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Zhang Z, Lobato I, Brown H, Jannis D, Verbeeck J, Van Aert S, Nellist P (2023) Generalised oscillator strength for core-shell electron excitation by fast electrons based on Dirac solutions
Abstract: Inelastic excitation as exploited in Electron Energy Loss Spectroscopy (EELS) contains a rich source of information that is revealed in the scattering process. To accurately quantify core-loss EELS, it is common practice to fit the observed spectrum with scattering cross-sections calculated using experimental parameters and a Generalized Oscillator Strength (GOS) database [1]. The GOS is computed using Fermi’s Golden Rule and orbitals of bound and excited states. Previously, the GOS was based on Hartree-Fock solutions [2], but more recently Density Functional Theory (DFT) has been used [3]. In this work, we have chosen to use the Dirac equation to incorporate relativistic effects and have performed calculations using Flexible Atomic Code (FAC) [4]. This repository contains a tabulated GOS database based on Dirac solutions for computing double differential cross-sections under experimental conditions. We hope the Dirac-based GOS database can benefit the EELS community for both academic use and industry integration. Database Details: – Covers all elements (Z: 1-108) and all edges – Large energy range: 0.01 – 4000 eV – Large momentum range: 0.05 -50 Å-1 – Fine log sampling: 128 points for energy and 256 points for momentum – Data format: GOSH [3] Calculation Details: – Single atoms only; solid-state effects are not considered – Unoccupied states before continuum states of ionization are not considered; no fine structure – Plane Wave Born Approximation – Frozen Core Approximation is employed; electrostatic potential remains unchanged for orthogonal states when – core-shell electron is excited – Self-consistent Dirac–Fock–Slater iteration is used for Dirac calculations; Local Density Approximation is assumed for electron exchange interactions; continuum states are normalized against asymptotic form at large distances – Both large and small component contributions of Dirac solutions are included in GOS – Final state contributions are included until the contribution of the previous three states falls below 0.1%. A convergence log is provided for reference. Version 1.1 release note: – Update to be consistent with GOSH data format [3], all the edges are now within a single hdf5 file. A notable change in particular, the sampling in momentum is in 1/m, instead of previously in 1/Å. Great thanks to Gulio Guzzinati for his suggestions and sending conversion script. Version 1.2 release note: – Add “File Type / File version” information [1] Verbeeck, J., and S. Van Aert. Ultramicroscopy 101.2-4 (2004): 207-224. [2] Leapman, R. D., P. Rez, and D. F. Mayers. The Journal of Chemical Physics 72.2 (1980): 1232-1243. [3] Segger, L, Guzzinati, G, & Kohl, H. Zenodo (2023). doi:10.5281/zenodo.7645765 [4] Gu, M. F. Canadian Journal of Physics 86(5) (2008): 675-689.
Keywords: Dataset; Electron microscopy for materials research (EMAT)
DOI: 10.5281/ZENODO.8360240
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Grü,newald L, Chezganov D, De Meyer R, Orekhov A, Van Aert S, Bogaerts A, Bals S, Verbeeck J (2023) Supplementary Information for “In-situ Plasma Studies using a Direct Current Microplasma in a Scanning Electron Microscope”
Abstract: Supplementary information for the article “In-situ Plasma Studies using a Direct Current Microplasma in a Scanning Electron Microscope” containing the videos of in-situ SEM imaging (mp4 files), raw data/images, and Jupyter notebooks (ipynb files) for data treatment and plots. Link to the preprint: https://doi.org/10.48550/arXiv.2308.15123 Explanation of the data files can be found in the Information.pdf file. The Videos folder contains the in-situ SEM image series mentioned in the paper. If there are any questions/bugs, feel free to contact me at lukas.grunewaldatuantwerpen.be
Keywords: Dataset; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
DOI: 10.5281/ZENODO.8042030
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Annys A, Jannis D, Verbeeck J (2023) Core-loss EELS dataset and neural networks for element identification
Abstract: We present a large dataset containing simulated core-loss electron energy loss spectroscopy (EELS) spectra with the elemental content as ground-truth labels. Additionally we present some neural networks trained on this data for element identification. The simulated dataset contains zero padded core-loss spectra from 0 to 3072 eV, which represents 107 core-loss edges through all 80 elements from Be up to Bi. The core-loss edges are calculated from the generalised oscillator strength (GOS) database presented by Zhang et al.[1] Generic fine structures using lifetime broadened peaks are used to imitate fine structure due to solid-state effects in experimental spectra. Generic low-loss regions are used to imitate the effect of multiple scattering. Each spectrum contains at least one edge of a given query element and possibly additional edges depending on samples drawn from The Materials Project [2]. The dataset contains for each of the 80 elements: 7000 training spectra, 1500 test spectra, 600 validation spectra and 100 spectra representing only the query element. This results in a total 736 000 labeled spectra. Code on how to – read the simulated data – transform HDF5 format to TFRecord format – train and evaluate neural networks using the simulated data – use the trained networks for automated element identification is available on GitHub at arnoannys/EELS_ID A full report on the simulation of the dataset and the training and evaluation of the neural networks can be found at: Annys, A., Jannis, D. & Verbeeck, J. Deep learning for automated materials characterisation in core-loss electron energy loss spectroscopy. Sci Rep 13, 13724 (2023). https://doi.org/10.1038/s41598-023-40943-7 [1] Zezhong Zhang, Ivan Lobato, Daen Jannis, Johan Verbeeck, Sandra Van Aert, & Peter Nellist. (2023). Generalised oscillator strength for core-shell electron excitation by fast electrons based on Dirac solutions (1.0) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.7729585 [2] Anubhav Jain, Shyue Ping Ong, Geoffroy Hautier, Wei Chen, William Davidson Richards, Stephen Dacek, Shreyas Cholia, Dan Gunter, David Skinner, Gerbrand Ceder, Kristin A. Persson; Commentary: The Materials Project: A materials genome approach to accelerating materials innovation. APL Mater 1 July 2013; 1 (1): 011002. [https://doi.org/10.1063/1.4812323](https://doi.org/10.1063/1.4812323)
Keywords: Dataset; Electron microscopy for materials research (EMAT)
DOI: 10.5281/ZENODO.8004912
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Guzzinati G, Das PP, Zompra A A., Nicopoulos S, Verbeeck J (2020) Electron energy loss spectra of several organic compounds
Abstract: We placed crystals of different compounds to explore the possibility of fingerprinting them through EELS. Here are representative datasets of 7 different compounds: b-cyclodextrin hexacarboxy cyclohexane tannin TH-15 peptide TH-27 peptide two different forms of piroxicam The datasets were collected at EMAT, using a monochromated FEI Titan3 TEM, within the scope of an EUSMI request. More information as well as analysis methodologies adopted for the data are detailed in the paper: Das et al. “Reliable Characterization of Organic & Pharmaceutical Compounds with High Resolution Monochromated EEL Spectroscopy”, Polymers 2020, 12(7), 1434.
Keywords: Dataset; Electron microscopy for materials research (EMAT)
DOI: 10.5281/zenodo.3975761
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Guzzinati G, Bé,ché, A, McGrouther D, Verbeeck J (2019) Rotation of electron beams in the presence of localised, longitudinal magnetic fields
Abstract: Electron Bessel beams have been generated by inserting an annular aperture in the illumination system of a TEM. These beams have passed through a localised magnetic field. As a result a low amount of image rotation (which is expected to be proportional to the longitudinal component of the magnetic field) is observed in the far field. A measure of this rotation should give access to the magneti field. The two datasets have been acquired in a FEI Titan3 microscope, operated at 300kV. The file focalseries.tif contains a series of images acquired varying the magnetic field through the objective lens. The file lineprofile.ser contains a series of images acquired by scanning the beam over a sample with several magnetised nanopillars. For reference, check the associated publication.
Keywords: Dataset; Electron microscopy for materials research (EMAT)
DOI: 10.5281/ZENODO.3232898
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Guzzinati G, Ghielens W, Mahr C, Bé,ché, A, Rosenauer A, Calders T, Verbeeck J (2019) Electron Bessel beam diffraction patterns, line scan of Si/SiGe multilayer
Keywords: Dataset; ADReM Data Lab (ADReM); Electron microscopy for materials research (EMAT)
DOI: 10.5281/ZENODO.2566137
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Jannis D, Mü,ller-Caspary K, Bé,ché, A, Oelsner A, Verbeeck J (2019) Spectrocopic coincidence experiment in transmission electron microscopy
Abstract: This dataset contains individual EEL and EDX events where for every event (electron or X-ray), their energy and time of arrival is stored. The experiment was performed in a transmission electron microscope (Tecnai Osiris) at 200 keV. The material investigated is an Al-Mg-Si-Cu alloy. The 'full_dataset.mat' contains the full dataset and the 'subset.mat' has the first five frames of the full dataset. The attached 'EELS-EDX.ipynb' is a jupyter notebook file. This file describes the data processing in order to observe the temporal correlation between the electrons and X-rays.
Keywords: Dataset; Electron microscopy for materials research (EMAT)
DOI: 10.5281/ZENODO.2563880
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“Fabrication, microstructure, and enhanced thermionic electron emission properties of vertically aligned nitrogen-doped nanocrystalline diamond nanorods”. Sankaran KJ, Deshmukh S, Korneychuk S, Yeh C-J, Thomas JP, Drijkoningen S, Pobedinskas P, Van Bael MK, Verbeeck J, Leou K-C, Leung K-T, Roy SS, Lin I-N, Haenen K, MRS communications 8, 1311 (2018). http://doi.org/10.1557/MRC.2018.158
Abstract: Vertically aligned nitrogen-doped nanocrystalline diamond nanorods are fabricated from nitrogen-doped nanocrystalline diamond films using reactive ion etching in oxygen plasma. These nanorods show enhanced thermionic electron emission (TEE) characteristics, viz.. a high current density of 12.0 mA/cm(2) and a work function value of 4.5 eV with an applied voltage of 3 Vat 923 K. The enhanced TEE characteristics of these nanorods are ascribed to the induction of nanographitic phases at the grain boundaries and the field penetration effect through the local field enhancement from nanorods owing to a high aspect ratio and an excellent field enhancement factor.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.01
Times cited: 1
DOI: 10.1557/MRC.2018.158
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“Orthorhombic vs. hexagonal epitaxial SrIrO3 thin films : structural stability and related electrical transport properties”. Bhat SG, Gauquelin N, Sebastian NK, Sil A, Béché, A, Verbeeck J, Samal D, Kumar PSA, Europhysics letters 122, 28003 (2018). http://doi.org/10.1209/0295-5075/122/28003
Abstract: Metastable orthorhombic SrIrO3 (SIO) is an arch-type spin-orbit coupled material. We demonstrate here a controlled growth of relatively thick (200 nm) SIO films that transform from bulk “6H-type” structure with monoclinic distortion to an orthorhombic lattice by controlling growth temperature. Extensive studies based on high-resolution X-ray diffraction and transmission electron microscopy infer a two distinct structural phases of SIO. Electrical transport reveals a weak temperature-dependent semi-metallic character for both phases. However, the temperature-dependent Hall-coefficient for the orthorhombic SIO exhibits a prominent sign change, suggesting a multiband character in the vicinity of E-F. Our findings thus unravel the subtle structure-property relation in SIO epitaxial thin films. Copyright (C) EPLA, 2018
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.957
Times cited: 4
DOI: 10.1209/0295-5075/122/28003
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“Fe and Co nanowires and nanotubes synthesized by template electrodeposition: a HRTEM and EELS study”. Verbeeck J, Lebedev OI, Van Tendeloo G, Cagnon L, Bougerol C, Tourillon T, Journal of the electrochemical society 150, E468 (2003). http://doi.org/10.1149/1.1601230
Abstract: Co and Fe nanowires and/or nanotubes are electrochemically synthesized through nanoporous membranes. By combining high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), and energy filtered TEM techniques, their structural and crystallographic characteristics are precisely determined. The synthesis was shown to produce cigar-shaped single monocrystalline Co and Fe nanowires with a diameter of about 60 nm. All wires were surrounded by an epitaxial oxide layer (Co3O4 or Fe3O4) of roughly 10 nm. The Fe nanotubes were built up of Fe3O4 nanocrystals. Electron diffraction showed that all nanocrystals had a common crystallographic axis, creating a pseudomonocrystalline wall in the nanotubes. (C) 2003 The Electrochemical Society.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.259
Times cited: 41
DOI: 10.1149/1.1601230
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“Quantitative electron microscopy of (Bi,Pb)2Sr2Ca2Cu3O10+\delta/Ag multifilament tapes during initial stages of annealing”. Bals S, Verbeeck J, Van Tendeloo G, Liu Y-L, Grivel J-C, Journal of the American Ceramic Society 88, 431 (2005). http://doi.org/10.1111/j.1551-2916.2005.00094.x
Abstract: The microstructural and compositional evolution during initial annealing of a superconducting (Bi,Pb)(2)Sr2Ca2Cu3O10+delta/Ag tape is studied using quantitative transmission electron microscopy. Special attention is devoted to the occurrence of Pb-rich liquids, which are crucial for the Bi2Sr2CaCu2O8+delta to (Bi,Pb)(2)Sr2Ca2Cu3O10+delta transformation. Ca and/or Pb-rich (Bi,Pb)(2)Sr2CaCu2O8+delta grains dissolve into a liquid, which reacts with Ca-rich phases to increase the liquid's Ca-content. This leads to (Bi,Pb)(2)Sr2Ca2Cu3O10+delta formation. Apparently, a Ca/Sr ratio of around I is sufficient to keep (Bi,Pb)(2)Sr2Ca2Cu3O10+delta nucleation going. It is confirmed that Ag particles are transported from the Ag-sheath into the oxide core by the liquid and not by mechanical treatment of the tape.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.841
Times cited: 1
DOI: 10.1111/j.1551-2916.2005.00094.x
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“Getting rid of anti-solvents: gas quenching for high performance perovskite solar cells”. Conings B, Babayigit A, Klug M, Bai S, Gauquelin N, Sakai N, Wang JT-W, Verbeeck J, Boyen H-G, Snaith H, 2018 Ieee 7th World Conference On Photovoltaic Energy Conversion (wcpec)(a Joint Conference Of 45th Ieee Pvsc, 28th Pvsec &, 34th Eu Pvsec) (2018). http://doi.org/10.1109/PVSC.2018.8547987
Abstract: As the field of perovskite optoelectronics developed, a plethora of strategies has arisen to control their electronic and morphological characteristics for the purpose of producing high efficiency devices. Unfortunately, despite this wealth of deposition approaches, the community experiences a great deal of irreproducibility between different laboratories, batches and preparation methods. Aiming to address this issue, we developed a simple deposition method based on gas quenching that yields smooth films for a wide range of perovskite compositions, in single, double, triple and quadruple cation varieties, and produces planar heterojunction devices with competitive efficiencies, so far up to 20%.
Keywords: P1 Proceeding; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
DOI: 10.1109/PVSC.2018.8547987
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“Retrieving the dielectric function of diamond from valence electron energy-loss spectroscopy”. Zhang L, Erni R, Verbeeck J, Van Tendeloo G, Physical review : B : condensed matter and materials physics 77, 195119 (2008). http://doi.org/10.1103/PhysRevB.77.195119
Abstract: A data-acquisition and data-processing method is proposed that aims at minimizing the effect of retardation on the Kramers-Kronig analysis of valence electron energy-loss spectra. This method is applied to diamond, which, due to its high dielectric constant, is a material that shows strong retardation effects and thus is a challenging material to be studied by valence electron energy-loss spectroscopy. The results obtained show a significant improvement but still show small discrepancies with respect to optical data, which are most likely due to the residual retardation contributions and the fact that nonzero momentum transfers are measured.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 16
DOI: 10.1103/PhysRevB.77.195119
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“Influence of finite size effects on exchange anisotropy in oxidized Co nanocluster assembled films”. Dobrynin AN, Ievlev DN, Hendrich C, Temst K, Lievens P, Hörmann U, Verbeeck J, Van Tendeloo G, Vantomme A, Physical review : B : condensed matter and materials physics 73, 245416 (2006). http://doi.org/10.1103/PhysRevB.73.245416
Abstract: We compare the magnetic properties of Co cluster assembled films with different degrees of oxidation. Clusters with grain size (2.3 +/- 0.7) nm are produced in a laser vaporization cluster source and soft-landed in ultrahigh vacuum conditions, forming highly porous nanogranular films. After exposure to air for different periods of time, the Co clusters oxidize and the sample may be considered as a thin antiferromagnetic Co oxide matrix containing ferromagnetic Co clusters. Magnetization measurements were performed in a temperature range from 300 down to 5 K, at applied magnetic fields up to 30 kOe. The exchange bias value at 5 K for the strongly oxidized sample is 4.8 kOe against the value of 0.75 kOe for the less oxidized sample. The mean values of the thicknesses of the Co oxide layers are estimated to be 0.6 and 0.3 nm for the more and less oxidized sample, respectively. We propose a method of measuring the exchange bias inducing temperature, i.e., the temperature at which exchange anisotropy is established. We determined the mean inducing temperatures for both samples, which are 55 and 25 K, respectively, for the more and less oxidized samples. Both temperatures are well below the bulk CoO Neel temperature of 292 K. A low value of the inducing temperature of the Co oxide layer is a consequence of its subnanometer thickness, while a large exchange bias value is a consequence of different dimensionality of Co clusters and Co oxide matrix.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 17
DOI: 10.1103/PhysRevB.73.245416
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“Structural phase transitions and stress accommodation in (La0.67Ca0.33MnO3)1.x:(MgO)x composite films”. Lebedev OI, Verbeeck J, Van Tendeloo G, Shapoval O, Belenchuk A, Moshnyaga V, Damaschke B, Samwer K, Physical review : B : condensed matter and materials physics 66, 104421 (2002). http://doi.org/10.1103/PhysRevB.66.104421
Abstract: Composite (La0.67Ca0.33MnO3)(1-x):(MgO)(x) films were prepared by metalorganic aerosol deposition on a (100)MgO substrate for different concentrations of the (MgO) phase (0less than or equal toxless than or equal to0.8). At xapproximate to0.3 a percolation threshold in conductivity is reached, at which an infinite insulating MgO cluster forms around the La0.67Ca0.33MnO3 grains. This yields a drastic increase of the electrical resistance for films with x>0.3. The film structure is characterized by x-ray diffraction and transmission electron microscopy. The local structure of the La0.67Ca0.33MnO3 within the film depends on the MgO concentration which grows epitaxially along the domain boundaries. A different structural phase transition from the orthorhombic Pnma structure to an unusual rhombohedral R (3) over barc structure at the percolation threshold xapproximate to0.3 is found for La0.67Ca0.33MnO3. A three-dimensional stress accommodation in thick films through a phase transition is suggested.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 48
DOI: 10.1103/PhysRevB.66.104421
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“Roadmap on structured waves”. Bliokh KY, Karimi E, Padgett MJ, Alonso MA, Dennis MR, Dudley A, Forbes A, Zahedpour S, Hancock SW, Milchberg HM, Rotter S, Nori F, Ozdemir SK, Bender N, Cao H, Corkum PB, Hernandez-Garcia C, Ren H, Kivshar Y, Silveirinha MG, Engheta N, Rauschenbeutel A, Schneeweiss P, Volz J, Leykam D, Smirnova DA, Rong K, Wang B, Hasman E, Picardi MF, Zayats AV, Rodriguez-Fortuno FJ, Yang C, Ren J, Khanikaev AB, Alu A, Brasselet E, Shats M, Verbeeck J, Schattschneider P, Sarenac D, Cory DG, Pushin DA, Birk M, Gorlach A, Kaminer I, Cardano F, Marrucci L, Krenn M, Marquardt F, Journal of optics 25, 103001 (2023). http://doi.org/10.1088/2040-8986/ACEA92
Abstract: Structured waves are ubiquitous for all areas of wave physics, both classical and quantum, where the wavefields are inhomogeneous and cannot be approximated by a single plane wave. Even the interference of two plane waves, or of a single inhomogeneous (evanescent) wave, provides a number of nontrivial phenomena and additional functionalities as compared to a single plane wave. Complex wavefields with inhomogeneities in the amplitude, phase, and polarization, including topological----- structures and singularities, underpin modern nanooptics and photonics, yet they are equally important, e.g. for quantum matter waves, acoustics, water waves, etc. Structured waves are crucial in optical and electron microscopy, wave propagation and scattering, imaging, communications, quantum optics, topological and non-Hermitian wave systems, quantum condensed-matter systems, optomechanics, plasmonics and metamaterials, optical and acoustic manipulation, and so forth. This Roadmap is written collectively by prominent researchers and aims to survey the role of structured waves in various areas of wave physics. Providing background, current research, and anticipating future developments, it will be of interest to a wide cross-disciplinary audience.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.1
Times cited: 7
DOI: 10.1088/2040-8986/ACEA92
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“Barrier efficiency of sponge-like La2Zr2O7 buffer layers for YBCO-coated conductors”. Molina L, Tan H, Biermans E, Batenburg KJ, Verbeeck J, Bals S, Van Tendeloo G, Superconductor science and technology 24, 065019 (2011). http://doi.org/10.1088/0953-2048/24/6/065019
Abstract: Solution derived La2Zr2O7 films have drawn much attention for potential applications as thermal barriers or low-cost buffer layers for coated conductor technology. Annealing and coating parameters strongly affect the microstructure of La2Zr2O7, but different film processing methods can yield similar microstructural features such as nanovoids and nanometer-sized La2Zr2O7 grains. Nanoporosity is a typical feature found in such films and the implications for the functionality of the films are investigated by a combination of scanning transmission electron microscopy (STEM), electron energy-loss spectroscopy (EELS) and quantitative electron tomography. Chemical solution based La2Zr2O7 films deposited on flexible Ni5 at.%W substrates with a {100}lang001rang biaxial texture were prepared for an in-depth characterization. A sponge-like structure composed of nanometer-sized voids is revealed by high-angle annular dark-field scanning transmission electron microscopy in combination with electron tomography. A three-dimensional quantification of nanovoids in the La2Zr2O7 film is obtained on a local scale. Mostly non-interconnected highly faceted nanovoids compromise more than one-fifth of the investigated sample volume. The diffusion barrier efficiency of a 170 nm thick La2Zr2O7 film is investigated by STEM-EELS, yielding a 1.8 ± 0.2 nm oxide layer beyond which no significant nickel diffusion can be detected and intermixing is observed. This is of particular significance for the functionality of YBa2Cu3O7 − δ coated conductor architectures based on solution derived La2Zr2O7 films as diffusion barriers.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.878
Times cited: 31
DOI: 10.1088/0953-2048/24/6/065019
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“Optimized fabrication of high-quality La0.67Sr0.33MnO3 thin films considering all essential characteristics”. Boschker H, Huijben M, Vailinois A, Verbeeck J, Van Aert S, Luysberg M, Bals S, Van Tendeloo G, Houwman EP, Koster G, Blank DHA, Rijnders G, Journal of physics: D: applied physics 44, 205001 (2011). http://doi.org/10.1088/0022-3727/44/20/205001
Abstract: In this paper, an overview of the fabrication and properties of high-quality La0.67Sr0.33MnO3 (LSMO) thin films is given. A high-quality LSMO film combines a smooth surface morphology with a large magnetization and a small residual resistivity, while avoiding precipitates and surface segregation. In the literature, typically only a few of these issues are adressed. We therefore present a thorough characterization of our films, which were grown by pulsed laser deposition. The films were characterized with reflection high energy electron diffraction, atomic force microscopy, x-ray diffraction, magnetization and transport measurements, x-ray photoelectron spectroscopy and scanning transmission electron microscopy. The films have a saturation magnetization of 4.0 µB/Mn, a Curie temperature of 350 K and a residual resistivity of 60 µΩ cm. These results indicate that high-quality films, combining both large magnetization and small residual resistivity, were realized. A comparison between different samples presented in the literature shows that focussing on a single property is insufficient for the optimization of the deposition process. For high-quality films, all properties have to be adressed. For LSMO devices, the thin-film quality is crucial for the device performance. Therefore, this research is important for the application of LSMO in devices.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.588
Times cited: 99
DOI: 10.1088/0022-3727/44/20/205001
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“Simulation of magnetic circular dichroism in the electron microscope”. Rubino S, Schattschneider P, Rusz J, Verbeeck J, Leifer K, Journal of physics: D: applied physics 43, 474005 (2010). http://doi.org/10.1088/0022-3727/43/47/474005
Abstract: As electron energy-loss spectroscopy (EELS) and x-ray absorption spectroscopy (XAS) probe the same transitions from coreshell states to unoccupied states above the Fermi energy, it should always be possible to apply the two techniques to the same physical phenomena, such as magnetic dichroism, and obtain the same information. Indeed, the similarity in the expression of the electron and x-ray cross-sections had been already exploited to prove the equivalence of x-ray magnetic linear dichroism and anisotropy in EELS, by noting that the polarization vector of a photon plays the same role as the momentum transfer in electron scattering. Recently, the same was proven true for x-ray magnetic circular dichroism (XMCD) by establishing a new TEM technique called EMCD (electron energy-loss magnetic chiral dichroism) (Schattschneider P et al 2006 Nature 441 4868), which makes use of special electron scattering conditions to force the absorption of a circularly polarized virtual photon. The intrinsic advantage of EMCD over XMCD is the high spatial resolution of electron microscopes, which are readily available. Among the particular obstacles in EMCD that do not exist for synchrotron radiation, is the notoriously low signal and the very particular scattering conditions necessary to observe a chiral dichroic signal. In spite of that, impressive progress has been made in recent years. The signal strength could be considerably increased, and some innovations such as using a convergent beam have been introduced. EMCD has evolved into several techniques, which make full use of the versatility of the TEM and energy filtering, spectroscopy or STEM conditions (Rubino S 2007 Magnetic circular dichroism in the transmission electron microscope PhD Thesis Vienna University of Technology, Vienna, Austria).
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.588
Times cited: 13
DOI: 10.1088/0022-3727/43/47/474005
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“Structure and microstructure of epitaxial SrnFenO3n-1 films”. Lebedev OI, Verbeeck J, Van Tendeloo G, Hayashi N, Terashima T, Takano M, Philosophical magazine 84, 3825 (2004). http://doi.org/10.1080/14786430412331313187
Abstract: Thin films of SrFeO3-x (0 less than or equal to x less than or equal to 0.5) (SFO) grown on a (LaAlO3)(0.3) (SrAl0.5Ta0.5O3)(0.7) (LSAT) substrate by Pulsed laser deposition have been structurally investigated by electron diffraction and high resolution transmission electron microscopy for different post-deposition oxygen treatments. During the deposition and post-growth oxidation, the oxygen-reduced SFO films accept extra oxygen along the tetrahedral layers to minimize the elastic strain energy. The oxidation process stops at a concentration SFO2.875 and/or SFO2.75 because a zero misfit with the LSAT substrate is reached. A possible growth mechanism and phase transition mechanism are suggested. The non-oxidized films exhibit twin boundaries having a local perovskite-type structure with a nominal composition close to SFO3.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 1.505
Times cited: 4
DOI: 10.1080/14786430412331313187
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“Thermal characterization of polycrystalline diamond thin film heat spreaders grown on GaN HEMTs”. Zhou Y, Ramaneti R, Anaya J, Korneychuk S, Derluyn J, Sun H, Pomeroy J, Verbeeck J, Haenen K, Kuball M, Applied physics letters 111, 041901 (2017). http://doi.org/10.1063/1.4995407
Abstract: Polycrystalline diamond (PCD) was grown onto high-k dielectric passivated AlGaN/GaN-on-Si high electron mobility transistor (HEMT) structures, with film thicknesses ranging from 155 to 1000 nm. Transient thermoreflectance results were combined with device thermal simulations to investigate the heat spreading benefit of the diamond layer. The observed thermal conductivity (k(Dia)) of PCD films is one-to-two orders of magnitude lower than that of bulk PCD and exhibits a strong layer thickness dependence, which is attributed to the grain size evolution. The films exhibit a weak temperature dependence of k(Dia) in the measured 25-225 degrees C range. Device simulation using the experimental jDia and thermal boundary resistance values predicts at best a 15% reduction in peak temperature when the source-drain opening of a passivated AlGaN/GaN-on-Si HEMT is overgrown with PCD. Published by AIP Publishing.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.411
Times cited: 78
DOI: 10.1063/1.4995407
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“Local bond length variations in boron-doped nanocrystalline diamond measured by spatially resolved electron energy-loss spectroscopy”. Lu Y-G, Turner S, Verbeeck J, Janssens SD, Haenen K, Van Tendeloo G, Applied physics letters 103, 032105 (2013). http://doi.org/10.1063/1.4813842
Abstract: Variations in local bond length and coordination in boron-doped nanocrystalline diamond (NCD) films have been studied through changes in the fine structure of boron and carbon K-edges in electron energy-loss spectra, acquired in a scanning transmission electron microscope. The presence of high concentrations of B in pristine diamond regions and enrichment of B at defects in single NCD grains is demonstrated. Local bond length variations are evidenced through an energy shift of the carbon 1s → σ* edge at B-rich defective regions within single diamond grains, indicating an expansion of the diamond bond length at sites with local high B content.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.411
Times cited: 15
DOI: 10.1063/1.4813842
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“Magnetic and magnetodielectric properties of erbium iron garnet ceramic”. Maignan A, Singh K, Simon C, Lebedev OI, Martin C, Tan H, Verbeeck J, Van Tendeloo G, Journal of applied physics 113, 033905 (2013). http://doi.org/10.1063/1.4776716
Abstract: An Er3Fe5O12 ceramic has been sintered in oxygen atmosphere at 1400 °C for dielectric measurements. Its structural quality at room temperature has been checked by combining transmission electron microscopy and X-ray diffraction. It crystallizes in the cubic space group Ia3d with a = 12.3488(1). The dielectric permittivity ([variantgreekepsilon]′) and losses (tan δ) measurements as a function of temperature reveal the existence of two anomalies, a broad one between 110 K and 80 K, attributed to the Er3+ spin reorientation, and a second sharper feature at about 45 K associated to the appearance of irreversibility on the magnetic susceptibility curves. In contrast to the lack of magnetic field impact on [variantgreekepsilon]′ for the former anomaly, a complex magnetic field effect has been evidenced below 45 K. The isothermal [variantgreekepsilon]′(H) curves show the existence of positive magnetodielectric effect, reaching a maximum of 0.14% at 3 T and 10 K. Its magnitude decreases as H is further increased. Interestingly, for the lowest H values, a linear regime in the [variantgreekepsilon]′(H) curve is observed. From this experimental study, it is concluded that the [variantgreekepsilon]′ anomaly, starting above the compensation temperature Tc (75 K) and driven by the internal magnetic field, is not sensitive to an applied external magnetic field. Thus, below 45 K, it is the magnetic structure which is responsible for the coupling between spin and charge in this iron garnet.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.068
Times cited: 15
DOI: 10.1063/1.4776716
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“Three-dimensional fabrication and characterisation of core-shell nano-columns using electron beam patterning of Ge-doped SiO2”. Gontard LC, Jinschek JR, Ou H, Verbeeck J, Dunin-Borkowski RE, Applied physics letters 100, 263113 (2012). http://doi.org/10.1063/1.4731765
Abstract: A focused electron beam in a scanning transmission electron microscope (STEM) is used to create arrays of core-shell structures in a specimen of amorphous SiO2 doped with Ge. The same electron microscope is then used to measure the changes that occurred in the specimen in three dimensions using electron tomography. The results show that transformations in insulators that have been subjected to intense irradiation using charged particles can be studied directly in three dimensions. The fabricated structures include core-shell nano-columns, sputtered regions, voids, and clusters. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4731765]
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.411
Times cited: 11
DOI: 10.1063/1.4731765
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“Magnetic and electronic properties of the interface between half metallic Fe3O4 and semiconducting ZnO”. Brück S, Paul M, Tian H, Müller A, Kufer D, Praetorius C, Fauth K, Audehm P, Goering E, Verbeeck J, Van Tendeloo G, Sing M, Claessen R;, Applied physics letters 100, 081603 (2012). http://doi.org/10.1063/1.3687731
Abstract: We have investigated the magnetic depth profile of an epitaxial Fe3O4 thin film grown directly on a semiconducting ZnO substrate by soft x-ray resonant magnetic reflectometry (XRMR) and electron energy loss spectroscopy (EELS). Consistent chemical profiles at the interface between ZnO and Fe3O4 are found from both methods. Valence selective EELS and XRMR reveal independently that the first monolayer of Fe at the interface between ZnO and Fe3O4 contains only Fe3+ ions. Besides this narrow 2.5 Å interface layer, Fe3O4 shows magnetic bulk properties throughout the whole film making highly efficient spin injection in this system feasible.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.411
Times cited: 12
DOI: 10.1063/1.3687731
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“Fe3O4/ZnO : a high-quality magnetic oxide-semiconductor heterostructure by reactive deposition”. Paul M, Kufer D, Müller A, Brück S, Goering E, Kamp M, Verbeeck J, Tian H, Van Tendeloo G, Ingle NJC, Sing M, Claessen R, Applied physics letters 98, 012512 (2011). http://doi.org/10.1063/1.3540653
Abstract: We demonstrate the epitaxial growth of Fe<sub>3</sub>O<sub>4</sub> films on ZnO by a simple reactive deposition procedure using molecular oxygen as an oxidizing agent. X-ray photoelectron spectroscopy results evidence that the iron-oxide surface is nearly stoichiometric magnetite. X-ray diffraction results indicate monocrystalline epitaxy and almost complete structural relaxation. Scanning transmission electron micrographs reveal that the microstructure consists of domains which are separated by antiphase boundaries or twin boundaries. The magnetite films show rather slow magnetization behavior in comparison with bulk crystals probably due to reduced magnetization at antiphase boundaries in small applied fields.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.411
Times cited: 27
DOI: 10.1063/1.3540653
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“Circular dichroism in the electron microscope: progress and applications (invited)”. Schattschneider P, Ennen I, Stoger-Pollach M, Verbeeck J, Journal of applied physics 107, 09d311 (2010). http://doi.org/10.1063/1.3365517
Abstract: According to theory, x-ray magnetic circular dichroism in a synchrotron is equivalent to energy loss magnetic chiral dichroism (EMCD) in a transmission electron microscope (TEM). After a synopsis of the development of EMCD, the theoretical background is reviewed and recent results are presented, focusing on the study of magnetic nanoparticles for ferrofluids and Heusler alloys for spintronic devices. Simulated maps of the dichroic strength as a function of atom position in the crystal allow evaluating the influence of specimen thickness and sample tilt on the experimental EMCD signal. Finally, the possibility of direct observation of chiral electronic transitions with atomic resolution in a TEM is discussed.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.068
Times cited: 28
DOI: 10.1063/1.3365517
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“Electrical switching in Fe/Cr/MgO/Fe magnetic tunnel junctions”. Halley D, Majjad H, Bowen M, Najjari N, Henry Y, Ulhaq-Bouillet C, Weber W, Bertoni G, Verbeeck J, Van Tendeloo G, Applied physics letters 92, 212115 (2008). http://doi.org/10.1063/1.2938696
Abstract: Hysteretic resistance switching is observed in epitaxial Fe/Cr/MgO/Fe magnetic tunnel junctions under bias voltage cycling between negative and positive values of about 1 V. The junctions switch back and forth between high- and low-resistance states, both of which depend on the device bias history. A linear dependence is found between the magnitude of the tunnel magnetoresistance and the crafted resistance of the junctions. To explain these results, a model is proposed that considers electron transport both by elastic tunneling and by defect-assisted transmission. (c) 2008 American Institute of Physics.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.411
Times cited: 33
DOI: 10.1063/1.2938696
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“Nanoscale analysis of interfaces in a metal/oxide/oxide trilayer obtained by pulsed laser deposition”. Fix T, Ulhaq-Bouillet C, Colis S, Dinia A, Bertoni G, Verbeeck J, Van Tendeloo G, Applied physics letters 91, 023106 (2007). http://doi.org/10.1063/1.2755699
Abstract: Sr2FeMoO6/SrTiO3/CoFe2 trilayers grown by pulsed laser deposition on SrTiO3 (001) are investigated by transmission electron microscopy and electron energy loss spectroscopy. The stack is epitaxial, independent of whether the CoFe2 electrode is grown at 500 or at 50 degrees C. Thus it is possible to obtain epitaxy near room temperature. The SrTiO3/CoFe2 interface is quite sharp, while the Sr2FeMoO6/SrTiO3 interface presents regions of Fe depletion. The chemical composition of the films is close to the nominal stoichiometries. These results could be useful for the growth of heteroepitaxial devices and magnetic tunnel junctions. (C) 2007 American Institute of Physics.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.411
Times cited: 16
DOI: 10.1063/1.2755699
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“Structure and properties of artificial [(La0.7Sr0.3MnO3)m(SrTiO3)n]15 superlattices on (001)SrTiO3”. Lebedev OI, Verbeeck J, Van Tendeloo G, Dubourdieu C, Rosina M, Chaudouët P, Journal of applied physics 94, 7646 (2003). http://doi.org/10.1063/1.1628407
Abstract: Complex [(La0.7Sr0.3MnO3)(m)(SrTiO3)(n)] [(LSMO)(m)/(STO)(8)](15) superlattices with different layer thicknesses (m=5, 8, 12, 16, 32) have been prepared using pulsed liquid injection metalorganic chemical vapor deposition. Transmission electron microscopy and electron diffraction reveal a very clear and well-separated layer sequence. The remarkable microstructure, as well as the ferromagnetic transition temperature, depends on the LSMO layer thickness. Apart from a very clear layer sequence, electron microscopy shows evidence of a self-assembled nanostructure formation: SrMnO3 nanoinclusions and associated SrTiO3-SrMnO3 thin walls. A formation model and growth mechanism for the self-assembled structure is proposed, based on high resolution and energy filtered elemental imaging. (C) 2003 American Institute of Physics.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.068
Times cited: 22
DOI: 10.1063/1.1628407
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