“Simultaneous heteroepitaxial growth of SrO (001) and SrO (111) during strontium-assisted deoxidation of the Si (001) surface”. Jovanović, Z, Gauquelin N, Koster G, Rubio-Zuazo J, Ghosez P, Verbeeck J, Suvorov D, Spreitzer M, Rsc Advances 10, 31261 (2020). http://doi.org/10.1039/D0RA06548J
Abstract: Epitaxial integration of transition-metal oxides with silicon brings a variety of functional properties to the well-established platform of electronic components. In this process, deoxidation and passivation of the silicon surface are one of the most important steps, which in our study were controlled by an ultra-thin layer of SrO and monitored by using transmission electron microscopy (TEM), electron energy-loss spectroscopy (EELS), synchrotron X-ray diffraction (XRD) and reflection high energy electron diffraction (RHEED) methods. Results revealed that an insufficient amount of SrO leads to uneven deoxidation of the silicon surface<italic>i.e.</italic>formation of pits and islands, whereas the composition of the as-formed heterostructure gradually changes from strontium silicide at the interface with silicon, to strontium silicate and SrO in the topmost layer. Epitaxial ordering of SrO, occurring simultaneously with silicon deoxidation, was observed. RHEED analysis has identified that SrO is epitaxially aligned with the (001) Si substrate both with SrO (001) and SrO (111) out-of-plane directions. This observation was discussed from the point of view of SrO desorption, SrO-induced deoxidation of the Si (001) surface and other interfacial reactions as well as structural ordering of deposited SrO. Results of the study present an important milestone in understanding subsequent epitaxial integration of functional oxides with silicon using SrO.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.9
Times cited: 1
DOI: 10.1039/D0RA06548J
|
“Investigation of strain and doping on the electronic properties of single layers of C₆N₆, and C₆N₈: a first principles study”. Bafekry A, Nguyen C V, Goudarzi A, Ghergherehchi M, Shafieirad M, Rsc Advances 10, 27743 (2020). http://doi.org/10.1039/D0RA04463F
Abstract: In this work, by performing first-principles calculations, we explore the effects of various atom impurities on the electronic and magnetic properties of single layers of C(6)N(6)and C6N8. Our results indicate that atom doping may significantly modify the electronic properties. Surprisingly, doping Cr into a holey site of C(6)N(6)monolayer was found to exhibit a narrow band gap of 125 meV upon compression strain, considering the spin-orbit coupling effect. Also, a C atom doped in C(6)N(8)monolayer shows semi-metal nature under compression strains larger than -2%. Our results propose that Mg or Ca doped into strained C(6)N(6)may exhibit small band gaps in the range of 10-30 meV. In addition, a magnetic-to-nonmagnetic phase transition can occur under large tensile strains in the Ca doped C(6)N(8)monolayer. Our results highlight the electronic properties and magnetism of C(6)N(6)and C(6)N(8)monolayers. Our results show that the electronic properties can be effectively modified by atom doping and mechanical strain, thereby offering new possibilities to tailor the electronic and magnetic properties of C(6)N(6)and C(6)N(8)carbon nitride monolayers.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.9
Times cited: 11
DOI: 10.1039/D0RA04463F
|
“The mechanical, electronic, optical and thermoelectric properties of two-dimensional honeycomb-like of XSb (X = Si, Ge, Sn) monolayers: a first-principles calculations”. Bafekry A, Shojai F, Hoat DM, Shahrokhi M, Ghergherehchi M, Nguyen C, Rsc Advances 10, 30398 (2020). http://doi.org/10.1039/D0RA05587E
Abstract: Herein, by using first-principles calculations, we demonstrate a two-dimensional (2D) of XSb (X = Si, Ge, and Sn) monolayers that have a honey-like crystal structure. The structural, mechanical, electronic, thermoelectric efficiency, and optical properties of XSb monolayers are studied.Ab initiomolecular dynamic simulations and phonon dispersion calculations suggests their good thermal and dynamical stabilities. The mechanical properties of XSb monolayers shows that the monolayers are considerably softer than graphene, and their in-plane stiffness decreases from SiSb to SnSb. Our results shows that the single layers of SiSb, GeSb and SnSb are semiconductor with band gap of 1.48, 0.77 and 0.73 eV, respectively. The optical analysis illustrate that the first absorption peaks of the SiSb, GeSb and SnSb monolayers along the in-plane polarization are located in visible range of light which may serve as a promising candidate to design advanced optoelectronic devices. Thermoelectric properties of the XSb monolayers, including Seebeck coefficient, electrical conductivity, electronic thermal conductivity, power factor and figure of merit are calculated as a function of doping level at temperatures of 300 K and 800 K. Between the studied two-dimensional materials (2DM), SiSb single layer may be the most promising candidate for application in the thermoelectric generators.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.9
Times cited: 2
DOI: 10.1039/D0RA05587E
|
“Two-dimensional silicon bismotide (SiBi) monolayer with a honeycomb-like lattice: first-principles study of tuning the electronic properties”. Bafekry A, Shojaei F, Obeid MM, Ghergherehchi M, Nguyen C, Oskouian M, Rsc Advances 10, 31894 (2020). http://doi.org/10.1039/D0RA05026A
Abstract: Using density functional theory, we investigate a novel two-dimensional silicon bismotide (SiBi) that has a layered GaSe-like crystal structure.Ab initiomolecular dynamic simulations and phonon dispersion calculations suggest its good thermal and dynamical stability. The SiBi monolayer is a semiconductor with a narrow indirect bandgap of 0.4 eV. Our results show that the indirect bandgap decreases as the number of layers increases, and when the number of layers is more than six layers, direct-to-indirect bandgap switching occurs. The SiBi bilayer is found to be very sensitive to an E-field. The bandgap monotonically decreases in response to uniaxial and biaxial compressive strain, and reaches 0.2 eV at 5%, while at 6%, the semiconductor becomes a metal. For both uniaxial and biaxial tensile strains, the material remains a semiconductor and indirect-to-direct bandgap transition occurs at a strain of 3%. Compared to a SiBi monolayer with a layer thickness of 4.89 angstrom, the bandgap decreases with either increasing or decreasing layer thickness, and at a thicknesses of 4.59 to 5.01 angstrom, the semiconductor-to-metal transition happens. In addition, under pressure, the semiconducting character of the SiBi bilayer with a 0.25 eV direct bandgap is preserved. Our results demonstrate that the SiBi nanosheet is a promising candidate for designing high-speed low-dissipation devices.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.9
Times cited: 8
DOI: 10.1039/D0RA05026A
|
“KITE : high-performance accurate modelling of electronic structure and response functions of large molecules, disordered crystals and heterostructures”. Joao SM, Andelkovic M, Covaci L, Rappoport TG, Lopes JMVP, Ferreira A, Royal Society Open Science 7, 191809 (2020). http://doi.org/10.1098/RSOS.191809
Abstract: We present KITE, a general purpose open-source tight-binding software for accurate real-space simulations of electronic structure and quantum transport properties of large-scale molecular and condensed systems with tens of billions of atomic orbitals (N similar to 10(10)). KITE's core is written in C++, with a versatile Python-based interface, and is fully optimized for shared memory multi-node CPU architectures, thus scalable, efficient and fast. At the core of KITE is a seamless spectral expansion of lattice Green's functions, which enables large-scale calculations of generic target functions with uniform convergence and fine control over energy resolution. Several functionalities are demonstrated, ranging from simulations of local density of states and photo-emission spectroscopy of disordered materials to large-scale computations of optical conductivity tensors and real-space wave-packet propagation in the presence of magneto-static fields and spin-orbit coupling. On-the-fly calculations of real-space Green's functions are carried out with an efficient domain decomposition technique, allowing KITE to achieve nearly ideal linear scaling in its multi-threading performance. Crystalline defects and disorder, including vacancies, adsorbates and charged impurity centres, can be easily set up with KITE's intuitive interface, paving the way to user-friendly large-scale quantum simulations of equilibrium and non-equilibrium properties of molecules, disordered crystals and heterostructures subject to a variety of perturbations and external conditions.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 3.5
Times cited: 19
DOI: 10.1098/RSOS.191809
|
“Asphalt mixture reinforced with banana fibres”. da Costa LF, de Barros AG, de Figueiredo Lopes Lucena LC, de Figueiredo Lopes Lucena AE, Road Materials And Pavement Design (2020). http://doi.org/10.1080/14680629.2020.1713866
Abstract: Stone Matrix Asphalt (SMA) is a gap-graded mixture which requires high contents of asphalt binder. To prevent draindown, natural or synthetic fibres and polymer-modified asphalt binders are conventionally used in SMA. Banana agribusiness is one of the major sources of post-harvest residue in Brazil. Amongst those residues, fibres extracted from the pseudostem of the banana plant are resistant and used in diverse purposes. The present study assesses the incorporation of fibres from the pseudostem of the banana plant in an SMA mixture. The fibre contents and lengths capable to prevent binder draindown were evaluated from draindown tests. Mechanical properties of an SMA mixture stabilised with different banana fibre lengths were analysed through the tests of Marshall stability, modified Lottman, Indirect Tensile Strength and Cantabro. The results indicated that the fibres studied are a viable alternative for SMA, stabilising draindown and improving its mechanical performance, especially at the length of 20 mm.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT); Energy and Materials in Infrastructure and Buildings (EMIB)
Impact Factor: 3.7
DOI: 10.1080/14680629.2020.1713866
|
“The effect of waste incineration taxation on industrial plastic waste generation: A panel analysis”. De Weerdt L, Sasao T, Compernolle T, Van Passel S, De Jaeger S, Resources Conservation And Recycling 157, 104717 (2020). http://doi.org/10.1016/j.resconrec.2020.104717
Abstract: Waste treatment taxation is a popular policy instrument in many European countries and regions. Its impact on household waste has extensively been researched. However, only little research exists which looks into the impact of waste treatment taxation on industrial waste generation. Nevertheless, industrial waste constitutes more than ninety percent of waste generated in the European Union. This study assesses the impact of an incineration tax on the generation of industrial plastic waste in Flanders, Belgium. We conduct different types of econometrical panel analyzes and provide statistical evidence that firms show lagged behavior, which means that the previous year’s waste generation partly determines the current year’s. The dynamic panel estimations show robust results, indicating that a growth of incineration taxes exert significant negative effects on the growth of industrial plastic waste generation. This result offers no argument to iteratively raise incineration taxes. We conclude that incineration taxation is meaningful if tax rates are set according to the prevailing market conditions, i.e. taking into account the marginal costs of alternatives for incineration. In the short run, the effectiveness of taxation will quickly diminish due to the rapidly rising marginal costs of waste reduction. In the long run, extra recycling capacity is needed to recycle the minimized waste fraction. The role of taxation in the long run is to maintain an equilibrium in which recycling is preferred by the market.
Keywords: A1 Journal Article; Engineering Management (ENM) ;
Impact Factor: 13.2
DOI: 10.1016/j.resconrec.2020.104717
|
“Circular economy as a COVID-19 cure?”.Wuyts W, Marin J, Brusselaers J, Vrancken K, Resources Conservation And Recycling 162, 105016 (2020). http://doi.org/10.1016/J.RESCONREC.2020.105016
Keywords: A1 Journal article; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 13.2
Times cited: 3
DOI: 10.1016/J.RESCONREC.2020.105016
|
“Evaluation of the resource effectiveness of circular economy strategies through multilevel statistical entropy analysis”. Parchomenko A, Nelen D, Gillabel J, Vrancken KCM, Rechberger H, Resources Conservation And Recycling 161, 104925 (2020). http://doi.org/10.1016/J.RESCONREC.2020.104925
Abstract: In a circular economy (CE), materials, components and products should be kept at the highest level of functionality, while phenomena like dilution, mixing and contamination, often referred to as the loss of resources, should be avoided. One method that can assess the performance of systems to concentrate or avoid dilution of resources is Statistical Entropy Analysis (SEA). Up till now, the method has been applied on the substance level (elements and compounds) only, but showed its applicability to various scales and a variety of systems. Further development of the method allowed to consider information on the product, component and material levels, which makes the method applicable to different combinations of CE strategies, both destructive (e.g. recycling) and non-destructive (e.g. reuse). The method is demonstrated on a simplified vehicle life-cycle, which is modeled through four component groups and six materials. It shows that the method allows to evaluate different CE strategies and identify critical stages which lead to the most severe resource and functionality losses. Based on the methods results, it is possible to determine a perfect circularity reference level, representing a system state that preserves functionality and avoids resource losses. The introduction of a circularity reference level enables the establishment of a framework for resource effectiveness in which diluting and concentrating effects of activities (e.g. sorting) are quantified. The distance of a system to an ideal circular state determines the deviation from a resource-effective system that maintains the original product functionality over a maximum period of time, with minimal efforts.
Keywords: A1 Journal article; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 13.2
DOI: 10.1016/J.RESCONREC.2020.104925
|
“A review on learning effects in prospective technology assessment”. Thomassen G, Van Passel S, Dewulf J, Renewable &, Sustainable Energy Reviews 130, 109937 (2020). http://doi.org/10.1016/j.rser.2020.109937
Abstract: Global environmental problems have urged the need for developing sustainable technologies. However, new technologies that enter the market have often higher economic costs and potentially higher environmental impacts than conventional technologies. This can be explained by learning effects: a production process that is performed for the first time runs less smooth than a production process that has been in operation for years. To obtain a fair estimation of the potential of a new technology, learning effects need to be included. A review on the current literature on learning effects was conducted in order to provide guidelines on how to include learning effects in prospective technology assessment. Based on the results of this review, five recommendations have been formulated and an integration of learning effects in the structure of prospective technology assessment has been proposed. These five recommendations include the combined use of learning effects on the component level and on the end product level; the combined use of learning effects on the technical, economic and environmental level; the combined use of extrapolated values and expert estimates; the combined use of learning-by-doing and learning-by-searching effects and; a tier-based method, including quality criteria, to calculate the learning effect. These five complementary strategies could lead to a clearer perspective on the environmental impact and cost structure of the new technology and a fairer comparison base with conventional technologies, potentially resulting in a faster adoption and a shorter time-to-market for sustainable technologies.
Keywords: A1 journal article; Learning effects; Life cycle assessment; Techno-economic assessment; Prospective technology assessment; Learning-by-doing; Learning curve; Progress rate; Experience curve; Engineering Management (ENM) ;
Impact Factor: 15.9
DOI: 10.1016/j.rser.2020.109937
|
“Reliable Characterization of Organic &, Pharmaceutical Compounds with High Resolution Monochromated EEL Spectroscopy”. Das PP, Guzzinati G, Coll C, Gomez Perez A, Nicolopoulos S, Estrade S, Peiro F, Verbeeck J, Zompra AA, Galanis AS, Polymers 12, 1434 (2020). http://doi.org/10.3390/polym12071434
Abstract: Organic and biological compounds (especially those related to the pharmaceutical industry) have always been of great interest for researchers due to their importance for the development of new drugs to diagnose, cure, treat or prevent disease. As many new API (active pharmaceutical ingredients) and their polymorphs are in nanocrystalline or in amorphous form blended with amorphous polymeric matrix (known as amorphous solid dispersion—ASD), their structural identification and characterization at nm scale with conventional X-Ray/Raman/IR techniques becomes difficult. During any API synthesis/production or in the formulated drug product, impurities must be identified and characterized. Electron energy loss spectroscopy (EELS) at high energy resolution by transmission electron microscope (TEM) is expected to be a promising technique to screen and identify the different (organic) compounds used in a typical pharmaceutical or biological system and to detect any impurities present, if any, during the synthesis or formulation process. In this work, we propose the use of monochromated TEM-EELS, to analyze selected peptides and organic compounds and their polymorphs. In order to validate EELS for fingerprinting (in low loss/optical region) and by further correlation with advanced DFT, simulations were utilized.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.364
Times cited: 6
DOI: 10.3390/polym12071434
|
“Chemistry reduction of complex CO2chemical kinetics: application to a gliding arc plasma”. Sun SR, Wang HX, Bogaerts A, Plasma Sources Science &, Technology 29, 025012 (2020). http://doi.org/10.1088/1361-6595/ab540f
Abstract: A gliding arc (GA) plasma has great potential for CO2 conversion into value-added chemicals, because of its high energy efficiency. To improve the application, a 2D/3D fluid model is needed to investigate the CO2 conversion mechanisms in the actual discharge geometry. Therefore, the complex CO2 chemical kinetics description must be reduced due to the huge computational cost associated with 2D/3D models. This paper presents a chemistry reduction method for CO2 plasmas, based on the so-called directed relation graph method. Depending on the defined threshold values, some marginal species are identified. By means of a sensitivity analysis, we can further reduce the chemistry set by removing one by one the marginal species. Based on the socalled flux-sensitivity coupling, we obtain a reduced CO2 kinetics model, consisting of 36 or 15 species (depending on whether the 21 asymmetric mode vibrational states of CO2 are explicitly included or lumped into one group), which is applied to a GA discharge. The results are compared with those predicted with the full chemistry set, and very good agreement is reached. Moreover, the range of validity of the reduced CO2 chemistry set is checked, telling us that this reduced set is suitable for low power GA discharges. Finally, the time and spatial evolution of the CO2 plasma characteristics are presented, based on a 2D model with the reduced kinetics.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.8
DOI: 10.1088/1361-6595/ab540f
|
“Zero-dimensional modeling of unpacked and packed bed dielectric barrier discharges: the role of vibrational kinetics in ammonia synthesis”. van ‘t Veer K, Reniers F, Bogaerts A, Plasma Sources Science &, Technology 29, 045020 (2020). http://doi.org/10.1088/1361-6595/ab7a8a
Abstract: We present a zero-dimensional plasma kinetics model, including both surface and gas phase kinetics, to determine the role of vibrationally excited states in plasma-catalytic ammonia synthesis. We defined a new method to systematically capture the conditions of dielectric barrier discharges (DBDs), including those found in packed bed DBDs. We included the spatial and temporal nature of such discharges by special consideration of the number of micro-discharges in the model. We introduce a parameter that assigns only a part of the plasma power to the microdischarges, to scale the model conditions from filamentary to uniform plasma. Because of the spatial and temporal behaviour of the micro-discharges, not all micro-discharges occurring in the plasma reactor during a certain gas residence time are affecting the molecules. The fraction of power considered in the model ranges from 0.005 %, for filamentary plasma, to 100 %, for uniform plasma. If vibrational excitation is included in the plasma chemistry, these different conditions, however, yield an ammonia density that is only varying within one order of magnitude. At only 0.05 % of the power put into the uniform plasma component, a model neglecting vibrational excitation clearly does not result in adequate amounts of ammonia. Thus, our new model, which accounts for the concept in which not all the power is deposited by the micro-discharges, but some part may also be distributed in between them, suggests that vibrational kinetic processes are really important in (packed bed) DBDs. Indeed, vibrational excitation takes place in both the uniform plasma between the micro-discharges and in the strong micro-discharges, and is responsible for an increased N2 dissociation rate. This is shown here for plasma-catalytic ammonia synthesis, but might also be valid for other gas conversion applications.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.8
DOI: 10.1088/1361-6595/ab7a8a
|
“Multi-dimensional modelling of a magnetically stabilized gliding arc plasma in argon and CO2”. Zhang H, Zhang H, Trenchev G, Li X, Wu Y, Bogaerts A, Plasma Sources Science &, Technology 29, 045019 (2020). http://doi.org/10.1088/1361-6595/ab7cbd
Abstract: This study focuses on a magnetically stabilized gliding arc (MGA) plasma. Two fully coupled flow-plasma models (in 3D and 2D) are presented. The 3D model is applied to compare the arc dynamics of the MGA with a traditional gas-driven gliding arc. The 2D model is used for a detailed parametric study on the effect of the external magnetic field. The results show that the relative velocity between the plasma and feed gas is generated due to the Lorentz force, which can increase the plasma-treated gas fraction. The magnetic field also helps to decrease the gas temperature by enhancing heat transfer and to increase the electron number density. This work shows the potential of an external magnetic field to control the gliding arc behavior, for enhanced gas conversion at low gas flow rates.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.8
DOI: 10.1088/1361-6595/ab7cbd
|
“The effect of H2O on the vibrational populations of CO2in a CO2/H2O microwave plasma: a kinetic modelling investigation”. Verheyen C, Silva T, Guerra V, Bogaerts A, Plasma Sources Science &, Technology 29, 095009 (2020). http://doi.org/10.1088/1361-6595/aba1c8
Abstract: Plasma has been studied for several years to convert CO2 into value-added products. If CO2 could be converted in the presence of H2O as a cheap H-source for making syngas and oxygenates, it would mimic natural photosynthesis. However, CO2/H2O plasmas have not yet been extensively studied, not by experiments, and certainly not computationally. Therefore, we present here a kinetic modelling study to obtain a greater understanding of the vibrational kinetics of a CO2/H2O microwave plasma. For this purpose, we first created an electron impact cross section set for H2O, using a swarm-derived method. We added the new cross section set and CO2/H2O-related chemistry to a pure CO2 model. While it was expected that H2O addition mainly causes quenching of the CO2 asymmetric mode vibrational levels due to the additional CO2/H2O vibrational-translational relaxation, our model shows that the modifications in the vibrational kinetics are mainly induced by the strong electron dissociative attachment to H2O molecules, causing a reduction in electron density, and the corresponding changes in the input of energy into the CO2 vibrational levels by electron impact processes.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.8
DOI: 10.1088/1361-6595/aba1c8
|
“The penetration of reactive oxygen and nitrogen species across the stratum corneum”. Duan J, Ma M, Yusupov M, Cordeiro RM, Lu X, Bogaerts A, Plasma Processes And Polymers (2020). http://doi.org/10.1002/ppap.202000005
Abstract: The penetration of reactive oxygen and nitrogen species (RONS) across the stratum corneum (SC) is a necessary and crucial process in many skin‐related plasma medical applications. To gain more insights into this penetration behavior, we combined experimental measurements of the permeability of dry and moist SC layers with computer simulations of model lipid membranes. We measured the permeation of relatively stable molecules, which are typically generated by plasma, namely H2O2, NO3−, and NO2−. Furthermore, we calculated the permeation free energy profiles of the major plasma‐generated RONS and their derivatives (i.e., H2O2, OH, HO2, O2, O3, NO, NO2, N2O4, HNO2, HNO3, NO2−, and NO3−) across native and oxidized SC lipid bilayers, to understand the mechanisms of RONS permeation across the SC. Our results indicate that hydrophobic RONS (i.e., NO, NO2, O2, O3, and N2O4) can translocate more easily across the SC lipid bilayer than hydrophilic RONS (i.e., H2O2, OH, HO2, HNO2, and HNO3) and ions (i.e., NO2− and NO3−) that experience much higher permeation barriers. The permeability of RONS through the SC skin lipids is enhanced when the skin is moist and the lipids are oxidized. These findings may help to understand the underlying mechanisms of plasma interaction with a biomaterial and to optimize the environmental parameters in practice in plasma medical applications.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.5
DOI: 10.1002/ppap.202000005
|
“H2S Decomposition into H2 and S2 by Plasma Technology: Comparison of Gliding Arc and Microwave Plasma”. Zhang Q-Z, Wang WZ, Thille C, Bogaerts A, Plasma Chemistry And Plasma Processing 40, 1163 (2020). http://doi.org/10.1007/s11090-020-10100-3
Abstract: We studied hydrogen sulfide (H2S) decomposition into hydrogen (H2) and sulfur (S2) in a gliding arc plasmatron (GAP) and microwave (MW) plasma by a combination of 0D and 2D models. The conversion, energy efficiency, and plasma distribution are examined for different discharge conditions, and validated with available experiments from literature. Furthermore, a comparison is made between GAP and MW plasma. The GAP operates at atmospheric pressure, while the MW plasma experiments to which comparison is made were performed at reduced pressure. Indeed, the MW discharge region becomes very much contracted near atmospheric pressure, at the conditions under study, as revealed by our 2D model. The models predict that thermal reactions play the most important role in H2S decomposition in both plasma types. The GAP has a higher energy efficiency but lower conversion than the MW plasma at their typical conditions. When compared at the same conversion, the GAP exhibits a higher energy efficiency and lower energy cost than the MW plasma.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.6
DOI: 10.1007/s11090-020-10100-3
|
“Graphene-like BC₆N single-layer: tunable electronic and magnetic properties via thickness, gating, topological defects, and adatom/molecule”. Bafekry A, Physica E-Low-Dimensional Systems &, Nanostructures 118, 113850 (2020). http://doi.org/10.1016/J.PHYSE.2019.113850
Abstract: By using density functional theory-based first-principles calculations, we investigate the structural, electronic, optical, and transport properties of pristine single-layer BC6N. Under different external actions and functionalization. Increasing the thickness of the structure results in a decrease of the band gap. Applying a perpendicular electric field decreases the band gap and a semiconductor-to-topological insulator transition is revealed. Uniaxial and biaxial strains of +8% result in a semiconductor-to-metal transition. Nanoribbons of BC6N having zigzag edge with even (odd) values of widths, become metal (semiconductor), while the armchair edge nanoribbons exhibit robust semiconducting behavior. In addition, we systematically investigate the effect of surface adatom and molecule, substitutional impurity and defect engineering on the electronic properties of single-layer BC6N and found transitions from metal to half-metal, to ferromagnetic metal, to dilute magnetic semiconductor, and even to spin-glass semiconductor. Furthermore we found that, topological defects including vacancies and Stone–Wales type, induce magnetism in single-layer BC6N.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.3
Times cited: 30
DOI: 10.1016/J.PHYSE.2019.113850
|
“Berry phase engineering at oxide interfaces”. Groenendijk DJ, Autieri C, van Thiel TC, Brzezicki W, Hortensius JR, Afanasiev D, Gauquelin N, Barone P, van den Bos KHW, van Aert S, Verbeeck J, Filippetti A, Picozzi S, Cuoco M, Caviglia AD, 2, 023404 (2020). http://doi.org/10.1103/PhysRevResearch.2.023404
Abstract: Three-dimensional strontium ruthenate (SrRuO3) is an itinerant ferromagnet that features Weyl points acting as sources of emergent magnetic fields, anomalous Hall conductivity, and unconventional spin dynamics. Integrating SrRuO3 in oxide heterostructures is potentially a novel route to engineer emergent electrodynamics, but its electronic band topology in the two-dimensional limit remains unknown. Here we show that ultrathin SrRuO3 exhibits spin-polarized topologically nontrivial bands at the Fermi energy. Their band anticrossings show an enhanced Berry curvature and act as competing sources of emergent magnetic fields. We control their balance by designing heterostructures with symmetric (SrTiO3/SrRuO3/SrTiO3 and SrIrO3/SrRuO3/SrIrO3) and asymmetric interfaces (SrTiO3/SrRuO3/SrIrO3). Symmetric structures exhibit an interface-tunable single-channel anomalous Hall effect, while ultrathin SrRuO3 embedded in asymmetric structures shows humplike features consistent with multiple Hall contributions. The band topology of two-dimensional SrRuO3 proposed here naturally accounts for these observations and harmonizes a large body of experimental results.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 58
DOI: 10.1103/PhysRevResearch.2.023404
|
“Thermal-strain-engineered ferromagnetism of LaMnO3/SrTiO3 heterostructures grown on silicon”. Chen B, Gauquelin N, Reith P, Halisdemir U, Jannis D, Spreitzer M, Huijben M, Abel S, Fompeyrine J, Verbeeck J, Hilgenkamp H, Rijnders G, Koster G, Physical review materials 4, 024406 (2020). http://doi.org/10.1103/PhysRevMaterials.4.024406
Abstract: The integration of oxides on Si remains challenging, which largely hampers the practical applications of oxide-based electronic devices with superior performance. Recently, LaMnO3/SrTiO3 (LMO/STO) heterostructures have gained renewed interest for the debating origin of the ferromagnetic-insulating ground state as well as for their spin-filter applications. Here we report on the structural and magnetic properties of high-quality LMO/STO heterostructures grown on silicon. The chemical abruptness across the interface was investigated by atomic-resolution scanning transmission electron microscopy. The difference in the thermal expansion coefficients between LMO and Si imposed a large biaxial tensile strain to the LMO film, resulting in a tetragonal structure with c/a∼ 0.983. Consequently, we observed a significantly suppressed ferromagnetism along with an enhanced coercive field, as compared to the less distorted LMO film (c/a∼1.004) grown on STO single crystal. The results are discussed in terms of tensile-strain enhanced antiferromagnetic instabilities. Moreover, the ferromagnetism of LMO on Si sharply disappeared below a thickness of 5 unit cells, in agreement with the LMO/STO case, pointing to a robust critical behavior irrespective of the strain state. Our results demonstrate that the growth of oxide films on Si can be a promising way to study the tensile-strain effects in correlated oxides, and also pave the way towards the integration of multifunctional oxides on Si with atomic-layer control.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.4
Times cited: 6
DOI: 10.1103/PhysRevMaterials.4.024406
|
“Co valence transformation in isopolar LaCoO3/LaTiO3 perovskite heterostructures via interfacial engineering”. Araizi-Kanoutas G, Geessinck J, Gauquelin N, Smit S, Verbeek XH, Mishra SK, Bencok P, Schlueter C, Lee T-L, Krishnan D, Fatermans J, Verbeeck J, Rijnders G, Koster G, Golden MS, Physical review materials 4, 026001 (2020). http://doi.org/10.1103/PhysRevMaterials.4.026001
Abstract: We report charge transfer up to a single electron per interfacial unit cell across nonpolar heterointerfaces from the Mott insulator LaTiO3 to the charge transfer insulator LaCoO3. In high-quality bi- and trilayer systems grown using pulsed laser deposition, soft x-ray absorption, dichroism, and scanning transmission electron microscopy-electron energy loss spectroscopy are used to probe the cobalt-3d electron count and provide an element-specific investigation of the magnetic properties. The experiments show the cobalt valence conversion is active within 3 unit cells of the heterointerface, and able to generate full conversion to 3d7 divalent Co, which displays a paramagnetic ground state. The number of LaTiO3/LaCoO3 interfaces, the thickness of an additional, electronically insulating “break” layer between the LaTiO3 and LaCoO3, and the LaCoO3 film thickness itself in trilayers provide a trio of control knobs for average charge of the cobalt ions in LaCoO3, illustrating the efficacy of O−2p band alignment as a guiding principle for property design in complex oxide heterointerfaces.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.4
Times cited: 13
DOI: 10.1103/PhysRevMaterials.4.026001
|
“On the importance of the work function and electron carrier density of oxide electrodes for the functional properties of ferroelectric capacitors”. Wang J, Nguyen MD, Gauquelin N, Verbeeck J, Do MT, Koster G, Rijnders G, Houwman E, Physica Status Solidi-Rapid Research Letters 14, 1900520 (2020). http://doi.org/10.1002/PSSR.201900520
Abstract: It is important to understand the effect of the interfaces between the oxide electrode layers and the ferroelectric layer on the polarization response for optimizing the device performance of all-oxide ferroelectric devices. Herein, the effects of the oxide La0.07Ba0.93SnO3 (LBSO) as an electrode material in an PbZr0.52Ti0.48O3 (PZT) ferroelectric capacitor are compared with those of the more commonly used SrRuO3 (SRO) electrode. SRO (top)/PZT/SRO (bottom), SRO/PZT/LBSO, and SRO/PZT/2 nm SRO/LBSO devices are fabricated. Only marginal differences in crystalline properties, determined by X-ray diffraction and scanning transmission electron microscopy, are found. High-quality polarization loops are obtained, but with a much larger coercive field for the SRO/PZT/LBSO device. In contrast to the SRO/PZT/SRO device, the polarization decreases strongly with increasing field cycling. This fatigue problem can be remedied by inserting a 2 nm SRO layer between PZT and LBSO. It is argued that strongly increased charge injection into the PZT occurs at the bottom interface, because of the low PZT/LBSO interfacial barrier and the much lower carrier density in LBSO, as compared with that in SRO, causing a low dielectric constant, depleted layer in LBSO. The charge injection creates a trapped space charge in the PZT, causing the difference in fatigue behavior.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.8
Times cited: 6
DOI: 10.1002/PSSR.201900520
|
“Ovonic threshold-switching GexSey chalcogenide materials : stoichiometry, trap nature, and material relaxation from first principles”. Clima S, Garbin D, Opsomer K, Avasarala NS, Devulder W, Shlyakhov I, Keukelier J, Donadio GL, Witters T, Kundu S, Govoreanu B, Goux L, Detavernier C, Afanas'ev V, Kar GS, Pourtois G, Physica Status Solidi-Rapid Research Letters , 1900672 (2020). http://doi.org/10.1002/PSSR.201900672
Abstract: Density functional theory simulations are used to identify the structural factors that define the material properties of ovonic threshold switches (OTS). They show that the nature of mobility-gap trap states in amorphous Ge-rich Ge50Se50 is related to Ge-Ge bonds, whereas in Se-rich Ge30Se70 the Ge valence-alternating-pairs and Se lone-pairs dominate. To obtain a faithful description of the electronic structure and delocalization of states, it is required to combine hybrid exchange-correlation functionals with large unit-cell models. The extent of localization of electronic states depends on the applied external electric field. Hence, OTS materials undergo structural changes during electrical cycling of the device, with a decrease in the population of less exothermic Ge-Ge bonds in favor of more exothermic Ge-Se. This reduces the amount of charge traps, which translates into coordination changes, an increase in mobility-gap, and subsequently changes in the selector-device electrical parameters. The threshold voltage drift process can be explained by natural evolution of the nonpreferred Ge-Ge bonds (or “chains”/clusters thereof) in Ge-rich GexSe1-x. The effect of extrinsic doping is shown for Si and N, which introduce strong covalent bonds into the system, increase both mobility-gap and crystallization temperature, and decrease the leakage current.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.8
Times cited: 3
DOI: 10.1002/PSSR.201900672
|
“The electronic, optical, and thermoelectric properties of monolayer PbTe and the tunability of the electronic structure by external fields and defects”. Bafekry A, Stampfl C, Peeters FM, Physica Status Solidi B-Basic Solid State Physics , 2000182 (2020). http://doi.org/10.1002/PSSB.202000182
Abstract: First‐principles calculations, within the framework of density functional theory, are used to investigate the structural, electronic, optical, and thermoelectric properties of monolayer PbTe. The effect of layer thickness, electric field, strain, and vacancy defects on the electronic and magnetic properties is systematically studied. The results show that the bandgap decreases as the layer thickness increases from monolayer to bulk. With application of an electric field on bilayer PbTe, the bandgap decreases from 70 meV (0.2 V Å⁻¹) to 50 meV (1 V Å⁻¹) when including spin–orbit coupling (SOC). Application of uniaxial strain induces a direct‐to‐indirect bandgap transition for strain greater than +6%. In addition, the bandgap decreases under compressive biaxial strain (with SOC). The effect of vacancy defects on the electronic properties of PbTe is also investigated. Such vacancy defects turn PbTe into a ferromagnetic metal (single vacancy Pb) with a magnetic moment of 1.3 μB, and into an indirect semiconductor with bandgap of 1.2 eV (single Te vacancy) and 1.5 eV (double Pb + Te vacancy). In addition, with change of the Te vacancy concentration, a bandgap of 0.38 eV (5.55%), 0.43 eV (8.33%), and 0.46 eV (11.11%) is predicted.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.6
Times cited: 40
DOI: 10.1002/PSSB.202000182
|
“Oxygen vacancies in the single layer of Ti₂CO₂, MXene: effects of gating voltage, mechanical strain, and atomic impurities”. Bafekry A, Van Nguyen C, Stampfl C, Akgenc B, Ghergherehchi M, Physica Status Solidi B-Basic Solid State Physics , 2000343 (2020). http://doi.org/10.1002/PSSB.202000343
Abstract: Herein, using first-principles calculations the structural and electronic properties of the Ti(2)CO(2)MXene monolayer with and without oxygen vacancies are systematically investigated with different defect concentrations and patterns, including partial, linear, local, and hexagonal types. The Ti(2)CO(2)monolayer is found to be a semiconductor with a bandgap of 0.35 eV. The introduction of oxygen vacancies tends to increase the bandgap and leads to electronic phase transitions from nonmagnetic semiconductors to half-metals. Moreover, the semiconducting characteristic of O-vacancy Ti(2)CO(2)can be adjusted via electric fields, strain, and F-atom substitution. In particular, an electric field can be used to alter the nonmagnetic semiconductor of O-vacancy Ti(2)CO(2)into a magnetic one or into a half-metal, whereas the electronic phase transition from a semiconductor to metal can be achieved by applying strain and F-atom substitution. The results provide a useful guide for practical applications of O-vacancy Ti(2)CO(2)monolayers in nanoelectronic and spinstronic nanodevices.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.6
DOI: 10.1002/PSSB.202000343
|
“Measuring Dynamic Structural Changes of Nanoparticles at the Atomic Scale Using Scanning Transmission Electron Microscopy”. De wael A, De Backer A, Jones L, Varambhia A, Nellist PD, Van Aert S, Physical Review Letters 124, 106105 (2020). http://doi.org/10.1103/PhysRevLett.124.106105
Abstract: We propose a new method to measure atomic scale dynamics of nanoparticles from experimental high-resolution annular dark field scanning transmission electron microscopy images. By using the so-called hidden Markov model, which explicitly models the possibility of structural changes, the number of atoms in each atomic column can be quantified over time. This newly proposed method outperforms the current atom-counting procedure and enables the determination of the probabilities and cross sections for surface diffusion. This method is therefore of great importance for revealing and quantifying the atomic structure when it evolves over time via adatom dynamics, surface diffusion, beam effects, or during in situ experiments.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 8.6
DOI: 10.1103/PhysRevLett.124.106105
|
“Secondary-Phase-Assisted Grain Boundary Migration in CuInSe2”. Li C, Sanli ES, Barragan-Yani D, Stange H, Heinemann M-D, Greiner D, Sigle W, Mainz R, Albe K, Abou-Ras D, van Aken P A, Physical Review Letters 124, 095702 (2020). http://doi.org/10.1103/PhysRevLett.124.095702
Abstract: Significant structural evolution occurs during the deposition of CuInSe2 solar materials when the Cu content increases. We use in situ heating in a scanning transmission electron microscope to directly observe how grain boundaries migrate during heating, causing nondefected grains to consume highly defected grains. Cu substitutes for In in the near grain boundary regions, turning them into a Cu-Se phase topotactic with the CuInSe2 grain interiors. Together with density functional theory and molecular dynamics calculations, we reveal how this Cu-Se phase makes the grain boundaries highly mobile.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 8.6
DOI: 10.1103/PhysRevLett.124.095702
|
“Boosting Monte Carlo simulations of spin glasses using autoregressive neural networks”. McNaughton B, Milošević, MV, Perali A, Pilati S, Physical Review E 101, 053312 (2020). http://doi.org/10.1103/PHYSREVE.101.053312
Abstract: The autoregressive neural networks are emerging as a powerful computational tool to solve relevant problems in classical and quantum mechanics. One of their appealing functionalities is that, after they have learned a probability distribution from a dataset, they allow exact and efficient sampling of typical system configurations. Here we employ a neural autoregressive distribution estimator (NADE) to boost Markov chain Monte Carlo (MCMC) simulations of a paradigmatic classical model of spin-glass theory, namely, the two-dimensional Edwards-Anderson Hamiltonian. We show that a NADE can be trained to accurately mimic the Boltzmann distribution using unsupervised learning from system configurations generated using standard MCMC algorithms. The trained NADE is then employed as smart proposal distribution for the Metropolis-Hastings algorithm. This allows us to perform efficient MCMC simulations, which provide unbiased results even if the expectation value corresponding to the probability distribution learned by the NADE is not exact. Notably, we implement a sequential tempering procedure, whereby a NADE trained at a higher temperature is iteratively employed as proposal distribution in a MCMC simulation run at a slightly lower temperature. This allows one to efficiently simulate the spin-glass model even in the low-temperature regime, avoiding the divergent correlation times that plague MCMC simulations driven by local-update algorithms. Furthermore, we show that the NADE-driven simulations quickly sample ground-state configurations, paving the way to their future utilization to tackle binary optimization problems.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.366
Times cited: 15
DOI: 10.1103/PHYSREVE.101.053312
|
“Out-of-plane permittivity of confined water”. Jalali H, Ghorbanfekr H, Hamid I, Neek-Amal M, Rashidi R, Peeters FM, Physical Review E 102, 022803 (2020). http://doi.org/10.1103/PHYSREVE.102.022803
Abstract: The dielectric properties of confined water is of fundamental interest and is still controversial. For water confined in channels with height smaller than h = 8 angstrom, we found a commensurability effect and an extraordinary decrease in the out-of-plane dielectric constant down to the limit of the dielectric constant of optical water. Spatial resolved polarization density data obtained from molecular dynamics simulations are found to be antisymmetric across the channel and are used as input in a mean-field model for the dielectric constant as a function of the height of the channel for h > 15 angstrom. Our results are in excellent agreement with a recent experiment [L. Fumagalli et al., Science 360, 1339 (2018)].
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.366
Times cited: 38
DOI: 10.1103/PHYSREVE.102.022803
|
“Ab initio methodology for magnetic exchange parameters: Generic four-state energy mapping onto a Heisenberg spin Hamiltonian”. Sabani D, Bacaksiz C, Milošević, MV, Physical Review B 102, 014457 (2020). http://doi.org/10.1103/PHYSREVB.102.014457
Abstract: The recent development in the field of two-dimensional magnetic materials urges reliable theoretical methodology for determination of magnetic properties. Among the available methods, ab initio four-state energy mapping based on density functional theory stands out as a powerful technique to calculate the magnetic exchange interaction in the Heisenberg spin model. Although the required formulas were explained in earlier works, the considered Hamiltonian in those studies always corresponded to the specific case that the off-diagonal part of J matrix is antisymmetric, which may be misleading in other cases. Therefore, using the most general form of the Heisenberg spin Hamiltonian, we here derive the generic formulas. With a proper choice of four different magnetic states, a single formula governs all elements of the exchange interaction matrix for any considered pair of spin sites.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.7
Times cited: 13
DOI: 10.1103/PHYSREVB.102.014457
|