the formation of the copper sulfide at all grain boundaries and surfaces in the CIGSe layer, which results in the noticeably efficiency drop. (C) 2015 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.879
Times cited: 5
DOI: 10.1016/j.tsf.2015.03.063
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“Effects of feedstock availability on the negative ion behavior in a C4F8 inductively coupled plasma”. Zhao S-X, Gao F, Wang Y-P, Wang Y-N, Bogaerts A, Journal of applied physics 118, 033301 (2015). http://doi.org/10.1063/1.4926867
Abstract: In this paper, the negative ion behavior in a C4F8 inductively coupled plasma (ICP) is investigated using a hybrid model. The model predicts a non-monotonic variation of the total negative ion density with power at low pressure (1030 mTorr), and this trend agrees well with experiments that were carried out in many fluorocarbon (fc) ICP sources, like C2F6, CHF3, and C4F8. This behavior is explained by the availability of feedstock C4F8 gas as a source of the negative ions, as well as by the presence of low energy electrons due to vibrational excitation at low power. The maximum of the negative ion density shifts to low power values upon decreasing pressure, because of the more pronounced depletion of C4F8 molecules, and at high pressure (∼50 mTorr), the anion density continuously increases with power, which is similar to fc CCP sources. Furthermore, the negative ion composition is identified in this paper. Our work demonstrates that for a clear understanding of the negative ion behavior in radio frequency C4F8 plasma sources, one needs to take into account many factors, like the attachment characteristics, the anion composition, the spatial profiles, and the reactor configuration. Finally, a detailed comparison of our simulation results with experiments is conducted.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.068
Times cited: 1
DOI: 10.1063/1.4926867
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Zhang L (2015) Effects of quantum confinement in nanoscale superconductors : from electronic density of states to vortex matter. Antwerpen
Keywords: Doctoral thesis; Condensed Matter Theory (CMT)
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“Efficient amorphous platinum catalyst cluster growth on porous carbon : a combined molecular dynamics and experimental study”. Xie L, Brault P, Coutanceau C, Bauchire J-M, Caillard A, Baranton S, Berndt J, Neyts EC, Applied catalysis : B : environmental 162, 21 (2015). http://doi.org/10.1016/j.apcatb.2014.06.032
Abstract: Amorphous platinum clusters supported on porous carbon have been envisaged for high-performance fuel cell electrodes. For this application, it is crucial to control the morphology of the Pt layer and the Ptsubstrate interaction to maximize activity and stability. We thus investigate the morphology evolution during Pt cluster growth on a porous carbon substrate employing atomic scale molecular dynamics simulations. The simulations are based on the Pt-C interaction potential using parameters derived from density functional theory and are found to yield a Pt cluster morphology similar to that observed in low loaded fuel cell electrodes prepared by plasma sputtering. Moreover, the simulations show amorphous Pt cluster growth in agreement with X-ray diffraction and transmission electron microscopy experiments on high performance low Pt content (10 μgPt cm−2) loaded fuel cell electrodes and provide a fundamental insight in the cluster growth mechanism.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 9.446
Times cited: 20
DOI: 10.1016/j.apcatb.2014.06.032
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“Electromagnetic effects in high-frequency large-area capacitive discharges : a review”. Liu Y-X, Zhang Y-R, Bogaerts A, Wang Y-N, Journal of vacuum science and technology: A: vacuum surfaces and films 33, 020801 (2015). http://doi.org/10.1116/1.4907926
Abstract: In traditional capacitively coupled plasmas, the discharge can be described by an electrostatic model, in which the Poisson equation is employed to determine the electrostatic electric field. However, current plasma reactors are much larger and driven at a much higher frequency. If the excitation wavelength k in the plasma becomes comparable to the electrode radius, and the plasma skin depth d becomes comparable to the electrode spacing, the electromagnetic (EM) effects will become significant and compromise the plasma uniformity. In this regime, capacitive discharges have to be described by an EM model, i.e., the full set of Maxwells equations should be solved to address the EM effects. This paper gives an overview of the theory, simulation and experiments that have recently been carried out to understand these effects, which cause major uniformity problems in plasma processing for microelectronics and flat panel display industries. Furthermore, some methods for improving the plasma uniformity are also described and compared.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 1.374
Times cited: 10
DOI: 10.1116/1.4907926
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“Self-Assembly of Pluronic F127—Silica Spherical Core–Shell Nanoparticles in Cubic Close-Packed Structures”. Kerkhofs S, Willhammar T, Van Den Noortgate H, Kirschhock CEA, Breynaert E, Van Tendeloo G, Bals S, Martens JA, Chemistry of materials 27, 5161 (2015). http://doi.org/10.1021/acs.chemmater.5b01772
Abstract: A new ordered mesoporous silica material (COK-19) with cubic symmetry is synthesized by silicate polycondensation in a citric acid/citrate buffered micellar solution of Pluronic F127 triblock copolymer near neutral pH. SAXS, nitrogen adsorption, TEM, and electron tomography reveal the final material has a cubic close packed symmetry (Fm3̅m) with isolated spherical mesopores interconnected through micropores. Heating of the synthesis medium from room temperature to 70 °C results in a mesopore size increase from 7.0 to 11.2 nm. Stepwise addition of the silicate source allows isolation of a sequence of intermediates that upon characterization with small-angle X-ray scattering uncovers the formation process via formation and aggregation of individual silica-covered Pluronic micelles.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 39
DOI: 10.1021/acs.chemmater.5b01772
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“Electron polarization function and plasmons in metallic armchair graphene nanoribbons”. Shylau AA, Badalyan SM, Peeters FM, Jauho AP, Physical review : B : condensed matter and materials physics 91, 205444 (2015). http://doi.org/10.1103/PhysRevB.91.205444
Abstract: Plasmon excitations in metallic armchair graphene nanoribbons are investigated using the random phase approximation. An exact analytical expression for the polarization function of Dirac fermions is obtained, valid for arbitrary temperature and doping. We find that at finite temperatures, due to the phase space redistribution among inter-band and intra-band electronic transitions in the conduction and valence bands, the full polarization function becomes independent of temperature and position of the chemical potential. It is shown that for a given width of nanoribbon there exists a single plasmon mode whose energy dispersion is determined by the graphene's fine structure constant. In the case of two Coulomb-coupled nanoribbons, this plasmon splits into in-phase and out-of-phase plasmon modes with splitting energy determined by the inter-ribbon spacing.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 13
DOI: 10.1103/PhysRevB.91.205444
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“Electron tomography based on highly limited data using a neural network reconstruction technique”. Bladt E, Pelt DM, Bals S, Batenburg KJ, Ultramicroscopy 158, 81 (2015). http://doi.org/10.1016/j.ultramic.2015.07.001
Abstract: Gold nanoparticles are studied extensively due to their unique optical and catalytical properties. Their exact shape determines the properties and thereby the possible applications. Electron tomography is therefore often used to examine the three-dimensional (3D) shape of nanoparticles. However, since the acquisition of the experimental tilt series and the 3D reconstructions are very time consuming, it is difficult to obtain statistical results concerning the 3D shape of nanoparticles. Here, we propose a new approach for electron tomography that is based on artificial neural networks. The use of a new reconstruction approach enables us to reduce the number of projection images with a factor of 5 or more. The decrease in acquisition time of the tilt series and use of an efficient reconstruction algorithm allows us to examine a large amount of nanoparticles in order to retrieve statistical results concerning the 3D shape.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 25
DOI: 10.1016/j.ultramic.2015.07.001
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“Electronic band structures and native point defects of ultrafine ZnO nanocrystals”. Zeng Y-J, Schouteden K, Amini MN, Ruan S-C, Lu Y-F, Ye Z-Z, Partoens B, Lamoen D, Van Haesendonck C, ACS applied materials and interfaces 7, 10617 (2015). http://doi.org/10.1021/acsami.5b02545
Abstract: Ultrafine ZnO nanocrystals with a thickness down to 0.25 nm are grown by a metalorganic chemical vapor deposition method. Electronic band structures and native point defects of ZnO nanocrystals are studied by a combination of scanning tunneling microscopy/spectroscopy and first-principles density functional theory calculations. Below a critical thickness of nm ZnO adopts a graphitic-like structure and exhibits a wide band gap similar to its wurtzite counterpart. The hexagonal wurtzite structure, with a well-developed band gap evident from scanning tunneling spectroscopy, is established for a thickness starting from similar to 1.4 nm. With further increase of the thickness to 2 nm, V-O-V-Zn defect pairs are easily produced in ZnO nanocrystals due to the self-compensation effect in highly doped semiconductors.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 7.504
Times cited: 15
DOI: 10.1021/acsami.5b02545
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“Enhanced biomedical heat-triggered carriers via nanomagnetism tuning in ferrite-based nanoparticles”. Angelakeris M, Li ZA, Hilgendorff M, Simeonidis K, Sakellari D, Filippousi M, Tian H, Van Tendeloo G, Spasova M, Acet M, Farle M, Journal of magnetism and magnetic materials 381, 179 (2015). http://doi.org/10.1016/j.jmmm.2014.12.069
Abstract: Biomedical nanomagnetic carriers are getting a higher impact in therapy and diagnosis schemes while their constraints and prerequisites are more and more successfully confronted. Such particles should possess a well-defined size with minimum agglomeration and they should be synthesized in a facile and reproducible high-yield way together with a controllable response to an applied static or dynamic field tailored for the specific application. Here, we attempt to enhance the heating efficiency in magnetic particle hyperthermia treatment through the proper adjustment of the core-shell morphology in ferrite particles, by controlling exchange and dipolar magnetic interactions at the nanoscale. Thus, core-shell nanoparticles with mutual coupling of magnetically hard (CoFe2O4) and soft (MnFe2O4) components are synthesized with facile synthetic controls resulting in uniform size and shell thickness as evidenced by high resolution transmission electron microscopy imaging, excellent crystallinity and size monodispersity. Such a magnetic coupling enables the fine tuning of magnetic anisotropy and magnetic interactions without sparing the good structural, chemical and colloidal stability. Consequently, the magnetic heating efficiency of CoFe2O4. and MnFe2O4 core-shell nanoparticles is distinctively different horn that of their counterparts, even though all these nanocrystals were synthesized under similar conditions. For better understanding of the AC magnetic hyperthermia response and its correlation with magnetic-origin features we study the effect of the volume ratio of magnetic hard and soft phases in the bimagnetic core-shell nanocrystals. Eventually, such particles may be considered as novel heating carriers that under further biomedical functionalization may become adaptable multifunctional heat-triggered nanoplatforms. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.63
Times cited: 20
DOI: 10.1016/j.jmmm.2014.12.069
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“Enhanced local magnetization by interface engineering in perovskite-type correlated oxide heterostructures”. Huijben M, Liu Y, Boschker H, Lauter V, Egoavil R, Verbeeck J, te Velthuis SGE, Rijnders G, Koster G, Advanced Materials Interfaces 2, 1400416 (2015). http://doi.org/10.1002/admi.201400416
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.279
Times cited: 30
DOI: 10.1002/admi.201400416
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“Environmental changes in MoTe2 excitonic dynamics by defects-activated molecular interaction”. Chen B, Sahin H, Suslu A, Ding L, Bertoni MI, Peeters FM, Tongay S, ACS nano 9, 5326 (2015). http://doi.org/10.1021/acsnano.5b00985
Abstract: Monolayers of group VI transition metal dichalcogenides possess direct gaps in the visible spectrum with the exception of MoTe2, where its gap is suitably located in the infrared region but its stability is of particular interest, as tellurium compounds are acutely sensitive to oxygen exposure. Here, our environmental (time-dependent) measurements reveal two distinct effects on MoTe2 monolayers: For weakly luminescent monolayers, photoluminescence signal and optical contrast disappear, as if they are decomposed, but yet remain intact as evidenced by AFM and Raman measurements. In contrast, strongly luminescent monolayers retain their optical contrast for a prolonged amount of time, while their PL peak blue-shifts and PL intensity saturates to slightly lower values. Our X-ray photoelectron spectroscopy measurements and DFT calculations suggest that the presence of defects and functionalization of these defect sites with O-2 molecules strongly dictate their material properties and aging response by changing the excitonic dynamics due to deep or shallow states that are created within the optical band gap. Presented results not only shed light on environmental effects on fundamental material properties and excitonic dynamics of MoTe2 monolayers but also highlight striking material transformation for metastable 20 systems such as WTe2, silicone, and phosphorene.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 13.942
Times cited: 150
DOI: 10.1021/acsnano.5b00985
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“Evaluation of the energy efficiency of CO2 conversion in microwave discharges using a reaction kinetics model”. Kozák T, Bogaerts A, Plasma sources science and technology 24, 015024 (2015). http://doi.org/10.1088/0963-0252/24/1/015024
Abstract: We use a zero-dimensional reaction kinetics model to simulate CO2 conversion in microwave discharges where the excitation of the vibrational levels plays a significant role in the dissociation kinetics. The model includes a description of the CO2 vibrational kinetics, taking into account state-specific VT and VV relaxation reactions and the effect of vibrational excitation on other chemical reactions. The model is used to simulate a general tubular microwave reactor, where a stream of CO2 flows through a plasma column generated by microwave radiation. We study the effects of the internal plasma parameters, namely the reduced electric field, electron density and the total specific energy input, on the CO2 conversion and its energy efficiency. We report the highest energy efficiency (up to 30%) for a specific energy input in the range 0.41.0 eV/molecule and a reduced electric field in the range 50100 Td and for high values of the electron density (an ionization degree greater than 10−5). The energy efficiency is mainly limited by the VT relaxation which contributes dominantly to the vibrational energy losses and also contributes significantly to the heating of the reacting gas. The model analysis provides useful insight into the potential and limitations of CO2 conversion in microwave discharges.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.302
Times cited: 100
DOI: 10.1088/0963-0252/24/1/015024
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“Exploring alternative metals to Cu and W for interconnects applications using automated first-principles simulations”. Sankaran K, Clima S, Mees M, Pourtois G, ECS journal of solid state science and technology 4, N3127 (2015). http://doi.org/10.1149/2.0181501jss
Abstract: The bulk properties of elementary metals and copper based binary alloys have been investigated using automated first-principles simulations to evaluate their potential to replace copper and tungsten as interconnecting wires in the coming CMOS technology nodes. The intrinsic properties of the screened candidates based on their cohesive energy and on their electronic properties have been used as a metrics to reflect their resistivity and their sensitivity to electromigration. Using these values, the 'performances' of the alloys have been benchmarked with respect to the Cu and W ones. It turns out that for some systems, alloying Cu with another element leads to a reduced tendency to electromigration. This is however done at the expense of a decrease of the conductivity of the alloy with respect to the bulk metal. (C) 2014 The Electrochemical Society. All rights reserved.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 1.787
Times cited: 19
DOI: 10.1149/2.0181501jss
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“Focused electron beam induced deposition as a tool to create electron vortices”. Béché, A, Winkler R, Plank H, Hofer F, Verbeeck J, Micron 80, 34 (2015). http://doi.org/10.1016/j.micron.2015.07.011
Abstract: Focused electron beam induced deposition (FEBID) is a microscopic technique that allows geometrically controlled material deposition with very high spatial resolution. This technique was used to create a spiral aperture capable of generating electron vortex beams in a transmission electron microscope (TEM). The vortex was then fully characterized using different TEM techniques, estimating the average orbital angular momentum to be approximately 0.8variant Planck's over 2pi per electron with almost 60% of the beam ending up in the l=1 state.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.98
Times cited: 21
DOI: 10.1016/j.micron.2015.07.011
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“Templated Growth of Surface Enhanced Raman Scattering -Active Branched Au Nanoparticles within Radial Mesoporous Silica Shells”. Sanz-Ortiz MN, Sentosun K, Bals S, Liz-Marzan LM, ACS nano 9, 10489 (2015). http://doi.org/10.1021/acsnano.5b04744
Abstract: Noble metal nanoparticles are widely used as probes or substrates for surface-enhanced Raman scattering (SERS), due to their characteristic plasmon resonances in the visible and NIR spectral ranges. Aiming at obtaining a versatile system with high SERS performance we developed the synthesis of quasi-monodisperse, non-aggregated gold nanoparticles protected by radial mesoporous silica shells. The radial channels of such shells were used as templates for the growth of gold tips branching from the cores, thereby improving the plasmonic performance of the particles while favoring the localization of analyte molecules at high electric field regions: close to the tips, inside the pores. The method, which allows control over tip length, was successfully applied to various gold nanoparticle shapes, leading to materials with highly efficient SERS performance. The obtained nanoparticles are stable in ethanol and water upon thermal consolidation and can be safely stored as a powder.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 13.942
Times cited: 110
DOI: 10.1021/acsnano.5b04744
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“Extreme mobility enhancement of two-dimensional electron gases at oxide interfaces by charge-transfer-induced modulation doping”. Chen YZ, Trier F, Wijnands T, Green RJ, Gauquelin N, Egoavil R, Christensen DV, Koster G, Huijben M, Bovet N, Macke S, He F, Sutarto R, Andersen NH, Sulpizio JA, Honig M, Prawiroatmodjo GEDK, Jespersen TS, Linderoth S, Ilani S, Verbeeck J, Van Tendeloo G, Rijnders G, Sawatzky GA, Pryds N, Nature materials 14, 801 (2015). http://doi.org/10.1038/nmat4303
Abstract: Two-dimensional electron gases (2DEGs) formed at the interface of insulating complex oxides promise the development of all-oxide electronic devices. These 2DEGs involve many-body interactions that give rise to a variety of physical phenomena such as superconductivity, magnetism, tunable metalinsulator transitions and phase separation. Increasing the mobility of the 2DEG, however, remains a major challenge. Here, we show that the electron mobility is enhanced by more than two orders of magnitude by inserting a single-unit-cell insulating layer of polar La1−xSrxMnO3 (x = 0, 1/8, and 1/3) at the interface between disordered LaAlO3 and crystalline SrTiO3 produced at room temperature. Resonant X-ray spectroscopy and transmission electron microscopy show that the manganite layer undergoes unambiguous electronic reconstruction, leading to modulation doping of such atomically engineered complex oxide heterointerfaces. At low temperatures, the modulation-doped 2DEG exhibits Shubnikovde Haas oscillations and fingerprints of the quantum Hall effect, demonstrating unprecedented high mobility and low electron density.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 39.737
Times cited: 170
DOI: 10.1038/nmat4303
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“Fano resonances in the conductance of graphene nanoribbons with side gates”. Petrovic MD, Peeters FM, Physical review : B : condensed matter and materials physics 91, 035444 (2015). http://doi.org/10.1103/PhysRevB.91.035444
Abstract: The control of side gates on the quantum electron transport in narrow graphene ribbons of different widths and edge types (armchair and zigzag) is investigated. The conductance exhibits Fano resonances with varying side gate potential. Resonant and antiresonant peaks in the conductance can be associated with the eigenstates of a closed system, and these peaks can be accurately fitted with a Fano line shape. The local density of states (LDOS) and the electron current show a specific behavior at these resonances, which depends on the ribbon edge type. In zigzag ribbons, transport is dominated by intervalley scattering, which is reflected in the transmission functions of individual modes. The side gates induce p-n interfaces near the edges at which the LDOS exhibits peaks. Near the resonance points, the electron current flows uniformly through the constriction, while near the antiresonances it creates vortices. In the armchair ribbons the LDOS spreads in areas of high potential, with current flowing near the edges.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 17
DOI: 10.1103/PhysRevB.91.035444
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“FFLO-wave-vector lock-in effect in quasi-1D superconductors”. Croitoru MD, Buzdin AI, Journal of superconductivity and novel magnetism 28, 1305 (2015). http://doi.org/10.1007/s10948-014-2910-8
Abstract: We study the phase transition into the Fulde-Ferrell-Larkin-Ovchinnikov state in high magnetic field in quasi-one dimensional superconductors within the quasi-classical formalism, taking into account the interchain Josephson coupling and the paramagnetic spin splitting. We show that anomalies in the field-direction dependence of the upper critical field when the magnetic field length equals to the FFLO period, previously described in [29], are characterized by the lock-in effect of the FFLO modulation wave vector, which is governed by the magnetic length.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.18
Times cited: 4
DOI: 10.1007/s10948-014-2910-8
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Sivek J (2015) First-principles characterization and functionalization of graphene-like materials. Antwerpen
Keywords: Doctoral thesis; Condensed Matter Theory (CMT)
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