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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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“Quantum ballistic transport in the junctionless nanowire pinch-off field effect transistor”. Sels D, Sorée B, Groeseneken G, Journal of computational electronics 10, 216 (2011). http://doi.org/10.1007/s10825-011-0350-2
Abstract: In this work we investigate quantum ballistic transport in ultrasmall junctionless and inversion mode semiconducting nanowire transistors within the framework of the self-consistent Schrödinger-Poisson problem. The quantum transmitting boundary method is used to generate open boundary conditions between the active region and the electron reservoirs. We adopt a subband decomposition approach to make the problem numerically tractable and make a comparison of four different numerical approaches to solve the self-consistent Schrödinger-Poisson problem. Finally we discuss the IV-characteristics for small (r≤5 nm) GaAs nanowire transistors. The novel junctionless pinch-off FET or junctionless nanowire transistor is extensively compared with the gate-all-around (GAA) nanowire MOSFET.
Keywords: A1 Journal article; Theory of quantum systems and complex systems; Condensed Matter Theory (CMT)
Impact Factor: 1.526
Times cited: 12
DOI: 10.1007/s10825-011-0350-2
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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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“Unexpected optical response of single ZnO nanowires probed using controllable electrical contacts”. Zeng YI, Menghini M, Li DY, Lin SS, Ye ZZ, Hadermann J, Moorkens T, Seo JW, Locquet J-P, van Haesendonck C, Physical chemistry, chemical physics 13, 6931 (2011). http://doi.org/10.1039/c1cp00012h
Abstract: Relying on combined electron-beam lithography and lift-off methods Au/Ti bilayer electrical contacts were attached to individual ZnO nanowires (NWs) that were grown by a vapor phase deposition method. Reliable Schottky-type as well as ohmic contacts were obtained depending on whether or not an ion milling process was used. The response of the ZnO NWs to ultraviolet light was found to be sensitive to the type of contacts. The intrinsic electronic properties of the ZnO NWs were studied in a field-effect transistor configuration. The transfer characteristics, including gate threshold voltage, hysteresis and operational mode, were demonstrated to unexpectedly respond to visible light. The origin of this effect could be accounted for by the presence of point defects in the ZnO NWs.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.123
Times cited: 7
DOI: 10.1039/c1cp00012h
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“Application of optical beams to electrons in graphene”. Matulis A, Masir MR, Peeters FM, Physical review : B : condensed matter and materials physics 83, 115458 (2011). http://doi.org/10.1103/PhysRevB.83.115458
Abstract: The technique of beam optics is applied to the description of the wave function of Dirac electrons. This approach is illustrated by considering electron transmission through simple nonhomogeneous structures, such as flat and bent p-n junctions and superlattices. We found that a convex p-n junction compresses the beam waist, while a concave interface widens it without loosing its focusing properties. At a flat p-n junction the waist of the transmitted Gaussian beam can be narrowed or widened, depending on the angle of incidence. A general condition is derived for the occurrence of beam collimation in a superlattice which is less stringent than previous discussed.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 13
DOI: 10.1103/PhysRevB.83.115458
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“Tunable optical Aharonov-Bohm effect in a semiconductor quantum ring”. Li B, Peeters FM, Physical review : B : condensed matter and materials physics 83, 115448 (2011). http://doi.org/10.1103/PhysRevB.83.115448
Abstract: By applying an electric field perpendicular to a semiconductor quantum ring we show that it is possible to modify the single particle wave function between quantum dot (QD)-like and ring-like. The constraints on the geometrical parameters of the quantum ring to realize such a transition are derived. With such a perpendicular electric field we are able to tune the Aharanov-Bohm (AB) effect for both the single particle and for excitons. The tunability is in both the strength of the AB effect as well as in its periodicity. We also investigate the strain induce potential inside the self-assembled quantum ring and the effect of the strain on the AB effect.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 25
DOI: 10.1103/PhysRevB.83.115448
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“Vortex states in layered mesoscopic superconductors”. Liu C-Y, Berdiyorov GR, Milošević, MV, Physical review : B : condensed matter and materials physics 83, 104524 (2011). http://doi.org/10.1103/PhysRevB.83.104524
Abstract: Within the Ginzburg-Landau theory, we study the vortex structures in three-dimensional anisotropic mesoscopic superconductors in the presence of a uniform magnetic field. Anisotropy is included through varied Tc in different layers of the sample and leads to distinct differences in the vortex states and their free energy. Several unconventional states are found, some comprising vortex clusters or exhibiting asymmetry. In a tilted magnetic field, we found second-order transitions between different vortex states, although vortex entry is generally a first-order transition in mesoscopic samples. In multilayered samples the kinked vortex strings are formed owing to the competing interactions of vortices with Meissner currents and the weak-link boundaries. The length and deformation of vortex fragments are determined solely by the inclination and strength of applied magnetic field, and this lock-in does not depend on the degree of anisotropy between the superconducting layers.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 22
DOI: 10.1103/PhysRevB.83.104524
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“Impact of field-induced quantum confinement in tunneling field-effect devices”. Vandenberghe WG, Sorée B, Magnus W, Groeseneken G, Fischetti MV, Applied physics letters 98, 143503 (2011). http://doi.org/10.1063/1.3573812
Abstract: Being the working principle of a tunnel field-effect transistor, band-to-band tunneling is given a rigorous quantum mechanical treatment to incorporate confinement effects, multiple electron and hole valleys, and interactions with phonons. The model reveals that the strong band bending near the gate dielectric, required to create short tunnel paths, results in quantization of the energy bands. Comparison with semiclassical models reveals a big shift in the onset of tunneling. The effective mass difference of the distinct valleys is found to reduce the subthreshold swing steepness.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.411
Times cited: 76
DOI: 10.1063/1.3573812
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“Tubular fullerenes inside carbon nanotubes : optimal molecular orientation versus tube radius”. Verberck B, Tarakina NV, European physical journal : B : condensed matter and complex systems 80, 355 (2011). http://doi.org/10.1140/epjb/e2011-10952-1
Abstract: We present an investigation of the orientations and positions of tubular fullerene molecules (C90, ..., C200) encapsulated in single-walled carbon nanotubes (SWCNT), a series of so-called fullerene nanopeapods. We find that increasing the tube radius leads to the following succession of energetically stable regimes: (1) lying molecules positioned on the tube's long axis; (2) tilted molecules on the tube's long axis; and (3) lying molecules shifted away from the tube's long axis. As opposed to C70 and C80 molecules encapsulated in a SWCNT, standing orientations do not develop. Our results are relevant for the possible application of molecular-orientation-dependent electronic properties of fullerene nanopeapods, and also for the interpretation of future experiments on double-walled carbon nanotube formation by annealing fullerene peapod systems.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 1.461
Times cited: 10
DOI: 10.1140/epjb/e2011-10952-1
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“Photocatalytic degradation of ethylene : an FTIR in situ study under atmospheric conditions”. Hauchecorne B, Tytgat T, Verbruggen SW, Hauchecorne D, Terrens D, Smits M, Vinken K, Lenaerts S, Applied catalysis : B : environmental 105, 111 (2011). http://doi.org/10.1016/J.APCATB.2011.03.041
Abstract: In this paper, the reaction mechanism of the photocatalytic oxidation of ethylene is elucidated by means of an in-house developed FTIR in situ reactor. This reactor allowed us to look at the catalytic surface at the moment the reactions actually occur. This new approach gave some exciting new insights in how ethylene is photocatalytically oxidised. It was found that there is a change in dipole moment of the ethylene molecule when it is brought in the neighbourhood of the catalyst. From this finding, a hypothesis was formulated on how the CC-bond from ethylene will break. It was found that the aforementioned interaction between the catalyst and the molecule, allows the excited electrons from the UV irradiated catalyst to occupy the lowest unoccupied molecular orbital (LUMO) of the ethylene molecule through a process known as backdonation. Following this hypothesis, it was found that the degradation occurs through the formation of two intermediates: formaldehyde and formic acid, for which formaldehyde is bound in two different ways (coordinatively and as bidentate). Finally CO2 and H2O are found as end products, resulting in the complete mineralisation of the pollutant.
Keywords: A1 Journal article; Engineering sciences. Technology; Molecular Spectroscopy (MolSpec); Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 9.446
Times cited: 29
DOI: 10.1016/J.APCATB.2011.03.041
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“The influence of laser-particle interaction in laser induced breakdown spectroscopy and laser ablation inductively coupled plasma spectrometry”. Lindner H, Loper KH, Hahn DW, Niemax K, Spectrochimica acta: part B : atomic spectroscopy 66, 179 (2011). http://doi.org/10.1016/j.sab.2011.01.002
Abstract: Particles produced by previous laser shots may have significant influence on the analytical signal in laser-induced breakdown spectroscopy (LIBS) and laser ablation inductively coupled plasma (LA-ICP) spectrometry if they remain close to the position of laser sampling. The effects of these particles on the laser-induced breakdown event are demonstrated in several ways. LIBS-experiments were conducted in an ablation cell at atmospheric conditions in argon or air applying a dual-pulse arrangement with orthogonal pre-pulse, i.e., plasma breakdown in a gas generated by a focussed laser beam parallel and close to the sample surface followed by a delayed crossing laser pulse in orthogonal direction which actually ablates material from the sample and produces the LIBS plasma. The optical emission of the LIBS plasma as well as the absorption of the pre-pulse laser was measured. In the presence of particles in the focus of the pre-pulse laser, the plasma breakdown is affected and more energy of the pre-pulse laser is absorbed than without particles. As a result, the analyte line emission from the LIBS plasma of the second laser is enhanced. It is assumed that the enhancement is not only due to an increase of mass ablated by the second laser but also to better atomization and excitation conditions favored by a reduced gas density in the pre-pulse plasma. Higher laser pulse frequencies increase the probability of particle-laser interaction and, therefore, reduce the shot-to-shot line intensity variation as compared to lower particle loadings in the cell. Additional experiments using an aerosol chamber were performed to further quantify the laser absorption by the plasma in dependence on time both with and without the presence of particles. The overall implication of laser-particle interactions for LIBS and LA-ICP-MS/OES are discussed.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.241
Times cited: 12
DOI: 10.1016/j.sab.2011.01.002
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“Compositional characterization of nickel silicides by HAADF-STEM imaging”. Verleysen E, Bender H, Richard O, Schryvers D, Vandervorst W, Journal of materials science 46, 2001 (2011). http://doi.org/10.1007/s10853-010-5191-z
Abstract: A methodology for the quantitative compositional characterization of nickel silicides by high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) imaging is presented. HAADF-STEM images of a set of nickel silicide reference samples Ni3Si, Ni31Si12, Ni2Si, NiSi and NiSi2 are taken at identical experimental conditions. The correlation between sample thickness and HAADF-STEM intensity is discussed. In order to quantify the relationship between the experimental Z-contrast intensities and the composition of the analysed layers, the ratio of the HAADF-STEM intensity to the sample thickness or to the intensity of the silicon substrate is determined for each nickel silicide reference sample. Diffraction contrast is still detected on the HAADF-STEM images, even though the detector is set at the largest possible detection angle. The influence on the quantification results of intensity fluctuations caused by diffraction contrast and channelling is examined. The methodology is applied to FUSI gate devices and to horizontal TFET devices with different nickel silicides formed on source, gate and drain. It is shown that, if the elements which are present are known, this methodology allows a fast quantitative 2-dimensional compositional analysis.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.599
Times cited: 1
DOI: 10.1007/s10853-010-5191-z
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“A method to determine the local surface profile from reconstructed exit waves”. Wang A, Chen FR, Van Aert S, van Dyck D, Ultramicroscopy 111, 1352 (2011). http://doi.org/10.1016/j.ultramic.2011.04.005
Abstract: Reconstructed exit waves are useful to quantify unknown structure parameters such as the position and composition of the atom columns at atomic scale. Existing techniques provide a complex wave in a flat plane which is close to the plane where the electrons leave the atom columns. However, due to local deviation in the flatness of the exit surface, there will be an offset between the plane of reconstruction and the actual exit of a specific atom column. Using the channelling theory, it has been shown that this defocus offset can in principle be determined atom column-by-atom column. As such, the surface roughness could be quantified at atomic scale. However, the outcome strongly depends on the initial plane of reconstruction especially in a crystalline structure. If this plane is further away from the true exit, the waves of the atom columns become delocalized and interfere mutually which strongly complicates the interpretation of the exit wave in terms of the local structure. In this paper, we will study the delocalization with defocus using the channelling theory in a more systematic way.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 3
DOI: 10.1016/j.ultramic.2011.04.005
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“Tailored vapor-phase growth of CuxO-TiO2(x=1,2) nanomaterials decorated with Au particles”. Barreca D, Carraro G, Gasparotto A, Maccato C, Lebedev OI, Parfenova A, Turner S, Tondello E, Van Tendeloo G, Langmuir: the ACS journal of surfaces and colloids 27, 6409 (2011). http://doi.org/10.1021/la200698t
Abstract: We report on the fabrication of CuxOTiO2 (x = 1, 2) nanomaterials by an unprecedented vapor-phase approach. The adopted strategy involves the growth of porous CuxO matrices by means of chemical vapor deposition (CVD), followed by the controlled dispersion of TiO2 nanoparticles. The syntheses are performed on Si(100) substrates at temperatures of 400550 °C under wet oxygen atmospheres, adopting Cu(hfa)2·TMEDA (hfa =1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; TMEDA = N,N,N′,N′-tetramethylethylenediamine) and Ti(O-iPr)2(dpm)2 (O-iPr = isopropoxy; dpm = 2,2,6,6-tetramethyl-3,5-heptanedionate) as copper and titanium precursors, respectively. Subsequently, finely dispersed gold nanoparticles are introduced in the as-prepared systems via radio frequency (RF)-sputtering under mild conditions. The synthesis process results in the formation of systems with chemical composition and nano-organization strongly dependent on the nature of the initial CuxO matrix and on the deposited TiO2 amount. The decoration with low-size gold clusters paves the way to the engineering of hierarchically organized nanomaterials.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.833
Times cited: 36
DOI: 10.1021/la200698t
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“In situ study of the parameters quantifying the corrosion in ballast tanks and an evaluation of improving alternative”. de Baere K, Verstraelen H, Lemmens L, Lenaerts S, Potters G, (2011)
Abstract: An in situ study of more than 100 ballast tanks of merchant marine vessels looks to the corrosion process in these tanks from another perspective. The developed corrosion model shows major similarities with earlier studies based on laboratory experiments. The field work exposes the influence of ship construction parameters such as land of construction, coating type and the presence of sacrificial anodes on the corrosion process in the ballast tanks. Possible alternatives for vessels constructed with ordinary grade A steel and coated according to IMO PSPC standards are presented, even though further research is required to come to final conclusions.
Keywords: P3 Proceeding; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
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“Influence of electron-electron interaction on the cyclotron resonance spectrum of magnetic quantum dots containing few electrons”. Nga TTN, Peeters FM, Physical review : B : condensed matter and materials physics 83, 075419 (2011). http://doi.org/10.1103/PhysRevB.83.075419
Abstract: The configuration interaction method is used to obtain the magneto-optical absorption spectrum of a few-electron (Ne=1,2,,5) quantum dot containing a single magnetic ion. We find that the IR spectrum (the position, the number, and the oscillator strength of the cyclotron resonance peaks) depends on the strength of the Coulomb interaction, the number of electrons, and the position of the magnetic ion. We find that the Kohn theorem is no longer valid as a consequence of the electron-spin-magnetic-ion-spin-exchange interaction.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 8
DOI: 10.1103/PhysRevB.83.075419
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“Orientational properties of C70 and C80 fullerenes in carbon nanotubes”. Verberck B, Physical review : B : condensed matter and materials physics 83, 045405 (2011). http://doi.org/10.1103/PhysRevB.83.045405
Abstract: We present energy calculations of a C80 molecule with D5d symmetry encapsulated in a carbon nanotube. The approximation of a continuous tube rather than a rolled-up graphene sheet, justified by comparison with atomistic calculations, allows an expansion of the energy field into symmetry-adapted rotator functions. For a given tube radius R, we observe a strong dependence of the interaction energy on the molecular tilt angle and on the molecules lateral position in the tube. We observe a transition from on-axis lying orientations to tilted orientations at R1≈6.95 Å and a subsequent transition to standing orientations at R2≈7.6 Å. For tube radii larger than R3≈8.0 Å, the molecule starts to occupy off-axis positions and assumes a lying orientation. Results are compared to the case of C70 molecules, with D5h symmetry. Our findings are consistent with recent high-resolution transmission electron microscopy measurements and are relevant for the design of new materials with tunable electronic properties.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 6
DOI: 10.1103/PhysRevB.83.045405
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“D- shallow donor near a semiconductor-metal and a semiconductor-dielectric interface”. Hao YL, Djotyan AP, Avetisyan AA, Peeters FM, Journal of physics : condensed matter 23, 115303 (2011). http://doi.org/10.1088/0953-8984/23/11/115303
Abstract: The ground state energy and the extent of the wavefunction of a negatively charged donor (D − ) located near a semiconductormetal or a semiconductordielectric interface are obtained. We apply the effective mass approximation and use a variational two-electron wavefunction that takes into account the influence of all image charges that arise due to the presence of the interface, as well as the correlation between the two electrons bound to the donor. For a semiconductormetal interface, the D − binding energy is enhanced for donor positions d > 1.5aB (aB is the effective Bohr radius) due to the additional attraction of the electrons with their images. When the donor approaches the interface (i.e. d < 1.5aB) the D − binding energy drops and eventually it becomes unbound. For a semiconductordielectric (or a semiconductorvacuum) interface the D − binding energy is reduced for any donor position as compared to the bulk case and the system becomes rapidly unbound when the donor approaches the interface.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.649
Times cited: 5
DOI: 10.1088/0953-8984/23/11/115303
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“Fluorinated heterometallic \beta-diketonates as volatile single-source precursors for the synthesis of low-valent mixed-metal fluorides”. Navulla A, Tsirlin AA, Abakumov AM, Shpanchenko RV, Zhang H, Dikarev EV, Journal of the American Chemical Society 133, 692 (2011). http://doi.org/10.1021/ja109128r
Abstract: Hexafluoroacetylacetonates that contain lead and divalent first-row transition metals, PbM(hfac)4 (M = Ni (1), Co (2), Mn (3), Fe (4), and Zn (5)), have been synthesized. Their heterometallic structures are held together by strong Lewis acid−base interactions between metal atoms and diketonate ligands acting in chelating−bridging fashion. Compounds 1−5 are highly volatile and decompose below 350 °C. Fluorinated heterometallic β-diketonates have been used for the first time as volatile single-source precursors for the preparation of mixed-metal fluorides. Complex fluorides of composition Pb2MF6 have been obtained by decomposition of 1−5 in a two-zone furnace under low-pressure nitrogen flow. Lead−transition metal fluorides conform to orthorhombically distorted Aurivillius-type structure with layers of corner-sharing [MF6] octahedra separated by α-PbO-type (Pb2F2) blocks. Pb2NiF6 and Pb2CoF6 were found to exhibit magnetic ordering below 80 and 43 K, respectively. The ordering is antiferromagnetic, with a weak, uncompensated moment due to the canting of spins. The Pb2MF6 fluorides represent a new class of prospective magnetoelectric materials combining transition metals and lone-pair main-group cations.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 13.858
Times cited: 28
DOI: 10.1021/ja109128r
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“Vortex-vortex interaction in bulk superconductors : Ginzburg-Landau theory”. Chaves A, Peeters FM, Farias GA, Milošević, MV, Physical review : B : condensed matter and materials physics 83, 054516 (2011). http://doi.org/10.1103/PhysRevB.83.054516
Abstract: The vortex-vortex interaction potential in bulk superconductors is calculated within the Ginzburg-Landau (GL) theory and is obtained from a numerical solution of a set of two coupled nonlinear GL differential equations for the vector potential and the superconducting order parameter, where the merger of vortices into a giant vortex is allowed. Further, the interaction potentials between a vortex and a giant vortex and between a vortex and an antivortex are obtained for both type-I and type-II superconductors. Our numerical results agree asymptotically with the analytical expressions for large intervortex separations that are available in the literature. We propose empirical expressions valid over the full interaction range, which are fitted to our numerical data for different values of the GL parameter.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 31
DOI: 10.1103/PhysRevB.83.054516
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“Degradation process of lead chromate in paintings by Vincent van Gogh studied by means of synchrotron X-ray spectromicroscopy and related methods : 2 : original paint layer samples”. Monico L, van der Snickt G, Janssens K, de Nolf W, Miliani C, Dik J, Radepont M, Hendriks E, Geldof M, Cotte M, Analytical chemistry 83, 1224 (2011). http://doi.org/10.1021/AC1025122
Abstract: The darkening of the original yellow areas painted with the chrome yellow pigment (PbCrO4, PbCrO4·xPbSO4, or PbCrO4·xPbO) is a phenomenon widely observed on several paintings by Vincent van Gogh, such as the famous different versions of Sunflowers. During our previous investigations on artificially aged model samples of lead chromate, we established for the first time that darkening of chrome yellow is caused by reduction of PbCrO4 to Cr2O3·2H2O (viridian green), likely accompanied by the presence of another Cr(III) compound, such as either Cr2(SO4)3·H2O or (CH3CO2)7Cr3(OH)2 [chromium(III) acetate hydroxide]. In the second part of this work, in order to demonstrate that this reduction phenomenon effectively takes place in real paintings, we study original paint samples from two paintings of V. van Gogh. As with the model samples, in view of the thin superficial alteration layers that are present, high lateral resolution spectroscopic methods that make use of synchrotron radiation (SR), such as microscopic X-ray absorption near edge (μ-XANES) and X-ray fluorescence spectrometry (μ-XRF) were employed. Additionally, μ-Raman and mid-FTIR analyses were carried out to completely characterize the samples. On both paint microsamples, the local presence of reduced Cr was demonstrated by means of μ-XANES point measurements. The presence of Cr(III) was revealed in specific areas, in some cases correlated to the presence of Ba(sulfate) and/or to that of aluminum silicate compounds.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.32
Times cited: 84
DOI: 10.1021/AC1025122
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“Degradation process of lead chromate in paintings by Vincent van Gogh studied by means of synchrotron X-ray spectromicroscopy and related methods : 1 : artificially aged model samples”. Monico L, van der Snickt G, Janssens K, de Nolf W, Miliani C, Verbeeck J, Tian H, Tan H, Dik J, Radepont M, Cotte M, Analytical chemistry 83, 1214 (2011). http://doi.org/10.1021/ac102424h
Abstract: On several paintings by artists of the end of the 19th century and the beginning of the 20th Century a darkening of the original yellow areas, painted with the chrome yellow pigment (PbCrO4, PbCrO4·xPbSO4, or PbCrO4·xPbO) is observed. The most famous of these are the various Sunflowers paintings Vincent van Gogh made during his career. In the first part of this work, we attempt to elucidate the degradation process of chrome yellow by studying artificially aged model samples. In view of the very thin (1−3 μm) alteration layers that are formed, high lateral resolution spectroscopic methods such as microscopic X-ray absorption near edge (μ-XANES), X-ray fluorescence spectrometry (μ-XRF), and electron energy loss spectrometry (EELS) were employed. Some of these use synchrotron radiation (SR). Additionally, microscopic SR X-ray diffraction (SR μ-XRD), μ-Raman, and mid-FTIR spectroscopy were employed to completely characterize the samples. The formation of Cr(III) compounds at the surface of the chrome yellow paint layers is particularly observed in one aged model sample taken from a historic paint tube (ca. 1914). About two-thirds of the chromium that is present at the surface has reduced from the hexavalent to the trivalent state. The EELS and μ-XANES spectra are consistent with the presence of Cr2O3·2H2O (viridian). Moreover, as demonstrated by μ-XANES, the presence of another Cr(III) compound, such as either Cr2(SO4)3·H2O or (CH3CO2)7Cr3(OH)2 [chromium(III) acetate hydroxide], is likely.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.32
Times cited: 113
DOI: 10.1021/ac102424h
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“Extension of the clathrate family : the type X clathrate Ge79P29S18Te6”. Kirsanova MA, Olenev AV, Abakumov AM, Bykov MA, Shevelkov AV, Angewandte Chemie: international edition in English 50, 2371 (2011). http://doi.org/10.1002/anie.201007483
Abstract: Now they are 10! The title compound displays a new type of crystal structure and is labeled clathrate X according to the general classification of clathrate structures. In contrast to typical clathrates, this compound has three-coordinate atoms within the framework and combines distorted 24-vertex polyhedra (see picture, green) centered around tellurium guest atoms with very irregular 10-vertex polyhedra around sulfur atoms (yellow).
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 11.994
Times cited: 23
DOI: 10.1002/anie.201007483
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“Monolayer graphene from graphite oxide”. Dideykin A, Aleksenskiy AE, Kirilenko D, Brunkov P, Goncharov V, Baidakova M, Sakseev D, Vul' AY, Diamond and related materials 20, 105 (2011). http://doi.org/10.1016/j.diamond.2010.10.007
Abstract: Graphene, a new carbon material, is attracting presently an increasing research interest. It stems from the unique electrical and mechanical properties of graphene predicted by theory. Experimental studies of graphene are, however, severely curtailed by a lack of an appropriate technique for its preparation. Mechanical cleavage of graphite proved to be ineffective, since it yields only very small (a few microns in size) particles of monolayer graphene. The rapidly developing approach based on chemical exfoliation of graphite produces large-area coatings composed primarily of arbitrarily oriented multilayer graphene particles. We have developed a technique for preparation of monolayer graphene sheets involving liquid exfoliation of crystalline graphite, which includes synthesis of graphite oxide by deep oxidation as an intermediate stage. Electron diffraction traces, as well as the variation of diffracted intensities with local orientation of graphene sheets, AFM, and HRTEM images testify to a remarkably good monolayer structure of the graphite oxide particles obtained by our technique. These results open a way to setting up high-efficiency production of monolayer graphene sheets appropriate for electrical and optical measurements and fabrication of structures for use in the field of applications.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.561
Times cited: 48
DOI: 10.1016/j.diamond.2010.10.007
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“Insight to ternary complexes of co-adsorption of norfloxacin and Cu(II) onto montmorillonite at different pH using EXAFS”. Pei Z-G, Shan X-Q, Zhang S-Z, Kong J-J, Wen B, Zhang J, Zheng L-R, Xie Y-N, Janssens K, Journal of hazardous materials 186, 842 (2011). http://doi.org/10.1016/J.JHAZMAT.2010.11.076
Abstract: Co-adsorption of norfloxacin (Nor) and Cu(II) on montmorillonite at pH 4.5, 7.0 and 9.0 was studied by integrated batch adsorption experiments and extended X-ray absorption fine structure (EXAFS) spectroscopy. Under such pH conditions the dominant species of Nor are cation (Nor+), zwitterion (Nor±), and anion (Nor−), respectively. Results indicated that Nor sorption decreased with an increase of solution pH. The presence of Cu(II) slightly suppressed the Nor+ sorption at pH 4.5, while increased Nor± and Nor−sorption on montmorillonite at pH 7.0 and 9.0, respectively. In contrast, Nor increased Cu(II) adsorption at pH 4.5, but had little effect on the adsorption of Cu(II) on montmorillonite at pH 7.0 and 9.0. Spectroscopic results showed that, at pH 4.5, Nor+ was sorbed on montmorillonite by the formation of outer-sphere montmorilloniteNorCu(II) ternary surface complex. At pH 7.0, montmorilloniteNorCu(II) and montmorilloniteCu(II)Nor ternary surface complexes co-exist. At pH 9.0, montmorilloniteCu(II)Nor ternary surface complex was likely formed, which was different to Cu(II)(Nor)2 precipitate of the solution.
Keywords: A1 Journal article; Engineering sciences. Technology; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.065
Times cited: 25
DOI: 10.1016/J.JHAZMAT.2010.11.076
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“Fitting the momentum dependent loss function in EELS”. Bertoni G, Verbeeck J, Brosens F, Microscopy research and technique 74, 212 (2011). http://doi.org/10.1002/jemt.20894
Abstract: Momentum dependent inelastic plasmon scattering can be measured by electron energy loss in a transmission electron microscope. From energy filtered diffraction, the characteristic angle of scattering and the cutoff angle are measured, using a thin film of aluminum as a model test. Rather than deconvolving the data (as done in previous works), a fitting technique is used to extract the loss function from angular resolved spectra, starting from a simple model simulation.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Theory of quantum systems and complex systems
Impact Factor: 1.147
Times cited: 6
DOI: 10.1002/jemt.20894
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“Yukawa particles confined in a channel and subject to a periodic potential : ground state and normal modes”. Carvalho JCN, Ferreira WP, Farias GA, Peeters FM, Physical review : B : condensed matter and materials physics 83, 094109 (2011). http://doi.org/10.1103/PhysRevB.83.094109
Abstract: We consider a classical system of two-dimensional (2D) charged particles, interacting through a repulsive Yukawa potential exp(-r/λ)/r, and confined in a parabolic channel that limits the motion of the particles in the y direction. Along the x direction, the particles are subject to a periodic potential. The ground-state configurations and the normal-mode spectra of the system are obtained as a function of the periodicity and strength of the periodic potential (V0) and density. An interesting set of tunable ground-state configurations are found, with first- or second-order structural transitions between them. A configuration with particles aligned, perpendicular to the x direction, in each minimum of the periodic potential is obtained for V0 larger than some critical value that has a power-law dependence on the density. The phonon spectrum of different configurations was also calculated. A localization of the modes into a small frequency interval is observed for sufficiently large strength of the periodic potential, and a tunable gap in the phonon spectrum is found as a function of V0.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 9
DOI: 10.1103/PhysRevB.83.094109
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“High-temperature conductance of a two-dimensional superlattice controlled by spin-orbit interaction”. Földi P, Szaszkó-Bogár V, Peeters FM, Physical review : B : condensed matter and materials physics 83, 115313 (2011). http://doi.org/10.1103/PhysRevB.83.115313
Abstract: Rashba-type spin-orbit interaction (SOI) controlled band structure of a two-dimensional superlattice allows for the modulation of the conductance of finite size devices by changing the strength of the SOI. We consider rectangular arrays and find that the temperature dependence of the conductance disappears for high temperatures, but the strength of the SOI still affects the conductance at these temperatures. The modulation effect can be seen even in the presence of strong dephasing, which can be important for practical applications.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 8
DOI: 10.1103/PhysRevB.83.115313
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“Manganese staining of archaeological glass : the characterization of Mn-rich inclusions in leached layers and a hypothesis of its formation”. Schalm O, Proost K, De Vis K, Cagno S, Janssens K, Mees F, Jacobs P, Caen J, Archaeometry 53, 103 (2011). http://doi.org/10.1111/J.1475-4754.2010.00534.X
Abstract: During the study of a large number of archaeological glass fragments, manganese-rich inclusions in leached layers were observed in a limited number of cases. This phenomenon occurs only in black-coloured leached layers. Since the formation mechanism of such manganese-rich inclusions is still unclear, a combination of several analytical techniques was used in order to investigate this phenomenon and, more specifically, to obtain more information on (a) the composition and morphology of the inclusions, (b) the chemical state of Mn and (c) the 3D morphology of the inclusions. A mechanism that might explain the formation of these inclusions is proposed.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 1.47
Times cited: 24
DOI: 10.1111/J.1475-4754.2010.00534.X
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“Nanodiamonds do not provide unique evidence for a Younger Dryas impact”. Tian H, Schryvers D, Claeys P, Proceedings of the National Academy of Sciences of the United States of America 108, 40 (2011). http://doi.org/10.1073/pnas.1007695108
Abstract: Microstructural, δ13C isotope and C/N ratio investigations were conducted on excavated material from the black Younger Dryas boundary in Lommel, Belgium, aiming for a characterisation of the carbon content and structures. Cubic diamond nanoparticles are found in large numbers. The larger ones with diameters around or above 10 nm often exhibit single or multiple twins. The smaller ones around 5 nm in diameter are mostly defect-free. Also larger flake-like particles, around 100 nm in lateral dimension, with a cubic diamond structure are observed as well as large carbon onion structures. The combination of these characteristics does not yield unique evidence for an exogenic impact related to the investigated layer.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.661
Times cited: 32
DOI: 10.1073/pnas.1007695108
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