17 results on '"Sven Cornelissen"'
Search Results
2. Voxel-wise segmentation for porosity investigation of additive manufactured parts with 3D unsupervised and (deeply) supervised neural networks.
- Author
-
Domenico Iuso, Soumick Chatterjee, Sven Cornelissen, Dries Verhees, Jan De Beenhouwer, and Jan Sijbers
- Published
- 2024
- Full Text
- View/download PDF
3. Evaluation of deeply supervised neural networks for 3D pore segmentation in additive manufacturing
- Author
-
Domenico Iuso, Soumick Chatterjee, Rob Heylen, Sven Cornelissen, Jan De Beenhouwer, and Jan Sijbers
- Subjects
Physics ,Engineering sciences. Technology - Abstract
Additive manufacturing (AM) is increasingly gaining interest as a low-waste production technique, capable of producing objects using a computer-aided design file. It is particularly interesting for rapid prototyping of parts and manufacturing objects that have complex shapes. However, as in the case of AM through selective laser melting (SLM), manufactured objects may contain defects that can seriously alter their properties. These defects may appear as pores, which can be detected by X-ray computed tomography (X-CT) in a non-destructive manner. CT images can simply be segmented by thresholding or through more advanced techniques such as discrete X-CT reconstruction or machine learning techniques. Nevertheless, these techniques are vulnerable to image reconstruction artefacts. In this work, we evaluate the performance of state-of-the-art, deeply supervised 3D deep learning networks (UNet++, UNet 3+ and UNet-MSS) in terms of segmentation performance of pores from X-ray CT images. The networks have been trained on a real CT dataset, with (noisy) labels produced from both conventional thresholding of the CT images as well as more advanced discrete polychromatic reconstructions. Furthermore, the performance of the networks was evaluated on a test dataset with severe CT artefacts. Pore segmentation from real CT images, which include noise and reconstruction artefacts, revealed that the best performing network was UNet++ with an average Sorensen-Dice score of 0.869 +/- 0.006.
- Published
- 2022
- Full Text
- View/download PDF
4. Injection locked CMOS buffer dedicated to nanomagnetic based voltage controlled oscillator.
- Author
-
Franck Badets, Lieven Lagae, Sven Cornelissen, Thibaut Devolder, and Claude Chappert
- Published
- 2008
- Full Text
- View/download PDF
5. Lessons learned in the design of reference fiducials for layer-wise analysis of test coupons made by laser powder bed fusion
- Author
-
Massimiliano Ferrucci, Sven Cornelissen, Michele Pavan, Tom Craeghs, Wim Dewulf, and Alkan Donmez
- Subjects
X-RAY TOMOGRAPHY ,Technology ,0209 industrial biotechnology ,Materials science ,Registration ,Additive manufacturing ,PREDICTION ,Materials Science ,Biomedical Engineering ,Materials Science, Multidisciplinary ,Computed tomography ,02 engineering and technology ,RESIDUAL-STRESS ,Industrial and Manufacturing Engineering ,POROSITY MEASUREMENT ,law.invention ,Engineering ,020901 industrial engineering & automation ,law ,Layer wise ,medicine ,QUALITY ,COMPUTED-TOMOGRAPHY ,General Materials Science ,Computer vision ,DEFECT DETECTION ,Engineering (miscellaneous) ,X-ray computed tomography ,Fusion ,Science & Technology ,Design for metrology ,PARTS ,medicine.diagnostic_test ,business.industry ,Geodetic datum ,METROLOGY ,021001 nanoscience & nanotechnology ,Laser ,Engineering, Manufacturing ,Powder bed ,Artificial intelligence ,0210 nano-technology ,Fiducial marker ,business ,Porosity - Abstract
The ability to align ex-situ inspection data of an additively manufactured (AM) part to its build geometry can be helpful, for example, to correlate observed in-situ monitoring events or features to measured discontinuities, such as pores and cracks, in ex-situ inspection. In some cases, the original part design does not lend itself to such an alignment due to the absence of datum surfaces. In this study, the concept of incorporating inclined, cylindrical protrusions as reference fiducials in the design of cylindrical AM test coupons is investigated. Six coupons with proposed fiducials were built and inspected using X-ray computed tomography (CT). Dimensional measurements performed on the fiducials expose shortcomings in the proposed fiducial design—mainly a result of limited dimensional fidelity of small features by AM—and allow us to make suggestions on how the design can be improved. Nevertheless, an alignment scheme based on the reference fiducials is compared with an approach based on inherent coupon surfaces on layer-wise porosity measurements by X-ray CT on one of the test coupons.
- Published
- 2021
- Full Text
- View/download PDF
6. Effect of Ta Insertion in Reference Layers of MTJs With Perpendicular Anisotropy
- Author
-
Nicolas Vernier, Tai Min, Sven Cornelissen, Adrien Le Goff, Thibaut Devolder, Karin Garcia, and Taiebeh Tahmasebi
- Subjects
Magnetization dynamics ,Materials science ,Condensed matter physics ,Magnetic domain ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Ferromagnetic resonance ,Magnetic susceptibility ,Electronic, Optical and Magnetic Materials ,Condensed Matter::Materials Science ,Magnetic anisotropy ,Magnetic shape-memory alloy ,Ferromagnetism ,Condensed Matter::Superconductivity ,Electrical and Electronic Engineering ,Anisotropy - Abstract
We analyze the opportunity of inserting a Ta layer between the polarizing section and the high anisotropy section in the reference subsystem of CoFeB-based tunnel junctions with perpendicular magnetic anisotropy. Using vector network analyzer ferromagnetic resonance, polar Kerr magnetometry, and magnetization dynamics modeling, we deduce the strength of the ferromagnetic interlayer exchange coupling energy J through various thickness of tantalum that impacts on the overall performance of the tunnel junctions. J culminates at 0.44 mJ/m 2 through 3 A of Ta, but the Co/Pt properties are then suboptimal. Our methodology can be used to rationally find the performance optimum in the reference layers of perpendicularly magnetized tunnel junctions.
- Published
- 2014
- Full Text
- View/download PDF
7. Interconnects scaling challenge for sub-20nm spin torque transfer magnetic random access memory technology
- Author
-
Taiebeh Tahmasebi, Gouri Sankar Kar, Praveen Raghavan, Laurent Souriau, Johan Swerts, Tai Min, D. Radisic, Sofie Mertens, Stefan Coseman, Joost Bekaert, Sven Cornelissen, Zsolt Tokei, and Kaidong Xu
- Subjects
Random access memory ,Magnetoresistive random-access memory ,Materials science ,Extreme ultraviolet lithography ,Electronic engineering ,Spin-transfer torque ,Process (computing) ,Scaling ,Lithography ,Engineering physics ,Cell size - Abstract
The scaling challenges of STT-MRAM read operation down to sub-20nm is discussed. Various contributing factors to the MTJ cell resistance variation were investigated with focus on MRAM cell variation due to lithography patterning technique and interconnects. With EUV SADP or single print process, the MRAM cell size can be scaled down to 18nm physical dimension with 4.2% sigma/ave cell area variation. For interconnects, the increasing resistance variation with shrinking dimensions poses most of the challenges.
- Published
- 2014
- Full Text
- View/download PDF
8. STT MRAM patterning challenges
- Author
-
Tetsuya Ohishi, D. Radisic, Koichi Yatsuda, Werner Boullart, Sven Cornelissen, Eiichi Nishimura, Mauricio Manfrini, Vasile Paraschiv, and Shigeru Tahara
- Subjects
Magnetoresistive random-access memory ,Materials science ,business.industry ,Etching (microfabrication) ,Computer data storage ,Nanotechnology ,business - Abstract
In this paper we report on the patterning challenges for the integration of Spin-Transfer Torque Magneto-Resistive- Random-Access Memory (STT MRAM). An overview of the different patterning approaches that have been evaluated in the past decade is presented. Plasma based etching, wet echting, but also none subtractive pattering approaches are covered. The paper also reports on the patterning strategies, currently under investigation at imec.
- Published
- 2013
- Full Text
- View/download PDF
9. Direct experimental measurement of phase-amplitude coupling in spin torque oscillators
- Author
-
Laurence Bianchini, Thibaut Devolder, Claude Chappert, W. Van Roy, Sven Cornelissen, Joo-Von Kim, and Liesbet Lagae
- Subjects
Physics ,Imagination ,Coupling ,Condensed Matter - Materials Science ,Physics and Astronomy (miscellaneous) ,Condensed matter physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,media_common.quotation_subject ,Phase (waves) ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Measure (mathematics) ,Power (physics) ,symbols.namesake ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,symbols ,Hilbert transform ,Time domain ,Voltage ,media_common - Abstract
We study spin-torque induced oscillations of MgO magnetic tunnel junctions in the time domain. By using the Hilbert transform on the time traces, we obtain for the first time a direct experimental measure of the coupling between the power and the phase fluctuations. We deduce the power restoration rate and we obtain low values for the coupling strength, which is consistent with the weak frequency dependence on the applied voltage., 3 pages, 3 figures
- Published
- 2010
10. Free layer versus synthetic ferrimagnet layer auto-oscillations in nanopillars processed from MgO-based magnetic tunnel junctions
- Author
-
W. Van Roy, Claude Chappert, L. Lagae, Sven Cornelissen, Thibaut Devolder, Joo-Von Kim, and Laurence Bianchini
- Subjects
Magnetization ,Tunnel magnetoresistance ,Magnetic anisotropy ,Materials science ,Condensed matter physics ,Ferrimagnetism ,Electron ,Condensed Matter Physics ,Excitation ,Electronic, Optical and Magnetic Materials ,Nanopillar ,Spin-½ - Abstract
We study nanopillar spin-torque oscillators processed from low-resistance-area product MgO-based magnetic tunnel junctions. The influence of spin torque can be seen in quasistatic experiments as a strong astroid distortion, consistent with a pure Slonczewski-type spin torque. At microwave frequencies, the spin-torque results in pronounced magnetization auto-oscillations with a clear threshold behavior, though only evidenced in the antiparallel configuration. Two kinds of auto-oscillations are seen depending on the polarity of the voltage applied to the junction. Free layer oscillations require a large easy axis applied field and electrons flowing from the reference layers to the free layer. Acoustic excitation of the reference synthetic ferrimagnet can be seen, provided the electron flow is reversed, indicating a clear similarity with the behavior of conventional all-metallic spin valves. The analysis of the threshold indicates that the amplitude of the spin torque is neither proportional to the current nor to the voltage and it is not accompanied by any significant fieldlike torque.
- Published
- 2010
- Full Text
- View/download PDF
11. Quantized spin-wave modes in magnetic tunnel junction nanopillars
- Author
-
Thibaut Devolder, L. Lagae, Sven Cornelissen, A. Helmer, Joo-Von Kim, Claude Chappert, and W. Van Roy
- Subjects
Physics ,Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed matter physics ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Magnetic field ,Tunnel magnetoresistance ,Magnetization ,Spin wave ,Excited state ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Antiferromagnetism ,Magnetic dipole–dipole interaction ,Nanopillar - Abstract
We present an experimental and theoretical study of the magnetic field dependence of the mode frequency of thermally excited spin waves in rectangular shaped nanopillars of lateral sizes 60x100, 75x150, and 105x190 nm2, patterned from MgO-based magnetic tunnel junctions. The spin wave frequencies were measured using spectrally resolved electrical noise measurements. In all spectra, several independent quantized spin wave modes have been observed and could be identified as eigenexcitations of the free layer and of the synthetic antiferromagnet of the junction. Using a theoretical approach based on the diagonalization of the dynamical matrix of a system of three coupled, spatially confined magnetic layers, we have modeled the spectra for the smallest pillar and have extracted its material parameters. The magnetization and exchange stiffness constant of the CoFeB free layer are thereby found to be substantially reduced compared to the corresponding thin film values. Moreover, we could infer that the pinning of the magnetization at the lateral boundaries must be weak. Finally, the interlayer dipolar coupling between the free layer and the synthetic antiferromagnet causes mode anticrossings with gap openings up to 2 GHz. At low fields and in the larger pillars, there is clear evidence for strong non-uniformities of the layer magnetizations. In particular, at zero field the lowest mode is not the fundamental mode, but a mode most likely localized near the layer edges., Comment: 16 pages, 4 figures, (re)submitted to PRB
- Published
- 2010
- Full Text
- View/download PDF
12. Auto-oscillation threshold and line narrowing in MgO-based spin-torque oscillators
- Author
-
M. Op de Beeck, Laurence Bianchini, Paul Crozat, Thomas Schrefl, Thibaut Devolder, Liesbet Lagae, Sven Cornelissen, Claude Chappert, Joo-Von Kim, and Gino Hrkac
- Subjects
Condensed Matter - Materials Science ,Materials science ,Condensed matter physics ,Oscillation ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,General Physics and Astronomy ,Spectral density ,Edge (geometry) ,Spectral line ,Magnetization ,Excited state ,Antiferromagnetism ,Micromagnetics - Abstract
We present an experimental study of the power spectrum of current-driven magnetization oscillations in MgO tunnel junctions under low bias. We find the existence of narrow spectral lines, down to 8 MHz in width at a frequency of 10.7 GHz, for small applied fields with clear evidence of an auto-oscillation threshold. Micromagnetics simulations indicate that the excited mode corresponds to an edge mode of the synthetic antiferromagnet.
- Published
- 2008
13. Spin-Hall assisted magnetic random access memory
- Author
-
Mauricio Manfrini, van W Roy, Stefan Cosemans, Tai Min, Sven Cornelissen, van den A Arno Brink, Hjm Henk Swagten, B Bert Koopmans, Adrien Vaysset, Physics of Nanostructures, and Eindhoven Hendrik Casimir institute
- Subjects
Physics ,Reduction (complexity) ,Tunnel magnetoresistance ,Physics and Astronomy (miscellaneous) ,Condensed matter physics ,Magnetoresistance ,Spin-transfer torque ,Torque ,Energy (signal processing) ,Pulse (physics) ,Spin-½ - Abstract
We propose a write scheme for perpendicular spin-transfer torque magnetoresistive random-access memory that significantly reduces the required tunnel current density and write energy. A sub-nanosecond in-plane polarized spin current pulse is generated using the spin-Hall effect, disturbing the stable magnetic state. Subsequent switching using out-of-plane polarized spin current becomes highly efficient. Through evaluation of the Landau-Lifshitz-Gilbert equation, we quantitatively assess the viability of this write scheme for a wide range of system parameters. A typical example shows an eight-fold reduction in tunnel current density, corresponding to a fifty-fold reduction in write energy, while maintaining a 1 ns write time.
- Published
- 2014
14. Performance analysis of MgO-based perpendicularly magnetized tunnel junctions
- Author
-
Tai Min, Mauricio Manfrini, Guillaume Agnus, Sven Cornelissen, Karin Garcia, and Thibaut Devolder
- Subjects
Magnetic anisotropy ,Materials science ,Physics and Astronomy (miscellaneous) ,Spin dynamics ,Condensed matter physics ,Remanence ,Perpendicular magnetic anisotropy ,Condensed Matter::Superconductivity ,Perpendicular ,Magnetic tunnelling ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Anisotropy - Abstract
We studied state of the art perpendicularly magnetized tunnel junctions to identify performance improvement opportunities. The free layer has both a low damping and a large anisotropy. Conversely, the perpendicular remanence of the reference layer requires its encapsulation and its coupling with the hard layer. The weak pinning and low damping of the reference layer may make it prone to fluctuations induced by spin-torque. The combined optimization of the interface anisotropies on both sides of the MgO, together with the reproducibility of the interlayer exchange coupling are the main material challenges for our type of magnetic tunnel junctions.
- Published
- 2013
- Full Text
- View/download PDF
15. Influence of oscillation modes on the line width of rf emissions in MgO based nanopillars
- Author
-
L. Lagae, Alexander F. Goncharov, W. Van Roy, Gino Hrkac, Sven Cornelissen, Claude Chappert, Thomas Schrefl, Julian S. Dean, Thibaut Devolder, and Joo-Von Kim
- Subjects
Physics ,Full width at half maximum ,Tunnel magnetoresistance ,Condensed matter physics ,Oscillation ,Analytical chemistry ,Precession ,General Physics and Astronomy ,Spectral density ,Coherence (signal processing) ,Line (formation) ,Nanopillar - Abstract
We present a numerical study of oscillation modes in magnetic tunnel junction nanopillars and investigate the frequency and the full width at half maximum of the power spectrum as a function of applied field and applied current. We show that the line width reaches a minimum of 14.5 MHz as the system approaches the threshold current, and increases sharply to 308 MHz as the current is increased beyond the threshold current. The initial line narrowing is due to an increased coherence in the uniform precession mode, while the line broadening above threshold arises from the intrinsic oscillator nonlinearity combined with overlapping contributions from edge modes. We show that these results are in good agreement with recent experiments on MgO-based oscillators.
- Published
- 2010
- Full Text
- View/download PDF
16. Auto-oscillation and narrow spectral lines in spin-torque oscillators based on MgO magnetic tunnel junctions
- Author
-
Claude Chappert, Paul Crozat, Sven Cornelissen, L. Lagae, M. Op de Beeck, Joo-Von Kim, Thibaut Devolder, and Laurence Bianchini
- Subjects
Condensed Matter::Materials Science ,Astroid ,Materials science ,Field (physics) ,Condensed matter physics ,Oscillation ,General Physics and Astronomy ,Flicker noise ,Electron ,Excitation ,Spectral line ,Envelope (waves) - Abstract
We demonstrate spin-torque induced coherent auto-oscillation in magnetic tunnel junctions of composition PtMn/CoFe/Ru/CoFeB/MgO/CoFeB and of low resistance-area product. At the generation threshold, we observe a strong line narrowing down to 6 MHz at 300 K and a dramatic increase in oscillator power, yielding spectrally pure oscillations with extremely low flicker noise. The induced auto-oscillations are observed even at zero applied field. The frequency of the oscillation mode, and its dependence with easy and hard axis fields are consistent with an acoustical excitation of the two layers of the synthetic ferrimagnet subsystem. Setting the synthetic ferrimagnet into auto-oscillation requires the current polarity that transfers electrons from the synthetic ferrimagnet to the free layer. In auto-oscillation mode, line jitter is observed such that it is the line envelope that is measured in most cases. The line properties for applied fields near the instability boundaries of the Stoner astroid of the free layer indicate that the phase coherence of the auto-oscillation is likely to be affected by the free layer magnetic noise.
- Published
- 2009
- Full Text
- View/download PDF
17. Effect of patterning on the saturation magnetization in MgO based nanopillars
- Author
-
W. Van Roy, Sven Cornelissen, Claude Chappert, Joo-Von Kim, L. Lagae, Laurence Bianchini, M. Op de Beeck, Thibaut Devolder, and A. Helmer
- Subjects
Materials science ,Condensed matter physics ,General Physics and Astronomy ,equipment and supplies ,Ferromagnetic resonance ,Condensed Matter::Materials Science ,Magnetization ,Magnetic anisotropy ,Etching (microfabrication) ,Spin wave ,Joule heating ,Anisotropy ,human activities ,Nanopillar - Abstract
We have studied the effect of nanopillar patterning on the saturation magnetization of the CoFeB free layer in MgO magnetic tunnel junctions. Before patterning, the free layer magnetization is measured by ferromagnetic resonance and is found to be close to the bulk value, with no detectable interface anisotropy. After patterning, the shape anisotropy and the frequency of the main spin wave mode indicate that the free layer magnetization is substantially reduced. Current dependent measurements indicate that this is not due to Joule heating. Size dependent measurements indicate that the magnetization reduction most likely arises from process damage during the etching step.
- Published
- 2009
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.