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	Author	de Backer, A.; Martinez, G.T.; MacArthur, K.E.; Jones, L.; Béché, A.; Nellist, P.D.; Van Aert, S.
	Title	Dose limited reliability of quantitative annular dark field scanning transmission electron microscopy for nano-particle atom-counting			Type	A1 Journal article
	Year	2015	Publication	Ultramicroscopy	Abbreviated Journal	Ultramicroscopy
	Volume	151	Issue	151	Pages	56-61
	Keywords	A1 Journal article; Electron microscopy for materials research (EMAT)
	Abstract	Quantitative annular dark field scanning transmission electron microscopy (ADF STEM) has become a powerful technique to characterise nano-particles on an atomic scale. Because of their limited size and beam sensitivity, the atomic structure of such particles may become extremely challenging to determine. Therefore keeping the incoming electron dose to a minimum is important. However, this may reduce the reliability of quantitative ADF STEM which will here be demonstrated for nano-particle atom-counting. Based on experimental ADF STEM images of a real industrial catalyst, we discuss the limits for counting the number of atoms in a projected atomic column with single atom sensitivity. We diagnose these limits by combining a thorough statistical method and detailed image simulations.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Amsterdam	Editor
	Language		Wos	000351237800008	Publication Date	2014-12-03
	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	29	Open Access
	Notes	312483 Esteem2; 278510 Vortex; Fwo G039311; G006410; G037413; esteem2ta; ECASJO;			Approved	Most recent IF: 2.843; 2015 IF: 2.436
	Call Number	c:irua:123927 c:irua:123927			Serial	753
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	Author	Verbeeck, J.; Béché, A.; van den Broek, W.
	Title	A holographic method to measure the source size broadening in STEM			Type	A1 Journal article
	Year	2012	Publication	Ultramicroscopy	Abbreviated Journal	Ultramicroscopy
	Volume	120	Issue		Pages	35-40
	Keywords	A1 Journal article; Electron microscopy for materials research (EMAT)
	Abstract	Source size broadening is an important resolution limiting effect in modern STEM experiments. Here, we propose an alternative method to measure the source size broadening making use of a holographic biprism to create interference patterns in an empty Ronchigram. This allows us to measure the exact shape of the source size broadening with a much better sampling than previously possible. We find that the shape of the demagnified source deviates considerably from a Gaussian profile that is often assumed. We fit the profile with a linear combination of a Gaussian and a bivariate Cauchy distribution showing that even though the full width at half maximum is similar to previously reported measurements, the tails of the profile are considerable wider. This is of fundamental importance for quantitative comparison of STEM simulations with experiments as these tails make the image contrast dependent on the interatomic distance, an effect that cannot be reproduced by a single Gaussian profile of fixed width alone.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Amsterdam	Editor
	Language		Wos	000308082600005	Publication Date	2012-06-01
	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	2.843	Times cited	29	Open Access
	Notes	This work was supported by funding from the European Research Council under the 7th Framework Program (FP7), ERC Grant no. 246791 COUNTATOMS and ERC Starting Grant 278510 VORTEX. The Qu-Ant-EM microscope was partly funded by the Hercules fund from the Flemish Government. W. Van den Broek acknowledges funding from the Condor project, a project under the supervision of the Embedded Systems Institute (ESI) and FEI. This project is partially supported by the Dutch Ministry of Economic Affairs under the BSIK program. ECASJO_;			Approved	Most recent IF: 2.843; 2012 IF: 2.470
	Call Number	UA @ lucian @ c:irua:100466UA @ admin @ c:irua:100466			Serial	1483
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	Author	Verbeeck, J.; Tian, H.; Béché, A.
	Title	A new way of producing electron vortex probes for STEM			Type	A1 Journal article
	Year	2012	Publication	Ultramicroscopy	Abbreviated Journal	Ultramicroscopy
	Volume	113	Issue		Pages	83-87
	Keywords	A1 Journal article; Electron microscopy for materials research (EMAT)
	Abstract	A spiral holographic aperture is used in the condensor plane of a scanning transmission electron microscope to produce a focussed electron vortex probe carrying a topological charge of either −1, 0 or +1. The spiral aperture design has a major advantage over the previously used forked aperture in that the three beams with topological charge m=−1, 0, and 1 are not side by side in the specimen plane, but rather on top of each other, focussed at different heights. This allows us to have only one selected beam in focus on the sample while the others contribute only to a background signal. In this paper we describe the working principle as well as first experimental results demonstrating atomic resolution HAADF STEM images obtained with electron vortex probes. These results pave the way for atomic resolution magnetic information when combined with electron energy loss spectroscopy.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Amsterdam	Editor
	Language		Wos	000300554400002	Publication Date	2011-10-31
	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	62	Open Access
	Notes	J.V. wants to thank Miles Padgett for suggesting this setup and pointing to the relevant optics literature. Peter Schattschneider is acknowledged for in depth discussions on related topics. J.V acknowledges funding from the European Research Council under the 7th Framework Program (FP7), ERC Grant no. 46791-COUN-TATOMS and ERC Starting Grant no. 278510 VORTEX. The Qu-Ant-EM microscope is partially funded by the Hercules fund of the Flemish Government. ECASJO_;			Approved	Most recent IF: 2.843; 2012 IF: 2.470
	Call Number	UA @ lucian @ c:irua:93624UA @ admin @ c:irua:93624			Serial	2336
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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	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	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	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	Béché, A.; Rouviere, J.L.; Barnes, J.P.; Cooper, D.
	Title	Strain measurement at the nanoscale : comparison between convergent beam electron diffraction, nano-beam electron diffraction, high resolution imaging and dark field electron holography			Type	A1 Journal article
	Year	2013	Publication	Ultramicroscopy	Abbreviated Journal	Ultramicroscopy
	Volume	131	Issue		Pages	10-23
	Keywords	A1 Journal article; Electron microscopy for materials research (EMAT)
	Abstract	Convergent beam electron diffraction (CBED), nano-beam electron diffraction (NBED or NBD), high resolution imaging (HRTEM and HRSTEM) and dark field electron holography (DFEH or HoloDark) are five TEM based techniques able to quantitatively measure strain at the nanometer scale. In order to demonstrate the advantages and disadvantages of each technique, two samples composed of epitaxial silicon-germanium layers embedded in a silicon matrix have been investigated. The five techniques are then compared in terms of strain precision and accuracy, spatial resolution, field of view, mapping abilities and ease of performance and analysis. (C) 2013 Elsevier By. All rights reserved.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Amsterdam	Editor
	Language		Wos	000322631200002	Publication Date	2013-04-06
	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
	Notes				Approved	Most recent IF: 2.843; 2013 IF: 2.745
	Call Number	UA @ lucian @ c:irua:109774			Serial	3171
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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	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	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	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	Béché, A.; Rouvière, J.L.; Barnes, J.P.; Cooper, D.
	Title	Dark field electron holography for strain measurement			Type	A1 Journal article
	Year	2011	Publication	Ultramicroscopy	Abbreviated Journal	Ultramicroscopy
	Volume	111	Issue	3	Pages	227-238
	Keywords	A1 Journal article; Electron microscopy for materials research (EMAT)
	Abstract	Dark field electron holography is a new TEM-based technique for measuring strain with nanometer scale resolution. Here we present the procedure to align a transmission electron microscope and obtain dark field holograms as well as the theoretical background necessary to reconstruct strain maps from holograms. A series of experimental parameters such as biprism voltage, sample thickness, exposure time, tilt angle and choice of diffracted beam are then investigated on a silicon-germanium layer epitaxially embedded in a silicon matrix in order to obtain optimal dark field holograms over a large field of view with good spatial resolution and strain sensitivity.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication	Amsterdam	Editor
	Language		Wos	000288638200007	Publication Date	2010-12-01
	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	31	Open Access
	Notes				Approved	Most recent IF: 2.843; 2011 IF: 2.471
	Call Number	UA @ lucian @ c:irua:136368			Serial	4496
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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	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	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	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	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	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	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	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	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	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	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	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.
	Address
	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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	Author	Jannis, D.; Velazco, A.; Béché, A.; Verbeeck, J.
	Title	Reducing electron beam damage through alternative STEM scanning strategies, Part II: Attempt towards an empirical model describing the damage process			Type	A1 Journal article
	Year	2022	Publication	Ultramicroscopy	Abbreviated Journal	Ultramicroscopy
	Volume		Issue		Pages	113568
	Keywords	A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
	Abstract	In this second part of a series we attempt to construct an empirical model that can mimick all experimental observations made regarding the role of an alternative interleaved scan pattern in STEM imaging on the beam damage in a specific zeolite sample. We make use of a 2D diffusion model that describes the dissipation of the deposited beam energy in the sequence of probe positions that are visited during the scan pattern. The diffusion process allows for the concept of trying to ‘outrun’ the beam damage by carefully tuning the dwell time and distance between consecutively visited probe positions. We add a non linear function to include a threshold effect and evaluate the accumulated damage in each part of the image as a function of scan pattern details. Together, these ingredients are able to describe qualitatively all aspects of the experimental data and provide us with a model that could guide a further optimisation towards even lower beam damage without lowering the applied electron dose. We deliberately remain vague on what is diffusing here which avoids introducing too many sample specific details. This provides hope that the model can be applied also in sample classes that were not yet studied in such great detail by adjusting higher level parameters: a sample dependent diffusion constant and damage threshold.
	Address
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language		Wos	000832788000003	Publication Date	0000-00-00
	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	D.J., A.V, 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 .; esteem3reported; esteem3jra;			Approved	Most recent IF: 2.2
	Call Number	EMAT @ emat @c:irua:188535			Serial	7071
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