“Effect of binder content in Cu-In-Se precursor ink on the physical and electrical properties of printed CuInSe2 solar cells”. Buffière M, Zaghi AE, Lenaers N, Batuk M, Khelifi S, Drijkoningen J, Hamon J, Stesmans A, Kepa J, Afanas’ev VV, Hadermann J, D’Haen J, Manca J, Vleugels J, Meuris M, Poortmans J;, The journal of physical chemistry: C : nanomaterials and interfaces 118, 27201 (2014). http://doi.org/10.1021/jp507209h
Abstract: Printed chalcopyrite thin films have attracted considerable attention in recent years due to their potential in the high-throughput production of photovoltaic devices. To improve the homogeneity of printed CuInSe2 (CISe) layers, chemical additives such as binder can be added to the precursor ink. In this contribution, we investigate the influence of the dicyandiamide (DCDA) content, used as a binder in the precursor ink, on the physical and electrical properties of printed CISe solar cells. It is shown that the use of the binder leads to a dense absorber, composed of large CISe grains close to the surface, while the bulk of the layer consists of CISe crystallites embedded in a CuxS particle based matrix, resulting from the limited sintering of the precursor in this region. The expected additional carbon contamination of the CISe layer due to the addition of the binder appears to be limited, and the optical properties of the CISe layer are similar to the reference sample without additive. The electrical characterization of the corresponding CISe/CdS solar cells shows a degradation of the efficiency of the devices, due to a modification in the predominant recombination mechanisms and a limitation of the space charge region width when using the binder; both effects could be explained by the inhomogeneity of the bulk of the CISe absorber and high defect density at the CISe/CuxS-based matrix interface.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 4.536
Times cited: 4
DOI: 10.1021/jp507209h
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“Facile synthesis of Ba1-xKxFe2As2 superconductors via hydride route”. Zaikina JV, Batuk M, Abakumov AM, Navrotsky A, Kauziarich SM, Journal of the American Chemical Society 136, 16932 (2014). http://doi.org/10.1021/ja509907r
Abstract: We have developed a fast, easy, and scalable synthesis method for Ba1xKxFe2As2 (0 ≤ x ≤ 1) superconductors using hydrides BaH2 and KH as a source of barium and potassium metals. Synthesis from hydrides provides better mixing and easier handling of the starting materials, consequently leading to faster reactions and/or lower synthesis temperatures. The reducing atmosphere provided by the evolved hydrogen facilitates preparation of oxygen-free powders. By a combination of methods we have shown that Ba1xKxFe2As2 obtained via hydride route has the same characteristics as when it is prepared by traditional solid-state synthesis. Refinement from synchrotron powder X-ray diffraction data confirms a linear dependence of unit cell parameters upon K content as well as the tetragonal to orthorhombic transition at low temperatures for compositions with x < 0.2. Magnetic measurements revealed dome-like dependence of superconducting transition temperature Tc upon K content with a maximum of 38 K for x close to 0.4. Electron diffraction and high-resolution high-angle annular dark-field scanning transmission electron microscopy indicates an absence of Ba/K ordering, while local inhomogeneity in the Ba/K distribution takes place at a scale of several angstroms along [110] crystallographic direction.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 13.858
Times cited: 13
DOI: 10.1021/ja509907r
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“Effect of selenium content of CuInSex alloy nanopowder precursors on recrystallization of printed CuInSe2 absorber layers during selenization heat treatment”. E Zaghi A, Buffière M, Koo J, Brammertz G, Batuk M, Verbist C, Hadermann J, Kim WK, Meuris M, Poortmans J, Vleugels J;, Thin solid films : an international journal on the science and technology of thin and thick films , 1 (2014). http://doi.org/10.1016/j.tsf.2014.10.003
Abstract: Polycrystalline CuInSe2 semiconductors are efficient light absorber materials for thin film solar cell technology, whereas printing is one of the promising low cost and non-vacuum approaches for the fabrication of thin film solar cells. The printed precursors are transformed into a dense polycrystalline CuInSe2 semiconductor film via thermal treatment in ambient selenium atmosphere (selenization). In this study, the effect of the selenium content in high purity mechanically synthesized CuInSex (x = 2, 1.5, 1 or 0.5) alloy precursors on the recrystallization of the CuInSe2 phase during the selenization process was investigated. The nanostructure and phase variation of CuInSex nanopowders were investigated by different characterization techniques. The recrystallization process of the 12 μm thick CuInSex coatings into the CuInSe2 phase during selenization in selenium vapor was investigated via in-situ high temperature X-ray diffraction. The CuInSex precursors with lower selenium content showed a more pronounced phase conversion into CuInSe2 compared to the higher selenium content CuInSex precursors. Moreover, the CuInSex (x = 0.5 and 1) precursor resulted in a denser polycrystalline CuInSe2 semiconductor film with larger crystals. This could be attributed to a more intensive atomic interdiffusion within the CuInSex precursor system compared to a CuInSe2 phase precursor, and the formation of intermediate CuSe and CuSe2 fluxing phases during selenization.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.879
Times cited: 7
DOI: 10.1016/j.tsf.2014.10.003
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“Microstructural analysis of 9.7% efficient Cu2ZnSnSe4 thin film solar cells”. Buffière M, Brammertz G, Batuk M, Verbist C, Mangin D, Koble C, Hadermann J, Meuris M, Poortmans J, Applied physics letters 105, 183903 (2014). http://doi.org/10.1063/1.4901401
Abstract: This work presents a detailed analysis of the microstructure and the composition of our record Cu 2ZnSnSe4 (CZTSe)-CdS-ZnO solar cell with a total area efficiency of 9.7%. The average composition of the CZTSe crystallites is Cu 1.94 Zn 1.12Sn0.95Se3.99. Large crystals of ZnSe secondary phase (up to 400 nm diameter) are observed at the voids between the absorber and the back contact, while smaller ZnSe domains are segregated at the grain boundaries and close to the surface of the CZTSe grains. An underlying layer and some particles of Cu xSe are observed at the Mo-MoSe2-Cu2ZnSnSe4 interface. The free surface of the voids at the back interface is covered by an amorphous layer containing Cu, S, O, and C, while the presence of Cd, Na, and K is also observed in this region.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.411
Times cited: 17
DOI: 10.1063/1.4901401
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“Critical influence of alumina content on the low temperature degradation of 2-3 mol% yttria-stabilized TZP for dental restorations”. Zhang F, Vanmeensel K, Inokoshi M, Batuk M, Hadermann J, Van Meerbeek B, Naert I, Vleugels J, Journal of the European Ceramic Society 35, 741 (2015). http://doi.org/10.1016/j.jeurceramsoc.2014.09.018
Abstract: The influence of 0.25, 2 and 5 wt.% alumina addition on the mechanical properties and low temperature degradation (LTD) of 3, 2.5 and 2 mol% yttria-stabilized TZP ceramics was investigated. The amount of alumina addition was observed to have a crucial impact on the degradation of Y-TZP ceramics. Independent on the yttria stabilizer content, 0.25 wt.% alumina had a higher degradation retarding effect to Y-TZP ceramics than 2 and 5 wt.% of alumina addition, which had a comparable effect. The apparent activation energy for the degradation process was increased by adding alumina, but it was the same for 0.255 wt.% alumina doped 3Y-TZP ceramics. For Y-TZPs containing a small amount of alumina addition, only the segregated Al3+ at the grain boundaries of the zirconia grains was effective to retard the degradation of Y-TZPs. The secondary phase Al2O3 grains increased the degradation kinetics, which might be attributed to the residual stresses.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.411
Times cited: 37
DOI: 10.1016/j.jeurceramsoc.2014.09.018
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“Reactive molecular dynamics simulations for a better insight in plasma medicine”. Bogaerts A, Yusupov M, Van der Paal J, Verlackt CCW, Neyts EC, Plasma processes and polymers 11, 1156 (2014). http://doi.org/10.1002/ppap.201400084
Abstract: In this review paper, we present several examples of reactive molecular dynamics simulations, which contribute to a better understanding of the underlying mechanisms in plasma medicine on the atomic scale. This includes the interaction of important reactive oxygen plasma species with the outer cell wall of both gram-positive and gram-negative bacteria, and with lipids present in human skin. Moreover, as most biomolecules are surrounded by a liquid biofilm, the behavior of these plasma species in a liquid (water) layer is presented as well. Finally, a perspective for future atomic scale modeling studies is given, in the field of plasma medicine in general, and for cancer treatment in particular.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.846
Times cited: 22
DOI: 10.1002/ppap.201400084
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“Dynamics of current-driven phase-slip centers in superconducting strips”. Berdiyorov G, Harrabi K, Oktasendra F, Gasmi K, Mansour AI, Maneval JP, Peeters FM, Physical review : B : condensed matter and materials physics 90, 054506 (2014). http://doi.org/10.1103/PhysRevB.90.054506
Abstract: Phase-slip centers/lines and hot spots are the main mechanisms for dissipation in current-carrying superconducting thin films. The pulsed-current method has recently been shown to be an effective tool in studying the dynamics of phase-slip centers and their evolution to hot spots. We use the time-dependent Ginzburg-Landau theory in the study of the dynamics of the superconducting condensate in superconducting strips under external current and zero external magnetic field. We show that both the flux-flow state (i.e., slow-moving vortices) and the phase-slip line state (i.e., fast-moving vortices) are dynamically stable dissipative units with temperature smaller than the critical one, whereas hot spots, which are localized normal regions where the local temperature exceeds the critical value, expand in time, resulting ultimately in a complete destruction of the condensate. The response time of the system to abrupt switching on of the overcritical current decreases with increasing both the value of the current (at all temperatures) and temperature (for a given value of the applied current). Our results are in good qualitative agreement with experiments we have conducted on Nb thin strips.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 42
DOI: 10.1103/PhysRevB.90.054506
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“Factors Influencing the Conductivity of Aqueous Sol(ution)-Gel-Processed Al-Doped ZnO Films”. Damm H, Adriaensens P, De Dobbelaere C, Capon B, Elen K, Drijkoningen J, Conings B, Manca JV, D’Haen J, Detavernier C, Magusin PCMM, Hadermann J, Hardy A, Van Bael MK;, Chemistry of materials 26, 5839 (2014). http://doi.org/10.1021/cm501820a
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 24
DOI: 10.1021/cm501820a
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“Multilayer graphene, Moire patterns, grain boundaries and defects identified by scanning tunneling microscopy on the m-plane, non-polar surface of SiC”. Xu P, Qi D, Schoelz JK, Thompson J, Thibado PM, Wheeler VD, Nyakiti LO, Myers-Ward RL, Eddy CR, Gaskill DK, Neek-Amal M, Peeters FM;, Carbon 80, 75 (2014). http://doi.org/10.1016/j.carbon.2014.08.028
Abstract: Epitaxial graphene is grown on a non-polar n(+) 6H-SiC m-plane substrate and studied using atomic scale scanning tunneling microscopy. Multilayer graphene is found throughout the surface and exhibits rotational disorder. Moire patterns of different spatial periodicities are found, and we found that as the wavelength increases, so does the amplitude of the modulations. This relationship reveals information about the interplay between the energy required to bend graphene and the interaction energy, i.e. van der Waals energy, with the graphene layer below. Our experiments are supported by theoretical calculations which predict that the membrane topographical amplitude scales with the Moire pattern wavelength, L as L-1 + alpha L-2. (C) 2014 Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 6.337
Times cited: 14
DOI: 10.1016/j.carbon.2014.08.028
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“Stability of CH3 molecules trapped on hydrogenated sites of graphene”. Berdiyorov GR, Milošević, MV, Peeters FM, van Duin AT, Physica: B : condensed matter 455, 60 (2014). http://doi.org/10.1016/j.physb.2014.07.046
Abstract: We study the effect of a hydrogen atom on the thermal stability of a trapped CH3 molecule on graphene using ReaxFF molecular dynamics simulations. Due to the hydrogen-molecule interaction, enhanced pinning of the CH3 molecule is observed when it is positioned adjacent to the graphene site with the hydrogen atom. We discuss the formation process of such a stable configuration, which originates from different adhesion and migration energies of the hydrogen atom and the CH3 molecule. We also studied the effect of the CH3-H configuration on the electronic transport properties of graphene nanoribbons using first principles density-functional calculations. We found that the formation of the CH3-H structure results in extra features in the transmission spectrum due to the formation of strongly localized states, which are absent when the CH3 molecule is trapped on pristine graphene. Our findings will be useful in exploiting gas sensing properties of graphene, especially for selective detection of individual molecules. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.386
Times cited: 5
DOI: 10.1016/j.physb.2014.07.046
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“Nanofilms as effectively multiband superconductors: Intraband-pairing approximation and Ginzburg-Landau theory”. Shanenko AA, Vagov A, Peeters FM, Aguiar JA, Physica: B : condensed matter 455, 3 (2014). http://doi.org/10.1016/j.physb.2014.06.032
Abstract: It is well-known that the Ginzburg-Landau (GL) theory is a reliable and powerful theoretical tool to investigate the magnetic response of a superconducting state. However, in its standard form, this approach is not applicable to atomically uniform nano-thin superconducting films which are effective multiband superconductors. Here we discuss a relevant generalization of the GL theory, focusing on the underlying intraband-pairing approximation. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.386
Times cited: 1
DOI: 10.1016/j.physb.2014.06.032
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“Formation and diffusion characteristics of Pt clusters on Graphene, 1H-MoS2 and 1T-TaS2”. Ozaydin HD, Sahin H, Senger RT, Peeters FM, Annalen der Physik 526, 423 (2014). http://doi.org/10.1002/andp.201400079
Abstract: Many experiments have revealed that the surfaces of graphene and graphene-like structures can play an active role as a host surface for clusterization of transition metal atoms. Motivated by these observations, we investigate theoretically the adsorption, diffusion and magnetic properties of Pt clusters on three different two-dimensional atomic crystals using first principles density functional theory. We found that monolayers of graphene, molybdenum disulfide (1H-MoS2) and tantalum disulfide (1T-TaS2) provide different nucleation characteristics for Pt cluster formation. At low temperatures, while the bridge site is the most favorable site where the growth of a Pt cluster starts on graphene, top-Mo and top-Ta sites are preferred on 1H-MoS2 and 1T-TaS2, respectively. Ground state structures and magnetic properties of Pt-n clusters (n= 2,3,4) on three different monolayer crystal structures are obtained. We found that the formation of Pt-2 dimer and a triangle-shaped Pt-3 cluster perpendicular to the surface are favored over the three different surfaces. While bent rhombus shaped Pt-4 is formed on graphene, the formation of tetrahedral shaped clusters are more favorable on 1H-MoS2 and 1T-TaS2. Our study of the formation of Pt-n clusters on three different monolayers provides a gateway for further exploration of nanocluster formations on various surfaces.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.039
Times cited: 10
DOI: 10.1002/andp.201400079
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“Parametric amplification of vortex-antivortex pair generation in a Josephson junction”. Berdiyorov GR, Milošević, MV, Savel'ev S, Kusmartsev F, Peeters FM, Physical review : B : condensed matter and materials physics 90, 134505 (2014). http://doi.org/10.1103/PhysRevB.90.134505
Abstract: Using advanced three-dimensional simulations, we show that an Abrikosov vortex, trapped inside a cavity perpendicular to an artificial Josephson junction, can serve as a very efficient source for generation of Josephson vortex-antivortex pairs in the presence of the applied electric current. In such a case, the nucleation rate of the pairs can be tuned in a broad range by an out-of-plane ac magnetic field in a broad range of frequencies. This parametrically amplified vortex-antivortex nucleation can be considered as a macroscopic analog of the dynamic Casimir effect, where fluxon pairs mimic the photons and the ac magnetic field plays the role of the oscillating mirrors. The emerging vortex pairs in our system can be detected by the pronounced features in the measured voltage characteristics, or through the emitted electromagnetic radiation, and exhibit resonant dynamics with respect to the frequency of the applied magnetic field. Reported tunability of the Josephson oscillations can be useful for developing high-frequency emission devices.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 22
DOI: 10.1103/PhysRevB.90.134505
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“The effect of microstructure on the hydrogenation of Mg/Fe thin film multilayers”. Mooij L, Perkisas T, Palsson G, Schreuders H, Wolff M, Hjorvarsson B, Bals S, Dam B, International journal of hydrogen energy 39, 17092 (2014). http://doi.org/10.1016/j.ijhydene.2014.08.035
Abstract: Nanoconfined magnesium hydride can be simultaneously protected and thermodynamically destabilized when interfaced with materials such as Ti and Fe. We study the hydrogenation of thin layers of Mg (<14 nm) nanoconfined in one dimension within thin film Fe/Mg/Fe/Pd multilayers by the optical technique Hydrogenography. The hydrogenation of nanosized magnesium layers in Fe/Mg/Fe multilayers surprisingly shows the presence of multiple plateau pressures, whose nature is thickness dependent. In contrast, hydrogen desorption occurs via a single plateau which does not depend on the Mg layer thickness. From structural and morphological analyses with X-ray diffraction/reflectometry and cross-section TEM, we find that the Mg layer roughness is large when deposited on Fe and furthermore contains high-angle grain boundaries (GB's). When grown on Ti, the Mg layer roughness is low and no high-angle GB's are detected. From a Ti/Mg/Fe multilayer, in which the Mg layer is flat and has little or no GB's, we conclude that MgH2 is indeed destabilized by the interface with Fe. In this case, both the ab- and desorption plateau pressures are increased by a factor two compared to the hydrogenation of Mg within Ti/Mg/Ti multilayers. We hypothesize that the GB's in the Fe/Mg/Fe multilayer act as diffusion pathways for Pd, which is known to greatly alter the hydrogenation behavior of Mg when the two materials share an interface. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.582
Times cited: 15
DOI: 10.1016/j.ijhydene.2014.08.035
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“Improved calculation of displacements per atom cross section in solids by gamma and electron irradiation”. Pinera I, Cruz CM, Leyva A, Abreu Y, Cabal AE, van Espen P, Van Remortel N, Interactions With Materials And Atoms 339, 1 (2014). http://doi.org/10.1016/J.NIMB.2014.08.020
Abstract: Several authors had estimated the displacements per atom cross sections under different approximations and models, including most of the main gamma- and electron-material interaction processes. These previous works used numerical approximation formulas which are applicable for limited energy ranges. We proposed the Monte Carlo assisted Classical Method (MCCM), which relates the established theories about atom displacements to the electron and positron secondary fluence distributions calculated from the Monte Carlo simulation. In this study the MCCM procedure is adapted in order to estimate the displacements per atom cross sections for gamma and electron irradiation. The results obtained through this procedure are compared with previous theoretical calculations. An improvement in about 10-90% for the gamma irradiation induced dpa cross section is observed in our results on regard to the previous evaluations for the studied incident energies. On the other hand, the dpa cross section values produced by irradiation with electrons are improved by our calculations in about 5-50% when compared with the theoretical approximations. When thin samples are irradiated with electrons, more precise results are obtained through the MCCM (in about 20-70%) with respect to the previous studies. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Particle Physics Group; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1016/J.NIMB.2014.08.020
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“Two New Arsenides, Eu7Cu44As23 and Sr7Cu44As23, With a New Filled Variety of the BaHg11 Structure”. Charkin DO, Demchyna R, Prots Y, Borrmann H, Burkhardt U, Schwarz U, Schnelle W, Plokhikh IV, Kazakov SM, Abakumov AM, Batuk D, Verchenko VY, Tsirlin AA, Curfs C, Grin Y, Shevelkov AV;, Inorganic chemistry 53, 11173 (2014). http://doi.org/10.1021/ic5017615
Abstract: Two new ternary arsenides, namely, Eu7Cu44As23 and Sr7Cu44As23, were synthesized from elements at 800 degrees C. Their crystal structure represents a new filled version of the BaHg11 motif with cubic voids alternately occupied by Eu(Sr) and As atoms, resulting in a 2 x 2 x 2 superstructure of the aristotype: space group Fm (3) over barm, a = 16.6707(2) angstrom and 16.7467(2) angstrom, respectively. The Eu derivative exhibits ferromagnetic ordering below 17.5 K. In agreement with band structure calculations both compounds are metals, exhibiting relatively low thermopower, but high electrical and low thermal conductivity.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
Times cited: 9
DOI: 10.1021/ic5017615
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“Highly Efficient Hyperbranched CNT Surfactants: Influence of Molar Mass and Functionalization”. Bertels E, Bruyninckx K, Kurttepeli, Smet M, Bals S, Goderis B, Langmuir: the ACS journal of surfaces and colloids 30, 12200 (2014). http://doi.org/10.1021/la503032g
Abstract: End-group-functionalized hyperbranched polymers were synthesized to act as a carbon nanotube (CNT) surfactant in aqueous solutions. Variation of the percentage of triphenylmethyl (trityl) functionalization and of the molar mass of the hyperbranched polyglycerol (PG) core resulted in the highest measured surfactant efficiency for a 5000 g/mol PG with 5.6% of the available hydroxyl end-groups replaced by trityl functions, as shown by UV-vis measurements. Semiempirical model calculations suggest an even higher efficiency for PG5000 with 2.5% functionalization and maximal molecule specific efficiency in general at low degrees of functionalization. Addition of trityl groups increases the surfactant-nanotube interactions in comparison to unfunctionalized PG because of pi-pi stacking interactions. However, at higher functionalization degrees mutual interactions between trityl groups come into play, decreasing the surfactant efficiency, while lack of water solubility becomes an issue at very high functionalization degrees. Low molar mass surfactants are less efficient compared to higher molar mass species most likely because the higher bulkiness of the latter allows for a better CNT separation and stabilization. The most efficient surfactant studied allowed dispersing 2.85 mg of CNT in 20 mL with as little as 1 mg of surfactant. These dispersions, remaining stable for at least 2 months, were mainly composed of individual CNTs as revealed by electron microscopy.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.833
Times cited: 15
DOI: 10.1021/la503032g
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“The interplay of microstructure and magnetism in La3Ni2SbO9”. Battle PD, Avdeev M, Hadermann J, Journal of solid state chemistry 220, 163 (2014). http://doi.org/10.1016/j.jssc.2014.08.024
Abstract: La3Ni2SbO9 adopts a perovskite-related structure in which the six-coordinate cation sites are occupied alternately by Ni2+ and a disordered arrangement of Ni2+/Sb5+. A polycrystalline sample has been studied by neutron diffraction in applied magnetic fields of 0 <= H/kOe <= 50 at 5 K. In 0 kOe, weak magnetic Bragg scattering consistent with the adoption of a G-type ferrimagnetic structure is observed; the ordered component of the magnetic moment was found to be 0.89(7) mu(B) per Ni2+ cation. This increased to 1.60(3) mu(B) in a field of 50 kOe. Transmission electron microscopy revealed variations in the Ni:Sb ratio across crystallites of the sample. It is proposed that these composition variations disrupt the magnetic superexchange interactions within the compound, leading to domain formation and a reduced average moment. The application of a magnetic field aligns the magnetisation vectors across the crystal and the average moment measured by neutron diffraction increases accordingly. The role played by variations in the local chemical composition in determining the magnetic properties invites comparison with the behaviour of relaxor ferroelectrics. (C) 2014 Elsevier Inc. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 13
DOI: 10.1016/j.jssc.2014.08.024
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“Thermal mirror buckling in freestanding graphene locally controlled by scanning tunnelling microscopy”. Neek-Amal M, Xu P, Schoelz JK, Ackerman ML, Barber SD, Thibado PM, Sadeghi A, Peeters FM, Nature communications 5, 4962 (2014). http://doi.org/10.1038/ncomms5962
Abstract: Knowledge of and control over the curvature of ripples in freestanding graphene are desirable for fabricating and designing flexible electronic devices, and recent progress in these pursuits has been achieved using several advanced techniques such as scanning tunnelling microscopy. The electrostatic forces induced through a bias voltage (or gate voltage) were used to manipulate the interaction of freestanding graphene with a tip (substrate). Such forces can cause large movements and sudden changes in curvature through mirror buckling. Here we explore an alternative mechanism, thermal load, to control the curvature of graphene. We demonstrate thermal mirror buckling of graphene by scanning tunnelling microscopy and large-scale molecular dynamic simulations. The negative thermal expansion coefficient of graphene is an essential ingredient in explaining the observed effects. This new control mechanism represents a fundamental advance in understanding the influence of temperature gradients on the dynamics of freestanding graphene and future applications with electro-thermal-mechanical nanodevices.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 12.124
Times cited: 36
DOI: 10.1038/ncomms5962
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“Interplay between snake and quantum edge states in a graphene Hall bar with a pn-junction”. Milovanović, SP, Masir MR, Peeters FM, Applied physics letters 105, 123507 (2014). http://doi.org/10.1063/1.4896769
Abstract: The magneto- and Hall resistance of a locally gated cross shaped graphene Hall bar is calculated. The edge of the top gate is placed diagonally across the center of the Hall cross. Four-probe resistance is calculated using the Landauer-Büttiker formalism, while the transmission coefficients are obtained using the non-equilibrium Green's function approach. The interplay between transport due to edge channels and snake states is investigated. When two edge channels are occupied, we predict oscillations in the Hall and the bend resistance as function of the magnetic field, which are a consequence of quantum interference between the occupied snake states.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.411
Times cited: 18
DOI: 10.1063/1.4896769
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“Sr21Bi8Cu2(CO3)(2)O-41, a Bi5+ Oxycarbonate with an Original 10L Structure”. Malo S, Abakumov AM, Daturi M, Pelloquin D, Van Tendeloo G, Guesdon A, Hervieu M, Inorganic chemistry 53, 10266 (2014). http://doi.org/10.1021/ic501322w
Abstract: The layered structure of Sr21Bi8Cu2(CO3)(2)O-41 (Z = 2) was determined by transmission electron microscopy, infrared spectroscopy, and powder X-ray diffraction refinement in space group P6(3)/mcm (No. 194), with a = 10.0966(3)angstrom and c = 26.3762(5)angstrom. This original 10L-type structure is built from two structural blocks, namely, [Sr15Bi6Cu2(CO3)O-29] and [Sr6Bi2(CO3)O-12]. The Bi5+ cations form [Bi2O10] dimers, whereas the Cu2+ and C atoms occupy infinite tunnels running along (c) over right arrow. The nature of the different blocks and layers is discussed with regard to the existing hexagonal layered compounds. Sr21Bi8Cu2(CO3)(2)O-41 is insulating and paramagnetic.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
DOI: 10.1021/ic501322w
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“Dynamical effects in strain measurements by dark-field electron holography”. Javon E, Lubk, Cours R, Reboh S, Cherkashin N, Houdellier F, Gatel C, Hytch MJ, Ultramicroscopy 147, 70 (2014). http://doi.org/10.1016/j.ultramic.2014.06.005
Abstract: Here, we study the effect of dynamic scattering on the projected geometric phase and strain maps reconstructed using dark-field electron holography (DFEH) for non-uniformly strained crystals. The investigated structure consists of a {SiGe/Si} superlattice grown on a (001)-Si substrate. The three dimensional strain held within the thin TEM lamella is modelled by the finite element method. The observed projected strain is simulated in two ways by multiplying the strain at each depth in the crystal by a weighting function determined from a recently developed analytical two-beam dynamical theory, and by simply taking the average value. We demonstrate that the experimental results need to be understood in terms of the dynamical theory and good agreement is found between the experimental and simulated results. Discrepancies do remain for certain cases and are likely to be from an imprecision in the actual two-beam diffraction conditions, notably the deviation parameter, and points to limitations in the 2-beam approximation. Finally, a route towards a 3D reconstruction of strain fields is proposed. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 10
DOI: 10.1016/j.ultramic.2014.06.005
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“Visible light activated room temperature gas sensors based on nanocrystalline ZnO sensitized with CdSe quantum dots”. Chizhov AS, Rumyantseva MN, Vasiliev RB, Filatova DG, Drozdov KA, Krylov IV, Abakumov AM, Gaskov AM, Sensors and actuators : B : chemical 205, 305 (2014). http://doi.org/10.1016/j.snb.2014.08.091
Abstract: This work reports the study of photoconductivity and visible light activated room temperature gas sensors properties of nanocrystalline ZnO thick films sensitized with colloidal CdSe quantum dots (QDs). Nanocrystalline zinc oxide (ZnO) was synthesized by the precipitation method. Colloidal CdSe quantum dots were obtained by high temperature colloidal synthesis. Sensitization was effectuated by three different procedures including direct adsorption of CdSe QDs stabilized with oleic acid on ZnO surface, anchoring to the ZnO surface through a bifunctional molecule of mercaptopropionic acid (MPA), and coating of CdSe QDs with a monolayer of MPA with subsequent adsorption on ZnO surface. Sensor measurements demonstrated that obtained QD CdSe/ZnO nanocomposites can be used for NO2 detection under visible (green) light illumination at room temperature without any thermal heating. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.401
Times cited: 36
DOI: 10.1016/j.snb.2014.08.091
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“Monolayers of MoS2 as an oxidation protective nanocoating material”. Sen HS, Sahin H, Peeters FM, Durgun E, Journal of applied physics 116, 083508 (2014). http://doi.org/10.1063/1.4893790
Abstract: First-principle calculations are employed to investigate the interaction of oxygen with ideal and defective MoS2 monolayers. Our calculations show that while oxygen atoms are strongly bound on top of sulfur atoms, the oxygen molecule only weakly interacts with the surface. The penetration of oxygen atoms and molecules through a defect-free MoS2 monolayer is prevented by a very high diffusion barrier indicating that MoS2 can serve as a protective layer for oxidation. The analysis is extended to WS2 and similar coating characteristics are obtained. Our calculations indicate that ideal and continuous MoS2 and WS2 monolayers can improve the oxidation and corrosion-resistance of the covered surface and can be considered as an efficient nanocoating material. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 52
DOI: 10.1063/1.4893790
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“Three-dimensional characterization of noble-metal nanoparticles and their assemblies by electron tomography”. Bals S, Goris B, Liz-Marzan LM, Van Tendeloo G, Angewandte Chemie: international edition in English 53, 10600 (2014). http://doi.org/10.1002/anie.201401059
Abstract: New developments in the field of nanomaterials drive the need for quantitative characterization techniques that yield information down to the atomic scale. In this Review, we focus on the three-dimensional investigations of metal nanoparticles and their assemblies by electron tomography. This technique has become a versatile tool to understand the connection between the properties and structure or composition of nanomaterials. The different steps of an electron tomography experiment are discussed and we show how quantitative three-dimensional information can be obtained even at the atomic scale.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 11.994
Times cited: 58
DOI: 10.1002/anie.201401059
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“Towards Novel Multifunctional Pillared Nanostructures: Effective Intercalation of Adamantylamine in Graphene Oxide and Smectite Clays”. Spyrou K, Potsi G, Diamanti EK, Ke X, Serestatidou E, Verginadis II, Velalopoulou AP, Evangelou AM, Deligiannakis Y, Van Tendeloo G, Gournis D, Rudolf P;, Advanced functional materials 24, 5841 (2014). http://doi.org/10.1002/adfm.201400975
Abstract: Multifunctional pillared materials are synthesized by the intercalation of cage-shaped adamantylamine (ADMA) molecules into the interlayer space of graphite oxide (GO) and aluminosilicate clays. The physicochemical and structural properties of these hybrids, determined by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman and X-ray photoemission (XPS) spectroscopies and transmission electron microscopy (TEM) show that they can serve as tunable hydrophobic/hydrophilic and stereospecific nanotemplates. Thus, in ADMA-pillared clay hybrids, the phyllomorphous clay provides a hydrophilic nanoenvironment where the local hydrophobicity is modulated by the presence of ADMA moieties. On the other hand, in the ADMA-GO hybrid, both the aromatic rings of GO sheets and the ADMA molecules define a hydrophobic nanoenvironment where sp(3)-oxo moieties (epoxy, hydroxyl and carboxyl groups), present on GO, modulate hydrophilicity. As test applications, these pillared nanostructures are capable of selective/stereospecific trapping of small chlorophenols or can act as cytotoxic agents.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 12.124
Times cited: 19
DOI: 10.1002/adfm.201400975
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“On the time scale associated with Monte Carlo simulations”. Bal KM, Neyts EC, The journal of chemical physics 141, 204104 (2014). http://doi.org/10.1063/1.4902136
Abstract: Uniform-acceptance force-bias Monte Carlo (fbMC) methods have been shown to be a powerful technique to access longer timescales in atomistic simulations allowing, for example, phase transitions and growth. Recently, a new fbMC method, the time-stamped force-bias Monte Carlo (tfMC) method, was derived with inclusion of an estimated effective timescale; this timescale, however, does not seem able to explain some of the successes the method. In this contribution, we therefore explicitly quantify the effective timescale tfMC is able to access for a variety of systems, namely a simple single-particle, one-dimensional model system, the Lennard-Jones liquid, an adatom on the Cu(100) surface, a silicon crystal with point defects and a highly defected graphene sheet, in order to gain new insights into the mechanisms by which tfMC operates. It is found that considerable boosts, up to three orders of magnitude compared to molecular dynamics, can be achieved for solid state systems by lowering of the apparent activation barrier of occurring processes, while not requiring any system-specific input or modifications of the method. We furthermore address the pitfalls of using the method as a replacement or complement of molecular dynamics simulations, its ability to explicitly describe correct dynamics and reaction mechanisms, and the association of timescales to MC simulations in general.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.965
Times cited: 26
DOI: 10.1063/1.4902136
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“Oxygen-driven competition between low-dimensional structures of Sr3CoMO6 and Sr3CoMO7-\delta with M = Ru,Ir”. Mikhailova D, Reichel P, Tsirlin AA, Abakumov AM, Senyshyn A, Mogare KM, Schmidt M, Kuo CY, Pao CW, Pi TW, Lee JF, Hu Z, Tjeng LH;, Journal of the Chemical Society : Dalton transactions 43, 13883 (2014). http://doi.org/10.1039/c4dt01893a
Abstract: We have realized a reversible structure transformation of one-dimensional 1D K4CdCl6-type Sr3CoMO6 with the Co2+/M4+ cation ordering into the two-dimensional 2D double layered Ruddlesden-Popper structure Sr3CoMO7-delta with a random distribution of Co and M (with M = Ru, Ir) upon increasing the partial oxygen pressure. The combined soft and hard X-ray absorption spectroscopy studies show that under transformation, Co and M cations were oxidized to Co3+ and M5+. During oxidation, high-spin Co2+ in Sr3CoMO6 first transforms into high-spin Co3+ in oxygen-deficient Sr3CoMO7-delta, and then further transforms into low-spin Co3+ in fully oxidized Sr3CoMO7 upon further increasing the partial pressure of oxygen. The 1D Sr3CoMO6 compound is magnetically ordered at low temperatures with the magnetic moments lying along the c-axis. Their alignment is parallel for Sr3CoRuO6 and antiparallel for Sr3CoIrO6. The 2D compounds reveal a spin-glass-like behavior related to the random distribution of magnetic cations in the structure.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.029
Times cited: 7
DOI: 10.1039/c4dt01893a
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“Ag and Au atoms intercalated in bilayer heterostructures of transition metal dichalcogenides and graphene”. Iyikanat F, Sahin H, Senger RT, Peeters FM, APL materials 2, 092801 (2014). http://doi.org/10.1063/1.4893543
Abstract: The diffusive motion of metal nanoparticles Au and Ag on monolayer and between bilayer heterostructures of transition metal dichalcogenides and graphene are investigated in the framework of density functional theory. We found that the minimum energy barriers for diffusion and the possibility of cluster formation depend strongly on both the type of nanoparticle and the type of monolayers and bilayers. Moreover, the tendency to form clusters of Ag and Au can be tuned by creating various bilayers. Tunability of the diffusion characteristics of adatoms in van der Waals heterostructures holds promise for controllable growth of nanostructures. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 4.335
Times cited: 10
DOI: 10.1063/1.4893543
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“Spin- and valley-dependent magnetotransport in periodically modulated silicene”. Shakouri K, Vasilopoulos P, Vargiamidis V, Peeters FM, Physical review : B : condensed matter and materials physics 90, 125444 (2014). http://doi.org/10.1103/PhysRevB.90.125444
Abstract: The low-energy physics of silicene is described by Dirac fermions with a strong spin-orbit interaction and its band structure can be controlled by an external perpendicular electric field E-z. We investigate the commensurability oscillations in silicene modulated by a weak periodic potential V = V-0 cos(2 pi y/a(0)) with a(0) as its period, in the presence of a perpendicular magnetic field B and of a weak sinusoidal electric field E-z = E-0 cos(2 pi y/b(0)), where b(0) is its period. We show that the spin and valley degeneracy of the Landau levels is lifted, due to the modulation, and that the interplay between the strong spin-orbit interaction and the potential and electric field modulations can result in spin- and valley-resolved magnetotransport. At very weak magnetic fields the commensurability oscillations induced by a weak potential modulation can exhibit a beating pattern depending on the strength of the homogenous electric field Ez but this is not the case when only Ez is modulated. The Hall conductivity plateaus acquire a step structure, due to spin and valley intra-Landau-level transitions, that is absent in unmodulated silicene. The results are critically contrasted with those for graphene and the two-dimensional electron gas.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 31
DOI: 10.1103/PhysRevB.90.125444
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