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“First-principles study of the optoelectronic properties and photovoltaic absorber layer efficiency of Cu-based chalcogenides”. Sarmadian N, Saniz R, Partoens B, Lamoen D, Journal of applied physics 120, 085707 (2016). http://doi.org/10.1063/1.4961562
Abstract: Cu-based chalcogenides are promising materials for thin-film solar cells with more than 20% measured
cell efficiency. Using first-principles calculations based on density functional theory, the
optoelectronic properties of a group of Cu-based chalcogenides Cu2-II-IV-VI4 is studied. They are
then screened with the aim of identifying potential absorber materials for photovoltaic applications.
The spectroscopic limited maximum efficiency (SLME) introduced by Yu and Zunger [Phys. Rev.
Lett. 108, 068701 (2012)] is used as a metric for the screening. After constructing the currentvoltage
curve, the SLME is calculated from the maximum power output. The role of the nature of
the band gap, direct or indirect, and also of the absorptivity of the studied materials on the maximum
theoretical power conversion efficiency is studied. Our results show that Cu2II-GeSe4 with
II¼ Cd and Hg, and Cu2-II-SnS4 with II ¼ Cd, Hg, and Zn have a higher theoretical efficiency
compared with the materials currently used as absorber layer.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 29
DOI: 10.1063/1.4961562
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“First-principles thermodynamics and defect kinetics guidelines for engineering a tailored RRAM device”. Clima S, Chen YY, Chen CY, Goux L, Govoreanu B, Degraeve R, Fantini A, Jurczak M, Pourtois G, Journal of applied physics 119, 225107 (2016). http://doi.org/10.1063/1.4953673
Abstract: Resistive Random Access Memories are among the most promising candidates for the next generation of non-volatile memory. Transition metal oxides such as HfOx and TaOx attracted a lot of attention due to their CMOS compatibility. Furthermore, these materials do not require the inclusion of extrinsic conducting defects since their operation is based on intrinsic ones (oxygen vacancies). Using Density Functional Theory, we evaluated the thermodynamics of the defects formation and the kinetics of diffusion of the conducting species active in transition metal oxide RRAM materials. The gained insights based on the thermodynamics in the Top Electrode, Insulating Matrix and Bottom Electrode and at the interfaces are used to design a proper defect reservoir, which is needed for a low-energy reliable switching device. The defect reservoir has also a direct impact on the retention of the Low Resistance State due to the resulting thermodynamic driving forces. The kinetics of the diffusing conducting defects in the Insulating Matrix determine the switching dynamics and resistance retention. The interface at the Bottom Electrode has a significant impact on the low-current operation and long endurance of the memory cell. Our first-principles findings are confirmed by experimental measurements on fabricated RRAM devices. Published by AIP Publishing.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.068
Times cited: 17
DOI: 10.1063/1.4953673
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“Inter-ribbon tunneling in graphene: An atomistic Bardeen approach”. Van de Put ML, Vandenberghe WG, Sorée B, Magnus W, Fischetti MV, Journal of applied physics 119, 214306 (2016). http://doi.org/10.1063/1.4953148
Abstract: A weakly coupled system of two crossed graphene nanoribbons exhibits direct tunneling due to the overlap of the wavefunctions of both ribbons. We apply the Bardeen transfer Hamiltonian formalism, using atomistic band structure calculations to account for the effect of the atomic structure on the tunneling process. The strong quantum-size confinement of the nanoribbons is mirrored by the one-dimensional character of the electronic structure, resulting in properties that differ significantly from the case of inter-layer tunneling, where tunneling occurs between bulk two-dimensional graphene sheets. The current-voltage characteristics of the inter-ribbon tunneling structures exhibit resonance, as well as stepwise increases in current. Both features are caused by the energetic alignment of one-dimensional peaks in the density-of-states of the ribbons. Resonant tunneling occurs if the sign of the curvature of the coupled energy bands is equal, whereas a step-like increase in the current occurs if the signs are opposite. Changing the doping modulates the onset-voltage of the effects as well as their magnitude. Doping through electrostatic gating makes these structures promising for application towards steep slope switching devices. Using the atomistic empirical pseudopotentials based Bardeen transfer Hamiltonian method, inter-ribbon tunneling can be studied for the whole range of two-dimensional materials, such as transition metal dichalcogenides. The effects of resonance and of step-like increases in the current we observe in graphene ribbons are also expected in ribbons made from these alternative two-dimensional materials, because these effects are manifestations of the one-dimensional character of the density-of-states. Published by AIP Publishing.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 6
DOI: 10.1063/1.4953148
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“Skyrmion-induced bound states on the surface of three-dimensional topological insulators”. Andrikopoulos D, Sorée B, De Boeck J, Journal of applied physics 119, 193903 (2016). http://doi.org/10.1063/1.4950759
Abstract: The interaction between the surface of a 3D topological insulator and a skyrmion/anti-skyrmion structure is studied in order to investigate the possibility of electron confinement due to the skyrmion presence. Both hedgehog (Neel) and vortex (Bloch) skyrmions are considered. For the hedgehog skyrmion, the in-plane components cannot be disregarded and their interaction with the surface state of the topological insulator (TI) has to be taken into account. A semi-classical description of the skyrmion chiral angle is obtained using the variational principle. It is shown that both the hedgehog and the vortex skyrmion can induce bound states on the surface of the TI. However, the number and the properties of these states depend strongly on the skyrmion type and the skyrmion topological number N-Sk. The probability densities of the bound electrons are also derived where it is shown that they are localized within the skyrmion region. Published by AIP Publishing.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 8
DOI: 10.1063/1.4950759
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“Superconductor-ferromagnet bilayer under external drive : the role of vortex-antivortex matter”. Frota DA, Chaves A, Ferreira WP, Farias GA, Milošević, MV, Journal of applied physics 119, 093912 (2016). http://doi.org/10.1063/1.4943364
Abstract: Using advanced Ginzburg-Landau simulations, we study the superconducting state of a thin superconducting film under a ferromagnetic layer, separated by an insulating oxide, in applied external magnetic field and electric current. The taken uniaxial ferromagnet is organized into a series of parallel domains with alternating polarization of out-of-plane magnetization, sufficiently strong to induce vortex-antivortex pairs in the underlying superconductor in absence of other magnetic field. We show the organization of such vortex-antivortex matter into rich configurations, some of which are not matching the periodicity of the ferromagnetic film. The variety of possible configurations is enhanced by applied homogeneous magnetic field, where additional vortices in the superconductor may lower the energy of the system by either annihilating the present antivortices under negative ferromagnetic domains or by lowering their own energy after positioning under positive ferromagnetic domains. As a consequence, both the vortex-antivortex reordering in increasing external field and the evolution of the energy of the system are highly nontrivial. Finally, we reveal the very interesting effects of applied dc electric current on the vortex-antivortex configurations, since resulting Lorentzian force has opposite direction for vortices and antivortices, while direction of the applied current with respect to ferromagnetic domains is of crucial importance for the interaction of the applied and the Meissner current, as well as the consequent vortex-antivortex dynamics-both of which are reflected in the anisotropic critical current of the system. (C) 2016 AIP Publishing LLC.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 4
DOI: 10.1063/1.4943364
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“On the structural and electronic properties of Ir-silicide nanowires on Si(001) surface”. Fatima, Oguz IC, Çakir D, Hossain S, Mohottige R, Gulseren O, Oncel N, Journal of applied physics 120, 095303 (2016). http://doi.org/10.1063/1.4961550
Abstract: Iridium (Ir) modified Silicon (Si) (001) surface is studied with Scanning Tunneling Microscopy/Spectroscopy (STM/STS) and Density Functional Theory (DFT). A model for Ir-silicide nanowires based on STM images and ab-initio calculations is proposed. According to our model, the Ir adatom is on the top of the substrate dimer row and directly binds to the dimer atoms. I-V curves measured at 77K shows that the nanowires are metallic. DFT calculations confirm strong metallic nature of the nanowires. Published by AIP Publishing.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 7
DOI: 10.1063/1.4961550
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“Electric-field induced quantum broadening of the characteristic energy level of traps in semiconductors and oxides”. Mohammed M, Verhulst AS, Verreck D, Van de Put M, Simoen E, Sorée B, Kaczer B, Degraeve R, Mocuta A, Collaert N, Thean A, Groeseneken G, Journal of applied physics 120, 245704 (2016). http://doi.org/10.1063/1.4972482
Abstract: The trap-assisted tunneling (TAT) current in tunnel field-effect transistors (TFETs) is one of the crucial factors degrading the sub-60 mV/dec sub-threshold swing. To correctly predict the TAT currents, an accurate description of the trap is required. Since electric fields in TFETs typically reach beyond 10(6) V/cm, there is a need to quantify the impact of such high field on the traps. We use a quantum mechanical implementation based on the modified transfer matrix method to obtain the trap energy level. We present the qualitative impact of electric field on different trap configurations, locations, and host materials, including both semiconductors and oxides. We determine that there is an electric-field related trap level shift and level broadening. We find that these electric-field induced quantum effects can enhance the trap emission rates. Published by AIP Publishing.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 6
DOI: 10.1063/1.4972482
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“Anisotropic electronic, mechanical, and optical properties of monolayer WTe2”. Torun E, Sahin H, Cahangirov S, Rubio A, Peeters FM, Journal of applied physics 119, 074307 (2016). http://doi.org/10.1063/1.4942162
Abstract: Using first-principles calculations, we investigate the electronic, mechanical, and optical properties of monolayer WTe2. Atomic structure and ground state properties of monolayer WTe2 (T-d phase) are anisotropic which are in contrast to similar monolayer crystals of transition metal dichalcogenides, such as MoS2, WS2, MoSe2, WSe2, and MoTe2, which crystallize in the H-phase. We find that the Poisson ratio and the in-plane stiffness is direction dependent due to the symmetry breaking induced by the dimerization of the W atoms along one of the lattice directions of the compound. Since the semimetallic behavior of the T-d phase originates from this W-W interaction (along the a crystallographic direction), tensile strain along the dimer direction leads to a semimetal to semiconductor transition after 1% strain. By solving the Bethe-Salpeter equation on top of single shot G(0)W(0) calculations, we predict that the absorption spectrum of T-d-WTe2 monolayer is strongly direction dependent and tunable by tensile strain. (C) 2016 AIP Publishing LLC.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 62
DOI: 10.1063/1.4942162
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“Effect of straining graphene on nanopore creation using Si cluster bombardment: A reactive atomistic investigation”. Berdiyorov GR, Mortazavi B, Ahzi S, Peeters FM, Khraisheh MK, Journal of applied physics 120, 225108 (2016). http://doi.org/10.1063/1.4971767
Abstract: Graphene nanosheets have recently received a revival of interest as a new class of ultrathin, high-flux, and energy-efficient sieving membranes because of their unique two-dimensional and atomically thin structure, good flexibility, and outstanding mechanical properties. However, for practical applications of graphene for advanced water purification and desalination technologies, the creation of well controlled, high-density, and subnanometer diameter pores becomes a key factor. Here, we conduct reactive force-field molecular dynamics simulations to study the effect of external strain on nanopore creation in the suspended graphene by bombardment with Si clusters. Depending on the size and energy of the clusters, different kinds of topography were observed in the graphene sheet. In all the considered conditions, tensile strain results in the creation of nanopores with regular shape and smooth edges. On the contrary, compressive strain increases the elastic response of graphene to irradiation that leads to the formation of net-like defective structures with predominantly carbon atom chains. Our findings show the possibility of creating controlled nanopores in strained graphene by bombardment with Si clusters. Published by AIP Publishing.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 10
DOI: 10.1063/1.4971767
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“Gaining new insight into low-temperature aqueous photochemical solution deposited ferroelectric PbTiO3 films”. De Dobbelaere C, Lourdes Calzada M, Bretos I, Jimenez R, Ricote J, Hadermann J, Hardy A, Van Bael MK, Materials chemistry and physics 174, 28 (2016). http://doi.org/10.1016/J.MATCHEMPHYS.2016.02.047
Abstract: The nature of the low-temperature photochemical assisted formation process of ferroelectric lead titanate (PbTiO3) films is studied in the present work. Films are obtained by the deposition of an aqueous solution containing citric acid based (citrato) metal ion complexes with intrinsic UV activity. This UV activity is crucial for the aqueous photochemical solution deposition (aqueous PCSD) route being used. UV irradiation enhances the early decomposition of organics and results in improved electrical properties for the crystalline oxide film, even if the film is crystallized at low temperature. GATR-FTIR shows that UV irradiation promotes the decomposition of organic precursor components, resulting in homogeneous films if applied in the right temperature window during film processing. The organic content, morphology and crystallinity of the irradiated films, achieved at different processing atmospheres and temperatures, is studied and eventually correlated to the functional behavior of the obtained films. This is an important issue, as crystalline films obtained at low temperatures often lack ferroelectric responses. In this work, the film prepared in pure oxygen at the very low temperature of 400 degrees C and after an optimized UV treatment presents a significant remanent polarization value of P-r = 8.8 mu C cm(-2). This value is attributed to the better crystallinity, the larger grain size and the reduced porosity obtained thanks to the early film crystallization effectively achieved through the UV treatment in oxygen. (C) 2016 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.084
Times cited: 4
DOI: 10.1016/J.MATCHEMPHYS.2016.02.047
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“Effect of substitutional impurities on the electronic transport properties of graphene”. Berdiyorov GR, Bahlouli H, Peeters FM, Physica. E: Low-dimensional systems and nanostructures 84, 22 (2016). http://doi.org/10.1016/j.physe.2016.05.024
Abstract: Density-functional theory in combination with the nonequilibrium Green's function formalism is used to study the effect of substitutional doping on the electronic transport properties of hydrogen passivated zig-zag graphene nanoribbon devices. B, N and Si atoms are used to substitute carbon atoms located at the center or at the edge of the sample. We found that Si -doping results in better electronic transport as compared to the other substitutions. The transmission spectrum also depends on the location of the substitutional dopants: for single atom doping the largest transmission is obtained for edge substitutions, whereas substitutions in the middle of the sample give larger transmission for double carbon substitutions. The obtained results are explained in terms of electron localization in the system due to the presence of impurities. (C) 2016 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 2.221
Times cited: 17
DOI: 10.1016/j.physe.2016.05.024
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“Attitudes of agricultural experts toward genetically modified crops : a case study in Southwest Iran”. Ghanian M, Ghoochani OM, Kitterlin M, Jahangiry S, Zarafshani K, Van Passel S, Azadi H, Science And Engineering Ethics 22, 509 (2016). http://doi.org/10.1007/S11948-015-9653-1
Abstract: The production of genetically modified (GM) crops is growing around the world, and with it possible opportunities to combat food insecurity and hunger, as well as solutions to current problems facing conventional agriculture. In this regard the use of GMOs in food and agricultural applications has increased greatly over the past decade. However, the development of GM crops has been a matter of considerable interest and worldwide public controversy. This, in addition to skepticism, has stifled the use of this practice on a large scale in many areas, including Iran. It stands to reason that a greater understanding of this practice could be formed after a review of the existing expert opinions surrounding GM crops. Therefore, the purpose of this study was to analyze the predictors that influence agricultural experts attitudes toward the development of and policies related to GM crops. Using a descriptive correlational research method, questionnaire data was collected from 65 experts from the Agricultural Organization in the Gotvand district in Southwest Iran. Results indicated that agricultural experts were aware of the environmental benefits and possible risks associated with GM crops. The majority of participants agreed that GM crops could improve food security and accelerate rural development, and were proponents of labeling practices for GM crops. Finally, there was a positive correlation between the perception of benefits and attitudes towards GM crops.
Keywords: A1 Journal article; Economics; Engineering Management (ENM)
Impact Factor: 2.229
Times cited: 5
DOI: 10.1007/S11948-015-9653-1
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“Synthesis, structure and electrochemical properties of LiNaCo0.5Fe0.5PO4F fluoride-phosphate”. Fedotov SS, Kuzovchikov SM, Khasanova NR, Drozhzhin OA, Filimonov DS, Karakulina OM, Hadermann J, Abakumov AM, Antipov EV, Journal of solid state chemistry 242, 70 (2016). http://doi.org/10.1016/j.jssc.2016.02.042
Abstract: LiNaCo 0.5 Fe 0.5 PO 4 F fluoride-phosphate was synthesized via conventional solid-state and novel freeze-drying routes. The crystal structure was refined based on neutron powder diffraction (NPD) data and validated by electron diffraction (ED) and high-resolution transmission electron microscopy (HRTEM). The alkali ions are ordered in LiNaCo 0.5 Fe 0.5 PO 4 F and the transition metals jointly occupy the same crystallographic sites. The oxidation state and oxygen coordination environment of the Fe atoms were verified by 57 Fe Mössbauer spectroscopy. Electrochemical tests of the LiNaCo 0.5 Fe 0.5 PO 4 F cathode material demonstrated a reversible activity of the Fe 3+ /Fe 2+ redox couple at the electrode potential near 3.4 V and minor activity of the Co 3+ /Co 2+ redox couple over 5 V vs Li/Li + . The material exhibits a good capacity retention in the 2.4÷4.6 V vs Li/Li + potential range with the delivered discharge capacity of more than 82% (theo.) regarding Fe 3+ /Fe 2+ .
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 1
DOI: 10.1016/j.jssc.2016.02.042
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“Structural chemistry and magnetic properties of the perovskite Sr3Fe2TeO9”. Tang Y, Hunter EC, Battle PD, Sena RP, Hadermann J, Avdeev M, Cadogan JM, Journal of solid state chemistry 242, 86 (2016). http://doi.org/10.1016/j.jssc.2016.06.024
Abstract: A polycrystalline sample of perovskite-like Sr3Fe2TeO9 has been prepared in a solid-state reaction and studied by a combination of electron microscopy, Mossbauer spectroscopy, magnetometry, X-ray diffraction and neutron diffraction. The majority of the reaction product is shown to be a trigonal phase with a 2:1 ordered arrangement of Fe3+ and Te6+ cations. However, the sample is prone to nano twinning and tetragonal domains with a different pattern of cation ordering exist within many crystallites. Antiferromagnetic ordering exists in the trigonal phase at 300 K and Sr3Fe2TeO9 is thus the first example of a perovskite with 2:1 trigonal cation ordering to show long-range magnetic order. At 300 K the antiferromagnetic phase coexists with two paramagnetic phases which show spin -glass behaviour below similar to 80 K. (C) 2016 The Authors. Published by Elsevier Inc.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 12
DOI: 10.1016/j.jssc.2016.06.024
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“Structural chemistry and magnetic properties of the perovskite SrLa2Ni2TeO9”. Sena RP, Hadermann J, Chin C-M, Hunter EC, Battle PD, Journal of solid state chemistry 243, 304 (2016). http://doi.org/10.1016/J.JSSC.2016.09.004
Abstract: A polycrystalline sample of SrLa2Ni2TeO9 has been synthesized using a standard ceramic method and characterized by neutron diffraction, magnetometry and electron microscopy. The compound adopts a monoclinic, perovskite-like structure with space group P2(1)/n in and unit cell parameters a=5.6008(1), b = 5.5872(1), c=7.9018(2) angstrom, p=90.021(6)degrees at room temperature. The two crystallographically-distinct B sites are occupied by Ni2+ and Te6+ in ratios of 83:17 and 50:50. Both ac and dc magnetometry suggest that the compound is a spin glass below 35 K but the neutron diffraction data show that some regions of the sample are antiferromagnetic. Electron microscopy revealed twinning on a nanoscale and local variations in composition. These defects are thought to be responsible for the presence of two distinct types of antiferromagnetic ordering. (C) 2016 The Authors. Published by Elsevier Inc.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.299
Times cited: 6
DOI: 10.1016/J.JSSC.2016.09.004
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“Special Issue of Papers by Plenary and Topical Invited Lecturers at the 22nd International Symposium on Plasma Chemistry (ISPC 22), 5–10 July 2015, Antwerp, Belgium: Introduction”. Bogaerts A, van de Sanden R, Plasma chemistry and plasma processing 36, 1 (2016). http://doi.org/10.1007/s11090-015-9691-0
Keywords: Editorial; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.355
DOI: 10.1007/s11090-015-9691-0
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“Plasma-Surface Interactions in Plasma Catalysis”. Neyts EC, Plasma chemistry and plasma processing 36, 185 (2016). http://doi.org/10.1007/s11090-015-9662-5
Abstract: In this paper the various elementary plasma—surface interaction processes occurring in plasma catalysis are critically evaluated. Specifically, plasma catalysis at atmospheric pressure is considered. The importance of the various processes is analyzed for the most common plasma catalysis sources, viz. the dielectric barrier discharge and the gliding arc. The role and importance of surface chemical reactions (including adsorption, surface-mediated association and dissociation reactions, and desorption), plasma-induced surface modification, photocatalyst activation, heating, charging, surface discharge formation and electric field enhancement are discussed in the context of plasma catalysis. Numerous examples are provided to demonstrate the importance of the various processes.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.355
Times cited: 66
DOI: 10.1007/s11090-015-9662-5
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“Comment on “Generalized exclusion processes : transport coefficients””. Becker T, Nelissen K, Cleuren B, Partoens B, Van den Broeck C, Physical review E 93, 046101 (2016). http://doi.org/10.1103/PHYSREVE.93.046101
Abstract: In a recent paper, Arita et al. [Phys. Rev. E 90, 052108 (2014)] consider the transport properties of a class of generalized exclusion processes. Analytical expressions for the transport-diffusion coefficient are derived by ignoring correlations. It is claimed that these expressions become exact in the hydrodynamic limit. In this Comment,we point out that (i) the influence of correlations upon the diffusion does not vanish in the hydrodynamic limit, and (ii) the expressions for the self- and transport diffusion derived by Arita et al. are special cases of results derived in Becker et al. [Phys. Rev. Lett. 111, 110601 (2013)].
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.366
Times cited: 3
DOI: 10.1103/PHYSREVE.93.046101
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“Fe3O4@MIL-101-A selective and regenerable adsorbent for the removal of as species from water”. Folens K, Leus K, Nicomel NR, Meledina M, Turner S, Van Tendeloo G, Du Laing G, Van Der Voort P, European journal of inorganic chemistry 2016, 4395 (2016). http://doi.org/10.1002/EJIC.201600160
Abstract: The chromium-based metal organic framework MIL-101(Cr) served as a host for the in situ synthesis of Fe3O4 nano particles. This hybrid nanomaterial was tested as an adsorbent for arsenite and arsenate species in groundwater and surface water and showed excellent affinity towards As-III and As-V species. The adsorption capacities of 121.5 and 80.0 mg g(-1) for arsenite and arsenate species, respectively, are unprecedented. The presence of Ca2+, Mg2+, and phosphate ions and natural organic matter does not affect the removal efficiency or the selectivity. The structural integrity of the hybrid nanomaterial was maintained during the adsorption process and even after desorption through phosphate elution. Additionally, no significant leaching of Cr or Fe species was observed.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.444
Times cited: 27
DOI: 10.1002/EJIC.201600160
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“CVD diamond growth from nanodiamond seeds buried under a thin chromium layer”. Degutis G, Pobedinskas P, Turner S, Lu Y-G, Al Riyami S, Ruttens B, Yoshitake T, D'Haen J, Haenen K, Verbeeck J, Hardy A, Van Bael MK, Diamond and related materials 64, 163 (2016). http://doi.org/10.1016/j.diamond.2016.02.013
Abstract: This work presents a morphological and structural analysis of CVD diamond growth on silicon from nanodiamond seeds covered by a 50 nm thick chromium layer. The role of carbon diffusion as well as chromium and carbon silicide formation is analyzed. The local diamond environment is investigated by scanning transmission electron microscopy in combination with electron energy-loss spectroscopy. The evolution of the diamond phase composition (sp3/sp2) is evaluated by micro-Raman spectroscopy. Raman and X-ray diffraction analysis are used to identify the interfacial phases formed during CVD growth. Based upon the observed morphological and structural evolution, a diamond growth model from nanodiamond seeds buried beneath a thin Cr layer is proposed.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.561
Times cited: 11
DOI: 10.1016/j.diamond.2016.02.013
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“Incorporation and study of SiV centers in diamond nanopillars”. Felgen N, Naydenov B, Turner S, Jelezko F, Reithmaier JP, Popov C, Diamond and related materials 64, 64 (2016). http://doi.org/10.1016/j.diamond.2016.01.011
Abstract: We report on the incorporation of SiV centers during hot filament chemical vapor deposition of diamond on top of diamond nanopillars with diameters down to 100 nm. The nanopillars themselves were prepared from nano crystalline diamond films by applying electron beam lithography and inductively coupled plasma reactive ion etching. The optical investigations revealed the presence of ensembles of SiV color centers incorporated during the overgrowth step. (C) 2016 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.561
Times cited: 14
DOI: 10.1016/j.diamond.2016.01.011
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“Integrated assessment of agro-ecological systems : the case study of the “Alta Murgia&rdquo, National park in Italy”. Moretti M, De Boni A, Roma R, Fracchiolla M, Van Passel S, Agricultural Systems 144, 144 (2016). http://doi.org/10.1016/J.AGSY.2016.02.007
Abstract: Several indicators and methods are already applied for sustainability assessment in agriculture. The links between sustainability indicators, agricultural management and policies are not well explained. The aim of this study is to combine biophysical and monetary sustainability assessment tools to support agriculture policy decision-making. Three methodological steps are considered: i) the environmental impacts of farms are assessed using terrestrial acidification, freshwater eutrophication, soil and freshwater ecotoxicity as well as natural land transformation; ii) the most relevant indicators of agriculture damages on ecosystems quality are aggregated into an index; iii) the farms' index scores are integrated with farm assets, land and labor, into the Sustainable Value approach (SVA), as indicator of natural resources used by farms. As a case study, the methodology was applied to arable farms with and without animal husbandry of the “Alta Murgia” National Park. The crop farms, in our sample, have a higher sustainable value using their economic and environmental resources. Mixed farms need to improve their resources use efficiency. Although crop farms have lower land-use efficiency compared to mixed farms, our results suggest supporting, by means of policy options, the specialized crop farms that, on average, perform better in terms of ecosystems quality preservation. Finally, we find that Life Cycle Assessment (LCA) to soundly measure the environmental impacts clearly enriches the SVA. (C) 2016 Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Engineering Management (ENM)
Impact Factor: 2.571
Times cited: 6
DOI: 10.1016/J.AGSY.2016.02.007
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“Multi-level molecular modelling for plasma medicine”. Bogaerts A, Khosravian N, Van der Paal J, Verlackt CCW, Yusupov M, Kamaraj B, Neyts EC, Journal of physics: D: applied physics 49, 054002 (2016). http://doi.org/10.1088/0022-3727/49/5/054002
Abstract: Modelling at the molecular or atomic scale can be very useful for obtaining a better insight in plasma medicine. This paper gives an overview of different atomic/molecular scale modelling approaches that can be used to study the direct interaction of plasma species with biomolecules or the consequences of these interactions for the biomolecules on a somewhat longer time-scale. These approaches include density functional theory (DFT), density functional based tight binding (DFTB), classical reactive and non-reactive molecular dynamics (MD) and united-atom or coarse-grained MD, as well as hybrid quantum mechanics/molecular mechanics (QM/MM) methods. Specific examples will be given for three important types of biomolecules, present in human cells, i.e. proteins, DNA and phospholipids found in the cell membrane. The results show that each of these modelling approaches has its specific strengths and limitations, and is particularly useful for certain applications. A multi-level approach is therefore most suitable for obtaining a global picture of the plasma–biomolecule interactions.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 11
DOI: 10.1088/0022-3727/49/5/054002
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“A parametric model for reactive high-power impulse magnetron sputtering of films”. Kozák T, Vlček J, Journal Of Physics D-Applied Physics 49, 055202 (2016). http://doi.org/10.1088/0022-3727/49/5/055202
Abstract: We present a time-dependent parametric model for reactive HiPIMS deposition of films. Specific features of HiPIMS discharges and a possible increase in the density of the reactive gas in front of the reactive gas inlets placed between the target and the substrate are considered in the model. The model makes it possible to calculate the compound fractions in two target layers and in one substrate layer, and the deposition rate of films at fixed partial pressures of the reactive and inert gas. A simplified relation for the deposition rate of films prepared using a reactive HiPIMS is presented. We used the model to simulate controlled reactive HiPIMS depositions of stoichiometric ZrO2 films, which were recently carried out in our laboratories with two different configurations of the O2 inlets in front of the sputtered target. The repetition frequency was 500 Hz at the deposition-averaged target power densities of 5 Wcm−2 and 50 Wcm−2 with a pulse-averaged target power density up to 2 kWcm−2. The pulse durations were 50 μs and 200 μs. Our model calculations show that the to-substrate O2 inlet provides systematically lower compound fractions in the target surface layer and higher compound fractions in the substrate surface layer, compared with the to-target O2 inlet. The low compound fractions in the target surface layer (being approximately 10% at the depositionaveraged target power density of 50 Wcm−2 and the pulse duration of 200 μs) result in high deposition rates of the films produced, which are in agreement with experimental values.
Keywords: A1 Journal article; Electron Microscopy for Materials Science (EMAT);
Impact Factor: 2.588
Times cited: 25
DOI: 10.1088/0022-3727/49/5/055202
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“Computational study of the CF4 /CHF3 / H2 /Cl2 /O2 /HBr gas phase plasma chemistry”. Tinck S, Bogaerts A, Journal of physics: D: applied physics 49, 195203 (2016). http://doi.org/10.1088/0022-3727/49/19/195203
Abstract: A modelling study is performed of high-density low-pressure inductively coupled CF4/CHF3/H2/Cl2/O2/HBr plasmas under different gas mixing ratios. A reaction set describing the complete plasma chemistry is presented and discussed. The gas fraction of each component in this mixture is varied to investigate the sensitivity of the plasma properties, like electron density, plasma potential and species densities, towards the gas mixing ratios. This research is of great interest for microelectronics applications because these gases are often combined in two (or more)-component mixtures, and mixing gases or changing the fraction of a gas can sometimes yield unwanted reaction products or unexpected changes in the overall plasma properties due to the increased chemical complexity of the system. Increasing the CF4 fraction produces more F atoms for chemical etching as expected, but also more prominently lowers the density of Cl atoms, resulting in an actual drop in the etch rate under certain conditions. Furthermore, CF4 decreases the free electron density when mixed with Cl2. However, depending on the other gas components, CF4 gas can also sometimes enhance free electron density. This is the case when HBr is added to the mixture. The addition of H2 to the gas mixture will lower the sputtering process, not only due to the lower overall positive ion density at higher H2 fractions, but also because more H+, H2 + and H3 + are present and they have very low sputter yields. In contrast, a larger Cl2 fraction results in more chemical etching but also in less physical sputtering due to a smaller abundance of positive ions. Increasing the O2 fraction in the plasma will always lower the etch rate due to more oxidation of the wafer surface and due to a lower plasma density. However, it is also observed that the density of F atoms can actually increase with rising O2 gas fraction. This is relevant to note because the exact balance between fluorination and oxidation is important for fine-tuning the overall etch rate and for control of the sidewall profile. Finally, HBr is often used as a chemical etcher, but when mixed with F- or Cl-containing gases, HBr creates the same diluting effects as Ar or He, because a
higher fraction results in less chemical etching but more (physical) sputtering.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 5
DOI: 10.1088/0022-3727/49/19/195203
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“Role of vibrationally excited HBr in a HBr/He inductively coupled plasma used for etching of silicon”. Tinck S, Bogaerts A, Journal of physics: D: applied physics 49, 245204 (2016). http://doi.org/10.1088/0022-3727/49/24/245204
Abstract: In this work, the role of vibrationally excited HBr (HBr(vib)) is computationally investigated for a HBr/He inductively coupled plasma applied for Si etching. It is found that at least 50% of all dissociations of HBr occur through HBr(vib). This additional dissociation pathway through HBr(vib) makes the plasma significantly more atomic. It also results in a slightly higher electron temperature (i.e. about 0.2 eV higher compared to simulation results where HBr(vib) is not included), as well as a higher gas temperature (i.e. about 50 K higher than without including HBr(vib)), due to the enhanced Franck–Condon heating through HBr(vib) dissociation,
at the conditions investigated. Most importantly, the calculated etch rate with HBr(vib) included in the model is a factor 3 higher than in the case without HBr(vib), due to the higher fluxes of etching species (i.e. H and Br), while the chemical composition of the wafer surface shows no significant difference. Our calculations clearly show the importance of including HBr(vib) for accurate modeling of HBr-containing plasmas.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
DOI: 10.1088/0022-3727/49/24/245204
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“Elucidating the effects of gas flow rate on an SF6inductively coupled plasma and on the silicon etch rate, by a combined experimental and theoretical investigation”. Tinck S, Tillocher T, Dussart R, Neyts EC, Bogaerts A, Journal of physics: D: applied physics 49, 385201 (2016). http://doi.org/10.1088/0022-3727/49/38/385201
Abstract: Experiments show that the etch rate of Si with SF6 inductively coupled plasma (ICP) is significantly influenced by the absolute gas flow rate in the range of 50–600 sccm, with a maximum at around 200 sccm. Therefore, we numerically investigate the effects of the gas flow rate on the bulk plasma properties and on the etch rate, to obtain more insight in the underlying reasons of this effect. A hybrid Monte Carlo—fluid model is applied to simulate an SF6 ICP. It is found that the etch rate is influenced by two simultaneous effects: (i) the residence time of the gas and (ii) the temperature profile of the plasma in the ICP volume, resulting indeed in a maximum etch rate at 200 sccm.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
Times cited: 1
DOI: 10.1088/0022-3727/49/38/385201
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“Multi-level molecular modelling for plasma medicine”. Bogaerts A, Khosravian N, Van der Paal J, Verlackt CCW, Yusupov M, Kamaraj B, Neyts EC, Journal Of Physics D-Applied Physics 49, 054002 (2016)
Keywords: A1 Journal article; Plasma, laser ablation and surface modeling – Antwerp (PLASMANT)
Impact Factor: 2.588
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“Microwave-assisted synthesis of mesoporous titania with increased crystallinity, specific surface area, and photocatalytic activity”. Meire M, Verbruggen SW, Lenaerts S, Lommens P, Van Der Voort P, Van Driessche I, Journal of materials science 51, 9822 (2016). http://doi.org/10.1007/S10853-016-0215-Y
Abstract: Mesoporous titanium dioxide is a material finding its use in a wide range of applications. For many of these, it is important to achieve a high degree of crystallinity in the material. It is generally accepted that the use of the soft templating approach to synthesize mesoporous titania, results in a compromise between crystallinity and specific surface area due to thermal instability of the used templates. In this paper, we explore how the use of microwave irradiation can influence the crystallinity, specific surface area, and the electronic properties of mesoporous titania. Therefore, we combined microwave radiation with an evaporation-induced self-assembly (EISA) synthesis. We show that additional microwave treatment at carefully chosen synthesis steps can enhance the crystallinity with 20 % without causing significant loss of surface area (>360 m2/g). Surface photovoltage measurements were used to investigate the electronic properties. The photocatalytic activity of the samples was evaluated in aqueous media by following the degradation of an industrial dye, methylene blue, and the herbicide isoproturon under UV irradiation and in gaseous media looking at the degradation of acetaldehyde, a common indoor pollutant under UVA irradiation. In all cases, the microwave treatment results in more active materials.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 2.599
Times cited: 8
DOI: 10.1007/S10853-016-0215-Y
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“Giant magnetic anisotropy in doped single layer molybdenum disulfide and fluorographene”. Sivek J, Sahin H, Partoens B, Peeters FM, Journal of physics : condensed matter 28, 195301 (2016). http://doi.org/10.1088/0953-8984/28/19/195301
Abstract: Stable monolayer materials based on existing, well known and stable two-dimensional crystal fluorographene and molybdenum disulfide are predicted to exhibit a huge magnetocrystalline anisotropy when functionalized with adsorbed transition metal atoms at vacant sides. Ab initio calculations within the density-functional theory formalism were performed to investigate the adsorption of the transitional metals in a single S (or F) vacancy of monolayer molybdenum disulfide (or fluorographene). We found strong bonding of the transitional metal atoms to the vacant sites with binding energies ranging from 2.5 to 5.2 eV. Our calculations revealed that these systems with adsorbed metal atoms exhibit a magnetic anisotropy, specifically the structures including Os and Ir show a giant magnetocrystalline anisotropy energy of 31-101 meV. Our results demonstrate the possibility of obtaining stable monolayer materials with huge magnetocrystalline anisotropy based on preexisting, well known and stable two-dimensional crystals: fluorographene and molybdenum disulfide. We believe that the results obtained here are useful not only for deeper understanding of the origin of magnetocrystalline anisotropy but also for the design of monolayer optoelectronic devices with novel functionalities.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.649
Times cited: 7
DOI: 10.1088/0953-8984/28/19/195301
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