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“Platinum and palladium on carbon nanotubes : experimental and theoretical studies”. Adjizian JJ, De Marco P, Suarez-Martinez I, El Mel AA, Snyders R, Gengler RYN, Rudolf P, Ke X, Van Tendeloo G, Bittencourt C, Ewels CP;, Chemical physics letters 571, 44 (2013). http://doi.org/10.1016/j.cplett.2013.03.079
Abstract: Pristine and oxygen plasma functionalised carbon nanotubes (CNTs) were studied after the evaporation of Pt and Pd atoms. High resolution transmission electron microscopy shows the formation of metal nanoparticles at the CNT surface. Oxygen functional groups grafted by the plasma functionalization act as nucleation sites for metal nanoparticles. Analysis of the C1s core level spectra reveals that there is no covalent bonding between the Pt or Pd atoms and the CNT surface. Unlike other transition metals such as titanium and copper, neither Pd nor Pt show strong oxygen interaction or surface oxygen scavenging behaviour.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.815
Times cited: 23
DOI: 10.1016/j.cplett.2013.03.079
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“Degradation process of lead chromate in paintings by Vincent van Gogh studied by means of spectromicroscopic methods : 3 : synthesis, characterization, and detection of different crystal forms of the chrome yellow pigment”. Monico L, Janssens K, Miliani C, Brunetti BG, Vagnini M, Vanmeert F, Falkenberg G, Abakumov A, Lu Y, Tian H, Verbeeck J, Radepont M, Cotte M, Hendriks E, Geldof M, van der Loeff L, Salvant J, Menu M;, Analytical chemistry 85, 860 (2013). http://doi.org/10.1021/ac302158b
Abstract: The painter, Vincent van Gogh, and some of his contemporaries frequently made use of the pigment chrome yellow that is known to show a tendency toward darkening. This pigment may correspond to various chemical compounds such as PbCrO4 and PbCr1-xSxO4, that may each be present in various crystallographic forms with different tendencies toward degradation. Investigations by X-ray diffraction (XRD), mid-Fourier Transform infrared (FTIR), and Raman instruments (benchtop and portable) and synchrotron radiation-based micro-XRD and X-ray absorption near edge structure spectroscopy performed on oil-paint models, prepared with in-house synthesized PbCrO4 and PbCr1-xSxO4, permitted us to characterize the spectroscopic features of the various forms. On the basis of these results, an extended study has been carried out on historic paint tubes and on embedded paint microsamples taken from yellow-orange/pale yellow areas of 12 Van Gogh paintings, demonstrating that Van Gogh effectively made use of different chrome yellow types. This conclusion was also confirmed by in situ mid-FTIR investigations on Van Goghs Portrait of Gauguin (Van Gogh Museum, Amsterdam).
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.32
Times cited: 79
DOI: 10.1021/ac302158b
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“Chemical insight into electroforming of resistive switching manganite heterostructures”. Borgatti F, Park C, Herpers A, Offi F, Egoavil R, Yamashita Y, Yang A, Kobata M, Kobayashi K, Verbeeck J, Panaccione G, Dittmann R;, Nanoscale 5, 3954 (2013). http://doi.org/10.1039/c3nr00106g
Abstract: We have investigated the role of the electroforming process in the establishment of resistive switching behaviour for Pt/Ti/Pr0.5Ca0.5MnO3/SrRuO3 layered heterostructures (Pt/Ti/PCMO/SRO) acting as non-volatile Resistance Random Access Memories (RRAMs). Electron spectroscopy measurements demonstrate that the higher resistance state resulting from electroforming of as-prepared devices is strictly correlated with the oxidation of the top electrode Ti layer through field-induced electromigration of oxygen ions. Conversely, PCMO exhibits oxygen depletion and downward change of the chemical potential for both resistive states. Impedance spectroscopy analysis, supported by the detailed knowledge of these effects, provides an accurate model description of the device resistive behaviour. The main contributions to the change of resistance from the as-prepared (low resistance) to the electroformed (high resistance) states are respectively due to reduced PCMO at the boundary with the Ti electrode and to the formation of an anisotropic np junction between the Ti and the PCMO layers.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.367
Times cited: 40
DOI: 10.1039/c3nr00106g
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“Annular dark-field transmission electron microscopy for low contrast materials”. Leroux F, Bladt E, Timmermans J-P, Van Tendeloo G, Bals S, Microscopy and microanalysis 19, 629 (2013). http://doi.org/10.1017/S1431927613000020
Abstract: Imaging soft matter by transmission electron microscopy (TEM) is anything but straightforward. Recently, interest has grown in developing alternative imaging modes that generate contrast without additional staining. Here, we present a dark-field TEM technique based on the use of an annular objective aperture. Our experiments demonstrate an increase in both contrast and signal-to-noise ratio in comparison to conventional bright-field TEM. The proposed technique is easy to implement and offers an alternative imaging mode to investigate soft matter.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.891
Times cited: 5
DOI: 10.1017/S1431927613000020
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“Wafer-level electrical evaluation of vertical carbon nanotube bundles as a function of growth temperature”. Vereecke B, van der Veen MH, Sugiura M, Kashiwagi Y, Ke X, Cott DJ, Hantschel T, Huyghebaert C, Tökei Z, Japanese journal of applied physics 52, 04cn02 (2013). http://doi.org/10.7567/JJAP.52.04CN02
Abstract: We have evaluated the resistance of carbon nanotubes (CNTs) grown at a CMOS-compatible temperature using a realistic integration scheme. The structural analysis of the CNTs by transmission electron microscopy (TEM) showed that the degree of graphitization decreased significantly when the growth temperature was decreased from 540 to 400 °C. The CNTs were integrated to form 150-nm-diameter vertical interconnects between a TiN layer and Cu metal trenches on 200 mm full wafers. Wafers with CNTs grown at low temperature were found to have a lower single-contact resistance than those produced at high temperatures. Thickness measurements showed that the low contact resistance is a result of small contact height. This height dependence is masking the impact of CNT graphitization quality on resistance. When benchmarking our results with data from the literature, a relationship between resistivity and growth temperature cannot be found for CNT-based vertical interconnects.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.384
Times cited: 5
DOI: 10.7567/JJAP.52.04CN02
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“Plasma nanoscience : from nano-solids in plasmas to nano-plasmas in solids”. Ostrikov K, Neyts EC, Meyyappan M, Advances in physics 62, 113 (2013). http://doi.org/10.1080/00018732.2013.808047
Abstract: The unique plasma-specific features and physical phenomena in the organization of nanoscale soild-state systems in a broad range of elemental composition, structure, and dimensionality are critically reviewed. These effects lead to the possibility to localize and control energy and matter at nanoscales and to produce self-organized nano-solids with highly unusual and superior properties. A unifying conceptual framework based on the control of production, transport, and self-organization of precursor species is introduced and a variety of plasma-specific non-equilibrium and kinetics-driven phenomena across the many temporal and spatial scales is explained. When the plasma is localized to micrometer and nanometer dimensions, new emergent phenomena arise. The examples range from semiconducting quantum dots and nanowires, chirality control of single-walled carbon nanotubes, ultra-fine manipulation of graphenes, nano-diamond, and organic matter to nano-plasma effects and nano-plasmas of different states of matter.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 21.818
Times cited: 380
DOI: 10.1080/00018732.2013.808047
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“Kinetic modelling for an atmospheric pressure argon plasma jet in humid air”. Van Gaens W, Bogaerts A, Journal of physics: D: applied physics 46, 275201 (2013). http://doi.org/10.1088/0022-3727/46/27/275201
Abstract: A zero-dimensional, semi-empirical model is used to describe the plasma chemistry in an argon plasma jet flowing into humid air, mimicking the experimental conditions of a setup from the Eindhoven University of Technology. The model provides species density profiles as a function of the position in the plasma jet device and effluent. A reaction chemistry set for an argon/humid air mixture is developed, which considers 84 different species and 1880 reactions. Additionally, we present a reduced chemistry set, useful for higher level computational models. Calculated species density profiles along the plasma jet are shown and the chemical pathways are explained in detail. It is demonstrated that chemically reactive H, N, O and OH radicals are formed in large quantities after the nozzle exit and H2, O2(1Δg), O3, H2O2, NO2, N2O, HNO2 and HNO3 are predominantly formed as 'long living' species. The simulations show that water clustering of positive ions is very important under these conditions. The influence of vibrational excitation on the calculated electron temperature is studied. Finally, the effect of varying gas temperature, flow speed, power density and air humidity on the chemistry is investigated.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 115
DOI: 10.1088/0022-3727/46/27/275201
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“Gas purification by nonthermal plasma : a case study of ethylene”. Aerts R, Tu X, Van Gaens W, Whitehead JC, Bogaerts A, Environmental science and technology 47, 6478 (2013). http://doi.org/10.1021/es400405c
Abstract: The destruction of ethylene in a dielectric barrier discharge plasma is investigated by the combination of kinetic modeling and experiments, as a case study for plasma-based gas purification. The influence of the specific energy deposition on the removal efficiency and the selectivity toward CO and CO2 is studied for different concentrations of ethylene. The model allows the identication of the destruction pathway in dry and humid air. The latter is found to be mainly initiated by metastable N2 molecules, but the further destruction steps are dominated by O atoms and OH radicals. Upon increasing air humidity, the removal efficiency drops by ±15% (from 85% to 70%), but the selectivity toward CO and CO2 stays more or less constant at 60% and 22%, respectively. Beside CO and CO2, we also identified acetylene, formaldehyde, and water as byproducts of the destruction process, with concentrations of 1606 ppm, 15033 ppm, and 185 ppm in humid air (with 20% RH), respectively. Finally, we investigated the byproducts generated by the humid air discharge itself, which are the greenhouse gases O3, N2O, and the toxic gas NO2.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.198
Times cited: 56
DOI: 10.1021/es400405c
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“Microstructure of bilayer manganite PrCa2Mn2O7 showing charge/orbital ordering”. He Z, Tian H, Deng G, Xu Q, Van Tendeloo G, Applied physics letters 102, 212902 (2013). http://doi.org/10.1063/1.4807758
Abstract: The microstructure of the charge/orbital ordering Ruddleden-Popper phase PrCa2Mn2O7 was studied by transmission electron microscopy along both the [001] and the [110] orientation. Three coexisting charge/orbital ordering phases CO1, CO2, and CO3 were observed along the [001] orientation at room temperature. Different from the one-dimensional modulation in the CO1 and CO2 phase, the CO3 phase is characterized by two sets of mutually perpendicular structural modulations. From [110] high angle annular dark field-scanning transmission electron microscopy, we found that the Pr atoms locate in-between the bilayer MnO6 octahedra, which is different from the previous reports.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.411
Times cited: 4
DOI: 10.1063/1.4807758
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“Perovskite-like Mn2O3 : a path to new manganites”. Ovsyannikov SV, Abakumov AM, Tsirlin AA, Schnelle W, Egoavil R, Verbeeck J, Van Tendeloo G, Glazyrin KV, Hanfland M, Dubrovinsky L, Angewandte Chemie 52, 1494 (2013). http://doi.org/10.1002/anie.201208553
Abstract: Korund-artiges ε-Mn2O3 und Perowskit-artiges ζ-Mn2O3, zwei neue Phasen von Mn2O3, wurden unter hohen Drücken bei hohen Temperaturen synthetisiert. Die Manganatome können vollständig die A- und B-Positionen der Perowskitstruktur besetzen. ζ-Mn2O3 (siehe Bild, A-Positionsordnung) enthält Mn in den drei Oxidationsstufen +II, +III und +IV.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 11.994
Times cited: 84
DOI: 10.1002/anie.201208553
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“First-principles study of possible shallow donors in ZnAl2O4 spinel”. Dixit H, Tandon N, Cottenier S, Saniz R, Lamoen D, Partoens B, Physical review : B : condensed matter and materials physics 87, 174101 (2013). http://doi.org/10.1103/PhysRevB.87.174101
Abstract: ZnAl2O4 (gahnite) is a ceramic which is considered a possible transparent conducting oxide (TCO) due to its wide band gap and transparency for UV. Defects play an important role in controlling the conductivity of a TCO material along with the dopant, which is the main source of conductivity in an otherwise insulating oxide. A comprehensive first-principles density functional theory study for point defects in ZnAl2O4 spinel is presented using the Heyd, Scuseria, and Ernzerhof hybrid functional (HSE06) to overcome the band gap problem. We have investigated the formation energies of intrinsic defects which include the Zn, Al, and O vacancy and the antisite defects: Zn at the Al site (ZnAl) and Al at the Zn site (AlZn). The antisite defect AlZn has the lowest formation energy and acts as a shallow donor, indicating possible n-type conductivity in ZnAl2O4 spinel by Al doping.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 50
DOI: 10.1103/PhysRevB.87.174101
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“Synthesis of uniformly dispersed anatase nanoparticles inside mesoporous silica thin films via controlled breakup and crystallization of amorphous TiO2 deposited using atomic layer deposition”. Sree SP, Dendooven J, Masschaele K, Hamed HM, Deng S, Bals S, Detavernier C, Martens JA, Nanoscale 5, 5001 (2013). http://doi.org/10.1039/c3nr00594a
Abstract: Amorphous titanium dioxide was introduced into the pores of mesoporous silica thin films with 75% porosity and 12 nm average pore diameter via Atomic Layer Deposition (ALD) using alternating pulses of tetrakis(dimethylamino)titanium and water. Calcination provoked fragmentation of the deposited amorphous TiO2 phase and its crystallization into anatase nanoparticles inside the nanoporous film. The narrow particle size distribution of 4 ± 2 nm and the uniform dispersion of the particles over the mesoporous silica support were uniquely revealed using electron tomography. These anatase nanoparticle bearing films showed photocatalytic activity in methylene blue degradation. This new synthesis procedure of the anatase nanophase in mesoporous silica films using ALD is a convenient fabrication method of photocatalytic coatings amenable to application on very small as well as very large surfaces
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.367
Times cited: 22
DOI: 10.1039/c3nr00594a
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“Multiband tunneling in trilayer graphene”. Van Duppen B, Sena SHR, Peeters FM, Physical review : B : condensed matter and materials physics 87, 195439 (2013). http://doi.org/10.1103/PhysRevB.87.195439
Abstract: The electronic tunneling properties of the two stable forms of trilayer graphene (TLG), rhombohedral ABC and Bernal ABA, are examined for p-n and p-n-p junctions as realized by using a single gate (SG) or a double gate (DG). For the rhombohedral form, due to the chirality of the electrons, the Klein paradox is found at normal incidence for SG devices, while at high-energy interband scattering between additional propagation modes can occur. The electrons in Bernal ABA TLG can have a monolayer- or bilayer-like character when incident on a SG device. Using a DG, however, both propagation modes will couple by breaking the mirror symmetry of the system, which induces intermode scattering and resonances that depend on the width of the DG p-n-p junction. For ABC TLG the DG opens up a band gap which suppresses Klein tunneling. The DG induces also an unexpected asymmetry in the tunneling angle for single-valley electrons.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 13
DOI: 10.1103/PhysRevB.87.195439
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“Graphene hall bar with an asymmetric pn-junction”. Milovanovic SP, Masir MR, Peeters FM, Journal of applied physics 113, 193701 (2013). http://doi.org/10.1063/1.4805350
Abstract: We investigated the magnetic field dependence of the Hall and the bend resistances in the ballistic regime for a single layer graphene Hall bar structure containing a pn-junction. When both regions are n-type the Hall resistance dominates and Hall type of plateaus are formed. These plateaus occur as a consequence of the restriction on the angle imposed by Snell's law allowing only electrons with a certain initial angles to transmit though the potential step. The size of the plateau and its position is determined by the position of the potential interface as well as the value of the applied potential. When the second region is p-type, the bend resistance dominates, which is asymmetric in field due to the presence of snake states. Changing the position of the pn-interface in the Hall bar strongly affects these states and therefore the bend resistance is also changed. Changing the applied potential, we observe that the bend resistance exhibits a peak around the charge-neutrality point (CNP), which is independent of the position of the pn-interface, while the Hall resistance shows a sign reversal when the CNP is crossed, which is in very good agreement with a recent experiment [J. R. Williams and C. M. Marcus, Phys. Rev. Lett. 107, 046602 (2011)].
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 7
DOI: 10.1063/1.4805350
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“Four-band tunneling in bilayer graphene”. Van Duppen B, Peeters FM, Physical review : B : condensed matter and materials physics 87, 205427 (2013). http://doi.org/10.1103/PhysRevB.87.205427
Abstract: The conductance, the transmission, and the reflection probabilities through rectangular potential barriers and p-n junctions are obtained for bilayer graphene taking into account the four bands of the energy spectrum. We have evaluated the importance of the skew hopping parameters gamma(3) and gamma(4) to these properties and show that for energies E > gamma(1)/100 their effect is negligible. For high energies two modes of propagation exist and we investigate scattering between these modes. For perpendicular incidence both propagation modes are decoupled, and scattering between them is forbidden. This extends the concept of pseudospin as defined within the two-band approximation to a four-band model and corresponds to the (anti) symmetry of the wave functions under in-plane mirroring. New transmission resonances are found that appear as sharp peaks in the conductance which are absent in the two-band approximation. The application of an interlayer bias to the system (1) breaks the pseudospin structure, (2) opens a band gap that results in a distinct feature of suppressed transmission in the conductance, and (3) breaks the angular symmetry with respect to normal incidence in the transmission and reflection.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 37
DOI: 10.1103/PhysRevB.87.205427
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“All-electrical control of quantum gates for single heavy-hole spin qubits”. Szumniak P, Bednarek S, Pawlowski J, Partoens B, Physical review : B : condensed matter and materials physics 87, 195307 (2013). http://doi.org/10.1103/PhysRevB.87.195307
Abstract: In this paper several nanodevices which realize basic single heavy-hole qubit operations are proposed and supported by time-dependent self-consistent Poisson-Schrodinger calculations using a four band heavy-hole-light-hole model. In particular we propose a set of nanodevices which can act as Pauli X, Y, Z quantum gates and as a gate that acts similar to a Hadamard gate (i.e., it creates a balanced superposition of basis states but with an additional phase factor) on the heavy-hole spin qubit. We also present the design and simulation of a gated semiconductor nanodevice which can realize an arbitrary sequence of all these proposed single quantum logic gates. The proposed devices exploit the self-focusing effect of the hole wave function which allows for guiding the hole along a given path in the form of a stable solitonlike wave packet. Thanks to the presence of the Dresselhaus spin-orbit coupling, the motion of the hole along a certain direction is equivalent to the application of an effective magnetic field which induces in turn a coherent rotation of the heavy-hole spin. The hole motion and consequently the quantum logic operation is initialized only by weak static voltages applied to the electrodes which cover the nanodevice. The proposed gates allow for an all electric and ultrafast (tens of picoseconds) heavy-hole spin manipulation and give the possibility to implement a scalable architecture of heavy-hole spin qubits for quantum computation applications.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 14
DOI: 10.1103/PhysRevB.87.195307
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“Interface-controlled magnetism and transport of ultrathin manganite films”. Shapoval O, Huehn S, Verbeeck J, Jungbauer M, Belenchuk A, Moshnyaga V, Journal of applied physics 113, 17c711 (2013). http://doi.org/10.1063/1.4795422
Abstract: We report ferromagnetic, T-C = 240 K, and metallic, T-MI = 250 K, behaviors of a three unit cell thick interface engineered lanthanum manganite film, grown by metalorganic aerosol deposition technique on SrTiO3(100) substrates. Atomically resolved electron microscopy and chemical analysis show that ultrathin manganite films start to grow with La-O layer on a strongly Mn/Ti-intermixed interface, engineered by an additional deposition of 2 u.c. of Sr-Mn-O. Such interface engineering results in a hole-doped manganite layer and stabilizes ferromagnetism and metallic conductivity down to the thickness of d = 3 u.c. The films with d = 8 u.c. demonstrate a bulk-like transport behavior with T-MI similar to T-C = 310 – 330 K. (C) 2013 American Institute of Physics.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.068
Times cited: 7
DOI: 10.1063/1.4795422
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“Thermomechanical properties of a single hexagonal boron nitride sheet”. Singh SK, Neek-Amal M, Costamagna S, Peeters FM, Physical review : B : condensed matter and materials physics 87, 184106 (2013). http://doi.org/10.1103/PhysRevB.87.184106
Abstract: Using atomistic simulations we investigate the thermodynamical properties of a single atomic layer of hexagonal boron nitride (h-BN). The thermal induced ripples, heat capacity, and thermal lattice expansion of large scale h-BN sheets are determined and compared to those found for graphene (GE) for temperatures up to 1000 K. By analyzing the mean-square height fluctuations < h(2)> and the height-height correlation function H(q) we found that the h-BN sheet is a less stiff material as compared to graphene. The bending rigidity of h-BN (i) is about 16% smaller than the one of GE at room temperature (300 K), and (ii) increases with temperature as in GE. The difference in stiffness between h-BN and GE results in unequal responses to external uniaxial and shear stress and different buckling transitions. In contrast to a GE sheet, the buckling transition of a h-BN sheet depends strongly on the direction of the applied compression. The molar heat capacity, thermal-expansion coefficient, and Gruneisen parameter are estimated to be 25.2 J mol(-1) K-1, 7.2 x 10(-6) K-1, and 0.89, respectively.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 80
DOI: 10.1103/PhysRevB.87.184106
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“Functional respiratory imaging as a tool to assess upper airway patency in children with obstructive sleep apnea”. Van Holsbeke C, Vos W, van Hoorenbeeck K, Boudewyns A, Salgado R, Verdonck PR, Ramet J, de Backer J, De Backer W, Verhulst SL, Sleep Medicine 14, 433 (2013). http://doi.org/10.1016/j.sleep.2012.12.005
Abstract: Objective: We aim to investigate if anatomical and functional properties of the upper airway using computerized 3D models derived from computed tomography (CT) scans better predict obstructive sleep apnea (OSA) severity than standard clinical markers. Methods: Consecutive children with suspected OSA underwent polysomnography, clinical assessment of upper airway patency, and a CT scan while awake. A three-dimensional (3D) reconstruction of the pharyngeal airway was built from these images, and computational fluid dynamics modeling of low inspiratory flow was performed using open-source software. Results: Thirty-three children were included (23 boys; mean age, was 6.0 +/- 3.2 y). OSA was diagnosed in 23 patients. Children with OSA had a significantly lower volume of the overlap region between tonsils and the adenoids (median volume, 1408 mm compared to 2173 mm; p = 0.04), a lower mean cross-sectional area at this location (median volume, 69.3 mm(2) compared to 114.3 mm(2); p = 0.04), and a lower minimal cross-sectional area (median volume, 17.9 mm(2) compared to 25.9 mm(2); p = 0.05). Various significant correlations were found between several imaging parameters and the severity of OSA, most pronounced for upper airway conductance (r = -0.46) (p < 0.01) for correlation between upper airway conductance and the apnea-hypopnea index. No differences or significant correlations were observed with clinical parameters of upper airway patency. Preliminary data after treatment showed that none of the patients with residual OSA had their smallest cross-sectional area located in segment 3, and this frequency was significantly lower than in their peers whose sleep study normalized (64%; p = 0.05). Conclusion: Functional imaging parameters are highly correlated with OSA severity and are a more powerful correlate than clinical scores of upper airway patency. Preliminary data also showed that we could identify differences in the upper airway of those subjects who did not benefit from a local upper airway treatment. (c) 2013 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Laboratory Experimental Medicine and Pediatrics (LEMP)
Impact Factor: 3.391
Times cited: 18
DOI: 10.1016/j.sleep.2012.12.005
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“Electron diffraction measurement of the binding rigidity of free-standing graphene”. Kirilenko DA, Technical physics letters 39, 325 (2013). http://doi.org/10.1134/S1063785013040081
Abstract: A method for measuring the binding rigidity of free-standing graphene from the dependence of the short-wavelength spectral range of transverse structural fluctuations of a crystal is proposed. The fluctuation spectrum is measured according to the variation in electron-diffraction patterns derived in a transmission electron microscope while tilting the sample.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 0.771
Times cited: 3
DOI: 10.1134/S1063785013040081
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“A mass spectrometric study of the dissolution behavior of sanidine”. Adriaens A, Van 't dack L, Adams F, Gijbels R, Microchimica acta 120, 139 (1995). http://doi.org/10.1007/BF01244427
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.741
Times cited: 1
DOI: 10.1007/BF01244427
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“Dimethylformamide-mediated synthesis of water-soluble platinum nanodendrites for ethanol oxidation electrocatalysis”. Mourdikoudis S, Chirea M, Altantzis T, Pastoriza-Santos I, Perez-Juste J, Silva F, Bals S, Liz-Marzan LM, Nanoscale 5, 4776 (2013). http://doi.org/10.1039/c3nr00924f
Abstract: Herein we describe the synthesis of water-soluble platinum nanodendrites in dimethylformamide (DMF), in the presence of polyethyleneimine (PEI) as a stabilizing agent. The average size of the dendrites is in the range of 20-25 nm while their porosity can be tuned by modifying the concentration of the metal precursor. Electron tomography revealed different crystalline orientations of nanocrystallites in the nanodendrites and allowed a better understanding of their peculiar branching and porosity. The high surface area of the dendrites (up to 22 m(2) g(-1)) was confirmed by BET measurements, while X-ray diffraction confirmed the abundance of high-index facets in the face-centered-cubic crystal structure of Pt. The prepared nanodendrites exhibit excellent performance in the electrocatalytic oxidation of ethanol in alkaline solution. Sensing, selectivity, cycleability and great tolerance toward poisoning were demonstrated by cyclic voltammetry measurements.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.367
Times cited: 50
DOI: 10.1039/c3nr00924f
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“The effect of the sampling cone position and diameter on the gas flow dynamics in an ICP”. Aghaei M, Lindner H, Bogaerts A, Journal of analytical atomic spectrometry 28, 1485 (2013). http://doi.org/10.1039/c3ja50107h
Abstract: An inductively coupled plasma, connected to a sampling cone of a mass spectrometer, is computationally investigated. The effects of the sampler orifice diameter (ranging from 1 to 2 mm) and distance of the sampler cone from the load coil (ranging from 7 to 17 mm) are studied. An increase in sampler orifice diameter leads to a higher central plasma temperature at the place of the sampler, as well as more efficient gas transfer through the sampler, by reducing the interaction of the plasma gas with the sampling cone. However, the flow velocity at the sampler position is found to be independent of the sampler orifice diameter. Moreover, by changing the sampler orifice diameter, we can control whether only the central gas or also the auxiliary gas can exit through the sampler. Finally, with the increasing distance of the sampler from the load coil, the plasma temperature at the place of the sampler decreases slightly, which might also have consequences for the ion generation and transport through the sampling cone.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.379
Times cited: 14
DOI: 10.1039/c3ja50107h
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“Local bond length variations in boron-doped nanocrystalline diamond measured by spatially resolved electron energy-loss spectroscopy”. Lu Y-G, Turner S, Verbeeck J, Janssens SD, Haenen K, Van Tendeloo G, Applied physics letters 103, 032105 (2013). http://doi.org/10.1063/1.4813842
Abstract: Variations in local bond length and coordination in boron-doped nanocrystalline diamond (NCD) films have been studied through changes in the fine structure of boron and carbon K-edges in electron energy-loss spectra, acquired in a scanning transmission electron microscope. The presence of high concentrations of B in pristine diamond regions and enrichment of B at defects in single NCD grains is demonstrated. Local bond length variations are evidenced through an energy shift of the carbon 1s → σ* edge at B-rich defective regions within single diamond grains, indicating an expansion of the diamond bond length at sites with local high B content.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.411
Times cited: 15
DOI: 10.1063/1.4813842
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“Structural and magnetic phase transitions in the AnBnO3n-2 anion-deficient perovskites Pb2Ba2BiFe5O13 and Pb1.5Ba2.5Bi2Fe6O16”. Abakumov AM, Batuk M, Tsirlin AA, Tyablikov OA, Sheptyakov DV, Filimonov DS, Pokholok KV, Zhidal VS, Rozova MG, Antipov EV, Hadermann J, Van Tendeloo G;, Inorganic chemistry 52, 7834 (2013). http://doi.org/10.1021/ic3026667
Abstract: Novel anion-deficient perovskite-based ferrites Pb2Ba2BiFe5O13 and Pb1.5Ba2.5Bi2Fe6O16 were synthesized by solid-state reaction in air. Pb2Ba2BiFe5O13 and Pb1.5Ba2.5Bi2Fe6O16 belong to the perovskite-based AnBnO3n2 homologous series with n = 5 and 6, respectively, with a unit cell related to the perovskite subcell ap as ap√2 × ap × nap√2. Their structures are derived from the perovskite one by slicing it with 1/2[110]p(1̅01)p crystallographic shear (CS) planes. The CS operation results in (1̅01)p-shaped perovskite blocks with a thickness of (n 2) FeO6 octahedra connected to each other through double chains of edge-sharing FeO5 distorted tetragonal pyramids which can adopt two distinct mirror-related configurations. Ordering of chains with a different configuration provides an extra level of structure complexity. Above T ≈ 750 K for Pb2Ba2BiFe5O13 and T ≈ 400 K for Pb1.5Ba2.5Bi2Fe6O16 the chains have a disordered arrangement. On cooling, a second-order structural phase transition to the ordered state occurs in both compounds. Symmetry changes upon phase transition are analyzed using a combination of superspace crystallography and group theory approach. Correlations between the chain ordering pattern and octahedral tilting in the perovskite blocks are discussed. Pb2Ba2BiFe5O13 and Pb1.5Ba2.5Bi2Fe6O16 undergo a transition into an antiferromagnetically (AFM) ordered state, which is characterized by a G-type AFM ordering of the Fe magnetic moments within the perovskite blocks. The AFM perovskite blocks are stacked along the CS planes producing alternating FM and AFM-aligned FeFe pairs. In spite of the apparent frustration of the magnetic coupling between the perovskite blocks, all n = 4, 5, 6 AnFenO3n2 (A = Pb, Bi, Ba) feature robust antiferromagnetism with similar Néel temperatures of 623632 K.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 10
DOI: 10.1021/ic3026667
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“Cationic clathrate of type-III Ge172-xPxTey (y\approx21,5, x\approx2y) : synthesis, crystal structure and thermoelectric properties”. Kirsanova MA, Mori T, Maruyama S, Abakumov AM, Van Tendeloo G, Olenev A, Shevelkov AV, Inorganic chemistry 52, 8272 (2013). http://doi.org/10.1021/ic401203r
Abstract: A first germanium-based cationic clathrate of type-III, Ge129.3P42.7Te21.53, was synthesized and structurally characterized (space group P42/mnm, a = 19.948(3) Å, c = 10.440(2) Å, Z = 1). In its crystal structure, germanium and phosphorus atoms form three types of polyhedral cages centered with Te atoms. The polyhedra share pentagonal and hexagonal faces to form a 3D framework. Despite the complexity of the crystal structure, the Ge129.3P42.7Te21.53 composition corresponds to the Zintl counting scheme with a good accuracy. Ge129.3P42.7Te21.53 demonstrates semiconducting/insulating behavior of electric resistivity, high positive Seebeck coefficient (500 μV K1 at 300 K), and low thermal conductivity (<0.92 W m1 K1) within the measured temperature range.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 3
DOI: 10.1021/ic401203r
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“Frustrated octahedral tilting distortion in the incommensurately modulated Li3xNd2/3-xTiO3 perovskites”. Abakumov AM, Erni R, Tsirlin AA, Rossell MD, Batuk D, Nénert G, Van Tendeloo G, Chemistry of materials 25, 2670 (2013). http://doi.org/10.1021/cm4012052
Abstract: Perovskite-structured titanates with layered A-site ordering form remarkably complex superstructures. Using transmission electron microscopy, synchrotron X-ray and neutron powder diffraction, and ab initio structure relaxation, we present the structural solution of the incommensurately modulated Li3xNd2/3xTiO3 perovskites (x = 0.05, superspace group Pmmm(α1,1/2,0)000(1/2,β2 0)000, a = 3.831048(5) Å, b = 3.827977(4) Å, c = 7.724356(8) Å, q1 = 0.45131(8)a* + 1/2b*, q2 = 1/2a* + 0.41923(4)b*). In contrast to earlier conjectures on the nanoscale compositional phase separation in these materials, all peculiarities of the superstructure can be understood in terms of displacive modulations related to an intricate octahedral tilting pattern. It involves fragmenting the pattern of the out-of-phase tilted TiO6 octahedra around the a- and b-axes into antiphase domains, superimposed on the pattern of domains with either pronounced or suppressed in-phase tilt component around the c-axis. The octahedral tilting competes with the second order JahnTeller distortion of the TiO6 octahedra. This competition is considered as the primary driving force for the modulated structure. The A cations are suspected to play a role in this modulation affecting it mainly through the tolerance factor and the size variance. The reported crystal structure calls for a revision of the structure models proposed for the family of layered A-site ordered perovskites exhibiting a similar type of modulated structure.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 23
DOI: 10.1021/cm4012052
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“Atomistic modelling of CVD synthesis of carbon nanotubes and graphene”. Elliott JA, Shibuta Y, Amara H, Bichara C, Neyts EC, Nanoscale 5, 6662 (2013). http://doi.org/10.1039/c3nr01925j
Abstract: We discuss the synthesis of carbon nanotubes (CNTs) and graphene by catalytic chemical vapour deposition (CCVD) and plasma-enhanced CVD (PECVD), summarising the state-of-the-art understanding of mechanisms controlling their growth rate, chiral angle, number of layers (walls), diameter, length and quality (defects), before presenting a new model for 2D nucleation of a graphene sheet from amorphous carbon on a nickel surface. Although many groups have modelled this process using a variety of techniques, we ask whether there are any complementary ideas emerging from the different proposed growth mechanisms, and whether different modelling techniques can give the same answers for a given mechanism. Subsequently, by comparing the results of tight-binding, semi-empirical molecular orbital theory and reactive bond order force field calculations, we demonstrate that graphene on crystalline Ni(111) is thermodynamically stable with respect to the corresponding amorphous metal and carbon structures. Finally, we show in principle how a complementary heterogeneous nucleation step may play a key role in the transformation from amorphous carbon to graphene on the metal surface. We conclude that achieving the conditions under which this complementary crystallisation process can occur may be a promising method to gain better control over the growth processes of both graphene from flat metal surfaces and CNTs from catalyst nanoparticles.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 7.367
Times cited: 52
DOI: 10.1039/c3nr01925j
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“The role of mass removal mechanisms in the onset of ns-laser induced plasma formation”. Autrique D, Clair G, L'Hermite D, Alexiades V, Bogaerts A, Rethfeld B, Journal of applied physics 114, 023301 (2013). http://doi.org/10.1063/1.4812577
Abstract: The present study focuses on the role of mass removal mechanisms in ns-laser ablation. A copper sample is placed in argon, initially set at standard pressure and temperature. Calculations are performed for a 6 ns laser pulse with a wavelength of 532 nm and laser fluences up to 10 J/cm2. The transient behavior in and above the copper target is described by a hydrodynamic model. Transmission profiles and ablation depths are compared with experimental results and similar trends are found. Our calculations reveal an interesting self-inhibiting mechanism: volumetric mass removal in the supercritical region triggers plasma shielding and therefore stops proceeding. This self-limiting process indicates that volumetric mass removal does not necessarily result in large ablation depths.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.068
Times cited: 31
DOI: 10.1063/1.4812577
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“Estimation of unknown structure parameters from high-resolution (S)TEM images : what are the limits?”.den Dekker AJ, Gonnissen J, de Backer A, Sijbers J, Van Aert S, Ultramicroscopy 134, 34 (2013). http://doi.org/10.1016/j.ultramic.2013.05.017
Abstract: Statistical parameter estimation theory is proposed as a quantitative method to measure unknown structure parameters from electron microscopy images. Images are then purely considered as data planes from which structure parameters have to be determined as accurately and precisely as possible using a parametric statistical model of the observations. For this purpose, an efficient algorithm is proposed for the estimation of atomic column positions and intensities from high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) images. Furthermore, the so-called CramérRao lower bound (CRLB) is reviewed to determine the limits to the precision with which continuous parameters such as atomic column positions and intensities can be estimated. Since this lower bound can only be derived for continuous parameters, alternative measures using the principles of detection theory are introduced for problems concerning the estimation of discrete parameters such as atomic numbers. An experimental case study is presented to show the practical use of these measures for the optimization of the experiment design if the purpose is to decide between the presence of specific atom types using STEM images.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 31
DOI: 10.1016/j.ultramic.2013.05.017
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