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Ultramicroscopy

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https://www.readbyqxmd.com/read/29772417/a-consistent-full-field-integrated-dic-framework-for-hr-ebsd
#1
T Vermeij, J P M Hoefnagels
A general, transparent, finite-strain Integrated Digital Image Correlation (IDIC) framework for high angular resolution EBSD (HR-EBSD) is proposed, and implemented through a rigorous derivation of the optimization scheme starting from the fundamental brightness conservation equation in combination with a clear geometric model of the Electron BackScatter Pattern (EBSP) formation. This results in a direct one-step correlation of the full field-of-view of EBSPs, which is validated here on dynamically simulated patterns...
May 5, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29758411/eds-tomographic-reconstruction-regularized-by-total-nuclear-variation-joined-with-haadf-stem-tomography
#2
Zhichao Zhong, Willem Jan Palenstijn, Jonas Adler, K Joost Batenburg
Energy-dispersive X-ray spectroscopy (EDS) tomography is an advanced technique to characterize compositional information for nanostructures in three dimensions (3D). However, the application is hindered by the poor image quality caused by the low signal-to-noise ratios and the limited number of tilts, which are fundamentally limited by the insufficient number of X-ray counts. In this paper, we explore how to make accurate EDS reconstructions from such data. We propose to augment EDS tomography by joining with it a more accurate high-angle annular dark-field STEM (HAADF-STEM) tomographic reconstruction, for which usually a larger number of tilt images are feasible...
May 5, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29751348/measuring-topographies-from-conventional-sem-acquisitions
#3
Qiwei Shi, Stéphane Roux, Félix Latourte, François Hild, Dominique Loisnard, Nicolas Brynaert
The present study extends the stereoscopic imaging principle for estimating the surface topography to two orientations, namely, normal to the electron beam axis and inclined at 70° as suited for EBSD analyses. In spite of the large angle difference, it is shown that the topography can be accurately determined using regularized global Digital Image Correlation. The surface topography is compared to another estimate issued from a 3D FIB-SEM procedure where the sample surface is first covered by a Pt layer, and its initial topography is progressively revealed from successive FIB-milling...
April 27, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29705643/exemplar-based-inpainting-as-a-solution-to-the-missing-wedge-problem-in-electron-tomography
#4
Patrick Trampert, Wu Wang, Delei Chen, Raimond B G Ravelli, Tim Dahmen, Peter J Peters, Christian Kübel, Philipp Slusallek
A new method for dealing with incomplete projection sets in electron tomography is proposed. The approach is inspired by exemplar-based inpainting techniques in image processing and heuristically generates data for missing projection directions. The method has been extended to work on three dimensional data. In general, electron tomography reconstructions suffer from elongation artifacts along the beam direction. These artifacts can be seen in the corresponding Fourier domain as a missing wedge. The new method synthetically generates projections for these missing directions with the help of a dictionary based approach that is able to convey both structure and texture at the same time...
April 21, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29689445/demonstration-of-a-2-%C3%A3-2-programmable-phase-plate-for-electrons
#5
Jo Verbeeck, Armand Béché, Knut Müller-Caspary, Giulio Guzzinati, Minh Anh Luong, Martien Den Hertog
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...
April 18, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29689446/a-continuous-control-mode-with-improved-imaging-rate-for-scanning-ion-conductance-microscope-sicm
#6
Jian Zhuang, Yangbohan Jiao, Zeqing Li, Jinxin Lang, Fei Li
Scanning ion conductance microscopy (SICM), one kind of scanning probe microscopy technique, featuring the advantage of non-contact imaging of sample surfaces in three dimensions with high resolution, has been widely applied in characterizations of sample topography, especially for soft materials. However, the time consuming imaging process of SICM restricts its further applications, such as in characterization of dynamic change of sample surface. In this work, a fast control mode of SICM, named as a continuous control mode, has been developed...
April 17, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29684905/entanglement-and-decoherence-in-electron-microscopy
#7
P Schattschneider, S Löffler
Interaction of the probe with the specimen in an electron microscope inevitably leads to entanglement between the probe and the scatterer. In spite of the importance of entanglement in many areas of modern physics, this subject has not been touched in the literature. Here, we develop some ideas about entanglement in electron microscopy for a number of scattering mechanisms. The relationship between entropy, density matrices, and coherence is discussed. In addition, we explore the questions "Why is Bragg scattering coherent and energy loss incoherent?" and "When does decoherence play a role?" It seems to be possible to measure decoherence on extremely short timescales of ∼10-8 s...
April 13, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29680520/a-new-method-for-mapping-the-three-dimensional-atomic-distribution-within-nanoparticles-by-atom-probe-tomography-apt
#8
Se-Ho Kim, Phil Woong Kang, O Ok Park, Jae-Bok Seol, Jae-Pyoung Ahn, Ji Yeong Lee, Pyuck-Pa Choi
We present a new method of preparing needle-shaped specimens for atom probe tomography from freestanding Pd and C-supported Pt nanoparticles. The method consists of two steps, namely electrophoresis of nanoparticles on a flat Cu substrate followed by electrodeposition of a Ni film acting as an embedding matrix for the nanoparticles. Atom probe specimen preparation can be subsequently carried out by means of focused-ion-beam milling. Using this approach, we have been able to perform correlative atom probe tomography and transmission electron microscopy analyses on both nanoparticle systems...
April 13, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29783102/strain-analysis-from-nano-beam-electron-diffraction-influence-of-specimen-tilt-and-beam-convergence
#9
Tim Grieb, Florian F Krause, Marco Schowalter, Dennis Zillmann, Roman Sellin, Knut Müller-Caspary, Christoph Mahr, Thorsten Mehrtens, Dieter Bimberg, Andreas Rosenauer
Strain analyses from experimental series of nano-beam electron diffraction (NBED) patterns in scanning transmission electron microscopy are performed for different specimen tilts. Simulations of NBED series are presented for which strain analysis gives results that are in accordance with experiment. This consequently allows to study the relation between measured strain and actual underlying strain. A two-tilt method which can be seen as lowest-order electron beam precession is suggested and experimentally implemented...
April 12, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29655113/evaluation-of-noise-and-blur-effects-with-sirt-fista-tv-reconstruction-algorithm-application-to-fast-environmental-transmission-electron-tomography
#10
Hussein Banjak, Thomas Grenier, Thierry Epicier, Siddardha Koneti, Lucian Roiban, Anne-Sophie Gay, Isabelle Magnin, Françoise Peyrin, Voichita Maxim
Fast tomography in Environmental Transmission Electron Microscopy (ETEM) is of a great interest for in situ experiments where it allows to observe 3D real-time evolution of nanomaterials under operating conditions. In this context, we are working on speeding up the acquisition step to a few seconds mainly with applications on nanocatalysts. In order to accomplish such rapid acquisitions of the required tilt series of projections, a modern 4K high-speed camera is used, that can capture up to 100 images per second in a 2K binning mode...
April 11, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29715521/how-should-a-fixed-budget-of-dwell-time-be-spent-in-scanning-electron-microscopy-to-optimize-image-quality
#11
Patrick Trampert, Faysal Bourghorbel, Pavel Potocek, Maurice Peemen, Christian Schlinkmann, Tim Dahmen, Philipp Slusallek
In scanning electron microscopy, the achievable image quality is often limited by a maximum feasible acquisition time per dataset. Particularly with regard to three-dimensional or large field-of-view imaging, a compromise must be found between a high amount of shot noise, which leads to a low signal-to-noise ratio, and excessive acquisition times. Assuming a fixed acquisition time per frame, we compared three different strategies for algorithm-assisted image acquisition in scanning electron microscopy. We evaluated (1) raster scanning with a reduced dwell time per pixel followed by a state-of-the-art Denoising algorithm, (2) raster scanning with a decreased resolution in conjunction with a state-of-the-art Super Resolution algorithm, and (3) a sparse scanning approach where a fixed percentage of pixels is visited by the beam in combination with state-of-the-art inpainting algorithms...
April 6, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29655973/robust-workflow-and-instrumentation-for-cryo-focused-ion-beam-milling-of-samples-for-electron-cryotomography
#12
João M Medeiros, Désirée Böck, Gregor L Weiss, Romain Kooger, Roger A Wepf, Martin Pilhofer
Electron cryotomography is able to visualize macromolecular complexes in their cellular context, in a frozen-hydrated state, and in three dimensions. The method, however, is limited to relatively thin samples. Cryo-focused ion beam (FIB) milling is emerging as a powerful technique for sample thinning prior to cryotomography imaging. Previous cryo-FIB milling reports utilized custom-built non-standard equipment. Here we present a workflow and the required commercially available instrumentation to either implement the method de novo, or as an upgrade of pre-existing dual beam milling instruments...
April 6, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29660686/measurements-of-the-energy-distribution-of-a-high-brightness-rubidium-ion-beam
#13
G Ten Haaf, S H W Wouters, D F J Nijhof, P H A Mutsaers, E J D Vredenbregt
The energy distribution of a high brightness rubidium ion beam, which is intended to be used as the source for a focused ion beam instrument, is measured with a retarding field analyzer. The ions are created from a laser-cooled and compressed atomic beam by two-step photoionization in which the ionization laser power is enhanced in a build-up cavity. Particle tracing simulations are performed to ensure the analyzer is able to resolve the distribution. The lowest achieved full width 50% energy spread is (0.205 ± 0...
April 5, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29660631/using-molecular-dynamics-for-multislice-tem-simulation-of-thermal-diffuse-scattering-in-algan
#14
Florian F Krause, Dennis Bredemeier, Marco Schowalter, Thorsten Mehrtens, Tim Grieb, Andreas Rosenauer
For simulation of transmission electron microscopic images and diffraction patterns, the accurate inclusion of thermal diffuse scattering by phonons is important. In the frozen phonon multislice algorithm, this is possible, if thermal displacements according to the realistic, quantum mechanical distribution can be generated. For pure crystals, quantum mechanical calculations based on DFT yield those displacements. But for alloys one is usually restricted to the Einstein approximation, where correlations between atoms are neglected...
March 30, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29660687/novel-in-situ-lamella-fabrication-technique-for-in-situ-tem
#15
Megan Canavan, Dermot Daly, Andreas Rummel, Eoin K McCarthy, Cathal McAuley, Valeria Nicolosi
In-situ transmission electron microscopy is rapidly emerging as the premier technique for characterising materials in a dynamic state on the atomic scale. The most important aspect of in-situ studies is specimen preparation. Specimens must be electron transparent and representative of the material in its operational state, amongst others. Here, a novel fabrication technique for the facile preparation of lamellae for in-situ transmission electron microscopy experimentation using focused ion beam milling is developed...
March 29, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29626837/accurate-interpolation-of-3d-fields-in-charged-particle-optics
#16
Michal Horák, Viktor Badin, Jakub Zlámal
Standard 3D interpolation polynomials often suffer from numerical errors of the calculated field and lack of node points in the 3D solution. We introduce a novel method for accurate and smooth interpolation of arbitrary electromagnetic fields in the vicinity of the optical axis valid up to 90% of the bore radius. Our method combines Fourier analysis and Gaussian wavelet interpolation and provides the axial multipole field functions and their derivatives analytically. The results are accurate and noiseless, usually up to the 5th derivative...
March 29, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29626836/optimal-sampling-and-reconstruction-of-undersampled-atomic-force-microscope-images-using-compressive-sensing
#17
Guoqiang Han, Bo Lin
Atomic force microscope (AFM) is an analytical instrument which is used to study the surface structure and morphology of materials. The AFM can measure and observe samples either in air or liquid environment. However, the standard AFM requires a long time to acquire accurate images and data. In our work, the compressive sensing (CS) was applied in order to reduce the imaging time, lower the interactions between the probe and the sample, finally avoid sample damage in AFM. Three samples (PAA film, TGG1 grating and BOPP film) were used as the testing samples...
March 29, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29626835/exploring-possibilities-of-band-gap-measurement-with-off-axis-eels-in-tem
#18
Svetlana Korneychuk, Bart Partoens, Giulio Guzzinati, Rajesh Ramaneti, Joff Derluyn, Ken Haenen, Jo Verbeeck
A technique to measure the band gap of dielectric materials with high refractive index by means of energy electron loss spectroscopy (EELS) is presented. The technique relies on the use of a circular (Bessel) aperture and suppresses Cherenkov losses and surface-guided light modes by enforcing a momentum transfer selection. The technique also strongly suppresses the elastic zero loss peak, making the acquisition, interpretation and signal to noise ratio of low loss spectra considerably better, especially for excitations in the first few eV of the EELS spectrum...
March 29, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29704728/atomic-force-microscope-scanning-head-with-3-dimensional-orthogonal-scanning-to-eliminate-the-curved-coupling
#19
Yushu Shi, Wei Li, Sitian Gao, Mingzhen Lu, Xiaodong Hu
An atomic force microscopy (AFM) scanning head is designed with the probe orthogonal scanning mode for metrological AFM to eliminate the curvature distortion. The AFM probe is driven by piezostage and the scanning trajectory of the probe in 3 directions are orthogonal to reduce the cross coupling. A new optical lever amplification optical path is developed to eliminate the coupling error. The tracing lens and probe tip are moved as an integrated part. The AFM is operated at contacting mode. The step approach process of the probe tip is tested to the sample surface and the noise of the AFM head is analyzed...
March 28, 2018: Ultramicroscopy
https://www.readbyqxmd.com/read/29649705/in-lens-bse-detector-with-energy-filtering
#20
Tomáš Radlička, Marek Unčovský, Martin Oral
We present a new type of an in-lens detector designed for Thermo Fisher Scientific (FEI) electron microscopes with the Elstar column. A key feature of it is high-pass energy filtering to enable the detection of low-loss backscattered electrons with their energy close to the primary beam energy. We show an application of the detector in imaging of a biological sample where the signal from these electrons leads to a significant improvement in resolution.
March 27, 2018: Ultramicroscopy
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