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“Electron-electron scattering induced capture in GaAs quantum wells”. Kálna K, Mo×ko M, Peeters FM, Lithuanian journal of physics 35, 435 (1995)
Keywords: A3 Journal article; Condensed Matter Theory (CMT)
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“Magnetoconductance of rectangular arrays of quantum rings”. Kálmán O, Földi P, Benedict MG, Peeters FM, Physical review : B : condensed matter and materials physics 78, 125306 (2008). http://doi.org/10.1103/PhysRevB.78.125306
Abstract: Electron transport through multiterminal rectangular arrays of quantum rings is studied in the presence of Rashba-type spin-orbit interaction (SOI) and of a perpendicular magnetic field. Using the analytic expressions for the transmission and reflection coefficients for single rings we obtain the conductance through such arrays as a function of the SOI strength, of the magnetic flux, and of the wave vector k of the incident electron. Due to destructive or constructive spin interferences caused by the SOI, the array can be totally opaque for certain ranges of k, while there are parameter values where it is completely transparent. Spin resolved transmission probabilities show nontrivial spin transformations at the outputs of the arrays. When pointlike random scattering centers are placed between the rings, the Aharonov-Bohm peaks split, and an oscillatory behavior of the conductance emerges as a function of the SOI strength.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 31
DOI: 10.1103/PhysRevB.78.125306
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“Spatial interference induced spin polarization in a three-terminal quantum ring”. Kálmán O, Földi P, Benedict MG, Peeters FM, Physica. E: Low-dimensional systems and nanostructures 40, 567 (2008). http://doi.org/10.1016/j.physe.2007.08.014
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.221
Times cited: 27
DOI: 10.1016/j.physe.2007.08.014
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“Resistive switching at manganite/manganite interfaces”. Kalkert C, Krisponeit J-O, Esseling M, Lebedev OI, Moshnyaga V, Damaschke B, Van Tendeloo G, Samwer K, Applied physics letters 99, 132512 (2011). http://doi.org/10.1063/1.3643425
Abstract: We report bipolar resistive switching between the interfaces of manganite nanocolumns. La0.7Sr0.3MnO3 films were prepared on Al2O3 substrates, where the films grow in nanocolumns from the substrate to the surface. Conductive atomic force microscopy directly detects that the resistive switching is located at the boundaries of the grains. Furthermore, mesoscopic transport measurements reveal a tunnel magnetoresistance. In combination with the resistive switching, this leads to a total of four different resistive states.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.411
Times cited: 10
DOI: 10.1063/1.3643425
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“Probing the impact of material properties of core-shell SiO₂@TiO₂, spheres on the plasma-catalytic CO₂, dissociation using a packed bed DBD plasma reactor”. Kaliyappan P, Paulus A, D’Haen J, Samyn P, Uytdenhouwen Y, Hafezkhiabani N, Bogaerts A, Meynen V, Elen K, Hardy A, Van Bael MK, Journal Of Co2 Utilization 46, 101468 (2021). http://doi.org/10.1016/J.JCOU.2021.101468
Abstract: Plasma catalysis, a promising technology for conversion of CO2 into value-added chemicals near room temperature, is gaining increasing interest. A dielectric barrier discharge (DBD) plasma has attracted attention due to its simple design and operation at near ambient conditions, ease to implement catalysts in the plasma zone and upscaling ability to industrial applications. To improve its main drawbacks, being relatively low conversion and energy efficiency, a packing material is used in the plasma discharge zone of the reactor, sometimes decorated by a catalytic material. Nevertheless, the extent to which different properties of the packing material influence plasma performance is still largely unexplored and unknown. In this study, the particular effect of synthesis induced differences in the morphology of a TiO2 shell covering a SiO2 core packing material on the plasma conversion of CO2 is studied. TiO2 has been successfully deposited around 1.6–1.8 mm sized SiO2 spheres by means of spray coating, starting from aqueous citratoperoxotitanate(IV) precursors. Parameters such as concentration of the Ti(IV) precursor solutions and addition of a binder were found to affect the shells’ properties and surface morphology and to have a major impact on the CO2 conversion in a packed bed DBD plasma reactor. Core-shell SiO2@TiO2 obtained from 0.25 M citratoperoxotitante(IV) precursors with the addition of a LUDOX binder showed the highest CO2 conversion 37.7% (at a space time of 70 s corresponding to an energy efficiency of 2%) and the highest energy efficiency of 4.8% (at a space time of 2.5 s corresponding to a conversion of 3%).
Keywords: A1 Journal article; Engineering sciences. Technology; Laboratory of adsorption and catalysis (LADCA); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.292
DOI: 10.1016/J.JCOU.2021.101468
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“Effect of high-frequency electromagnetic field on Te+-implanted (001) Si</tex>”. Kalitzova M, Vlakhov E, Marinov Y, Gesheva K, Ignatova VA, Lebedev O, Muntele C, Gijbels R, Vacuum: the international journal and abstracting service for vacuum science and technology 76, 325 (2004). http://doi.org/10.1016/j.vacuum.2004.07.055
Abstract: The analysis of high-frequency electromagnetic field (HFEMF) effects on the microstructure and electrical properties of Te+ implanted (0 0 1) Si is reported. Cross-sectional high-resolution transmission electron microscopy (XHRTEM) demonstrates the formation of Te nanoclusters (NCs) embedded in the Si layer amorphized by implantation (a-Si) at fluences greater than or equal to 1 x 10(16) cm(-2). Post-implantation treatment with 0.45 MHz HFEMF leads to enlargement of Te NCs, their diffusion and accumulation at the a-Si surface and formation of laterally connected extended tellurium structures above the percolation threshold, appearing at an ion fluence of 1 x 10(17) cm(-2). AC electrical conductivity measurements show nearly four orders of magnitude decrease of impedance resistivity in this case, which is in good agreement with the results of our structural studies. The results obtained are discussed in terms of the two-phase isotropic spinodal structure. (C) 2004 Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 1.53
Times cited: 2
DOI: 10.1016/j.vacuum.2004.07.055
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“Ion beam synthesis of Te and Bi nanoclusters in silicon: the effect of post-implantation high frequency electromagnetic field”. Kalitzova M, Peeva A, Ignatova V, Lebedev OI, Zollo G, Vitali G, Nuclear instruments and methods in physics research: B: beam interactions with materials and atoms 242, 209 (2006). http://doi.org/10.1016/j.nimb.2005.08.017
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.109
Times cited: 1
DOI: 10.1016/j.nimb.2005.08.017
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“Magnetic-field asymmetry of electron wave packet transmission in bent channels capacitively coupled to a metal gate”. Kalina R, Szafran B, Bednarek S, Peeters FM, Physical review letters 102, 066807 (2009). http://doi.org/10.1103/PhysRevLett.102.066807
Abstract: We study the electron wave packet moving through a bent channel. We demonstrate that the packet transmission probability becomes an asymmetric function of the magnetic field when the electron packet is capacitively coupled to a metal plate. The coupling occurs through a nonlinear potential which translates a different kinetics of the transport for opposite magnetic-field orientations into a different potential felt by the scattered electron.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 8.462
Times cited: 14
DOI: 10.1103/PhysRevLett.102.066807
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“Lewis base mediated efficient synthesis and solvation-like host-guest chemistry of covalent organic framework-1”. Kalidindi SB, Wiktor C, Ramakrishnan A, Weßing J, Schneemann A, Van Tendeloo G, Fischer RA, Chemical communications 49, 463 (2013). http://doi.org/10.1039/c2cc37183a
Abstract: N-Lewis base mediated room temperature synthesis of covalent organic frameworks (COFs) starting from a solution of building blocks instead of partially soluble building blocks was developed. This protocol shifts COF synthetic chemistry from sealed tubes to open beakers. Non-conventional inclusion compounds of COF-1 were obtained by vapor phase infiltration of ferrocene and azobenzene, and solvation like effects were established.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 6.319
Times cited: 17
DOI: 10.1039/c2cc37183a
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“Metal@COFs : covalent organic frameworks as templates for Pd nanoparticles and hydrogen storage properties of Pd@COF-102 hybrid material”. Kalidindi SB, Hyunchul O, Hirscher M, Esken D, Wiktor C, Turner S, Van Tendeloo G, Fischer RA, Chemistry: a European journal 18, 10848 (2012). http://doi.org/10.1002/chem.201201340
Abstract: Three-dimensional covalent organic frameworks (COFs) have been demonstrated as a new class of templates for nanoparticles. Photodecomposition of the [Pd(eta 3-C3H5)(eta 5-C5H5)]@COF-102 inclusion compound (synthesized by a gas-phase infiltration method) led to the formation of the Pd@COF-102 hybrid material. Advanced electron microscopy techniques (including high-angle annular dark-field scanning transmission electron microscopy and electron tomography) along with other conventional characterization techniques unambiguously showed that highly monodisperse Pd nanoparticles ((2.4 +/- 0.5) nm) were evenly distributed inside the COF-102 framework. The Pd@COF-102 hybrid material is a rare example of a metal-nanoparticle-loaded porous crystalline material with a very narrow size distribution without any larger agglomerates even at high loadings (30 wt %). Two samples with moderate Pd content (3.5 and 9.5 wt %) were used to study the hydrogen storage properties of the metal-decorated COF surface. The uptakes at room temperature from these samples were higher than those of similar systems such as Pd@metalorganic frameworks (MOFs). The studies show that the H2 capacities were enhanced by a factor of 2-3 through Pd impregnation on COF-102 at room temperature and 20 bar. This remarkable enhancement is not just due to Pd hydride formation and can be mainly ascribed to hydrogenation of residual organic compounds, such as bicyclopentadiene. The significantly higher reversible hydrogen storage capacity that comes from decomposed products of the employed organometallic Pd precursor suggests that this discovery may be relevant to the discussion of the spillover phenomenon in metal/MOFs and related systems.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.317
Times cited: 88
DOI: 10.1002/chem.201201340
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“Preparation and study of 2-D semiconductors with Dirac type bands due to the honeycomb nanogeometry”. Kalesaki E, Boneschanscher MP, Geuchies JJ, Delerue C, Morais Smith C, Evers WH, Allan G, Altantzis T, Bals S, Vanmaekelbergh D, Proceedings of the Society of Photo-optical Instrumentation Engineers
T2 –, Proceedings of SPIE 8981, 898107 (2014). http://doi.org/10.1117/12.2042882
Abstract: The interest in 2-dimensional systems with a honeycomb lattice and related Dirac-type electronic bands has exceeded the prototype graphene1. Currently, 2-dimensional atomic2,3 and nanoscale4-8 systems are extensively investigated in the search for materials with novel electronic properties that can be tailored by geometry. The immediate question that arises is how to fabricate 2-D semiconductors that have a honeycomb nanogeometry, and as a consequence of that, display a Dirac-type band structure? Here, we show that atomically coherent honeycomb superlattices of rocksalt (PbSe, PbTe) and zincblende (CdSe, CdTe) semiconductors can be obtained by nanocrystal self-assembly and facet-to-facet atomic bonding, and subsequent cation exchange. We present a extended structural analysis of atomically coherent 2-D honeycomb structures that were recently obtained with self-assembly and facet-to-facet bonding9. We show that this process may in principle lead to three different types of honeycomb structures, one with a graphene type-, and two others with a silicene-type structure. Using TEM, electron diffraction, STM and GISAXS it is convincingly shown that the structures are from the silicene-type. In the second part of this work, we describe the electronic structure of graphene-type and silicene type honeycomb semiconductors. We present the results of advanced electronic structure calculations using the sp3d5s* atomistic tight-binding method10. For simplicity, we focus on semiconductors with a simple and single conduction band for the native bulk semiconductor. When the 3-D geometry is changed into 2-D honeycomb, a conduction band structure transformation to two types of Dirac cones, one for S- and one for P-orbitals, is observed. The width of the bands depends on the honeycomb period and the coupling between the nanocrystals. Furthermore, there is a dispersionless P-orbital band, which also forms a landmark of the honeycomb structure. The effects of considerable intrinsic spin-orbit coupling are briefly considered. For heavy-element compounds such as CdTe, strong intrinsic spin-‐orbit coupling opens a non-trivial gap at the P-orbital Dirac point, leading to a quantum Spin Hall effect10-12. Our work shows that well known semiconductor crystals, known for centuries, can lead to systems with entirely new electronic properties, by the simple action of nanogeometry. It can be foreseen that such structures will play a key role in future opto-electronic applications, provided that they can be fabricated in a straightforward way.
Keywords: P1 Proceeding; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Times cited: 2
DOI: 10.1117/12.2042882
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“Slippage dynamics of confined water in graphene oxide capillaries”. Kalashami HG, Neek-Amal M, Peeters FM, Physical review materials 2, 074004 (2018). http://doi.org/10.1103/PHYSREVMATERIALS.2.074004
Abstract: The permeation of water between neighboring graphene oxide (GO) flakes, i.e., 2D nanochannels, are investigated using a simple model for the GO membrane. We simulate the hydrophilic behavior of nanocapillaries and study the effect of surface charge on the dynamical properties of water flow and the influence of Na+ and Cl- ions on water permeation. Our approach is based on extensive equilibrium molecular dynamics simulations to obtain a better understanding of water permeation through charged nanochannels in the presence of ions. We found significant change in the slippage dynamics of confined water such as a profound increase in viscosity/slip length with increasing charges over the surface. The slip length decreases one order of magnitude (i.e., 1/30) with increasing density of surface charge, while it increases by a factor of 2 with ion concentration. We found that commensurability induced by nanoconfinement plays an important role on the intrinsic dynamical properties of water.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Times cited: 1
DOI: 10.1103/PHYSREVMATERIALS.2.074004
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“Machine Learning for Fast Characterization of Magnetic Logic Devices”. Kaintura A, Foss K, Couckuyt I, Dhaene T, Zografos O, Vaysset A, Sorée B, (edaps 2018) (2018)
Abstract: Non-charge-based logic devices are promising candidates for future logic circuits. Interest in studying and developing these devices has grown dramatically in the past decade as they possess key advantages over conventional CMOS technology. Due to their novel designs, a large number of micromagnetic simulations are required to fully characterize the behavior of these devices. The number and complexity of these simulations place large computational requirements on device development. We use state-of-the-art machine learning techniques to expedite identification of their behavior. Several intelligent sampling strategies are combined with machine learning multi-class classification models. These techniques are applied to a recently developed exchange-driven magnetic logic scheme that utilizes direct exchange coupling as the main driver.
Keywords: P1 Proceeding; Condensed Matter Theory (CMT)
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“Functionalization of single-layer TaS₂, and formation of ultrathin Janus structures”. Kahraman Z, Yagmurcukardes M, Sahin H, Journal Of Materials Research 35, 1397 (2020). http://doi.org/10.1557/JMR.2020.64
Abstract: Ab initio calculations are performed to investigate the structural, vibrational, electronic, and piezoelectric properties of functionalized single layers of TaS2. We find that single-layer TaS2 is a suitable host material for functionalization via fluorination and hydrogenation. The one-side fluorinated (FTaS2) and hydrogenated (HTaS2) single layers display indirect gap semiconducting behavior in contrast to bare metallic TaS2. On the other hand, it is shown that as both surfaces of TaS2 are saturated anti-symmetrically, the formed Janus structure is a dynamically stable metallic single layer. In addition, it is revealed that out-of-plane piezoelectricity is created in all anti-symmetric structures. Furthermore, the Janus-type single-layer has the highest specific heat capacity to which longitudinal and transverse acoustical phonon modes have contribution at low temperatures. Our findings indicate that single-layer TaS2 is suitable for functionalization via H and F atoms that the formed, anti-symmetric structures display distinctive electronic, vibrational, and piezoelectric properties.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.7
Times cited: 1
DOI: 10.1557/JMR.2020.64
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“Single-layer Janus-type platinum dichalcogenides and their heterostructures”. Kahraman Z, Kandemir A, Yagmurcukardes M, Sahin H, The journal of physical chemistry: C : nanomaterials and interfaces 123, 4549 (2019). http://doi.org/10.1021/ACS.JPCC.8B11837
Abstract: Ultrathin two-dimensional Janus-type platinum dichalcogenide crystals formed by two different atoms at opposite surfaces are investigated by performing state-of-the-art density functional theory calculations. First, it is shown that single-layer PtX2 structures (where X = S, Se, or Te) crystallize into the dynamically stable IT phase and are indirect band gap semiconductors. It is also found that the substitutional chalcogen doping in all PtX2 structures is favorable via replacement of surface atoms with a smaller chalcogen atom, and such a process leads to the formation of Janus-type platinum dichalcogenides (XPtY, where X and Y stand for S, Se, or Te) which are novel single-layer crystals. While all Janus structures are indirect band gap semiconductors as their binary analogues, their Raman spectra show distinctive features that stem from the broken out-of-plane symmetry. In addition, it is revealed that the construction of Janus crystals enhances the piezoelectric constants of PtX2 crystals significantly both in the in plane and in the out-of-plane directions. Moreover, it is shown that vertically stacked van der Waals heterostructures of binary and ternary (Janus) platinum dichalcogenides offer a wide range of electronic features by forming bilayer heterojunctions of type-I, type-II, and type-III, respectively. Our findings reveal that Janus-type ultrathin platinum dichalcogenide crystals are quite promising materials for optoelectronic device applications.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 4.536
Times cited: 20
DOI: 10.1021/ACS.JPCC.8B11837
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“Stable Janus TaSe₂, single-layers via surface functionalization”. Kahraman Z, Baskurt M, Yagmurcukardes M, Chaves A, Sahin H, Applied Surface Science 538, 148064 (2021). http://doi.org/10.1016/J.APSUSC.2020.148064
Abstract: First-principles calculations are performed in order to investigate the formation of Janus structures of single layer TaSe2. The structural optimizations and phonon band dispersions reveal that the formation and stability of hydrogenated (HTaSe2), fluorinated (FTaSe2), and the one-side hydrogenated and one-side fluorinated (Janus-HTaSe2F) single-layers are feasible in terms of their phonon band dispersions. It is shown that bare metallic single-layer TaSe2 can be turned into a semiconductor as only one of its surface is functionalized while it remains as a metal via its two surfaces functionalization. In addition, the semiconducting nature of single-layers HTaSe2 and FTaSe2 and the metallic behavior of Janus TaSe2 are found to be robust under applied uniaxal strains. Further analysis on piezoelectric properties of the predicted single-layers reveal the enhanced in-plane and out of-plane piezoelectricity via formed Janus-HTaSe2F. Our study indicates that single-layer TaSe2 is a suitable host material for surface functionalization via fluorination and hydrogenation which exhibit distinctive electronic and vibrational properties.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.387
DOI: 10.1016/J.APSUSC.2020.148064
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“Investigation of the electron distribution functions in low pressure electron cyclotron resonance discharges”. Kaganovich I, Misina M, Bogaerts A, Gijbels R Kluwer Academic, Dordrecht, page 543 (1999).
Keywords: H1 Book chapter; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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“Electron Boltzmann kinetic equation averaged over fast electron bouncing and pitch-angle scattering for fast modeling of electron cyclotron resonance discharge”. Kaganovich I, Misina M, Berezhnoi S, Gijbels R, Physical review : E : statistical, nonlinear, and soft matter physics 61, 1875 (2000). http://doi.org/10.1103/PhysRevE.61.1875
Abstract: The electron distribution function (EDF) in an electron cyclotron resonance (ECR) discharge is far from Maxwellian. The self-consistent simulation of ECR discharges requires a calculation of the EDF on every magnetic line for various ion density profiles. The straightforward self-consistent simulation of ECR discharges using the Monte Carlo technique for the EDF calculation is very computer time expensive, since the electron and ion time scales are very different. An electron Boltzmann kinetic equation averaged over the fast electron bouncing and pitch-angle scattering was derived in order to develop an effective and operative tool for the fast modeling (FM) of low-pressure ECR discharges. An analytical solution for the EDF in a loss cone was derived. To check the validity of the FM, one-dimensional (in coordinate) and two-dimensional (in velocity) Monte Carlo simulation codes were developed. The validity of the fast modeling method is proved by comparison with the Monte Carlo simulations. The complete system of equations for FM is presented and ready for use in a comprehensive study of ECR discharges. The variations of plasma density and of wall and sheath potentials are analyzed by solving a self-consistent set of equations for the EDF.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.366
Times cited: 31
DOI: 10.1103/PhysRevE.61.1875
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“CoShaRP : a convex program for single-shot tomographic shape sensing”. Kadu A, van Leeuwen T, Batenburg KJ, Inverse Problems 37, 105005 (2021). http://doi.org/10.1088/1361-6420/AC1776
Abstract: We introduce single-shot x-ray tomography that aims to estimate the target image from a single cone-beam projection measurement. This linear inverse problem is extremely under-determined since the measurements are far fewer than the number of unknowns. Moreover, it is more challenging than conventional tomography, where a sufficiently large number of projection angles forms the measurements, allowing for a simple inversion process. However, single-shot tomography becomes less severe if the target image is only composed of known shapes. This paper restricts analysis to target image function that can be decomposed into known compactly supported non-negative-valued functions termed shapes. Hence, the shape prior transforms a linear ill-posed image estimation problem to a non-linear problem of estimating the roto-translations of the shapes. We circumvent the non-linearity by using a dictionary of possible roto-translations of the shapes. We propose a convex program CoShaRP, to recover the dictionary coefficients successfully. CoShaRP relies on simplex-type constraints and can be solved quickly using a primal-dual algorithm. The numerical experiments show that CoShaRP recovers shape stably from moderately noisy measurements.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.62
DOI: 10.1088/1361-6420/AC1776
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“Single-shot tomography of discrete dynamic objects”. Kadu A, Lucka F, Batenburg KJ, IEEE transactions on computational imaging 10, 941 (2024). http://doi.org/10.1109/TCI.2024.3414320
Abstract: This paper presents a novel method for the reconstruction of high-resolution temporal images in dynamic tomographic imaging, particularly for discrete objects with smooth boundaries that vary over time. Addressing the challenge of limited measurements per time point, we propose a technique that incorporates spatial and temporal information of the dynamic objects. Our method uses the explicit assumption of homogeneous attenuation values of discrete objects. We achieve this computationally through the application of the level-set method for image segmentation and the representation of motion via a sinusoidal basis. The result is a computationally efficient and easily optimizable variational framework that enables the reconstruction of high-quality 2D or 3D image sequences with a single projection per frame. Compared to variational regularization-based methods using similar image models, our approach demonstrates superior performance on both synthetic and pseudo-dynamic real X-ray tomography datasets. The implications of this research extend to improved visualization and analysis of dynamic processes in tomographic imaging, finding potential applications in diverse scientific and industrial domains. The supporting data and code are provided.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 5.4
DOI: 10.1109/TCI.2024.3414320
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“Removal of natural organic matter from water by using ion-exchange resins”. Kabsch-Korbutowicz M, Krupinska B, Przemysl chemiczny
T2 –, Scientific and Technical Conference on Water and Wastewater Basis for, Environmental Protection (School of Quality Water 2008), MAY 28-30, 2008, Kolobrzeg, POLAND 87, 473 (2008)
Abstract: Four aq. solns. contg. natural peat components and the water from Odra river were treated with 3 anion-exchange resins (2.5 to 15 cm(3) of resin per 1 dm(3) of the sample) for 5-60 min to remove the org. matter. The process efficiency was detd. by UV absorbance (254 nm) and colour intensity measurements. The treatment resulted in discoloration of the solns. A resin with weak alky, was the most efficient. The degree of removal increased with increasing the resin dose and contact time. The presence of inorg. anions in the soins. contributed to a decrease of process effectivity.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Ion exchange-ultrafiltration integrated process as a useful method in removing natural organic matter from water”. Kabsch-Korbutowicz M, Kozak A, Krupińska B, Environment protection engineering 34, 79 (2008)
Abstract: The experiments conducted are focused on natural organic substances, removal from water in ion-exchange process, ultrafiltration process and ion exchange-ultrafiltration integrated process. The water from the Odra River and model solution were investigated. In treatment processes, various doses of 5 anion-exchange resins as well as polyethersulphone membranes with different cut-offs were used. The efficiency of process was determined by measuring a decrease both in the colour intensity and the UV 254 nm absorbance. The results show that separation efficiency in integrated process depends on resin dose added to water before ultrafiltration and on the membrane cut-off as well. Among the resins tested the most efficient was MIEX (R) resin. The ion-exchange process carried out prior to the ultrafiltration increased, especially for high cut-off membranes, NOM retention and resulted in the decrease of membrane fouling intensity.
Keywords: A1 Journal article; Engineering sciences. Technology; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
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“Multiple dot-in-rod PbS/CdS heterostructures with high photoluminescence quantum yield in the near-infrared”. Justo Y, Goris B, Sundar Kamal J, Geiregat P, Bals S, Hens Z, Journal of the American Chemical Society 134, 5484 (2012). http://doi.org/10.1021/ja300337d
Abstract: Pb cations in PbS quantum rods made from CdS quantum rods by successive complete cationic exchange reactions are partially re-exchanged for Cd cations. Using STEM-HAADF, we show that this leads to the formation of unique multiple dot-in-rod PbS/CdS heteronanostructures, with a photoluminescence quantum yield of 4555%. We argue that the formation of multiple dot-in-rods is related to the initial polycrystallinity of the PbS quantum rods, where each PbS crystallite transforms in a separate PbS/CdS dot-in-dot. Effective mass modeling indicates that electronic coupling between the different PbS conduction band states is feasible for the multiple dot-in-rod geometries obtained, while the hole states remain largely uncoupled.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 13.858
Times cited: 41
DOI: 10.1021/ja300337d
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“Atomic layer epitaxy of Ruddlesden-Popper SrO(SrTiO3)n films by means of metalorganic aerosol deposition”. Jungbauer M, Huehn S, Egoavil R, Tan H, Verbeeck J, Van Tendeloo G, Moshnyaga V, Applied physics letters 105, 251603 (2014). http://doi.org/10.1063/1.4905055
Abstract: We report an atomic layer epitaxial growth of Ruddlesden-Popper (RP) thin films of SrO(SrTiO3)(n) (n = infinity, 2, 3, 4) by means of metalorganic aerosol deposition (MAD). The films are grown on SrTiO3(001) substrates by means of a sequential deposition of Sr-O/Ti-O-2 atomic monolayers, monitored in-situ by optical ellipsometry. X-ray diffraction and transmission electron microscopy (TEM) reveal the RP structure with n = 2-4 in accordance with the growth recipe. RP defects, observed by TEM in a good correlation with the in-situ ellipsometry, mainly result from the excess of SrO. Being maximal at the film/substrate interface, the SrO excess rapidly decreases and saturates after 5-6 repetitions of the SrO(SrTiO3)(4) block at the level of 2.4%. This identifies the SrTiO3 substrate surface as a source of RP defects under oxidizing conditions within MAD. Advantages and limitations of MAD as a solution-based and vacuum-free chemical deposition route were discussed in comparison with molecular beam epitaxy. (C) 2014 AIP Publishing LLC.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.411
Times cited: 32
DOI: 10.1063/1.4905055
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“Quasiparticle twist dynamics in non-symmorphic materials”. Juneja R, Thebaud S, Pandey T, Polanco CA, Moseley DH, Manley ME, Cheng YQ, Winn B, Abernathy DL, Hermann RP, Lindsay L, Materials Today Physics 21, 100548 (2021). http://doi.org/10.1016/J.MTPHYS.2021.100548
Abstract: Quasiparticle physics underlies our understanding of the microscopic dynamical behaviors of materials that govern a vast array of properties, including structural stability, excited states and interactions, dynamical structure factors, and electron and phonon conductivities. Thus, understanding band structures and quasiparticle interactions is foundational to the study of condensed matter. Here we advance a 'twist' dynamical description of quasiparticles (including phonons and Bloch electrons) in nonsymmorphic chiral and achiral materials. Such materials often have structural complexity, strong thermal resistance, and efficient thermoelectric performance for waste heat capture and clean refrigeration technologies. The twist dynamics presented here provides a novel perspective of quasiparticle behaviors in such complex materials, in particular highlighting how non-symmorphic symmetries determine band crossings and anti-crossings, topological behaviors, quasiparticle interactions that govern transport, and observables in scattering experiments. We provide specific context via neutron scattering measurements and first-principles calculations of phonons and electrons in chiral tellurium dioxide. Building twist symmetries into the quasiparticle dynamics of non-symmorphic materials offers intuition into quasi particle behaviors, materials properties, and guides improved experimental designs to probe them. More specifically, insights into the phonon and electron quasiparticle physics presented here will enable materials design strategies to control interactions and transport for enhanced thermoelectric and thermal management applications. (C) 2021 Published by Elsevier Ltd.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
DOI: 10.1016/J.MTPHYS.2021.100548
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“Local orbital angular momentum revealed by spiral-phase-plate imaging in transmission-electron microscopy”. Juchtmans R, Verbeeck J, Physical Review A 93, 023811 (2016). http://doi.org/10.1103/PhysRevA.93.023811
Abstract: The orbital angular momentum (OAM) of light and matter waves is a parameter that has been getting increasingly more attention over the past couple of years. Beams with a well-defined OAM, the so-called vortex beams, are applied already in, e.g., telecommunication, astrophysics, nanomanipulation, and chiral measurements in optics and electron microscopy. Also, the OAM of a wave induced by the interaction with a sample has attracted a lot of interest. In all these experiments it is crucial to measure the exact (local) OAM content of the wave, whether it is an incoming vortex beam or an exit wave after interacting with a sample. In this work we investigate the use of spiral phase plates (SPPs) as an alternative to the programmable phase plates used in optics to measure OAM. We derive analytically how these can be used to study the local OAM components of any wave function. By means of numerical simulations we illustrate how the OAM of a pure vortex beam can be measured. We also look at a sum of misaligned vortex beams and show how, by using SPPs, the position and the OAM of each individual beam can be detected. Finally, we look at the OAM induced by a magnetic dipole on a free-electron wave and show how the SPP can be used to localize the magnetic poles and measure their “magnetic charge.” Although our findings can be applied to study the OAM of any wave function, our findings are of particular interest for electron microscopy where versatile programmable phase plates do not yet exist.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.925
Times cited: 12
DOI: 10.1103/PhysRevA.93.023811
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“Orbital angular momentum in electron diffraction and its use to determine chiral crystal symmetries”. Juchtmans R, Verbeeck J, Physical review: B: condensed matter and materials physics 92, 134108 (2015). http://doi.org/10.1103/PhysRevB.92.134108
Abstract: In this work we present an alternative way to look at electron diffraction in a transmission electron microscope.
Instead of writing the scattering amplitude in Fourier space as a set of plane waves,we use the cylindrical Fourier transform to describe the scattering amplitude in a basis of orbital angular momentum (OAM) eigenstates. We show how working in this framework can be very convenient when investigating, e.g., rotation and screw-axis symmetries. For the latter we find selection rules on the OAM coefficients that unambiguously reveal the handedness of the screw axis. Detecting the OAM coefficients of the scattering amplitude thus offers the possibility to detect the handedness of crystals without the need for dynamical simulations, the thickness of the sample, nor the exact crystal structure. We propose an experimental setup to measure the OAM components where an image of the crystal is taken after inserting a spiral phase plate in the diffraction plane and perform multislice simulations on α quartz to demonstrate how the method indeed reveals the chirality. The experimental feasibility of the technique is discussed together with its main advantages with respect to chirality determination of screw axes. The method shows how the use of a spiral phase plate can be extended from a simple phase imaging technique to a tool to measure the local OAM decomposition of an electron wave, widening the field of interest well beyond chiral space group determination.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 16
DOI: 10.1103/PhysRevB.92.134108
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“Extension of Friedel's law to vortex-beam diffraction”. Juchtmans R, Guzzinati G, Verbeeck J, Physical Review A 94, 033858 (2016). http://doi.org/10.1103/PhysRevA.94.033858
Abstract: Friedel's law states that the modulus of the Fourier transform of real functions is centrosymmetric, while the phase is antisymmetric. As a consequence of this, elastic scattering of plane-wave photons or electrons within the first-order Born-approximation, as well as Fraunhofer diffraction on any aperture, is bound to result in centrosymmetric diffraction patterns. Friedel's law, however, does not apply for vortex beams, and centrosymmetry in general is not present in their diffraction patterns. In this work we extend Friedel's law for vortex beams by showing that the diffraction patterns of vortex beams with opposite topological charge, scattered on the same two-dimensional potential, always are centrosymmetric to one another, regardless of the symmetry of the scattering object. We verify our statement by means of numerical simulations and experimental data. Our research provides deeper understanding in vortex-beam diffraction and can be used to design new experiments to measure the topological charge of vortex beams with diffraction gratings or to study general vortex-beam diffraction.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.925
Times cited: 13
DOI: 10.1103/PhysRevA.94.033858
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“Spiral phase plate contrast in optical and electron microscopy”. Juchtmans R, Clark L, Lubk A, Verbeeck J, Physical review A 94, 023838 (2016). http://doi.org/10.1103/PhysRevA.94.023838
Abstract: The use of phase plates in the back focal plane of a microscope is a well-established technique in optical microscopy to increase the contrast of weakly interacting samples and is gaining interest in electron microscopy as well. In this paper we study the spiral phase plate (SPP), also called helical, vortex, or two-dimensional Hilbert phase plate, which adds an angularly dependent phase of the form exp(iℓϕk) to the exit wave in Fourier space. In the limit of large collection angles, we analytically calculate that the average of a pair of l=+-1
SPP filtered images is directly proportional to the gradient squared of the exit wave, explaining the edge contrast previously seen in optical SPP work. We discuss the difference between a clockwise-anticlockwise pair of SPP filtered images and derive conditions under which the modulus of the wave's gradient can be seen directly from one SPP filtered image. This work provides the theoretical background to interpret images obtained with a SPP, thereby opening new perspectives for new experiments to study, for example, magnetic materials in an electron microscope.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.925
Times cited: 10
DOI: 10.1103/PhysRevA.94.023838
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“Using electron vortex beams to determine chirality of crystals in transmission electron microscopy”. Juchtmans R, Béché, A, Abakumov A, Batuk M, Verbeeck J, Physical review : B : condensed matter and materials physics 91, 094112 (2015). http://doi.org/10.1103/PhysRevB.91.094112
Abstract: We investigate electron vortex beams elastically scattered on chiral crystals. After deriving a general expression for the scattering amplitude of a vortex electron, we study its diffraction on point scatterers arranged on a helix. We derive a relation between the handedness of the helix and the topological charge of the electron vortex on one hand and the symmetry of the higher-order Laue zones in the diffraction pattern on the other for kinematically and dynamically scattered electrons. We then extend this to atoms arranged on a helix as found in crystals which belong to chiral space groups and propose a method to determine the handedness of such crystals by looking at the symmetry of the diffraction pattern. In contrast to alternative methods, our technique does not require multiple scattering, which makes it possible to also investigate extremely thin samples in which multiple scattering is suppressed. In order to verify the model, elastic scattering simulations are performed, and an experimental demonstration on Mn2Sb2O7 is given in which we find the sample to belong to the right-handed variant of its enantiomorphic pair. This demonstrates the usefulness of electron vortex beams to reveal the chirality of crystals in a transmission electron microscope and provides the required theoretical basis for further developments in this field.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 54
DOI: 10.1103/PhysRevB.91.094112
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