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Author |
Gao, C.; Hofer, C.; Pennycook, T.J. |
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Title |
On central focusing for contrast optimization in direct electron ptychography of thick samples |
Type |
A1 Journal article |
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Year |
2024 |
Publication |
Ultramicroscopy |
Abbreviated Journal |
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Volume |
256 |
Issue |
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Pages |
113879-7 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
Ptychography provides high dose efficiency images that can reveal light elements next to heavy atoms. However, despite ptychography having an otherwise single signed contrast transfer function, contrast reversals can occur when the projected potential becomes strong for both direct and iterative inversion ptychography methods. It has recently been shown that these reversals can often be counteracted in direct ptychography methods by adapting the focus. Here we provide an explanation of why the best contrast is often found with the probe focused to the middle of the sample. The phase contribution due to defocus at each sample slice above and below the central plane in this configuration effectively cancels out, which can prevent contrast reversals when dynamical scattering effects are not overly strong. In addition we show that the convergence angle can be an important consideration for removal of contrast reversals in relatively thin samples. |
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Wos |
001112166400001 |
Publication Date |
2023-11-03 |
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Series Issue |
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Edition |
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ISSN |
0304-3991 |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
2.2 |
Times cited |
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Open Access |
Not_Open_Access |
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Approved |
Most recent IF: 2.2; 2024 IF: 2.843 |
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Call Number |
UA @ admin @ c:irua:202029 |
Serial |
9066 |
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Permanent link to this record |
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Author |
Zanaga, D.; Altantzis, T.; Sanctorum, J.; Freitag, B.; Bals, S. |
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Title |
An alternative approach for ζ-factor measurement using pure element nanoparticles |
Type |
A1 Journal article |
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Year |
2016 |
Publication |
Ultramicroscopy |
Abbreviated Journal |
Ultramicroscopy |
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Volume |
164 |
Issue |
164 |
Pages |
11-16 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
It is very challenging to measure the chemical composition of hetero nanostructures in a reliable and quantitative manner. Here, we propose a novel and straightforward approach that can be used to quantify energy dispersive X-ray spectra acquired in a transmission electron microscope. Our method is based on a combination of electron tomography and the so-called ζ-factor technique. We will demonstrate the reliability of our approach as well as its applicability by investigating Au-Ag and Au-Pt hetero nanostructures. Given its simplicity, we expect that the method could become a new standard in the field of chemical characterization using electron microscopy. |
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Wos |
000373526200002 |
Publication Date |
2016-03-10 |
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Series Volume |
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Edition |
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ISSN |
0304-3991 |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
2.843 |
Times cited |
19 |
Open Access |
OpenAccess |
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Notes |
The authors acknowledge financial support from the European Research Council (ERC Starting Grant # 335078-COLOURATOMS) and the European Union under the FP7 (Integrated Infrastructure Initiative N. 312483 – ESTEEM2). The authors would also like to thank Luis M. Liz-Marzán, Ana Sánchez-Iglesias, Stefanos Mourdikoudis and Cristina Fernández-López for sample provision and useful discussions.; esteem2jra4; ECASSara; (ROMEO:green; preprint:; postprint:can ; pdfversion:cannot); |
Approved |
Most recent IF: 2.843 |
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Call Number |
EMAT @ emat @ |
Serial |
4019 |
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Permanent link to this record |
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Author |
Kirilenko, D.A.; Brunkov, P.N. |
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Title |
Measuring the height-to-height correlation function of corrugation in suspended graphene |
Type |
A1 Journal article |
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Year |
2016 |
Publication |
Ultramicroscopy |
Abbreviated Journal |
Ultramicroscopy |
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Volume |
165 |
Issue |
165 |
Pages |
1-7 |
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Keywords |
A1 Journal article; Electron Microscopy for Materials Science (EMAT); |
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Abstract |
Nanocorrugation of 2D crystals is an important phenomenon since it affects their electronic and mechanical properties. The corrugation may have various sources; one of them is flexural phonons that, in particular, are responsible for the thermal conductivity of graphene. A study of corrugation of just the suspended graphene can reveal much of valuable information on the physics of this complicated phenomenon. At the same time, the suspended crystal nanorelief can hardly be measured directly because of high flexibility of the 2D crystal. Moreover, the relief portion related to rapid out-of-plane oscillations (flexural phonons) is also inaccessible by such measurements. Here we present a technique for measuring the Fourier components of the height-height correlation function H(q) of suspended graphene which includes the effect of flexural phonons. The technique is based on the analysis of electron diffraction patterns. The H(q) is measured in the range of wavevectors q approximately 0.4-4.5nm(-1). At the upper limit of this range H(q) does follow the T/kappaq(4) law. So, we measured the value of suspended graphene bending rigidity kappa=1.2+/-0.4eV at ambient temperature T approximately 300K. At intermediate wave vectors, H(q) follows a slightly weaker exponent than theoretically predicted q(-3.15) but is closer to the results of the molecular dynamics simulation. At low wave vectors, the dependence becomes even weaker, which may be a sign of influence of charge carriers on the dynamics of undulations longer than 10nm. The technique presented can be used for studying physics of flexural phonons in other 2D materials. |
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Address |
Ioffe Institute, Politekhnicheskaya ul. 26, 194021 St-Petersburg, Russia; ITMO University, Kronverksky pr. 49, 197101 St. Petersburg, Russia |
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Language |
English |
Wos |
000375946200001 |
Publication Date |
2016-03-28 |
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ISSN |
0304-3991 |
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Impact Factor |
2.843 |
Times cited |
3 |
Open Access |
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Notes |
D.K. thanks the RFBR (Grant no. 16-32-60165) for the partial support of this research. The work was carried out in part at the Joint Research Center “Material Science and Characterization in Advanced Technologies” (St-Petersburg, Russia) under the financial support from the Ministry of Education and Science of the Russian Federation (Agreement 14.621.21.0007, 04.12.2014, id RFMEFI62114X0007, the use of the Jeol JEM-2100F microscope) and at EMAT, Universiteit Antwerpen (Antwerpen, Belgium), (the use of the FEI Tecnai G2 microscope). |
Approved |
Most recent IF: 2.843 |
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Call Number |
EMAT @ emat @ |
Serial |
4124 |
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Permanent link to this record |
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Author |
Hofer, C.; Pennycook, T.J. |
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Title |
Reliable phase quantification in focused probe electron ptychography of thin materials |
Type |
A1 Journal Article |
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Year |
2023 |
Publication |
Ultramicroscopy |
Abbreviated Journal |
Ultramicroscopy |
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Volume |
254 |
Issue |
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Pages |
113829 |
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Keywords |
A1 Journal Article; Electron Microscopy for Materials Science (EMAT) ; |
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Abstract |
Electron ptychography provides highly sensitive, dose efficient phase images which can be corrected for aberrations after the data has been acquired. This is crucial when very precise quantification is required, such as with sensitivity to charge transfer due to bonding. Drift can now be essentially eliminated as a major impediment to focused probe ptychography, which benefits from the availability of easily interpretable simultaneous Z-contrast imaging. However challenges have remained when quantifying the ptychographic phases of atomic sites. The phase response of a single atom has a negative halo which can cause atoms to reduce in phase when brought closer together. When unaccounted for, as in integrating methods of quantification, this effect can completely obscure the effects of charge transfer. Here we provide a new method of quantification that overcomes this challenge, at least for 2D materials, and is robust to experimental parameters such as noise, sample tilt. |
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Wos |
001071608700001 |
Publication Date |
2023-08-18 |
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Series Title ![sorted by Series Title field, ascending order (up)](img/sort_asc.gif) |
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ISSN |
0304-3991 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
2.2 |
Times cited |
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Open Access |
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Notes |
FWO, G013122N ; Horizon 2020 Framework Programme; Horizon 2020; European Research Council, 802123-HDEM ; European Research Council; |
Approved |
Most recent IF: 2.2; 2023 IF: 2.843 |
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Call Number |
EMAT @ emat @c:irua:200272 |
Serial |
8987 |
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Permanent link to this record |
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Author |
Van den Broek, W.; Jannis, D.; Verbeeck, J. |
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Title |
Convexity constraints on linear background models for electron energy-loss spectra |
Type |
A1 Journal Article |
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Year |
2023 |
Publication |
Ultramicroscopy |
Abbreviated Journal |
Ultramicroscopy |
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Volume |
254 |
Issue |
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Pages |
113830 |
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Keywords |
A1 Journal Article; Electron Microscopy for Materials Science (EMAT) ; |
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Abstract |
In this paper convexity constraints are derived for a background model of electron energy loss spectra (EELS) that is linear in the fitting parameters. The model outperforms a power-law both on experimental and simulated backgrounds, especially for wide energy ranges, and thus improves elemental quantification results. Owing to the model’s linearity, the constraints can be imposed through fitting by quadratic programming. This has important advantages over conventional nonlinear power-law fitting such as high speed and a guaranteed unique solution without need for initial parameters. As such, the need for user input is significantly reduced, which is essential for unsupervised treatment of large datasets. This is demonstrated on a demanding spectrum image of a semiconductor device sample with a high number of elements over a wide energy range. |
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Wos |
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Publication Date |
2023-08-15 |
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Series Title ![sorted by Series Title field, ascending order (up)](img/sort_asc.gif) |
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Series Volume |
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Edition |
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ISSN |
0304-3991 |
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Additional Links |
UA library record |
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Impact Factor |
2.2 |
Times cited |
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Open Access |
Not_Open_Access |
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Notes |
ECSEL, 875999 ; Horizon 2020; Horizon 2020 Framework Programme; Electronic Components and Systems for European Leadership; |
Approved |
Most recent IF: 2.2; 2023 IF: 2.843 |
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Call Number |
EMAT @ emat @c:irua:200588 |
Serial |
8961 |
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Permanent link to this record |
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Author |
Şentürk, D.G.; De Backer, A.; Van Aert, S. |
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Title |
Element specific atom counting for heterogeneous nanostructures: Combining multiple ADF STEM images for simultaneous thickness and composition determination |
Type |
A1 Journal Article |
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Year |
2024 |
Publication |
Ultramicroscopy |
Abbreviated Journal |
Ultramicroscopy |
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Volume |
259 |
Issue |
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Pages |
113941 |
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Keywords |
A1 Journal Article; Electron Microscopy for Materials Science (EMAT) ; |
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Abstract |
In this paper, a methodology is presented to count the number of atoms in heterogeneous nanoparticles based on the combination of multiple annular dark field scanning transmission electron microscopy (ADF STEM) images. The different non-overlapping annular detector collection regions are selected based on the principles of optimal statistical experiment design for the atom-counting problem. To count the number of atoms, the total intensities of scattered electrons for each atomic column, the so-called scattering cross-sections, are simultaneously compared with simulated library values for the different detector regions by minimising the squared differences. The performance of the method is evaluated for simulated Ni@Pt and Au@Ag core-shell nanoparticles. Our approach turns out to be a dose efficient alternative for the investigation of beam-sensitive heterogeneous materials as compared to the combination of ADF STEM and energy dispersive X-ray spectroscopy. |
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Publication Date |
2024-02-19 |
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Series Editor |
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Series Title ![sorted by Series Title field, ascending order (up)](img/sort_asc.gif) |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0304-3991 |
ISBN |
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Additional Links |
UA library record |
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Impact Factor |
2.2 |
Times cited |
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Open Access |
OpenAccess |
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Notes |
This work was supported by the European Research Council (Grant 770887 PICOMETRICS to S. Van Aert). The authors acknowledge financial support from the Research Foundation Flanders (FWO, Belgium) through project fundings (G.0346.21N, GOA7723N, and EOS 40007495) and a postdoctoral grant to A. De Backer. S. Van Aert acknowledges funding from the University of Antwerp Research fund (BOF). |
Approved |
Most recent IF: 2.2; 2024 IF: 2.843 |
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Call Number |
EMAT @ emat @c:irua:204353 |
Serial |
8996 |
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Permanent link to this record |