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“Solving the structure of Li ion battery materials with precession electron diffraction : application to Li2CoPo4F”. Hadermann J, Abakumov AM, Turner S, Hafideddine Z, Khasanova NR, Antipov EV, Van Tendeloo G, Chemistry of materials 23, 3540 (2011). http://doi.org/10.1021/cm201257b
Abstract: The crystal structure of the Li2CoPO4F high-voltage cathode for Li ion rechargeable batteries has been completely solved from precession electron diffraction (PED) data, including the location of the Li atoms. The crystal structure consists of infinite chains of CoO4F2 octahedra sharing common edges and linked into a 3D framework by PO4 tetrahedra. The chains and phosphate anions together delimit tunnels filled with the Li atoms. This investigation demonstrates that PED can be successfully applied for obtaining structural information on a variety of Li-containing electrode materials even from single micrometer-sized crystallites.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 46
DOI: 10.1021/cm201257b
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“Design of Ru-zeolites for hydrogen-free production of conjugated linoleic acid”. Philippaerts A, Goossens S, Vermandel W, Tromp M, Turner S, Geboers J, Van Tendeloo G, Jacobs PA, Sels BF, Chemsuschem 4, 757 (2011). http://doi.org/10.1002/cssc.201100015
Abstract: While conjugated vegetable oils are currently used as additives in the drying agents of oils and paints, they are also attractive molecules for making bio-plastics. Moreover, conjugated oils will soon be accepted as nutritional additives for functional food products. While current manufacture of conjugated vegetable oils or conjugated linoleic acids (CLAs) uses a homogeneous base as isomerisation catalyst, a heterogeneous alternative is not available today. This contribution presents the direct production of CLAs over Ru supported on different zeolites, varying in topology (ZSM-5, BETA, Y), Si/Al ratio and countercation (H+, Na+, Cs+). Ru/Cs-USY, with a Si/Al ratio of 40, was identified as the most active and selective catalyst for isomerisation of methyl linoleate (cis-9,cis-12 (C18:2)) to CLA at 165 °C. Interestingly, no hydrogen pre-treatment of the catalyst or addition of hydrogen donors is required to achieve industrially relevant isomerisation productivities, namely, 0.7 g of CLA per litre of solvent per minute. Moreover, the biologically most active CLA isomers, namely, cis-9,trans-11, trans-10,cis-12 and trans-9,trans-11, were the main products, especially at low catalyst concentrations. Ex situ physicochemical characterisation with CO chemisorption, extended X-ray absorption fine structure measurements, transmission electron microscopy analysis, and temperature-programmed oxidation reveals the presence of highly dispersed RuO2 species in Ru/Cs-USY(40).
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 7.226
Times cited: 24
DOI: 10.1002/cssc.201100015
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“Structural and vibrational properties of amorphous GeO2 from first-principles”. Scalise E, Houssa M, Pourtois G, Afanas'ev VV, Stesmans A, Applied physics letters 98, 202110 (2011). http://doi.org/10.1063/1.3593036
Abstract: The structural and vibrational properties of amorphous germanium oxide (a-GeO<sub>2</sub>) are investigated using first-principles calculations based on density functional theory. We first generate an a-GeO<sub>2</sub> structure by first-principles molecular dynamics and analyze its structural properties. The vibrational spectra is then calculated within a density-functional approach. Both static and dynamic properties are in good agreement with experimental data. We next generate defects in our structure (oxygen vacancies with several density and charge states) and consider the most stable atomic configurations, focusing on the vibrational features of threefold coordinated O and divalent Ge centers.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.411
Times cited: 226
DOI: 10.1063/1.3593036
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“Single neutral excitons confined in AsBr3 in situ etched InGaAs quantum rings”. Ding F, Li B, Akopian N, Perinetti U, Chen YH, Peeters FM, Rastelli A, Zwiller V, Schmidt OG, Journal of nanoelectronics and optoelectronics 6, 51 (2011). http://doi.org/10.1166/jno.2011.1132
Abstract: We observe the evolution of single self-assembled semiconductor quantum dots into quantum rings during AsBr3 in situ etching. The direct three-dimensional imaging of In(Ga)As nanostructures embedded in GaAs matrix is demonstrated by selective wet chemical etching combined with atomic force microscopy. Single neutral excitons confined in these quantum rings are studied by magneto-photoluminescence. Oscillations in the exciton radiative recombination energy and in the emission intensity are observed under an applied magnetic field. Further, we demonstrate that the period of the oscillations can be tuned by a gate potential that modifies the exciton confinement. The experimental results, combined with calculations, indicate that the exciton Aharonov-Bohm effect may account for the observed effects.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 0.497
Times cited: 3
DOI: 10.1166/jno.2011.1132
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“FIB/SEM applied to quantitative 3D analysis of precipitates in Ni-Ti”. Cao S, Nishida M, Schryvers D, Diffusion and defect data : solid state data : part B : solid state phenomena 172/174, 1284 (2011). http://doi.org/10.4028/www.scientific.net/SSP.172-174.1284
Abstract: Ni4Ti3 precipitates with a heterogeneous distribution growing in a polycrystalline Ni50.8Ti49.2 alloy have been investigated in a Dual-Beam FIB/SEM system. The volume ratio, mean volume, central plane diameter, thickness, aspect ratio and sphericity of the precipitates in the grain interior as well as near to the grain boundary were measured or calculated. The morphology of the precipitates was classified according to the Zingg scheme. The multistage martensitic transformation occurring in these kinds of samples is interpreted in view of the data of this heterogeneous microstructure of matrix and precipitates.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
DOI: 10.4028/www.scientific.net/SSP.172-174.1284
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“Layered perovskite-like Pb2Fe2O5 structure as a parent matrix for the nucleation and growth of crystallographic shear planes”. Batuk D, Hadermann J, Abakumov A, Vranken T, Hardy A, van Bael M, Van Tendeloo G, Inorganic chemistry 50, 4978 (2011). http://doi.org/10.1021/ic200211x
Abstract: The Pb2Fe2O5 compound with a layered intergrowth structure has been prepared by a solid-state reaction at 700 °C. The incommensurate compound crystallizes in a tetragonal system with a = 3.9037(2) Å, c = 3.9996(4) Å, and q = 0.1186(4)c*, or when treated as a commensurate approximant, a = 3.9047(2) Å, c = 36.000(3) Å, space group I4/mmm. The crystal structure of Pb2Fe2O5 was resolved from transmission electron microscopy data. Atomic coordinates and occupancies of the cation positions were estimated from high-angle annular dark-field scanning transmission electron microscopy data. Direct visualization of the positions of the oxygen atoms was possible using annular bright-field scanning transmission electron microscopy. The structure can be represented as an intergrowth of perovskite blocks and partially disordered blocks with a structure similar to that of the Bi2O2 blocks in Aurivillius-type phases. The A-cation positions at the border of the perovskite block and the cation positions in the Aurivillius-type blocks are jointly occupied by Pb2+ and Fe3+ cations, resulting in a layer sequence along the c axis: PbOFeO2PbOFeO2Pb7/8Fe1/8O1xFe5/8Pb3/8O2Fe5/8Pb3/8. Upon heating, the layered Pb2Fe2O5 structure transforms into an anion-deficient perovskite modulated by periodically spaced crystallographic shear (CS) planes. Considering the layered Pb2Fe2O5 structure as a parent matrix for the nucleation and growth of CS planes allows an explanation of the specific microstructure observed for the CS structures in the PbFeO system.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 16
DOI: 10.1021/ic200211x
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“Ultrahigh strain hardening in thin palladium films with nanoscale twins”. Idrissi H, Wang B, Colla MS, Raskin JP, Schryvers D, Pardoen T, Advanced materials 23, 2119 (2011). http://doi.org/10.1002/adma.201004160
Abstract: Nanocrystalline Pd thin films containing coherent growth twin boundaries are deformed using on-chip nanomechanical testing. A large work-hardening capacity is measured. The origin of the observed behavior is unraveled using transmission electron microscopy and shows specific dislocations and twin boundaries interactions. The results indicate the potential for large strength and ductility balance enhancement in Pd films, as needed in membranes for H technologies.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 19.791
Times cited: 57
DOI: 10.1002/adma.201004160
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“Metallic nanograins : spatially nonuniform pairing induced by quantum confinement”. Croitoru MD, Shanenko AA, Kaun CC, Peeters FM, Physical review : B : condensed matter and materials physics 83, 214509 (2011). http://doi.org/10.1103/PhysRevB.83.214509
Abstract: It is well known that the formation of discrete electron levels strongly influences the pairing in metallic nanograins. Here, we focus on another effect of quantum confinement in superconducting grains that was not studied previously, i.e., spatially nonuniform pairing. This effect is very significant when single-electron levels form bunches and/or a kind of shell structure. We find that, in highly symmetric grains, the order parameter can exhibit variations with position by an order of magnitude. Nonuniform pairing is closely related to a quantum-confinement-induced modification of the pairing-interaction matrix elements and size-dependent pinning of the chemical potential to groups of degenerate or nearly degenerate levels. For illustrative purposes, we consider spherical metallic nanograins and also rectangular shapes. We show that the relevant matrix elements are, as a rule, enhanced in the presence of quantum confinement, which favors spatial variations of the order parameter, compensating the corresponding energy cost. The size-dependent pinning of the chemical potential further increases the spatial variation of the pair condensate. The role of nonuniform pairing is smaller in less symmetric confining geometries and/or in the presence of disorder. However, it always remains of importance when the energy spacing between discrete electron levels δ is approaching the scale of the bulk gap ΔB, i.e., δ>0.10.2 ΔB.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 23
DOI: 10.1103/PhysRevB.83.214509
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“Spiral ground state against ferroelectricity in the frustrated magnet BiMnFe2O6”. Abakumov AM, Tsirlin AA, Perez-Mato JM, Petřiček V, Rosner H, Yang T, Greenblatt M, Physical review : B : condensed matter and materials physics 83, 214402 (2011). http://doi.org/10.1103/PhysRevB.83.214402
Abstract: The spiral magnetic structure and underlying spin lattice of BiMnFe2O6 are investigated by low-temperature neutron powder diffraction and density functional theory band structure calculations. In spite of the random distribution of the Mn3+ and Fe3+ cations, this centrosymmetric compound undergoes a transition into an incommensurate antiferromagnetically ordered state below TN≃220 K. The magnetic structure is characterized by the propagation vector k=[0,β,0] with β≃0.14 and the P221211′(0β0)0s0s magnetic superspace symmetry. It comprises antiferromagnetic helixes propagating along the b axis. The magnetic moments lie in the ac plane and rotate about π(1+β)≃204.8-deg angle between the adjacent magnetic atoms along b. The spiral magnetic structure arises from the peculiar frustrated arrangement of exchange couplings in the ab plane. The antiferromagnetic coupling along the c axis cancels the possible electric polarization and prevents ferroelectricity in BiMnFe2O6.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 12
DOI: 10.1103/PhysRevB.83.214402
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“Three-dimensional ferromagnetic architectures with multiple metastable states”. Nasirpouri F, Engbarth MA, Bending SJ, Peter LM, Knittel A, Fangohr H, Milošević, MV, Applied physics letters 98, 222506 (2011). http://doi.org/10.1063/1.3595339
Abstract: We demonstrate controllable dual-bath electrodeposition of nickel on architecture-tunable three-dimensional (3D) silver microcrystals. Magnetic hysteresis loops of individual highly faceted Ag-Ni core-shell elements reveal magnetization reversal that comprises multiple sharp steps corresponding to different stable magnetic states. Finite-element micromagnetic simulations on smaller systems show several jumps during magnetization reversal which correspond to transitions between different magnetic vortex states. Structures of this type could be realizations of an advanced magnetic data storage architecture whereby each element represents one multibit, storing a combination of several conventional bits depending on the overall number of possible magnetic states associated with the 3D core-shell shape.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.411
Times cited: 8
DOI: 10.1063/1.3595339
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“Spin and momentum filtering of electrons on the surface of a topological insulator”. Wu Z, Peeters FM, Chang K, Applied physics letters 98, 162101 (2011). http://doi.org/10.1063/1.3581887
Abstract: We investigate theoretically the transport properties of Dirac fermions on the surface of a three-dimensional topological insulator. Dirac electrons can be totally reflected in front of a magnetic/electric p-n junction. For a p-n-p structure, multiple total internal reflections at the interfaces result in the bound states in the channel, which behaves like an electronic waveguide. This p-n-p like structure exhibits spin and momentum filtering features and could be used as a spin and/or charge diode.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.411
Times cited: 33
DOI: 10.1063/1.3581887
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“Tunable exciton Aharonov-Bohm effect in a quantum ring”. Li B, Magnus W, Peeters FM, Journal of physics : conference series
T2 –, Proceedings of the 11th International Conference on Optics of Excitons in Confined Systems, September 7-11, 2009, Spain / Vina, L. [edit.], et al. [edit.] 210, 012030 (2010). http://doi.org/10.1088/1742-6596/210/1/012030
Abstract: We studied the optical Aharonov-Bohm effect for an exciton in a semiconductor quantum ring. A perpendicular electric field applied to a quantum ring with large height, is able to tune the exciton ground state energy such that it exhibits a weak observable Aharonov-Bohm oscillations. This Aharonov-Bohm effect is tunable in strength and period.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Times cited: 3
DOI: 10.1088/1742-6596/210/1/012030
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“Superconducting nanowires : new type of BCS-BEC crossover driven by quantum-size effects”. Shanenko AA, Croitoru MD, Vagov A, Peeters FM, , 119 (2011). http://doi.org/10.1007/978-94-007-0044-4_9
Abstract: We show that a superconducting quantum nanowire undergoes a new type of BCS-BEC crossover each time when an electron subband approaches the Fermi surface. In this case the longitudinal Cooper-pair size drops by two-three orders of magnitude down to a few nanometers. This unconventional BCS-BEC crossover is driven by quantum-size effects rather than by tuning the fermion-fermion interaction.
Keywords: P1 Proceeding; Condensed Matter Theory (CMT)
DOI: 10.1007/978-94-007-0044-4_9
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“Short-range layered A-site ordering in double perovskites NaLaBB'O6 (B = Mn, Fe, B' = Nb, Ta)”. Dachraoui W, Yang T, Liu C, Ling G, Hadermann J, Van Tendeloo G, Llobet A, Greenblatt M, Chemistry of materials 23, 2398 (2011). http://doi.org/10.1021/cm200226u
Abstract: The new compounds NaLaFeTaO6, NaLaFeNbO6, NaLaMnTaO6, and NaLaMnNbO6 have been synthesized and characterized with a combination of transmission electron microscopy, X-ray powder diffraction (XRPD), neutron powder diffraction (NPD), and magnetization measurements. Through electron microscopy study, a local layered order of the A-cations has been detected without the typical occurrence of rock salt order at the B-cation site. Satellite reflections in the electron diffraction related to the local layered order are not visible on the XRPD or NPD patterns. The occurrence of local layered order is supported by pair distribution function analysis, which also reveals the presence of uncorrelated displacements of the Nb and Ta cations. The octahedra are tilted according to the system a−b+a−, and the coordinates were refined from XRPD and NPD with a disordered cation distribution in the space group Pnma. The magnetic exchange interactions in NaLaFeTaO6 and NaLaFeNbO6 are antiferromagnetic, while they are ferromagnetic in NaLaMnTaO6 and NaLaMnNbO6. Long-range magnetic ordering is not observed down to 4 K for any of the compositions.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 14
DOI: 10.1021/cm200226u
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“Anisotropic superconductivity and vortex dynamics in magnetically coupled F/S and F/S/F hybrids”. Karapetrov G, Belkin A, Iavarone M, Fedor J, Novosad V, Milošević, MV, Peeters FM, Journal of superconductivity and novel magnetism 24, 905 (2011). http://doi.org/10.1007/s10948-010-0880-z
Abstract: Magnetically coupled superconductorferromagnet hybrids offer advanced routes for nanoscale control of superconductivity. Magnetotransport characteristics and scanning tunneling microscopy images of vortex structures in superconductorferromagnet hybrids reveal rich superconducting phase diagrams. Focusing on a particular combination of a ferromagnet with a well-ordered periodic magnetic domain structure with alternating out-of-plane component of magnetization, and a small coherence length superconductor, we find directed nucleation of superconductivity above the domain wall boundaries. We show that near the superconductor-normal state phase boundary the superconductivity is localized in narrow mesoscopic channels. In order to explore the Abrikosov flux line ordering in F/S hybrids, we use a combination of scanning tunneling microscopy and GinzburgLandau simulations. The magnetic stripe domain structure induces periodic local magnetic induction in the superconductor, creating a series of pinninganti-pinning channels for externally added magnetic flux quanta. Such laterally confined Abrikosov vortices form quasi-1D 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. In F/S/F hybrids we demonstrate the evolution of the anisotropic conductivity in the superconductor that is magnetically coupled with two adjacent ferromagnetic layers. Stripe magnetic domain structures in both F-layers are aligned under each other, resulting in a directional superconducting order parameter in the superconducting layer. The conductance anisotropy strongly depends on the period of the magnetic domains and the strength of the local magnetization. The anisotropic conductivity of up to three orders of magnitude can be achieved with a spatial critical temperature modulation of 5% of T c. Induced anisotropic properties in the F/S and F/S/F hybrids have a potential for future application in switching and nonvolatile memory elements operating at low temperatures.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.18
Times cited: 2
DOI: 10.1007/s10948-010-0880-z
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Eckert M (2010) Combined molecular dynamics and Monte Carlo simulations for the deposition of (ultra)nanocrystalline diamond. Antwerpen
Keywords: Doctoral thesis; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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“Semiclathrates of the GePTe system : synthesis and crystal structures”. Kirsanova MA, Reshetova LN, Olenev AV, Abakumov AM, Shevelkov AV, Chemistry: a European journal 17, 5719 (2011). http://doi.org/10.1002/chem.201003553
Abstract: Novel compounds [Ge46−xPx]Tey (13.9≤x≤15.6, 5.92≤y≤7.75) with clathrate-like structures have been prepared and structurally characterized. They crystallize in the space group Fmequation image with the unit cell parameter changing from 20.544(2) to 20.698(2) Å (Z=8) on going from x=13.9 to x=15.6. Their crystal structure is composed of a covalently bonded Ge[BOND]P framework that hosts tellurium atoms in the guest positions and can be viewed as a peculiar variant of the type I clathrate superstructure. In contrast to the conventional type I clathrates, [Ge46−xPx]Tey contain tricoordinated (3b) atoms and no vacancies in the framework positions. As a consequence of the transformation of the framework, the majority of the guest tellurium atoms form a single covalent bond with the host framework and thus the title compounds are the first representative of semiclathrates with covalent bonding. A comparison is made with silicon clathrates and the evolution of the crystal structure upon changing the tellurium content is discussed.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.317
Times cited: 17
DOI: 10.1002/chem.201003553
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“Impact of spin-orbit coupling on the Holstein polaron”. Li Z, Covaci L, Berciu M, Baillie D, Marsiglio F, Physical review : B : condensed matter and materials physics 83, 195104 (2011). http://doi.org/10.1103/PhysRevB.83.195104
Abstract: We utilize an exact variational numerical procedure to calculate the ground state properties of a polaron in the presence of a Rashba-like spin-orbit interaction. Our results corroborate previous work performed with the momentum average approximation and with weak-coupling perturbation theory. We find that spin-orbit coupling increases the effective mass in the regime with weak electron-phonon coupling, and decreases the effective mass in the regimes of intermediate and strong electron-phonon coupling. Analytical strong-coupling perturbation theory results confirm our numerical results in the small-polaron regime. A large amount of spin-orbit coupling can lead to a significant lowering of the polaron effective mass.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 9
DOI: 10.1103/PhysRevB.83.195104
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“Binary dusty plasma Coulomb balls”. Apolinario SWS, Peeters FM, Physical review : E : statistical physics, plasmas, fluids, and related interdisciplinary topics 83, 041136 (2011). http://doi.org/10.1103/PhysRevE.83.041136
Abstract: We investigated the mixing and segregation of a system consisting of two different species of particles, having different charges, interacting through a pure Coulomb potential, and confined in a three-dimensional parabolic trap. The structure of the cluster and its normal mode spectrum are analyzed as a function of the relative charge and the relative number of different types of particles. We found that (a) the system can be in a mixed or segregated state depending on the relative charge ratio parameter and (b) the segregation process is mediated by a first or second order structural phase transition which strongly influences the magic cluster properties of the system.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.366
Times cited: 10
DOI: 10.1103/PhysRevE.83.041136
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“Valley-dependent brewster angles and Goos-Hänchen effect in strained graphene”. Wu Z, Zhai F, Peeters FM, Xu HQ, Chang K, Physical review letters 106, 176802 (2011). http://doi.org/10.1103/PhysRevLett.106.176802
Abstract: We demonstrate theoretically how local strains in graphene can be tailored to generate a valley-polarized current. By suitable engineering of local strain profiles, we find that electrons in opposite valleys (K or K′) show different Brewster-like angles and Goos-Hänchen shifts, exhibiting a close analogy with light propagating behavior. In a strain-induced waveguide, electrons in K and K′ valleys have different group velocities, which can be used to construct a valley filter in graphene without the need for any external fields.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 8.462
Times cited: 235
DOI: 10.1103/PhysRevLett.106.176802
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“Optimized fabrication of high-quality La0.67Sr0.33MnO3 thin films considering all essential characteristics”. Boschker H, Huijben M, Vailinois A, Verbeeck J, Van Aert S, Luysberg M, Bals S, Van Tendeloo G, Houwman EP, Koster G, Blank DHA, Rijnders G, Journal of physics: D: applied physics 44, 205001 (2011). http://doi.org/10.1088/0022-3727/44/20/205001
Abstract: In this paper, an overview of the fabrication and properties of high-quality La0.67Sr0.33MnO3 (LSMO) thin films is given. A high-quality LSMO film combines a smooth surface morphology with a large magnetization and a small residual resistivity, while avoiding precipitates and surface segregation. In the literature, typically only a few of these issues are adressed. We therefore present a thorough characterization of our films, which were grown by pulsed laser deposition. The films were characterized with reflection high energy electron diffraction, atomic force microscopy, x-ray diffraction, magnetization and transport measurements, x-ray photoelectron spectroscopy and scanning transmission electron microscopy. The films have a saturation magnetization of 4.0 µB/Mn, a Curie temperature of 350 K and a residual resistivity of 60 µΩ cm. These results indicate that high-quality films, combining both large magnetization and small residual resistivity, were realized. A comparison between different samples presented in the literature shows that focussing on a single property is insufficient for the optimization of the deposition process. For high-quality films, all properties have to be adressed. For LSMO devices, the thin-film quality is crucial for the device performance. Therefore, this research is important for the application of LSMO in devices.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.588
Times cited: 99
DOI: 10.1088/0022-3727/44/20/205001
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“Electronic structure and band gap of zinc spinel oxides beyond LDA : ZnAl2O4, ZnGa2O4 and ZnIn2O4”. Dixit H, Tandon N, Cottenier S, Saniz R, Lamoen D, Partoens B, van Speybroeck V, Waroquier M, New journal of physics 13, 063002 (2011). http://doi.org/10.1088/1367-2630/13/6/063002
Abstract: We examine the electronic structure of the family of ternary zinc spinel oxides ZnX2O4 (X=Al, Ga and In). The band gap of ZnAl2O4 calculated using density functional theory (DFT) is 4.25 eV and is overestimated compared with the experimental value of 3.83.9 eV. The DFT band gap of ZnGa2O4 is 2.82 eV and is underestimated compared with the experimental value of 4.45.0 eV. Since DFT typically underestimates the band gap in the oxide system, the experimental measurements for ZnAl2O4 probably require a correction. We use two first-principles techniques capable of describing accurately the excited states of semiconductors, namely the GW approximation and the modified BeckeJohnson (MBJ) potential approximation, to calculate the band gap of ZnX2O4. The GW and MBJ band gaps are in good agreement with each other. In the case of ZnAl2O4, the predicted band gap values are >6 eV, i.e. ~2 eV larger than the only reported experimental value. We expect future experimental work to confirm our results. Our calculations of the electron effective masses and the second band gap indicate that these compounds are very good candidates to act as transparent conducting host materials.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 3.786
Times cited: 98
DOI: 10.1088/1367-2630/13/6/063002
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“The influence of Cr and Y on the micro structural evolution of Mg―Cr―O and Mg―Y―O thin films”. Jehanathan N, Georgieva V, Saraiva M, Depla D, Bogaerts A, Van Tendeloo G, Thin solid films : an international journal on the science and technology of thin and thick films 519, 5388 (2011). http://doi.org/10.1016/j.tsf.2011.02.050
Abstract: The compositional influence of Cr and Y on the microstructure of Mg―Cr―O, and Mg―Y―O films synthesized by reactive magnetron sputtering has been investigated by transmission electron microscopy, X-ray diffraction and molecular dynamics simulations. A decrease in crystallinity is observed in these films as the M (Cr or Y) content is increased. It is found that M forms a solid solution with MgO for metal ratios up to ~ 70% and ~ 50% for Cr and Y respectively. Above ~ 70% Cr metal ratio the Mg―Cr―O films are found to be completely amorphous. The Mg―Y―O films are composed of Mg(Y)O and Y2O3 nano crystallites, up to ~ 50% Y metal ratio. Above this ratio, only Y2O3 nano crystallites are found. The preferential < 111> MgO grain alignment is strongly affected by the increase in M content. For M metal ratios up to ~ 50%, there is a selective promotion of the < 100> MgO grain alignments and a decline in the < 111> grain alignments.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Electron microscopy for materials research (EMAT)
Impact Factor: 1.879
Times cited: 4
DOI: 10.1016/j.tsf.2011.02.050
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“Novel device concepts for nanotechnology : the nanowire pinch-off FET and graphene tunnelFET”. Sorée B, Magnus W, Szepieniec M, Vandenbreghe W, Verhulst A, Pourtois G, Groeseneken G, de Gendt S, Heyns M, ECS transactions 28, 15 (2010)
Abstract: We explain the basic operation of a nanowire pinch-off FET and graphene nanoribbon tunnelFET. For the nanowire pinch-off FET we construct an analytical model to obtain the threshold voltage as a function of radius and doping density. We use the gradual channel approximation to calculate the current-voltage characteristics of this device and we show that the nanowire pinch-off FET has a subthreshold slope of 60 mV/dec and good ION and ION/IOFF ratios. For the graphene nanoribbon tunnelFET we show that an improved analytical model yields more realistic results for the transmission probability and hence the tunneling current. The first simulation results for the graphene nanoribbon tunnelFET show promising subthreshold slopes.
Keywords: A2 Journal article; Condensed Matter Theory (CMT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
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“Modeling the capacitance-voltage response of In0.53Ga0.47As metal-oxide-semiconductor structures : charge quantization and nonparabolic corrections”. O'Regan TP, Hurley PK, Sorée B, Fischetti MV, Applied Physics Letters 96, 213514 (2010). http://doi.org/10.1063/1.3436645
Abstract: The capacitance-voltage (C-V) characteristic is calculated for p-type In<sub>0.53</sub>Ga<sub>0.47</sub>As metal-oxide-semiconductor (MOS) structures based on a self-consistent PoissonSchrödinger solution. For strong inversion, charge quantization leads to occupation of the satellite valleys which appears as a sharp increase in the capacitance toward the oxide capacitance. The results indicate that the charge quantization, even in the absence of interface defects (D<sub>it</sub>), is a contributing factor to the experimental observation of an almost symmetric C-V response for In<sub>0.53</sub>Ga<sub>0.47</sub>As MOS structures. In addition, nonparabolic corrections are shown to enhance the depopulation of the Γ valley, shifting the capacitance increase to lower inversion charge densities.
Keywords: A1 Journal article; Electron Microscopy for Materials Science (EMAT);
Impact Factor: 3.411
Times cited: 26
DOI: 10.1063/1.3436645
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“Tuning the Fermi level of SiO2-supported single-layer graphene by thermal annealing”. Nourbakhsh A, Cantoro M, Klekachev A, Clemente F, Sorée B, van der Veen MH, Vosch T, Stesmans A, Sels B, de Gendt S, Journal Of Physical Chemistry C 114, 6894 (2010). http://doi.org/10.1021/jp910085n
Abstract: The effects of thermal annealing in inert Ar gas atmosphere of SiO2-supported, exfoliated single-layer graphene are investigated in this work. A systematic, reproducible change in the electronic properties of graphene is observed after annealing. The most prominent Raman features in graphene, the G and 2D peaks, change in accord to what is expected in the case of hole doping. The results of electrical characterization performed on annealed, back-gated field-effect graphene devices show that the neutrality point voltage VNP increases monotonically with the annealing temperature, confirming the occurrence of excess hole accumulation. No degradation of the structural properties of graphene is observed after annealing at temperatures as high as 400 °C. Thermal annealing of single-layer graphene in controlled Ar atmosphere can therefore be considered a technique to reproducibly modify the electronic structure of graphene by tuning its Fermi level.
Keywords: A1 Journal article; Electron Microscopy for Materials Science (EMAT);
Impact Factor: 4.536
Times cited: 54
DOI: 10.1021/jp910085n
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“General 2D Schrödinger-Poisson solver with open boundary conditions for nano-scale CMOS transistors”. Pourghaderi MA, Magnus W, Sorée B, de Meyer K, Meuris M, Heyns M, Journal of computational electronics 7, 475 (2008). http://doi.org/10.1007/s10825-008-0257-8
Abstract: Employing the quantum transmitting boundary (QTB) method, we have developed a two-dimensional Schrödinger-Poisson solver in order to investigate quantum transport in nano-scale CMOS transistors subjected to open boundary conditions. In this paper we briefly describe the building blocks of the solver that was originally written to model silicon devices. Next, we explain how to extend the code to semiconducting materials such as germanium, having conduction bands with energy ellipsoids that are neither parallel nor perpendicular to the channel interfaces or even to each other. The latter introduces mixed derivatives in the 2D effective mass equation, thereby heavily complicating the implementation of open boundary conditions. We present a generalized quantum transmitting boundary method that mainly leans on the completeness of the eigenstates of the effective mass equation. Finally, we propose a new algorithm to calculate the chemical potentials of the source and drain reservoirs, taking into account their mutual interaction at high drain voltages. As an illustration, we present the potential and carrier density profiles obtained for a (111) Ge NMOS transistor as well as the ballistic current characteristics.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.526
Times cited: 3
DOI: 10.1007/s10825-008-0257-8
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“Long-wavelength, confined optical phonons in InAs nanowires probed by Raman spectroscopy”. Cantoro M, Klekachev AV, Nourbakhsh A, Sorée B, Heyns MM, de Gendt S, European physical journal : B : condensed matter and complex systems 79, 423 (2011). http://doi.org/10.1140/epjb/e2011-10705-2
Abstract: Strongly confined nano-systems, such as one-dimensional nanowires, feature deviations in their structural, electronic and optical properties from the corresponding bulk. In this work, we investigate the behavior of long-wavelength, optical phonons in vertical arrays of InAs nanowires by Raman spectroscopy. We attribute the main changes in the spectral features to thermal anharmonicity, due to temperature effects, and rule out the contribution of quantum confinement and Fano resonances. We also observe the appearance of surface optical modes, whose details allow for a quantitative, independent estimation of the nanowire diameter. The results shed light onto the mechanisms of lineshape change in low-dimensional InAs nanostructures, and are useful to help tailoring their electronic and vibrational properties for novel functionalities.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.461
Times cited: 10
DOI: 10.1140/epjb/e2011-10705-2
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“Temperature-dependent modeling and characterization of through-silicon via capacitance”. Katti G, Stucchi M, Velenis D, Sorée B, de Meyer K, Dehaene W, IEEE electron device letters 32, 563 (2011). http://doi.org/10.1109/LED.2011.2109052
Abstract: A semianalytical model of the through-silicon via (TSV) capacitance for elevated operating temperatures is derived and verified with electrical measurements. The effect of temperature on the increase in TSV capacitance over different technology parameters is explored, and it is shown that higher oxide thickness reduces the impact of temperature rise on TSV capacitance, while with low doped substrates, which are instrumental for reducing the TSV capacitance, the sensitivity of TSV capacitance to temperature is large and cannot be ignored.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.048
Times cited: 27
DOI: 10.1109/LED.2011.2109052
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“Reactions of high FeO-olivine rock with groundwater and redox-sensitive elements studied by surface-analytical methods and autoradiography”. Hellmuth KH, Siitari-Kaupi M, Rauhala E, Johansson B, Zilliacus R, Gijbels R, Adriaens A, Materials Research Society symposium proceedings 333, 947 (1994)
Keywords: P1 Proceeding; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Times cited: 6
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