| Records |
| 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 |
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 |
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| Corporate Author |
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Thesis |
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| Publisher |
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Place of Publication |
Amsterdam |
Editor |
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| Language |
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Wos |
000281216600016 |
Publication Date |
2009-12-07 |
| Series Editor |
|
Series Title |
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Abbreviated Series Title |
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| 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 |
| Permanent link to this record |
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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 |
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 |
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| Corporate Author |
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Thesis |
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| Publisher |
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Place of Publication |
Amsterdam |
Editor |
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| Language |
|
Wos |
000258747600009 |
Publication Date |
2008-03-07 |
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
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| 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 |
| Permanent link to this record |
| |
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| |
| Author |
de Backer, A.; Van Aert, S.; van Dyck, D. |
| Title |
High precision measurements of atom column positions using model-based exit wave reconstruction |
Type |
A1 Journal article |
| Year |
2011 |
Publication |
Ultramicroscopy |
Abbreviated Journal |
Ultramicroscopy |
| Volume |
111 |
Issue |
9/10 |
Pages |
1475-1482 |
| Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab |
| Abstract |
In this paper, it has been investigated how to measure atom column positions as accurately and precisely as possible using a focal series of images. In theory, it is expected that the precision would considerably improve using a maximum likelihood estimator based on the full series of focal images. As such, the theoretical lower bound on the variances of the unknown atom column positions can be attained. However, this approach is numerically demanding. Therefore, maximum likelihood estimation has been compared with the results obtained by fitting a model to a reconstructed exit wave rather than to the full series of focal images. Hence, a real space model-based exit wave reconstruction technique based on the channelling theory is introduced. Simulations show that the reconstructed complex exit wave contains the same amount of information concerning the atom column positions as the full series of focal images. Only for thin samples, which act as weak phase objects, this information can be retrieved from the phase of the reconstructed complex exit wave. |
| Address |
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| Corporate Author |
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Thesis |
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| Publisher |
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Place of Publication |
Amsterdam |
Editor |
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| Language |
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Wos |
000300461200004 |
Publication Date |
2011-07-28 |
| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| 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 |
Fwo |
Approved |
Most recent IF: 2.843; 2011 IF: 2.471 |
| Call Number |
UA @ lucian @ c:irua:91879 |
Serial |
1438 |
| Permanent link to this record |
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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 |
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 |
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| Corporate Author |
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Thesis |
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| Publisher |
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Place of Publication |
Amsterdam |
Editor |
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| Language |
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Wos |
000300461200002 |
Publication Date |
2011-07-26 |
| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| Series Volume |
|
Series Issue |
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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 |
| Permanent link to this record |
| |
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| |
| Author |
Alania, M.; Lobato Hoyos, I.P.; Van Aert, S. |
| Title |
Frozen lattice and absorptive model for high angle annular dark field scanning transmission electron microscopy : a comparison study in terms of integrated intensity and atomic column position measurement |
Type |
A1 Journal article |
| Year |
2018 |
Publication |
Ultramicroscopy |
Abbreviated Journal |
Ultramicroscopy |
| Volume |
184 |
Issue |
A |
Pages |
188-198 |
| Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
| Abstract |
<script type='text/javascript'>document.write(unpmarked('In this paper, both the frozen lattice (FL) and the absorptive potential (AP) approximation models are compared in terms of the integrated intensity and the precision with which atomic columns can be located from an image acquired using high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). The comparison is made for atoms of Cu, Ag, and Au. The integrated intensity is computed for both an isolated atomic column and an atomic column inside an FCC structure. The precision has been computed using the so-called Cramer-Rao Lower Bound (CRLB), which provides a theoretical lower bound on the variance with which parameters can be estimated. It is shown that the AP model results into accurate measurements for the integrated intensity only for small detector ranges under relatively low angles and for small thicknesses. In terms of the attainable precision, both methods show similar results indicating picometer range precision under realistic experimental conditions. (C) 2017 Elsevier B.V. All rights reserved.')); |
| Address |
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| Corporate Author |
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Thesis |
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| Publisher |
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Place of Publication |
Amsterdam |
Editor |
|
| Language |
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Wos |
000415650200022 |
Publication Date |
2017-09-12 |
| Series Editor |
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Series Title |
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Abbreviated Series Title |
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| 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 |
|
Open Access |
OpenAccess |
| Notes |
; 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). A. Rosenauer is acknowledged for providing the STEMsim program. ; |
Approved |
Most recent IF: 2.843 |
| Call Number |
UA @ lucian @ c:irua:147658 |
Serial |
4877 |
| Permanent link to this record |
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| |
| Author |
Grieb, T.; Tewes, M.; Schowalter, M.; Müller-Caspary, K.; Krause, F.F.; Mehrtens, T.; Hartmann, J.-M.; Rosenauer, A. |
| Title |
Quantitative HAADF STEM of SiGe in presence of amorphous surface layers from FIB preparation |
Type |
A1 Journal article |
| Year |
2018 |
Publication |
Ultramicroscopy |
Abbreviated Journal |
Ultramicroscopy |
| Volume |
184 |
Issue |
B |
Pages |
29-36 |
| Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
| Abstract |
<script type='text/javascript'>document.write(unpmarked('The chemical composition of four Si1-xGex layers grown on silicon was determined from quantitative scanning transmission electron microscopy (STEM). The chemical analysis was performed by a comparison of the high-angle annular dark field (HAADF) intensity with multislice simulations. It could be shown that amorphous surface layers originating from the preparation process by focused-ion beam (FIB) at 30 kV have a strong influence on the quantification: the local specimen thickness is overestimated by approximately a factor of two, and the germanium concentration is substantially underestimated. By means of simulations, the effect of amorphous surface layers on the HAADF intensity of crystalline silicon and germanium is investigated. Based on these simulations, a method is developed to analyze the experimental HAADF-STEM images by taking the influence of the amorphous layers into account which is done by a reduction of the intensities by multiplication with a constant factor. This suggested modified HAADF analysis gives germanium concentrations which are in agreement with the nominal values. The same TEM lamella was treated with low-voltage ion milling which removed the amorphous surface layers completely. The results from subsequent quantitative HAADF analyses are in agreement with the nominal concentrations which validates the applicability of the used frozen-lattice based multislice simulations to describe the HAADF scattering of Si1-xGex in STEM. (C) 2017 Elsevier B.V. All rights reserved.')); |
| Address |
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| Corporate Author |
|
Thesis |
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| Publisher |
|
Place of Publication |
Amsterdam |
Editor |
|
| Language |
|
Wos |
000417779800004 |
Publication Date |
2017-10-14 |
| Series Editor |
|
Series Title |
|
Abbreviated Series Title |
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| 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 |
Not_Open_Access |
| Notes |
; This work was supported by the German Research Foundation (DFG) under Contract No. RO2057/11-1. ; |
Approved |
Most recent IF: 2.843 |
| Call Number |
UA @ lucian @ c:irua:148500 |
Serial |
4893 |
| Permanent link to this record |
