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Author Verbeeck, J.; Hébert; Rubino, S.; Novák, P.; Rusz, J.; Houdellier, F.; Gatel, C.; Schattschneider, P.
Title Optimal aperture sizes and positions for EMCD experiments Type A1 Journal article
Year 2008 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 108 Issue 9 Pages 865-872
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract The signal-to-noise ratio (SNR) in energy-loss magnetic chiral dichroism (EMCD)the equivalent of X-ray magnetic circular dichroism (XMCD) in the electron microscopeis optimized with respect to the detector shape, size and position. We show that an important increase in SNR over previous experiments can be obtained when taking much larger detector sizes. We determine the ideal shape of the detector but also show that round apertures are a good compromise if placed in their optimal position. We develop the theory for a simple analytical description of the EMCD experiment and then apply it to dynamical multibeam Bloch wave calculations and to an experimental data set. In all cases it is shown that a significant and welcome improvement of the SNR is possible.
Address
Corporate Author Thesis
Publisher Place of Publication Amsterdam Editor
Language Wos 000258747600009 Publication Date 2008-03-07
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991; ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 27 Open Access
Notes This work was supported by the European Commission under contract no. 508971 CHIRALTEM. J.V. and F.H. thank the financial support from the European Union under the Framework 6 program under a contract for an Integrated Infrastructure Initiative. Reference 026019 ESTEEM. Thanks to J.P. Morniroli for making the Fe sample available. Approved Most recent IF: 2.843; 2008 IF: 2.629
Call Number UA @ lucian @ c:irua:76492UA @ admin @ c:irua:76492 Serial 2480
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Author Tan, H.; Verbeeck, J.; Abakumov, A.; Van Tendeloo, G.
Title Oxidation state and chemical shift investigation in transition metal oxides by EELS Type A1 Journal article
Year 2012 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 116 Issue Pages 24-33
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract Transition metal L2,3 electron energy-loss spectra for a wide range of V-, Mn- and Fe-based oxides were recorded and carefully analyzed for their correlation with the formal oxidation states of the transition metal ions. Special attention is paid to obtain an accurate energy scale which provides absolute energy positions for all core-loss edges. The white-line ratio method, chemical shift method, ELNES fitting method, two-parameter method and other methods are compared and their validity is discussed. Both the ELNES fitting method and the chemical shift method have the advantage of a wide application range and good consistency but require special attention to accurately measure the core-loss edge position. The obtained conclusions are of fundamental importance, e.g., for obtaining atomic resolution oxidation state information in modern experiments.
Address
Corporate Author Thesis
Publisher Place of Publication Amsterdam Editor
Language Wos 000304473700004 Publication Date 2012-03-10
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991; ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 413 Open Access
Notes Fwo Approved Most recent IF: 2.843; 2012 IF: 2.470
Call Number UA @ lucian @ c:irua:96959UA @ admin @ c:irua:96959 Serial 2541
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Author Verbeeck, J.; van Dyck, D.; Lichte, H.; Potapov, P.; Schattschneider, P.
Title Plasmon holographic experiments: theoretical framework Type A1 Journal article
Year 2005 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 102 Issue 3 Pages 239-255
Keywords A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Abstract A theoretical framework is described to understand the results of plasmon holography experiments leading to insight in the meaning of the experimental results and pointing out directions for future experiments. The framework is based on the formalism of mutual intensity to describe how coherence is transferred through an optical system. For the inelastic interaction with the object, an expression for the volume. plasmon excitations in a free electron gas is used as a model for the behaviour of aluminium. The formalism leads to a clear graphical intuitive tool for under-standing the experiments. It becomes evident that the measured coherence is solely related to the angular distribution of the plasmon scattering in the case of bulk plasmons. After describing the framework, the special case of coherence outside a spherical particle is treated and the seemingly controversial idea of a plasmon with a limited coherence length obtained front experiments is clarified. (C) 2004 Elsevier B.V. All rights reserved.
Address
Corporate Author Thesis
Publisher Place of Publication Amsterdam Editor
Language Wos 000226436600010 Publication Date 2004-11-05
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991; ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 43 Open Access
Notes Fwo Approved Most recent IF: 2.843; 2005 IF: 2.490
Call Number UA @ lucian @ c:irua:57133UA @ admin @ c:irua:57133 Serial 2643
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Author Guzzinati, G.; Clark, L.; Béché, A.; Juchtmans, R.; Van Boxem, R.; Mazilu, M.; Verbeeck, J.
Title Prospects for versatile phase manipulation in the TEM : beyond aberration correction Type A1 Journal article
Year 2015 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 151 Issue 151 Pages 85-93
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract In this paper we explore the desirability of a transmission electron microscope in which the phase of the electron wave can be freely controlled. We discuss different existing methods to manipulate the phase of the electron wave and their limitations. We show how with the help of current techniques the electron wave can already be crafted into specific classes of waves each having their own peculiar properties. Assuming a versatile phase modulation device is feasible, we explore possible benefits and methods that could come into existence borrowing from light optics where the so-called spatial light modulators provide programmable phase plates for quite some time now. We demonstrate that a fully controllable phase plate building on Harald Rose׳s legacy in aberration correction and electron optics in general would open an exciting field of research and applications.
Address
Corporate Author Thesis
Publisher Place of Publication Amsterdam Editor
Language Wos 000351237800012 Publication Date 2014-10-22
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991; ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 19 Open Access
Notes 278510 Vortex; Fwo; 312483 Esteem2; esteem2jra2; esteem2jra3 ECASJO_; Approved Most recent IF: 2.843; 2015 IF: 2.436
Call Number c:irua:121405 c:irua:121405UA @ admin @ c:irua:121405 Serial 2731
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Author Bertoni, G.; Beyers, E.; Verbeeck, J.; Mertens, M.; Cool, P.; Vansant, E.F.; Van Tendeloo, G.
Title Quantification of crystalline and amorphous content in porous TiO2 samples from electron energy loss spectroscopy Type A1 Journal article
Year 2006 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 106 Issue 7 Pages 630-635
Keywords A1 Journal article; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
Abstract We present an efficient method for the quantification of crystalline versus amorphous phase content in mesoporous materials, making use of electron energy loss spectroscopy. The method is based on fitting a superposition of core-loss edges using the maximum likelihood method with measured reference spectra. We apply the method to mesoporous TiO2 samples. We show that the absolute amount of the crystalline phase can be determined with an accuracy below 5%. This method takes also the amorphous phase into account, where standard X-ray diffraction is only quantitative for crystalline phases and not for amorphous phase. (c) 2006 Elsevier B.V.. All rights reserved.
Address
Corporate Author Thesis
Publisher Place of Publication Amsterdam Editor
Language Wos 000238479300011 Publication Date 2006-04-28
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991; ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 83 Open Access
Notes Iap-V; Goa-2005; Fwo Approved Most recent IF: 2.843; 2006 IF: 1.706
Call Number UA @ lucian @ c:irua:58823UA @ admin @ c:irua:58823 Serial 2741
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Author Van Aert, S.; Verbeeck, J.; Erni, R.; Bals, S.; Luysberg, M.; van Dyck, D.; Van Tendeloo, G.
Title Quantitative atomic resolution mapping using high-angle annular dark field scanning transmission electron microscopy Type A1 Journal article
Year 2009 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 109 Issue 10 Pages 1236-1244
Keywords A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Abstract A model-based method is proposed to relatively quantify the chemical composition of atomic columns using high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) images. The method is based on a quantification of the total intensity of the scattered electrons for the individual atomic columns using statistical parameter estimation theory. In order to apply this theory, a model is required describing the image contrast of the HAADF STEM images. Therefore, a simple, effective incoherent model has been assumed which takes the probe intensity profile into account. The scattered intensities can then be estimated by fitting this model to an experimental HAADF STEM image. These estimates are used as a performance measure to distinguish between different atomic column types and to identify the nature of unknown columns with good accuracy and precision using statistical hypothesis testing. The reliability of the method is supported by means of simulated HAADF STEM images as well as a combination of experimental images and electron energy-loss spectra. It is experimentally shown that statistically meaningful information on the composition of individual columns can be obtained even if the difference in averaged atomic number Z is only 3. Using this method, quantitative mapping at atomic resolution using HAADF STEM images only has become possible without the need of simultaneously recorded electron energy loss spectra.
Address
Corporate Author Thesis
Publisher Place of Publication Amsterdam Editor
Language Wos 000270015200004 Publication Date 2009-05-28
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991; ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 166 Open Access
Notes Fwo; Esteem 026019 Approved Most recent IF: 2.843; 2009 IF: 2.067
Call Number UA @ lucian @ c:irua:78585UA @ admin @ c:irua:78585 Serial 2748
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Author Martinez, G.T.; Rosenauer, A.; de Backer, A.; Verbeeck, J.; Van Aert, S.
Title Quantitative composition determination at the atomic level using model-based high-angle annular dark field scanning transmission electron microscopy Type A1 Journal article
Year 2014 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 137 Issue Pages 12-19
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract High angle annular dark field scanning transmission electron microscopy (HAADF STEM) images provide sample information which is sensitive to the chemical composition. The image intensities indeed scale with the mean atomic number Z. To some extent, chemically different atomic column types can therefore be visually distinguished. However, in order to quantify the atomic column composition with high accuracy and precision, model-based methods are necessary. Therefore, an empirical incoherent parametric imaging model can be used of which the unknown parameters are determined using statistical parameter estimation theory (Van Aert et al., 2009, [1]). In this paper, it will be shown how this method can be combined with frozen lattice multislice simulations in order to evolve from a relative toward an absolute quantification of the composition of single atomic columns with mixed atom types. Furthermore, the validity of the model assumptions are explored and discussed.
Address
Corporate Author Thesis
Publisher Place of Publication Amsterdam Editor
Language Wos 000331092200003 Publication Date 2013-11-09
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991; ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 74 Open Access
Notes FWO; FP7; ERC Countatoms; ESTEEM2; esteem2_ta Approved Most recent IF: 2.843; 2014 IF: 2.436
Call Number UA @ lucian @ c:irua:111579UA @ admin @ c:irua:111579 Serial 2749
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Author Martinez, G.T.; Jones, L.; de Backer, A.; Béché, A.; Verbeeck, J.; Van Aert, S.; Nellist, P.D.
Title Quantitative STEM normalisation : the importance of the electron flux Type A1 Journal article
Year 2015 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 159 Issue 159 Pages 46-58
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract Annular dark-field (ADF) scanning transmission electron microscopy (STEM) has become widely used in quantitative studies based on the opportunity to directly compare experimental and simulated images. This comparison merely requires the experimental data to be normalised and expressed in units of fractional beam-current. However, inhomogeneities in the response of electron detectors can complicate this normalisation. The quantification procedure becomes both experiment and instrument specific, requiring new simulations for the particular response of each instrument's detector, and for every camera-length used. This not only impedes the comparison between different instruments and research groups, but can also be computationally very time consuming. Furthermore, not all image simulation methods allow for the inclusion of an inhomogeneous detector response. In this work, we propose an alternative method for normalising experimental data in order to compare these with simulations that consider a homogeneous detector response. To achieve this, we determine the electron flux distribution reaching the detector by means of a camera-length series or a so-called atomic column cross-section averaged convergent beam electron diffraction (XSACBED) pattern. The result is then used to determine the relative weighting of the detector response. Here we show that the results obtained by this new electron flux weighted (EFW) method are comparable to the currently used method, while considerably simplifying the needed simulation libraries. The proposed method also allows one to obtain a metric that describes the quality of the detector response in comparison with the ideal detector response.
Address
Corporate Author Thesis
Publisher Place of Publication Amsterdam Editor
Language Wos 000366220000006 Publication Date 2015-08-01
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991; ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 27 Open Access
Notes 246791 Countatoms; 278510 Vortex; 312483 Esteem2; Fwo G036815; G036915; G037413; G004413; esteem2ta ECASJO; Approved Most recent IF: 2.843; 2015 IF: 2.436
Call Number c:irua:127293 c:irua:127293UA @ admin @ c:irua:127293 Serial 2762
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Author Schattschneider, P.; Verbeeck, J.; Hamon, A.L.
Title Real space maps of atomic transitions Type A1 Journal article
Year 2009 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 109 Issue 7 Pages 781-787
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract Considering the rapid technical development of transmission electron microscopes, we investigate the possibility to map electronic transitions in real space on the atomic scale. To this purpose, we analyse the information carried by the scatterer's initial and final state wave functions and the role of the different atomic transition channels for the inelastic scattering cross section. It is shown that the change in the magnetic quantum number in the transition can be mapped. Two experimental set-ups are proposed, one blocking half the diffraction plane, the other one using a cylinder lens for imaging. Both methods break the conventional circular symmetry in the electron microscope making it possible to detect the handedness of electronic transitions as an asymmetry in the image intensity. This finding is of important for atomic resolution energy-loss magnetic chiral dichroism (EMCD), allowing to obtain the magnetic moments of single atoms.
Address
Corporate Author Thesis
Publisher Place of Publication Amsterdam Editor
Language Wos 000266787900002 Publication Date 2009-03-01
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991; ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 10 Open Access
Notes J.V. acknowledges the FWO-Vlaanderen for support (contract no. G.0147.06) and the European Union under the Framework 6 program under a contract for an Integrated Infrastructure Initiative. Reference 026019 ESTEEM. Approved Most recent IF: 2.843; 2009 IF: 2.067
Call Number UA @ lucian @ c:irua:77360UA @ admin @ c:irua:77360 Serial 2829
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Author Schattschneider, P.; Ennen, I.; Stoger-Pollach, M.; Verbeeck, J.; Mauchamp, V.; Jaouen, M.
Title Real space maps of magnetic moments on the atomic scale: theory and feasibility Type A1 Journal article
Year 2010 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 110 Issue 8 Pages 1038-1041
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract The recently discovered EMCD technique (energy loss magnetic chiral dichroism) can detect atom specific magnetic moments with nanometer resolution, exploiting the spin selectivity of electronic transitions in energy loss spectroscopy. Yet, direct imaging of magnetic moments on the atomic scale is not possible. In this paper we present an extension of EMCD that can overcome this limit. As a model system we chose bcc Fe. We present image simulations of the L3 white line signal, based on the kinetic equation for the density matrix of the 200 kV probe electron. With actual progress in instrumentation (high brightness sources, aberration corrected lenses) this technique should allow direct imaging of spin moments on the atomic scale.
Address
Corporate Author Thesis
Publisher Place of Publication Amsterdam Editor
Language Wos 000281216600016 Publication Date 2009-12-07
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991; ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 10 Open Access
Notes --- Approved Most recent IF: 2.843; 2010 IF: 2.063
Call Number UA @ lucian @ c:irua:84439UA @ admin @ c:irua:84439 Serial 2830
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Author Lichtert, S.; Verbeeck, J.
Title Statistical consequences of applying a PCA noise filter on EELS spectrum images Type A1 Journal article
Year 2013 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 125 Issue Pages 35-42
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract Principal component analysis (PCA) noise filtering is a popular method to remove noise from experimental electron energy loss (EELS) spectrum images. Here, we investigate the statistical behaviour of this method by applying it on a simulated data set with realistic noise levels. This phantom data set provides access to the true values contained in the data set as well as to many different realizations of the noise. Using least squares fitting and parameter estimation theory, we demonstrate that even though the precision on the estimated parameters can be better as the CramérRao lower bound, a significant bias is introduced which can alter the conclusions drawn from experimental data sets. The origin of this bias is in the incorrect retrieval of the principal loadings for noisy data. Using an expression for the bias and precision of the singular values from literature, we present an evaluation criterion for these singular values based on the noise level and the amount of information present in the data set. This criterion can help to judge when to avoid PCA noise filtering in practical situations. Further we show that constructing elemental maps of PCA noise filtered data using the background subtraction method, does not guarantee an increase in the signal to noise ratio due to correlation of the spectral data as a result of the filtering process.
Address
Corporate Author Thesis
Publisher Place of Publication Amsterdam Editor
Language Wos 000314679700006 Publication Date 2012-10-27
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991; ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 54 Open Access
Notes Fwo; Countatoms; Vortex; Esteem 312483; esteem2jra3 ECASJO; Approved Most recent IF: 2.843; 2013 IF: 2.745
Call Number UA @ lucian @ c:irua:105293 Serial 3153
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Author Schattschneider, P.; Stöger-Pollach, M.; Löffler, S.; Steiger-Thirsfeld, A.; Hell, J.; Verbeeck, J.
Title Sub-nanometer free electrons with topological charge Type A1 Journal article
Year 2012 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 115 Issue Pages 21-25
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract The holographic mask technique is used to create freely moving electrons with quantized angular momentum. With electron optical elements they can be focused to vortices with diameters below the nanometer range. The understanding of these vortex beams is important for many applications. Here, we produce electron vortex beams and compare them to a theory of electrons with topological charge. The experimental results show excellent agreement with simulations. As an immediate application, fundamental experimental parameters like spherical aberration and partial coherence are determined. (C) 2012 Elsevier B.V. All rights reserved.
Address
Corporate Author Thesis
Publisher Place of Publication Amsterdam Editor
Language Wos 000302962400004 Publication Date 2012-01-30
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991; ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 24 Open Access
Notes vortex ECASJO_; Approved Most recent IF: 2.843; 2012 IF: 2.470
Call Number UA @ lucian @ c:irua:98279 Serial 3344
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Author Verbeeck, J.; Bertoni, G.; Schattschneider, P.
Title The Fresnel effect of a defocused biprism on the fringes in inelastic holography Type A1 Journal article
Year 2008 Publication Ultramicroscopy T2 – 16th International Microscopy Congress, SEP 03-08, 2006, Sapporo, JAPAN Abbreviated Journal (up) Ultramicroscopy
Volume 108 Issue 3 Pages 263-269
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract We present energy filtered holography experiments on a thin foil of Al. By propagating the reduced density matrix of the probe electron through the microscope, we quantitatively predict the fringe contrast as a function of energy loss. Fringe contrast simulations include the effect of Fresnel fringes created at the edges of the defocused biprism, the effect of partial coherence in combination with inelastic scattering, and the effect of a finite energy distribution of the incoming beam. (c) 2007 Elsevier B.V. All rights reserved.
Address
Corporate Author Thesis
Publisher Place of Publication Amsterdam Editor
Language Wos 000253389100011 Publication Date 2007-11-02
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991; ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 15 Open Access
Notes Fwo G.0147.06; Esteem 026019 Approved Most recent IF: 2.843; 2008 IF: 2.629
Call Number UA @ lucian @ c:irua:104035 Serial 3582
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Author Schattschneider, P.; Verbeeck, J.
Title Theory of free electron vortices Type A1 Journal article
Year 2011 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 111 Issue 9/10 Pages 1461-1468
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract The recent creation of electron vortex beams and their first practical application motivates a better understanding of their properties. Here, we develop the theory of free electron vortices with quantized angular momentum, based on solutions of the Schrödinger equation for cylindrical boundary conditions. The principle of transformation of a plane wave into vortices with quantized angular momentum, their paraxial propagation through round magnetic lenses, and the effect of partial coherence are discussed.
Address
Corporate Author Thesis
Publisher Place of Publication Amsterdam Editor
Language Wos 000300461200002 Publication Date 2011-07-26
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991; ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 57 Open Access
Notes Esteem 026019 Approved Most recent IF: 2.843; 2011 IF: 2.471
Call Number UA @ lucian @ c:irua:91882 Serial 3617
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Author van den Broek, W.; Verbeeck, J.; Schryvers, D.; de Backer, S.; Scheunders, P.
Title Tomographic spectroscopic imaging; an experimental proof of concept Type A1 Journal article
Year 2009 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 109 Issue 4 Pages 296-303
Keywords A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Abstract Recording the electron energy loss spectroscopy data cube with a series of energy filtered images is a dose inefficient process because the energy slit blocks most of the electrons. When recording the data cube by scanning an electron probe over the sample, perfect dose efficiency is attained; but due to the low current in nanoprobes, this often is slower, with a smaller field of view. In W. Van den Broek et al. [Ultramicroscopy, 106 (2006) 269], we proposed a new method to record the data cube, which is more dose efficient than an energy filtered series. It produces a set of projections of the data cube and then tomographically reconstructs it. In this article, we demonstrate these projections in practice, we present a simple geometrical model that allows for quantification of the projection angles and we present the first successful experimental reconstruction, all on a standard post-column instrument.
Address
Corporate Author Thesis
Publisher Place of Publication Amsterdam Editor
Language Wos 000265345400003 Publication Date 2008-12-10
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991; ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 1 Open Access
Notes Esteem 026019 Approved Most recent IF: 2.843; 2009 IF: 2.067
Call Number UA @ lucian @ c:irua:77271 Serial 3671
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Author Lobato, I.; Van Aert, S.; Verbeeck, J.
Title Progress and new advances in simulating electron microscopy datasets using MULTEM Type A1 Journal article
Year 2016 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 168 Issue 168 Pages 17-27
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract A new version of the open source program MULTEM is presented here. It includes a graphical user interface, tapering truncation of the atomic potential, CPU multithreading functionality, single/double precision calculations, scanning transmission electron microscopy (STEM) simulations using experimental detector sensitivities, imaging STEM (ISTEM) simulations, energy filtered transmission electron microscopy (EFTEM) simulations, STEM electron energy loss spectroscopy (EELS) simulations along with other improvements in the algorithms. We also present a mixed channeling approach for the calculation of inelastic excitations, which allows one to considerably speed up time consuming EFTEM/STEM-EELS calculations.
Address EMAT, University of Antwerp, Department of Physics, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Wos 000380754100003 Publication Date 2016-06-11
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 43 Open Access
Notes The authors acknowledge financial support from the European Union under the Seventh Framework Program under a contract for an Integrated Infrastructure Initiative. Reference No. 312483- ESTEEM2. The authors acknowledge financial support from the Research Foundation Flanders (FWO, Belgium) through project fundings (G.0374.13N, G.0369.15N and G.0368.15N).; esteem2jra3; esteem2na3; esteem2_jra2 Approved Most recent IF: 2.843
Call Number c:irua:134088 c:irua:134088UA @ admin @ c:irua:134088 Serial 4093
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Author Béché, A.; Juchtmans, R.; Verbeeck, J.
Title Efficient creation of electron vortex beams for high resolution STEM imaging Type A1 Journal article
Year 2017 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 178 Issue 178 Pages 12-19
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract The recent discovery of electron vortex beams carrying quantised angular momentum in the TEM has led to an active field of research, exploring a variety of potential applications including the possibility of mapping magnetic states at the atomic scale. A prerequisite for this is the availability of atomic sized electron vortex beams at high beam current and mode purity. In this paper we present recent progress showing that by making use of the Aharonov-Bohm effect near the tip of a long single domain ferromagnetic Nickel needle, a very efficient aperture for the production of electron vortex beams can be realised. The aperture transmits more than 99% of all electrons and provides a vortex mode purity of up to 92%. Placing this aperture in the condenser plane of a state of the art Cs corrected microscope allows us to demonstrate atomic resolution HAADF STEM images with spatial resolution better than 1 Angstrom, in agreement with theoretical expectations and only slightly inferior to the performance of a non-vortex probe on the same instrument.
Address EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Wos 000403862900003 Publication Date 2016-05-10
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 30 Open Access OpenAccess
Notes A.B. and J.V. acknowledge funding from the European Research Council under the 7th Framework Program (FP7), ERC Starting Grant No. 278510 VORTEX. J.V. acknowledges funding from FWO project G.0044.13N ('Charge ordering').; ECASJO_; Approved Most recent IF: 2.843
Call Number c:irua:134085 c:irua:134085UA @ admin @ c:irua:134085 Serial 4094
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Author Muller-Caspary, K.; Krause, F.F.; Grieb, T.; Loffler, S.; Schowalter, M.; Béché, A.; Galioit, V.; Marquardt, D.; Zweck, J.; Schattschneider, P.; Verbeeck, J.; Rosenauer, A.
Title Measurement of atomic electric fields and charge densities from average momentum transfers using scanning transmission electron microscopy Type A1 Journal article
Year 2016 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 178 Issue 178 Pages 62-80
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract This study sheds light on the prerequisites, possibilities, limitations and interpretation of high-resolution differential phase contrast (DPC) imaging in scanning transmission electron microscopy (STEM). We draw particular attention to the well-established DPC technique based on segmented annular detectors and its relation to recent developments based on pixelated detectors. These employ the expectation value of the momentum transfer as a reliable measure of the angular deflection of the STEM beam induced by an electric field in the specimen. The influence of scattering and propagation of electrons within the specimen is initially discussed separately and then treated in terms of a two-state channeling theory. A detailed simulation study of GaN is presented as a function of specimen thickness and bonding. It is found that bonding effects are rather detectable implicitly, e.g., by characteristics of the momentum flux in areas between the atoms than by directly mapping electric fields and charge densities. For strontium titanate, experimental charge densities are compared with simulations and discussed with respect to experimental artifacts such as scan noise. Finally, we consider practical issues such as figures of merit for spatial and momentum resolution, minimum electron dose, and the mapping of larger-scale, built-in electric fields by virtue of data averaged over a crystal unit cell. We find that the latter is possible for crystals with an inversion center. Concerning the optimal detector design, this study indicates that a sampling of 5mrad per pixel is sufficient in typical applications, corresponding to approximately 10x10 available pixels.
Address Institut fur Festkr perphysik, Universitat Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Wos 000403862900009 Publication Date 2016-05-12
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 93 Open Access
Notes K.M.-C. acknowledges support from the Deutsche Forschungsgemeinschaft (DFG) under contract MU3660/1-1. This work was further supported by the DFG under contract RO2057/4-2 and O2057/11-1. J.V. and A.B. acknowledge funding from the European Research Council (ERC) under the 7th Framework Program (FP7), and ERC Starting Grant No. 278510-VORTEX. Experimental results are obtained on the Qu-Ant-EM microscope partly funded by the Hercules fund from the Flemish government. J.V. also acknowledges funding through a GOA project “Solarpaint” of the University of Antwerp. SL and PS acknowledge financial support by the Austrian Science Fund (FWF) under grants No. I543-N20 and J3732-N27. ECASJO_; Approved Most recent IF: 2.843
Call Number c:irua:134125UA @ admin @ c:irua:134125 Serial 4098
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Author van den Bos, K.H.W.; Krause, F.F.; Béché, A.; Verbeeck, J.; Rosenauer, A.; Van Aert, S.
Title Locating light and heavy atomic column positions with picometer precision using ISTEM Type A1 Journal article
Year 2016 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 172 Issue 172 Pages 75-81
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract Recently, imaging scanning transmission electron microscopy (ISTEM) has been proposed as a promising new technique combining the advantages of conventional TEM (CTEM) and STEM [1]. The ability to visualize light and heavy elements together makes it a particularly interesting new, spatially incoherent imaging mode. Here, we evaluate this technique in term of precision with which atomic column locations can be measured. By using statistical parameter estimation theory, we will show that these locations can be accurately measured with a precision in the picometer range. Furthermore, a quantitative comparison is made with HAADF STEM imaging to investigate the advantages of ISTEM.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000390600200009 Publication Date 2016-10-09
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 8 Open Access
Notes The authors acknowledge financial support from the Research Foundation Flanders (FWO, Belgium) through project fundings (G.0374.13N, G.0368.15N, G.0369.15N), and by a Ph.D. grant to K.H.W. van den Bos. The research leading to these results has received funding from the Deutsche Forschungsgemeinschaft under Contract No. RO 2057/4-2 and the European Union Seventh Framework Programme under Grant Agreement 312483 – ESTEEM2. We thank Prof. G. Koster from the University of Twente for kindly providing us with the PbTiO3 test sample. Approved Most recent IF: 2.843
Call Number EMAT @ emat @ c:irua:136109UA @ admin @ c:irua:136109 Serial 4288
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Author Gauquelin, N.; van den Bos, K.H.W.; Béché, A.; Krause, F.F.; Lobato, I.; Lazar, S.; Rosenauer, A.; Van Aert, S.; Verbeeck, J.
Title Determining oxygen relaxations at an interface: A comparative study between transmission electron microscopy techniques Type A1 Journal article
Year 2017 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 181 Issue 181 Pages 178-190
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract Nowadays, aberration corrected transmission electron microscopy (TEM) is a popular method to characterise nanomaterials at the atomic scale. Here, atomically resolved images of nanomaterials are acquired, where the contrast depends on the illumination, imaging and detector conditions of the microscope. Visualization of light elements is possible when using low angle annular dark field (LAADF) STEM, annular bright field (ABF) STEM, integrated differential phase contrast (iDPC) STEM, negative spherical aberration imaging (NCSI) and imaging STEM (ISTEM). In this work, images of a NdGaO3-La0.67Sr0.33MnO3 (NGO-LSMO) interface are quantitatively evaluated by using statistical parameter estimation theory. For imaging light elements, all techniques are providing reliable results, while the techniques based on interference contrast, NCSI and ISTEM, are less robust in terms of accuracy for extracting heavy column locations. In term of precision, sample drift and scan distortions mainly limits the STEM based techniques as compared to NCSI. Post processing techniques can, however, partially compensate for this. In order to provide an outlook to the future, simulated images of NGO, in which the unavoidable presence of Poisson noise is taken into account, are used to determine the ultimate precision. In this future counting noise limited scenario, NCSI and ISTEM imaging will provide more precise values as compared to the other techniques, which can be related to the mechanisms behind the image recording.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000411170800022 Publication Date 2017-06-03
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 34 Open Access OpenAccess
Notes The authors acknowledge financial support from Flanders (FWO, Belgium) through project fundings (G.0044.13N, G.0374.13N, G.0368.15N, G.0369.15N), and by a Ph.D. grant to K.H.W.v.d.B. The Qu-Ant-EM microscope used for this study was partly funded by the Hercules fund from the Flemish Government. A.B. and N.G. acknowledge the EUROTAPES project (FP7-NMP.2011.2.2-1 Grant no.280432) which partly funded this study. N.G., A.B. and J.V. acknowledge funding from the European Research Council under the 7th Framework Program (FP7), ERC Starting Grant 278510 VORTEX. The research leading to these results has received funding from the Deutsche Forschungsgemeinschaft under Contract No. RO 2057/4-2 and the European Union Seventh Framework Programme under Grant Agreement 312483 – ESTEEM2. We thank Prof. G. Koster from the University of Twente for kindly providing us with the LSMO-NGO test sample. Approved Most recent IF: 2.843
Call Number EMAT @ emat @ c:irua:144435UA @ admin @ c:irua:144435 Serial 4620
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Author Vatanparast, M.; Egoavil, R.; Reenaas, T.W.; Verbeeck, J.; Holmestad, R.; Vullum, P.E.
Title Bandgap measurement of high refractive index materials by off-axis EELS Type A1 Journal article
Year 2017 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 182 Issue Pages 92-98
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract In the present work Cs aberration corrected and monochromated scanning transmission electron microscopy electron energy loss spectroscopy (STEM-EELS) has been used to explore experimental setups that allow bandgaps of high refractive index materials to be determined. Semi-convergence and collection angles in the mu rad range were combined with off-axis or dark field EELS to avoid relativistic losses and guided light modes in the low loss range to contribute to the acquired EEL spectra. Off-axis EELS further supressed the zero loss peak and the tail of the zero loss peak. The bandgap of several GaAs-based materials were successfully determined by simple regression analyses of the background subtracted EEL spectra. The presented set-up does not require that the acceleration voltage is set to below the. Cerenkov limit and can be applied over the entire acceleration voltage range of modern TEMs and for a wide range of specimen thicknesses. (C) 2017 Elsevier B.V. All rights reserved.
Address
Corporate Author Thesis
Publisher Place of Publication Amsterdam Editor
Language Wos 000413436500013 Publication Date 2017-06-21
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 3 Open Access Not_Open_Access
Notes ; The authors would like to thank Professor Shu Min Wang and Mahdad Sadeghi at the Nanofabrication Laboratory at Chalmers University, Sweden for providing the samples. The Norwegian Research Council is acknowledged for funding the HighQ-IB project under contract no. 10415201. M.V. and T.W.R. acknowledge funding from the EEA Financial Mechanism 2009-2014 under the project contract no 23SEE/30.06.2014. The research leading to these results has received funding from the European Union Seventh Framework Programme under Grant Agreement 312483 – ESTEEM2(Integrated Infrastructure Initiative-I3) through the system of transnational access. R.E. and J.V. acknowledge funding from GOA project “Solarpaint” of the University of Antwerp. ; Approved Most recent IF: 2.843
Call Number UA @ lucian @ c:irua:146639UA @ admin @ c:irua:146639 Serial 4778
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Author Verbeeck, J.; Béché, A.; Müller-Caspary, K.; Guzzinati, G.; Luong, M.A.; Den Hertog, M.
Title Demonstration of a 2 × 2 programmable phase plate for electrons Type A1 Journal article
Year 2018 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 190 Issue Pages 58-65
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract First results on the experimental realisation of a 2 × 2 programmable phase plate for electrons are presented. The design consists of an array of electrostatic elements that influence the phase of electron waves passing through 4 separately controllable aperture holes. This functionality is demonstrated in a conventional transmission electron microscope operating at 300 kV and results are in very close agreement with theoretical predictions. The dynamic creation of a set of electron probes with different phase symmetry is demonstrated, thereby bringing adaptive optics in TEM one step closer to reality. The limitations of the current design and how to overcome these in the future are discussed. Simulations show how further evolved versions of the current proof of concept might open new and exciting application prospects for beam shaping and aberration correction.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000432868800007 Publication Date 2018-04-18
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 73 Open Access Not_Open_Access: Available from 19.04.2020
Notes J.V. and A.B. acknowledge funding from the Fund for Scientific Research Flanders FWO project G093417N and the European Research Council under the 7th Framework Program (FP7), ERC Starting Grant 278510 VORTEX and ERC proof of concept project DLV-789598 ADAPTEM. The Qu-Ant-EM microscope used in this work was partly funded by the Hercules fund from the Flemish Government. MdH acknowledges financial support from the ANRCOSMOS (ANR-12-JS10-0002). MdH and ML acknowledge funding from the Laboratoire d’excellence LANEF in Grenoble (ANR-10-LABX-51-01). Approved Most recent IF: 2.843
Call Number EMAT @ emat @c:irua:150459UA @ admin @ c:irua:150459 Serial 4920
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Author Korneychuk, S.; Partoens, B.; Guzzinati, G.; Ramaneti, R.; Derluyn, J.; Haenen, K.; Verbeeck, J.
Title Exploring possibilities of band gap measurement with off-axis EELS in TEM Type A1 Journal article
Year 2018 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 189 Issue 189 Pages 76-84
Keywords A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Abstract A technique to measure the band gap of dielectric materials with high refractive index by means of energy electron loss spectroscopy (EELS) is presented. The technique relies on the use of a circular (Bessel) aperture and suppresses Cherenkov losses and surface-guided light modes by enforcing a momentum transfer selection. The technique also strongly suppresses the elastic zero loss peak, making the acquisition, interpretation and signal to noise ratio of low loss spectra considerably better, especially for excitations in the first few eV of the EELS spectrum. Simulations of the low loss inelastic electron scattering probabilities demonstrate the beneficial influence of the Bessel aperture in this setup even for high accelerating voltages. The importance of selecting the optimal experimental convergence and collection angles is highlighted. The effect of the created off-axis acquisition conditions on the selection of the transitions from valence to conduction bands is discussed in detail on a simplified isotropic two band model. This opens the opportunity for deliberately selecting certain transitions by carefully tuning the microscope parameters. The suggested approach is experimentally demonstrated and provides good signal to noise ratio and interpretable band gap signals on reference samples of diamond, GaN and AlN while offering spatial resolution in the nm range. (C) 2018 Elsevier B.V. All rights reserved.
Address
Corporate Author Thesis
Publisher Place of Publication Amsterdam Editor
Language Wos 000432868500008 Publication Date 2018-03-29
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 7 Open Access OpenAccess
Notes ; S.K., B.P. and J.V. acknowledge funding from the “Geconcentreerde Onderzoekacties” (GOA) project “Solarpaint” of the University of Antwerp. S.K. and J.V. also acknowledge the FWO-Vlaanderen for financial support under contract G.0044.13N 'Charge ordering'. Financial support via the Methusalem “NANO” network is acknowledged. GG acknowledges support from a postdoctoral fellowship grant from the Fonds Wetenschappelijk Onderzoek-Vlaanderen (FWO). ; Approved Most recent IF: 2.843
Call Number UA @ lucian @ c:irua:151472UA @ admin @ c:irua:151472 Serial 5026
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Author Müller-Caspary, K.; Krause, F.F.; Winkler, F.; Béché, A.; Verbeeck, J.; Van Aert, S.; Rosenauer, A.
Title Comparison of first moment STEM with conventional differential phase contrast and the dependence on electron dose Type A1 Journal article
Year 2019 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 203 Issue 203 Pages 95-104
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract This study addresses the comparison of scanning transmission electron microscopy (STEM) measurements of momentum transfers using the first moment approach and the established method that uses segmented annular detectors. Using an ultrafast pixelated detector to acquire four-dimensional, momentum-resolved STEM signals, both the first moment calculation and the calculation of the differential phase contrast (DPC) signals are done for the same experimental data. In particular, we investigate the ability to correct the segment-based signal to yield a suitable approximation of the first moment for cases beyond the weak phase object approximation. It is found that the measurement of momentum transfers using segmented detectors can approach the first moment measurement as close as 0.13 h/nm in terms of a root mean square (rms) difference in 10 nm thick SrTiO3 for a detector with 16 segments. This amounts to 35% of the rms of the momentum transfers. In addition, we present a statistical analysis of the precision of first moment STEM as a function of dose. For typical experimental settings with recent hardware such as a Medipix3 Merlin camera attached to a probe-corrected STEM, we find that the precision of the measurement of momentum transfers stagnates above certain doses. This means that other instabilities such as specimen drift or scan noise have to be taken into account seriously for measurements that target, e.g., the detection of bonding effects in the charge density.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000465021000013 Publication Date 2018-12-30
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 25 Open Access OpenAccess
Notes ; The direct electron detector (Medipix3 Merlin) was funded by the Hercules fund from the Flemish Government. K. Muller-Caspary acknowledges funding from the Initiative and Network Fund of the Helmholtz Association within the framework of the Helmholtz Young Investigator Group moreSTEM (VH-NG-1317) at Forschungszentrum Julich, Germany. F. F. Krause acknowledges funding from the Central Research Development Fund of the University of Bremen, Germany. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant Agreement No. 770887). The authors acknowledge financial support from the Research Foundation Flanders (FWO, Belgium) and the Research Fund of the University of Antwerp. ; Approved Most recent IF: 2.843
Call Number UA @ admin @ c:irua:160213 Serial 5242
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Author Velazco, A.; Nord, M.; Béché, A.; Verbeeck, J.
Title Evaluation of different rectangular scan strategies for STEM imaging Type A1 Journal article
Year 2020 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume Issue Pages 113021
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract STEM imaging is typically performed by raster scanning a focused electron probe over a sample. Here we investigate and compare three different scan patterns, making use of a programmable scan engine that allows to arbitrarily set the sequence of probe positions that are consecutively visited on the sample. We compare the typical raster scan with a so-called ‘snake’ pattern where the scan direction is reversed after each row and a novel Hilbert scan pattern that changes scan direction rapidly and provides an homogeneous treatment of both scan directions. We experimentally evaluate the imaging performance on a single crystal test sample by varying dwell time and evaluating behaviour with respect to sample drift. We demonstrate the ability of the Hilbert scan pattern to more faithfully represent the high frequency content of the image in the presence of sample drift. It is also shown that Hilbert scanning provides reduced bias when measuring lattice parameters from the obtained scanned images while maintaining similar precision in both scan directions which is especially important when e.g. performing strain analysis. Compared to raster scanning with flyback correction, both snake and Hilbert scanning benefit from dose reduction as only small probe movement steps occur.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000544042800007 Publication Date 2020-05-21
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.2 Times cited 13 Open Access OpenAccess
Notes A.V., A.B. and J.V. acknowledge funding through FWO project G093417N ('Compressed sensing enabling low dose imaging in transmission electron microscopy') from the Flanders Research Fund. M.N. received support for this work from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 838001. J.V acknowledges funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 823717 – ESTEEM3. Approved Most recent IF: 2.2; 2020 IF: 2.843
Call Number EMAT @ emat @c:irua:169225 Serial 6369
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Author Fatermans, J.; den Dekker, Aj.; Müller-Caspary, K.; Gauquelin, N.; Verbeeck, J.; Van Aert, S.
Title Atom column detection from simultaneously acquired ABF and ADF STEM images Type A1 Journal article
Year 2020 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 219 Issue Pages 113046
Keywords A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Abstract In electron microscopy, the maximum a posteriori (MAP) probability rule has been introduced as a tool to determine the most probable atomic structure from high-resolution annular dark-field (ADF) scanning transmission electron microscopy (STEM) images exhibiting low contrast-to-noise ratio (CNR). Besides ADF imaging, STEM can also be applied in the annular bright-field (ABF) regime. The ABF STEM mode allows to directly visualize light-element atomic columns in the presence of heavy columns. Typically, light-element nanomaterials are sensitive to the electron beam, limiting the incoming electron dose in order to avoid beam damage and leading to images exhibiting low CNR. Therefore, it is of interest to apply the MAP probability rule not only to ADF STEM images, but to ABF STEM images as well. In this work, the methodology of the MAP rule, which combines statistical parameter estimation theory and model-order selection, is extended to be applied to simultaneously acquired ABF and ADF STEM images. For this, an extension of the commonly used parametric models in STEM is proposed. Hereby, the effect of specimen tilt has been taken into account, since small tilts from the crystal zone axis affect, especially, ABF STEM intensities. Using simulations as well as experimental data, it is shown that the proposed methodology can be successfully used to detect light elements in the presence of heavy elements.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000594768500005 Publication Date 2020-06-01
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.2 Times cited 9 Open Access OpenAccess
Notes The authors acknowledge financial support from the Research Foundation Flanders (FWO, Belgium) through project fundings (No. W.O.010.16N, No. G.0368.15N, No. G.0502.18N, EOS 30489208). This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 770887). The authors acknowledge funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 823717 – ESTEEM3. The direct electron detector (Medipix3, Quantum Detectors) was funded by the Hercules fund from the Flemish Government. K. M. C. acknowledges funding from the Initiative and Network Fund of the Helmholtz Association (Germany) under contract VH-NG-1317. The authors thank Mark Huijben from the University of Twente (Enschede, The Netherlands) for providing the LiMn2O4 sample used in section 4.2 of this study. N. G., J. V., and S. V. A. acknowledge funding from the University of Antwerp through the Concerted Research Actions (GOA) project Solarpaint and the TOP project. Approved Most recent IF: 2.2; 2020 IF: 2.843
Call Number EMAT @ emat @c:irua:169706 Serial 6373
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Author Prabhakara, V.; Jannis, D.; Guzzinati, G.; Béché, A.; Bender, H.; Verbeeck, J.
Title HAADF-STEM block-scanning strategy for local measurement of strain at the nanoscale Type A1 Journal article
Year 2020 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 219 Issue Pages 113099
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract Lattice strain measurement of nanoscale semiconductor devices is crucial for the semiconductor industry as strain substantially improves the electrical performance of transistors. High resolution scanning transmission electron microscopy (HR-STEM) imaging is an excellent tool that provides spatial resolution at the atomic scale and strain information by applying Geometric Phase Analysis or image fitting procedures. However, HR-STEM images regularly suffer from scanning distortions and sample drift during image acquisition. In this paper, we propose a new scanning strategy that drastically reduces artefacts due to drift and scanning distortion, along with extending the field of view. It consists of the acquisition of a series of independent small subimages containing an atomic resolution image of the local lattice. All subimages are then analysed individually for strain by fitting a nonlinear model to the lattice images. The method allows flexible tuning of spatial resolution and the field of view within the limits of the dynamic range of the scan engine while maintaining atomic resolution sampling within the subimages. The obtained experimental strain maps are quantitatively benchmarked against the Bessel diffraction technique. We demonstrate that the proposed scanning strategy approaches the performance of the diffraction technique while having the advantage that it does not require specialized diffraction cameras.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000594768500006 Publication Date 2020-09-01
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.2 Times cited 4 Open Access OpenAccess
Notes A.B. D.J. and J.V. acknowledge funding through FWO project G093417N ('Compressed sensing enabling low dose imaging in transmission electron microscopy') from the Flanders Research Fund. J.V acknowledges funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 823717 – ESTEEM3. The Qu-Ant-EM microscope and the direct electron detector used in the diffraction experiments was partly funded by the Hercules fund from the Flemish Government. This project has received funding from the GOA project “Solarpaint” of the University of Antwerp. GG acknowledges support from a postdoctoral fellowship grant from the Fonds Wetenschappelijk Onderzoek – Vlaanderen (FWO). Special thanks to Dr. Thomas Nuytten, Prof. Dr. Wilfried Vandervorst, Dr. Paola Favia, Dr. Olivier Richard from IMEC, Leuven and Prof. Dr. Sara Bals from EMAT, Antwerp for their continuous support and collaboration with the project and to the IMEC processing group for the device fabrication. Approved Most recent IF: 2.2; 2020 IF: 2.843
Call Number EMAT @ emat @c:irua:172485 Serial 6404
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Author Vanrompay, H.; Skorikov, A.; Bladt, E.; Béché, A.; Freitag, B.; Verbeeck, J.; Bals, S.
Title Fast versus conventional HAADF-STEM tomography of nanoparticles: advantages and challenges Type A1 Journal article
Year 2021 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 221 Issue Pages 113191
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract HAADF-STEM tomography is a widely used experimental technique for analyzing nanometer-scale crystalline structures of a large variety of materials in three dimensions. Unfortunately, the acquisition of conventional HAADF-STEM tilt series can easily take up one hour or more, depending on the complexity of the experiment. It is therefore far from straightforward to investigate samples that do not withstand long acquisition or to acquire large amounts of tilt series during a single TEM experiment. The latter would lead to the ability to obtain statistically meaningful 3D data, or to perform in situ 3D characterizations with a much shorter time resolution. Various HAADF-STEM acquisition strategies have been proposed to accelerate the tomographic acquisition and reduce the required electron dose. These methods include tilting the holder continuously while acquiring a projection “movie” and a hybrid, incremental, methodology which combines the benefits of the conventional and continuous technique. However, until now an experimental evaluation has been lacking. In this paper, the different acquisition strategies will be experimentally compared in terms of speed, resolution and electron dose. This evaluation will be performed based on experimental tilt series acquired for various metallic nanoparticles with different shapes and sizes. We discuss the data processing involved with the fast HAADF-STEM tilt series and provide a general guideline when which acquisition strategy should be preferentially used.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000612539600003 Publication Date 2020-12-08
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.843 Times cited 15 Open Access OpenAccess
Notes We acknowledge Prof. Luis M. Liz-Marzán and co-workers of the Bionanoplasmonics Laboratory, CIC biomaGUNE, Spain for providing the Au@Ag nanoparticles, Prof. Sara. E. Skrabalak and co-workers of Indiana University, United States for the provision of the Au octopods and Prof. Teri W. Odom of Northwestern University, United States for the provision of the Au nanostars. H.V. acknowledges financial support by the Research Foundation Flanders (FWO grant 1S32617N). S.B acknowledges financial support by the Research Foundation Flanders (FWO grant G.0381.16N). This project received funding as well from the European Union’s Horizon 2020 research and innovation program under grant agreement No 731019 (EUSMI) and No 815128 (REALNANO). The authors acknowledge the entire EMAT technical staff for their support.; sygma Approved Most recent IF: 2.843
Call Number EMAT @ emat @c:irua:174551 Serial 6660
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Author Velazco, A.; Béché, A.; Jannis, D.; Verbeeck, J.
Title Reducing electron beam damage through alternative STEM scanning strategies, Part I: Experimental findings Type A1 Journal article
Year 2022 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 232 Issue Pages 113398
Keywords A1 Journal article; Electron microscopy for materials research (EMAT)
Abstract The highly energetic electrons in a transmission electron microscope (TEM) can alter or even completely destroy the structure of samples before sufficient information can be obtained. This is especially problematic in the case of zeolites, organic and biological materials. As this effect depends on both the electron beam and the sample and can involve multiple damage pathways, its study remained difficult and is plagued with irreproducibility issues, circumstantial evidence, rumors, and a general lack of solid data. Here we take on the experimental challenge to investigate the role of the STEM scan pattern on the damage behavior of a commercially available zeolite sample with the clear aim to make our observations as reproducible as possible. We make use of a freely programmable scan engine that gives full control over the tempospatial distribution of the electron probe on the sample and we use its flexibility to obtain multiple repeated experiments under identical conditions comparing the difference in beam damage between a conventional raster scan pattern and a newly proposed interleaved scan pattern that provides exactly the same dose and dose rate and visits exactly the same scan points. We observe a significant difference in beam damage for both patterns with up to 11 % reduction in damage (measured from mass loss). These observations demonstrate without doubt that electron dose, dose rate and acceleration voltage are not the only parameters affecting beam damage in (S)TEM experiments and invite the community to rethink beam damage as an unavoidable consequence of applied electron dose.
Address
Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000714819200002 Publication Date 2021-10-02
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.2 Times cited 18 Open Access OpenAccess
Notes A.V., D.J., A.B. and J.V. acknowledge funding from FWO project G093417N (’Compressed sensing enabling low dose imaging in transmission electron microscopy’) and G042920N (’Coincident event detection for advanced spectroscopy in transmission electron microscopy’). This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 823717 ESTEEM3. The Qu-Ant-EM microscope was partly funded by the Hercules fund from the Flemish Government. J.V. acknowledges funding from GOA project “Solarpaint” of the University of Antwerp.; JRA; reported Approved Most recent IF: 2.2
Call Number EMAT @ emat @c:irua:183282 Serial 6818
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Author Jannis, D.; Hofer, C.; Gao, C.; Xie, X.; Béché, A.; Pennycook, Tj.; Verbeeck, J.
Title Event driven 4D STEM acquisition with a Timepix3 detector: Microsecond dwell time and faster scans for high precision and low dose applications Type A1 Journal article
Year 2022 Publication Ultramicroscopy Abbreviated Journal (up) Ultramicroscopy
Volume 233 Issue Pages 113423
Keywords A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Abstract Four dimensional scanning transmission electron microscopy (4D STEM) records the scattering of electrons in a material in great detail. The benefits offered by 4D STEM are substantial, with the wealth of data it provides facilitating for instance high precision, high electron dose efficiency phase imaging via centre of mass or ptychography based analysis. However the requirement for a 2D image of the scattering to be recorded at each probe position has long placed a severe bottleneck on the speed at which 4D STEM can be performed. Recent advances in camera technology have greatly reduced this bottleneck, with the detection efficiency of direct electron detectors being especially well suited to the technique. However even the fastest frame driven pixelated detectors still significantly limit the scan speed which can be used in 4D STEM, making the resulting data susceptible to drift and hampering its use for low dose beam sensitive applications. Here we report the development of the use of an event driven Timepix3 direct electron camera that allows us to overcome this bottleneck and achieve 4D STEM dwell times down to 100 ns; orders of magnitude faster than what has been possible with frame based readout. We characterize the detector for different acceleration voltages and show that the method is especially well suited for low dose imaging and promises rich datasets without compromising dwell time when compared to conventional STEM imaging.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Wos 000734396800003 Publication Date 2021-11-13
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0304-3991 ISBN Additional Links UA library record; WoS full record; WoS citing articles
Impact Factor 2.2 Times cited 31 Open Access OpenAccess
Notes This project has received funding from the Euro- pean Union’s Horizon 2020 Research Infrastructure – Integrating Activities for Advanced Communities under grant agreement No 823717 – ESTEEM3. J.V. and A.B. acknowledge funding from FWO project G093417N (‘Compressed sensing enabling low dose imaging in transmission electron microscopy’). J.V. and D.J. ac- knowledge funding from FWO project G042920N ‘Co- incident event detection for advanced spectroscopy in transmission electron microscopy’. We acknowledge funding under the European Union’s Horizon 2020 re- search and innovation programme (J.V. and D.J un- der grant agreement No 101017720, FET-Proactive EBEAM, and C.H., C.G., X.X. and T.J.P. from the Eu- ropean Research Council (ERC) Grant agreement No. 802123-HDEM).; esteem3JRA; esteem3reported Approved Most recent IF: 2.2
Call Number EMAT @ emat @c:irua:183948 Serial 6828
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