“Transverse instabilities of multiple vortex chains in magnetically coupled NbSe2/permalloy superconductor/ferromagnet bilayers”. Karapetrov G, Milošević, MV, Iavarone M, Fedor J, Belkin A, Novosad V, Peeters FM, Physical review : B : solid state 80, 180506 (2009). http://doi.org/10.1103/PhysRevB.80.180506
Abstract: Using scanning tunneling microscopy and Ginzburg-Landau simulations, we explore vortex configurations in magnetically coupled NbSe2/permalloy superconductor/ferromagnet bilayer. The permalloy film with stripe domain structure induces periodic local magnetic induction in the superconductor, creating a series of pinning-antipinning channels for externally added magnetic flux quanta. Such laterally confined Abrikosov vortices form quasi-one-dimensional arrays (chains). The transitions between multichain states occur through propagation of kinks at the intermediate fields. At high fields we show that the system becomes nonlinear due to a change in both the number of vortices and the confining potential. The longitudinal instabilities of the resulting vortex structures lead to vortices levitating in the antipinning channels.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 38
DOI: 10.1103/PhysRevB.80.180506
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“Time dependent transport in 1D micro- and nanostructures: solving the Boltzmann and Wigner-Boltzmann equations”. Magnus W, Brosens F, Sorée B, Journal of physics : conference series 193, 012004 (2009). http://doi.org/10.1088/1742-6596/193/1/012004
Abstract: For many decades the Boltzmann distribution function has been used to calculate the non-equilibrium properties of mobile particles undergoing the combined action of various scattering mechanisms and externally applied force fields. When the latter give rise to the occurrence of inhomogeneous potential profiles across the region through which the particles are moving, the numerical solution of the Boltzmann equation becomes a highly complicated task. In this work we highlight a particular algorithm that can be used to solve the time dependent Boltzmann equation as well as its quantum mechanical extension, the WignerBoltzmann equation. As an illustration, we show the calculated distribution function describing electrons propagating under the action of both a uniform and a pronouncedly non-uniform electric field.
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Theory of quantum systems and complex systems
Times cited: 2
DOI: 10.1088/1742-6596/193/1/012004
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“Ab initio calculation of the energy-loss near-edge structure of some carbon allotropes: comparison with n-diamond”. Dadsetani M, Titantah JT, Lamoen D, Diamond and related materials 19, 73 (2010). http://doi.org/10.1016/j.diamond.2009.11.004
Abstract: The energy-loss near-edge structure (ELNES) spectra of several carbon allotropes (non-hydrogenated and hydrogenated face-centered cubic (FCC) carbon, rhombohedral carbon, glitter, hexagonite and lonsdaleite) are calculated within the supercell-core-excited density functional theory approach. In particular an experimental ELNES spectrum of new diamond (n-diamond) [Konyashin et al., Diamond Relat. Mater. 10, (2001) 99102] is compared with the ELNES spectra of FCC carbon, rhombohedral carbon and the so-called glitter structure. Our calculations show that the ELNES spectrum considered in that publication cannot be that of FCC carbon.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.561
Times cited: 11
DOI: 10.1016/j.diamond.2009.11.004
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“Numerical simulation of hydrocarbon plasmas for nanoparticle formation and the growth of nanostructured thin films”. Neyts E, Eckert M, Mao M, Bogaerts A, Plasma physics and controlled fusion 51, 124034 (2009). http://doi.org/10.1088/0741-3335/51/12/124034
Abstract: This paper outlines two different numerical simulation approaches, carried out by our group, used for describing hydrocarbon plasmas in their applications for either nanoparticle formation in the plasma or the growth of nanostructured thin films, such as nanocrystalline diamond (NCD). A plasma model based on the fluid approach is utilized to study the initial mechanisms giving rise to nanoparticle formation in an acetylene plasma. The growth of NCD is investigated by molecular dynamics simulations, describing the interaction of the hydrocarbon species with a substrate.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.392
Times cited: 2
DOI: 10.1088/0741-3335/51/12/124034
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“Theoretical phonon dispersions in monolayers and multilayers of hexagonal boron-nitride”. Michel KH, Verberck B, Physica status solidi: B: basic research 246, 2802 (2009). http://doi.org/10.1002/pssb.200982307
Abstract: Starting from an empirical force constant model of valence interactions and calculating by Ewald's method the electrostatic force constants, we derive the dynamical matrix for a monolayer and for multilayer systems of hexagonal boron nitride (h-BN). Solution of the secular problem leads to the corresponding phonon dispersion relations. The interplay between valence forces and Coulomb forces is discussed. A comparison with previous results on graphene and graphene multilayers is made. Our spectra on the h-BN monolayer are rather similar to previous ab initio theory results. Comparison is also made with Raman and infrared experimental results.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.674
Times cited: 10
DOI: 10.1002/pssb.200982307
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“Dynamics of colloids in a narrow channel driven by a nonuniform force”. Tkachenko DV, Misko VR, Peeters FM, Physical review : E : statistical physics, plasmas, fluids, and related interdisciplinary topics 80, 051401 (2009). http://doi.org/10.1103/PhysRevE.80.051401
Abstract: Using Brownian dynamics simulations, we investigate the dynamics of colloids confined in two-dimensional narrow channels driven by a nonuniform force Fdr(y). We considered linear-gradient, parabolic, and deltalike driving-force profiles. This driving force induces melting of the colloidal solid (i.e., shear-induced melting), and the colloidal motion experiences a transition from elastic to plastic regime with increasing Fdr. For intermediate Fdr (i.e., in the transition region) the response of the system, i.e., the distribution of the velocities of the colloidal chains õi(y), in general does not coincide with the profile of the driving force Fdr(y), and depends on the magnitude of Fdr, the width of the channel, and the density of colloids. For example, we show that the onset of plasticity is first observed near the boundaries while the motion in the central region is elastic. This is explained by: (i) (in)commensurability between the chains due to the larger density of colloids near the boundaries, and (ii) the gradient in Fdr. Our study provides a deeper understanding of the dynamics of colloids in channels and could be accessed in experiments on colloids (or in dusty plasma) with, e.g., asymmetric channels or in the presence of a gradient potential field.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.366
Times cited: 14
DOI: 10.1103/PhysRevE.80.051401
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“Electric-field control of the band gap and Fermi energy in graphene multilayers by top and back gates”. Avetisyan AA, Partoens B, Peeters FM, Physical review : B : solid state 80, 195401 (2009). http://doi.org/10.1103/PhysRevB.80.195401
Abstract: It is known that a perpendicular electric field applied to multilayers of graphene modifies the electronic structure near the K point and may induce an energy gap in the electronic spectrum which is tunable by the gate voltage. Here we consider a system of graphene multilayers in the presence of a positively charged top and a negatively charged back gate to control independently the density of electrons on the graphene layers and the Fermi energy of the system. The band structure of three- and four-layer graphene systems in the presence of the top and back gates is obtained using a tight-binding approach. A self-consistent Hartree approximation is used to calculate the induced charges on the different graphene layers. We predict that for opposite and equal charges on the top and bottom layers an energy gap is opened at the Fermi level. For an even number of layers this gap is larger than in the case of an odd number of graphene layers. We find that the circular asymmetry of the spectrum, which is a consequence of the trigonal warping, changes the size of the induced electronic gap, even when the total density of the induced electrons on the graphene layers is low.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 106
DOI: 10.1103/PhysRevB.80.195401
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“Supercooled molecular liquids and the glassy phases of chemically bonded N, P, As, Si and Ge”. Matthai CC, March NH, Lamoen D, Physics and chemistry of liquids 47, 607 (2009). http://doi.org/10.1080/00319100903148553
Abstract: Glassy phases which have insulating character exist for a variety of monatomic species. By contrast, until recently, it has been possible to make bulk metallic glasses (BMG) by vitrification only for multicomponent systems. After a relatively brief summary on supercooling of a few molecular liquids, we review some of the recently reported results on molecular assemblies of the series N, P, As and amorphous Si and Ge. Based on these results, we suggest that the transition metals with their directional bonding might be suitable candidates for the production of BMG by vitrification.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.145
Times cited: 1
DOI: 10.1080/00319100903148553
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“Micro X-ray diffraction and fluorescence tomography for the study of multilayered automotive paints”. de Nolf W, Janssens K, Surface and interface analysis 42, 411 (2010). http://doi.org/10.1002/SIA.3125
Abstract: Combined microscopic X-ray fluorescence/microscopic X-ray diffraction (µ-XRF/µ-XRD) tomography is a recently developed method that allows the visualization of the distribution of chemical elements and the associated crystalline phases inside complex, heterogeneous materials of extended thickness (millimeter range) in a nondestructive fashion. In this paper, the accuracy and resolution with which the individual layers in a multilayer stack of automotive paints can be distinguished is evaluated, and some of their properties measured. A paint layer system of eight layers was investigated, in which eight different crystalline substances were identified, each layer consisting of an organic, synthetic resin doped with finely milled inorganic compounds that serve as pigments or to strengthen the layer. In the XRD tomograms, all paint layers could be straightforwardly distinguished and their average thickness calculated. In case the filtered back projection method was used for tomogram reconstruction, a spatial resolution comparable to the microbeam size was obtained indicating no significant reconstruction blurring. When a more robust reconstruction method, such as the maximum-likelihood expectation maximization method, was employed, tomograms showing fewer artifacts were obtained, but with a spatial resolution that was two times worse. In the corresponding XRF tomograms, significant self-absorption distorted the element-specific tomograms corresponding to the low-energy (<7 keV) characteristic radiation and limited their usefulness. It can be concluded that microbeam XRD tomography allows the accurate visualization of the distribution of crystalline phases in multilayered automotive paint materials of millimeter dimensions with sufficient resolution to allow separate characterization of each layer in terms of its crystal-phase composition and thickness.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 1.132
Times cited: 70
DOI: 10.1002/SIA.3125
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“Work and dissipation in 2D clusters”. Nelissen K, Partoens B, van den Broeck C, Europhysics letters 88, 30001 (2009). http://doi.org/10.1209/0295-5075/88/30001
Abstract: We show by extensive numerical simulations, that far-from-equilibrium experiments on dusty plasmas and on dipole particles in a circular cavity are good candidates for the verification of the Jarzynski equality, the Crooks relation and, to a lesser extent, of the recently obtained microscopic expression for the dissipated work.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.957
Times cited: 2
DOI: 10.1209/0295-5075/88/30001
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“Dyakonov-Perel spin relaxation in InSb/AlxIn1-xSb quantum wells”. Li J, Chang K, Peeters FM, Physical review : B : solid state 80, 153307 (2009). http://doi.org/10.1103/PhysRevB.80.153307
Abstract: We investigate theoretically the Dyakonov-Perel spin relaxation time by solving the eight-band Kane model and Poisson equation self-consistently. Our results show distinct behavior with the single-band model due to the anomalous spin-orbit interactions in narrow band-gap semiconductors, and agree well with the experiment values reported in recent experiment [K. L. Litvinenko et al., New J. Phys. 8, 49 (2006)]. We find a strong resonant enhancement of the spin relaxation time appears for spin align along [11̅ 0] at a certain electron density at 4 K. This resonant peak is smeared out with increasing the temperature.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 6
DOI: 10.1103/PhysRevB.80.153307
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“Estimation of ecotoxicity of petroleum hydrocarbon mixtures in soil based on HPLC-GCXGC analysis”. Mao D, Lookman R, van de Weghe H, Weltens R, Vanermen G, Brucker N, Diels L, Chemosphere 77, 1508 (2009). http://doi.org/10.1016/J.CHEMOSPHERE.2009.10.004
Abstract: Detailed HPLCGCXGC/FID (high performance liquid chromatography followed by comprehensive two-dimensional gas chromatography with flame-ionization detection) analysis of oil-contaminated soils was performed to interpret results of selected acute ecotoxicity assays. For the five ecotoxicity assays tested, plant seed germination and Microtox® were selected as most sensitive for evaluating ecotoxicity of the oil in the soil phase and in the leaching water, respectively. The measured toxicity for cress when testing the soil samples did not correspond to TPH concentration in the soil. A detailed chemical composition analysis of the oil contamination using HPLCGCXGC/FID allows to better predict the ecotoxicological risk and leaching potential of petroleum hydrocarbons in soil. Cress biomass production per plant was well correlated to the total aromatic hydrocarbon concentration (R2 = 0.79, n = 6), while cress seed germination was correlated (R2 = 0.82, n = 6) with total concentration of highly water-soluble aromatic hydrocarbons (HSaromatics). The observed ecotoxicity of the leaching water for Microtox-bacteria related well to calculated (based on the HPLCGCXGC/FID results) petroleum hydrocarbon equilibrium concentrations in water.
Keywords: A1 Journal article; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1016/J.CHEMOSPHERE.2009.10.004
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“Rational design of Ag/TiO2 nanosystems by a combined RF-sputtering/sol-gel approach”. Armelao L, Barreca D, Bottaro G, Gasparotto A, Maccato C, Tondello E, Lebedev OI, Turner S, Van Tendeloo G, Štangar UL, ChemPhysChem : a European journal of chemical physics and physical chemistry 10, 3249 (2009). http://doi.org/10.1002/cphc.200900571
Abstract: The present work is devoted to the preparation of Ag/TiO2 nanosystems by an original synthetic strategy, based on the radio-frequency (RF) sputtering of silver particles on titania-based xerogels prepared by the sol-gel (SG) route. This approach takes advantage of the synergy between the microporous xerogel structure and the infiltration power characterizing RF-sputtering, whose combination enables the obtainment of a tailored dispersion of Ag-containing particles into the titania matrix. In addition, the systems chemico-physical features can be tuned further through proper ex situ thermal treatments in air at 400 and 600 °C. The synthesized composites are extensively characterized by the joint use of complementary techniques, that is, X-ray photoelectron and X-ray excited Auger electron spectroscopies (XPS, XE-AES), secondary ion mass spectrometry (SIMS), glancing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), electron diffraction (ED), high-angle annular dark field scanning TEM (HAADF-STEM), energy-filtered TEM (EF-TEM) and optical absorption spectroscopy. Finally, the photocatalytic performances of selected samples in the decomposition of the azo-dye Plasmocorinth B are preliminarily investigated. The obtained results highlight the possibility of tailoring the system characteristics over a broad range, directly influencing their eventual functional properties.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.075
Times cited: 56
DOI: 10.1002/cphc.200900571
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“Fabrication and oxygen permeability of gastight, macrovoid-free Ba0.5Sr0.5Co0.8Fe0.2O3-\delta capillaries for high temperature gas separation”. Buysse C, Kovalevsky A, Snijkers F, Buekenhoudt A, Mullens S, Luyten J, Kretzschmar J, Lenaerts S, Journal of membrane science 359, 86 (2010). http://doi.org/10.1016/J.MEMSCI.2009.10.030
Abstract: Oxygen-permeable perovskites with mixed ionic-electronic conducting properties can play an important role in the separation of oxygen from air which is needed in the oxy-fuel and pre-combustion technologies for the removal and capture of CO2. In this work, gastight, macrovoid-free Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) capillaries were successfully shaped by a phase-inversion spinning technique, followed by calcination and sintering. It was found that both the rheology of the ceramic suspension and the composition of bore liquid and coagulation bath are key factors for making macrovoid-free green capillaries. Gastight BSCF capillaries were obtained by sintering for 5 h at 1100 °C. The sintered BSCF capillaries contained a significant amount of BaSO4 due to a reaction with the polysulfone binder during calcination. The oxygen permeation flux through the BSCF capillaries was measured and compared to literature data on BSCF disk and hollow fiber membranes measured in similar conditions.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 6.035
Times cited: 38
DOI: 10.1016/J.MEMSCI.2009.10.030
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“Synthesis and structural characterization of La1-xAxMnO2.5 (A = Ba, Sr, Ca) phases: mapping the variants of the brownmillerite structure”. Parsons TG, d' Hondt H, Hadermann J, Hayward MA, Chemistry of materials 21, 5527 (2009). http://doi.org/10.1021/cm902535m
Abstract: Analysis of the structural parameters of phases that adopt brownmillerite-type structures suggests the distribution of the different complex ordering schemes adopted within this structure type can be rationalized by considering both the size of the separation between the tetrahedral layers and the tetrahedral chain distortion angle. A systematic study using structural data obtained from La1−xAxMnO2,5 (A = Ba, Sr, Ca,) phases, prepared by the topotactic reduction of the analogous La1−xAxMnO3 perovskite phases, was performed to investigate this relationship. By manipulating the A-cation composition, both the tetrahedral layer separation and tetrahedral chain distortion angle in the La1−xAxMnO2,5 phases were controlled and from the data obtained a ¡°structure map¡± of the different brownmillerite variants was plotted as a function of these structural parameters. This map has been extended to include a wide range of reported brownmillerite phases showing the structural ideas presented are widely applicable. The complete structural characterization of La1−xAxMnO2,5 0.1 ¡Ü x ¡Ü 0.33, A = Ba; 0.15 ¡Ü x ¡Ü 0.5 A = Sr, and 0.22 ¡Ü x ¡Ü 0.5 A = Ca is described and includes compositions which exhibit complex intralayer ordered structures and Mn2+/Mn3+ charge ordering.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 60
DOI: 10.1021/cm902535m
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“EELS of niobium and stoichiometric niobium-oxide phases: part 1: plasmon and Near-edges fine structure”. Bach D, Schneider R, Gerthsen D, Verbeeck J, Sigle W, Microscopy and microanalysis 15, 505 (2009). http://doi.org/10.1017/S143192760999105X
Abstract: A comprehensive electron energy-loss spectroscopy study of niobium (Nb) and stable Nb-oxide phases (NbO, NbO2, Nb2O5) was carried out. In this work (Part I), the plasmons and energy-loss near-edge structures (ELNES) of all relevant Nb edges (Nb-N2,3, Nb-M4,5, Nb-M2,3, Nb-M1, and Nb-L2,3) up to energy losses of about 2600 eV and the O-K edge are analyzed with respect to achieving characteristic fingerprints of Nb in different formal oxidation states (0 for metallic Nb, +2 for NbO, +4 for NbO2, and +5 for Nb2O5). Chemical shifts of the Nb-N2,3, Nb-M4,5, Nb-M2,3, and Nb-L2,3 edges are extracted from the spectra that amount to about 4 eV as the oxidation state increases from 0 for Nb to +5 for Nb2O5. Four different microscopes, including a 200 keV ZEISS Libra with monochromator, were used. The corresponding wide range of experimental parameters with respect to the primary electron energy, convergence, and collection semi-angles as well as energy resolution allows an assessment of the influence of the experimental setup on the ELNES of the different edges. Finally, the intensity of the Nb-L2,3 white-line edges is correlated with niobium 4d-state occupancy in the different reference materials.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.891
Times cited: 55
DOI: 10.1017/S143192760999105X
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“Effects of oxygen addition to argon glow discharges: a hybrid Monte Carlo-fluid modeling investigation”. Bogaerts A, Spectrochimica acta: part B : atomic spectroscopy 64, 1266 (2009). http://doi.org/10.1016/j.sab.2009.10.003
Abstract: A hybrid model is developed for describing the effects of oxygen addition to argon glow discharges. The species taken into account in the model include Ar atoms in the ground state and the metastable level, O2 gas molecules in the ground state and two metastable levels, O atoms in the ground state and one metastable level, O3 molecules, Ar+, O+, O2+ and O− ions, as well as the electrons. The hybrid model consists of a Monte Carlo model for electrons and fluid models for the other plasma species. In total, 87 different reactions between the various plasma species are taken into account. Calculation results include the species densities and the importance of their production and loss processes, as well as the dissociation degree of oxygen. The effect of different O2 additions on these calculation results, as well as on the sputtering rates, is discussed.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.241
Times cited: 39
DOI: 10.1016/j.sab.2009.10.003
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“Mechanical resonance of the austenite/martensite interface and the pinning of the martensitic microstructures by dislocations in Cu74.08Al23.13Be2.79”. Salje EKH, Zhang H, Idrissi H, Schryvers D, Carpenter MA, Moya X, Planes A, Physical review: B: condensed matter and materials physics 80, 134114 (2009). http://doi.org/10.1103/PhysRevB.80.134114
Abstract: A single crystal of Cu74.08Al23.13Be2.79 undergoes a martensitic phase transition at 246 and 232 K under heating and cooling, respectively. The phase fronts between the austenite and martensite regions of the sample are weakly mobile with a power-law resonance under external stress fields. Surprisingly, the martensite phase is elastically much harder than the austenite phase showing that interfaces between various crystallographic variants are strongly pinned and cannot be moved by external stress while the phase boundary between the austenite and martensite regions in the sample remains mobile. This unusual behavior was studied by dynamical mechanical analysis (DMA) and resonant ultrasound spectroscopy. The remnant strain, storage modulus, and internal friction were recorded simultaneously for different applied forces in DMA. With increasing forces, the remnant strain increases monotonously while the internal friction peak height shows a minimum at 300 mN. Transmission electron microscopy shows that the pinning is generated by dislocations which are inherited from the austenite phase.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 38
DOI: 10.1103/PhysRevB.80.134114
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“Holstein polarons near surfaces”. Goodvin GL, Covaci L, Berciu M, Physical Review Letters 103, 176402 (2009). http://doi.org/10.1103/PhysRevLett.103.176402
Abstract: We study the effects of a nearby surface on the spectral weight of a Holstein polaron, using the inhomogeneous momentum average approximation which is accurate over the entire range of electron-phonon (e-ph) coupling strengths. The broken translational symmetry is taken into account exactly. We find that the e-ph coupling gives rise to a large additional surface potential, with strong retardation effects, which may bind surface states even when they are not normally expected. The surface, therefore, has a significant effect and bulk properties are recovered only very far away from it. These results demonstrate that interpretation in terms of bulk quantities of spectroscopic data sensitive only to a few surface layers is not always appropriate.
Keywords: A1 Journal article
Impact Factor: 8.462
Times cited: 8
DOI: 10.1103/PhysRevLett.103.176402
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“Physico-chemical fate of chromium compounds in the lung sheep model”. Perrault G, Dufresne A, Strati G, McNeil M, Michaud D, Baril M, Bégin R, Labbé, J, Larivière P, Eeckhaoudt S, Van Grieken R, Journal of toxicology and environmental health 44, 247 (1995). http://doi.org/10.1080/15287399509531958
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1080/15287399509531958
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“Physical modeling of strain-dependent hole mobility in Ge p-channel inversion layers”. Zhang Y, Fischetti MV, Sorée B, Magnus W, Heyns M, Meuris M, Journal of applied physics 106, 083704 (2009). http://doi.org/10.1063/1.3245327
Abstract: We present comprehensive calculations of the low-field hole mobility in Ge p-channel inversion layers with SiO2 insulator using a six-band k·p band-structure model. The cases of relaxed, biaxially, and uniaxially (both tensily and compressively) strained Ge are studied employing an efficient self-consistent methodmaking use of a nonuniform spatial mesh and of the Broyden second methodto solve the coupled envelope-wave function k·p and Poisson equations. The hole mobility is computed using the KuboGreenwood formalism accounting for nonpolar hole-phonon scattering and scattering with interfacial roughness. Different approximations to handle dielectric screening are also investigated. As our main result, we find a large enhancement (up to a factor of 10 with respect to Si) of the mobility in the case of uniaxial compressive stress similarly to the well-known case of Si. Comparison with experimental data shows overall qualitative agreement but with significant deviations due mainly to the unknown morphology of the rough Ge-insulator interface, to additional scattering with surface optical phonon from the high- insulator, to Coulomb scattering interface traps or oxide chargesignored in our calculationsand to different channel structures employed.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 29
DOI: 10.1063/1.3245327
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“Cavity nucleation and growth in Cu-Zn-Al irradiated with Cu+ ions at different temperatures”. Zelaya E, Schryvers D, Tolley A, Fitchner PFP, Intermetallics 18, 493 (2010). http://doi.org/10.1016/j.intermet.2009.09.010
Abstract: The effects of high dose ion irradiation in β CuZnAl were investigated between room temperature and 150 °C. Single crystal samples with surface normal close to [001]β were irradiated with 300 keV Cu+ ions. Microstructural changes were characterized using transmission electron microscopy. Irradiation induced cavities located on the surface exposed to the irradiation were observed. The morphology, size and density distribution of these cavities were analyzed as a function of different irradiation conditions. The shape and location of the cavities with respect to the irradiation surface were not affected by irradiation temperature or irradiation dose. Instead, the cavity size distribution showed a bi-modal shape for a dose of 15 dpa, regardless of irradiation temperature. For a dose of 30 dpa the bi-modal distribution was only observed after room temperature irradiation. The diffusion effects of vacancies produced by irradiation are analyzed in shape memory CuZnAl alloys, which main characteristic is the diffusionless martensitic transformation. Particularly, the cavity size distributions were analyzed in terms of nucleation, growth and coalescence.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.14
Times cited: 1
DOI: 10.1016/j.intermet.2009.09.010
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“Magnetic flux periodicity in mesoscopic d-wave symmetric and asymmetric superconducting loops”. Zha G-Q, Milošević, MV, Zhou S-P, Peeters FM, Physical review : B : solid state 80, 144501 (2009). http://doi.org/10.1103/PhysRevB.80.144501
Abstract: The magnetic flux dependence of energy and supercurrent in mesoscopic d-wave symmetric and asymmetric superconducting loops is investigated by numerically solving the Bogoliubov-de Gennes equations self-consistently. For square loops, we find an hc/e-flux periodicity in energy and supercurrent and demonstrate that the flux periodicity is sensitive to the hole size and the superconducting pairing strength as well as temperature. The hc/2e-periodic behavior can be restored almost entirely when we displace the central hole sufficiently out of the center of the sample. In rectangular loops, the discrete current-carrying low-energy spectrum can exist for an odd winding number of the order parameter.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 13
DOI: 10.1103/PhysRevB.80.144501
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“Synthesis and characterization of the new cyclosilicate hydrate (hexamethyleneimine)4.[Si8O16(OH)4].12H2O”. Verlooy PLH, Robeyns K, van Meervelt L, Lebedev OI, Van Tendeloo G, Martens JA, Kirschhock CEA, Microporous and mesoporous materials: zeolites, clays, carbons and related materials 130, 14 (2010). http://doi.org/10.1016/j.micromeso.2009.10.006
Abstract: A new cyclosilicate hydrate with composition (C6H14N)4·[Si8O16(OH)4]·12H2O was crystallized and the structure determined by single-crystal X-ray diffraction. The structure, described by the tetragonal space group I41/a, with unit cell dimensions of a = 39.2150(2) Å and c = 14.1553(2) Å, contains columns of hydrogen-bonded cubic octamer silicate anions. The space between silicate columns holds hydrogen-bonded water and protonated hexamethyleneimine molecules compensating the negative charge of the silicate. The crystal water can be removed resulting in a rearrangement of the columns into orthorhombic symmetry. Removal of the organic moiety causes amorphisation. Flash evacuation results in a new microporous material with pore volumes typical of a zeolite.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.615
Times cited: 5
DOI: 10.1016/j.micromeso.2009.10.006
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“Quantum rings with time-dependent spin-orbit coupling: Spintronic Rabi oscillations and conductance properties”. Földi P, Benedict MG, Kalman O, Peeters FM, Physical review : B : solid state 80, 165303 (2009). http://doi.org/10.1103/PhysRevB.80.165303
Abstract: The strength of the (Rashba-type) spin-orbit coupling in mesoscopic semiconductor rings can be tuned with external gate voltages. Here we consider the case of a periodically changing spin-orbit interaction strength in time as induced by sinusoidal voltages. In a closed one dimensional quantum ring with weak spin-orbit coupling, Rabi oscillations are shown to appear. We find that the time evolution of initially localized wave packets exhibits a series of collapse and revival phenomena. Partial revivalsthat are typical in nonlinear systemsare shown to correspond to superpositions of states localized at different spatial positions along the ring. These spintronic Schrödinger-cat states appear periodically, and similarly to their counterparts in other physical systems, they are found to be sensitive to disturbances caused by the environment. The time-dependent spin transport problem, when leads are attached to the ring, is also solved. We show that the sideband currents induced by the oscillating spin-orbit interaction strength can become the dominant output channel, even in the presence of moderate thermal fluctuations and random scattering events.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 26
DOI: 10.1103/PhysRevB.80.165303
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“Superconducting nanowires: quantum confinement and spatially dependent Hartree-Fock potential”. Chen Y, Croitoru MD, Shanenko AA, Peeters FM, Journal of physics : condensed matter 21, 435701 (2009). http://doi.org/10.1088/0953-8984/21/43/435701
Abstract: It is well known that, in bulk, the solution of the Bogoliubovde Gennes equations is the same whether or not the HartreeFock term is included. Here the HartreeFock potential is position independent and so gives the same contribution to both the single-electron energies and the Fermi level (the chemical potential). Thus, the single-electron energies measured from the Fermi level (they control the solution) stay the same. This is not the case for nanostructured superconductors, where quantum confinement breaks the translational symmetry and results in a position-dependent HartreeFock potential. In this case its contribution to the single-electron energies depends on the relevant quantum numbers. We numerically solved the Bogoliubovde Gennes equations with the HartreeFock term for a clean superconducting nanocylinder and found a shift of the curve representing the thickness-dependent oscillations of the critical superconducting temperature to larger diameters.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 2.649
Times cited: 12
DOI: 10.1088/0953-8984/21/43/435701
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“Theoretical characterization of an atmospheric pressure glow discharge used for analytical spectrometry”. Martens T, Mihailova D, van Dijk J, Bogaerts A, Analytical chemistry 81, 9096 (2009). http://doi.org/10.1021/ac9017742
Abstract: We have investigated the plasma processes in an atmospheric pressure glow discharge (APGD) in He used for analytical spectrometry by means of fluid and Monte Carlo (MC) simulations. Typical results include the potential and electric field distributions in the plasma, the density profiles of the various plasma species throughout the discharge, the mean electron energy, as well as the rates of the various collision processes in the plasma, and the relative importance of the different production and loss rates for the various species. The similarities and differences with low-pressure glow discharges are discussed. The main differences are a very small cathode dark space region and a large positive column as well as the dominant role of molecular ions. Some characteristic features of the APGD, such as the occurrence of the different spatial zones in the discharge, are illustrated, with links to experimental observations.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.32
Times cited: 15
DOI: 10.1021/ac9017742
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“Particle-in-cell/Monte Carlo collisions treatment of an Ar/O2 magnetron discharge used for the reactive sputter deposition of TiOx films”. Bultinck E, Bogaerts A, New journal of physics 11, 103010 (2009). http://doi.org/10.1088/1367-2630/11/10/103010
Abstract: The physical processes in an Ar/O2 magnetron discharge used for the reactive sputter deposition of TiOx thin films were simulated with a 2d3v particle-in-cell/Monte Carlo collisions (PIC/MCC) model. The plasma species taken into account are electrons, Ar+ ions, fast Arf atoms, metastable Arm* atoms, Ti+ ions, Ti atoms, O+ ions, O2+ ions, O− ions and O atoms. This model accounts for plasmatarget interactions, such as secondary electron emission and target sputtering, and the effects of target poisoning. Furthermore, the deposition process is described by an analytical surface model. The influence of the O2/Ar gas ratio on the plasma potential and on the species densities and fluxes is investigated. Among others, it is shown that a higher O2 pressure causes the region of positive plasma potential and the O− density to be more spread, and the latter to decrease. On the other hand, the deposition rates of Ti and O are not much affected by the O2/Ar proportion. Indeed, the predicted stoichiometry of the deposited TiOx film approaches x=2 for nearly all the investigated O2/Ar proportions.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.786
Times cited: 24
DOI: 10.1088/1367-2630/11/10/103010
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“Artificial molecular quantum rings under magnetic field influence”. Castelano LK, Hai GQ, Partoens B, Peeters FM, Journal of applied physics 106, 073702 (2009). http://doi.org/10.1063/1.3223360
Abstract: The ground states of a few electrons confined in two vertically coupled quantum rings in the presence of an external magnetic field are studied systematically within the current spin-density functional theory. Electron-electron interactions combined with inter-ring tunneling affect the electronic structure and the persistent current. For small values of the external magnetic field, we recover the zero magnetic field molecular quantum ring ground state configurations. Increasing the magnetic field many angular momentum, spin, and isospin transitions are predicted to occur in the ground state. We show that these transitions follow certain rules, which are governed by the parity of the number of electrons, the single-particle picture, Hunds rules, and many-body effects.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 5
DOI: 10.1063/1.3223360
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“Magnetic Kronig-Penney model for Dirac electrons in single-layer graphene”. Masir MR, Vasilopoulos P, Peeters FM, New journal of physics 11, 095009 (2009). http://doi.org/10.1088/1367-2630/11/9/095009
Abstract: he properties of Dirac electrons in a magnetic superlattice (SL) on graphene consisting of very high and thin (δ-function) barriers are investigated. We obtain the energy spectrum analytically and study the transmission through a finite number of barriers. The results are contrasted with those for electrons described by the Schrödinger equation. In addition, a collimation of an incident beam of electrons is obtained along the direction perpendicular to that of the SL. We also highlight an analogy with optical media in which the refractive index varies in space.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.786
Times cited: 89
DOI: 10.1088/1367-2630/11/9/095009
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