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Rik V Mom, Willem G Onderwaater, Marcel J Rost, Maciej Jankowski, Sabine Wenzel, Leon Jacobse, Paul F A Alkemade, Vincent Vandalon, Matthijs A van Spronsen, Matthijs van Weeren, Bert Crama, Peter van der Tuijn, Roberto Felici, Wilhelmus M M Kessels, Francesco Carlà, Joost W M Frenken, Irene M N Groot
A combined X-ray and scanning tunneling microscopy (STM) instrument is presented that enables the local detection of X-ray absorption on surfaces in a gas environment. To suppress the collection of ion currents generated in the gas phase, coaxially shielded STM tips were used. The conductive outer shield of the coaxial tips can be biased to deflect ions away from the tip core. When tunneling, the X-ray-induced current is separated from the regular, 'topographic' tunneling current using a novel high-speed separation scheme...
July 14, 2017: Ultramicroscopy
Florina Lucica Zorila, Cristina Ionescu, Liviu Stefan Craciun, Bogdan Zorila
In this paper we used atomic force microscopy (AFM) to investigate the surface morphology of Escherichia coli, after being subjected to decontamination treatments, at sub-MICs levels (minimal inhibitory concentrations), with different disinfectants used in hospitals, pharmaceutical, food industry and even in our home, as an essential means to prevent the spreading of microorganisms. This article focuses on different morphological modifications adopted by E. coli cells as responses to the different modes of action of these substances...
July 14, 2017: Ultramicroscopy
Yu Masuda, Masashi Kamiya, Atsushi Sugita, Wataru Inami, Yoshimasa Kawata, Hiroko Kominami, Yoichiro Nakanishi
This study presents relationship between acceleration voltage and spatial resolution of electron-beam assisted (EXA) optical microscope. The nanometric illumination light sources of the present EXA microscope was red-emitting cathodoluminescence (CL) in the Y2O3:Eu(3+) thin film excited by focused electron beam. Our experimental results demonstrated that the spatial resolutions of the EXA microscope were higher as the acceleration voltage was higher. We managed to make images of the scattered gold particles with approximately 90 nm-resolutions at the voltages higher than 20 kV...
July 13, 2017: Ultramicroscopy
Andrey V Kudryavtsev, Sounkalo Dembélé, Nadine Piat
The sharpness of the images coming from a Scanning Electron Microscope (SEM) is a very important property for many computer vision applications at micro- and nanoscale. It represents how much object details are distinctive in the images: the object may be perceived sharp or blurred. Image sharpness highly depends on the value of focal distance, or working distance in the case of the SEM. Autofocus is the technique allowing to automatically adjust the working distance to maximize the sharpness. Most of the existing algorithms allows working only with a static object which is enough for the tasks of visualization, manual microanalysis or microcharacterization...
July 12, 2017: Ultramicroscopy
Jakob Spiegelberg, Shunsuke Muto, Masahiro Ohtsuka, Kristiaan Pelckmans, Ján Rusz
This paper demonstrates how Signal Subspace Sampling (SSS) is an effective pre-processing step for Non-negative Matrix Factorization (NMF) or Vertex Component Analysis (VCA). The approach allows to uniquely extract non-negative source signals which are orthogonal in at least one observation channel, respectively. It is thus well suited for processing hyperspectral images from X-ray microscopy, or other emission spectroscopies, into its non-negative source components. The key idea is to resample the given data so as to satisfy better the necessity and sufficiency conditions for the subsequent NMF or VCA...
July 10, 2017: Ultramicroscopy
Lei Yu, Haibo Li, Weishi Wan, Zheng Wei, Krzysztof P Grzelakowski, Rudolf M Tromp, Wen-Xin Tang
The effects of space charge, aberrations and relativity on temporal compression are investigated for a compact spherical electrostatic capacitor (α-SDA). By employing the three-dimensional (3D) field simulation and the 3D space charge model based on numerical General Particle Tracer and SIMION, we map the compression efficiency for a wide range of initial beam size and single-pulse electron number and determine the optimum conditions of electron pulses for the most effective compression. The results demonstrate that both space charge effects and aberrations prevent the compression of electron pulses into the sub-ps region if the electron number and the beam size are not properly optimized...
July 6, 2017: Ultramicroscopy
G Schönhense, K Medjanik, S Chernov, D Kutnyakhov, O Fedchenko, M Ellguth, D Vasilyev, A Zaporozhchenko-Zymaková, D Panzer, A Oelsner, C Tusche, B Schönhense, J Braun, J Minár, H Ebert, J Viefhaus, W Wurth, H J Elmers
The combination of momentum microscopy (high resolution imaging of the Fourier plane) with an imaging spin filter has recently set a benchmark in k-resolution and spin-detection efficiency. Here we show that the degree of parallelization can be further increased by time-of-flight energy recording. On the quest towards maximum information (in earlier work termed "complete" photoemission experiment) we have studied the prototypical high-Z fcc metal iridium. Large partial bandgaps and strong spin-orbit interaction lead to a sequence of spin-polarized surface resonances...
July 6, 2017: Ultramicroscopy
Pavel Potapov
Principal Component Analysis (PCA) can drastically denoise STEM spectrum-images but might distort or cut off the important variations in data. The present paper analyzes various approaches to estimate such deviations and compares them with the simulated data. A spiked covariance model by Nadler (2008) appears to be most appropriated for application in STEM spectrum-imaging.
July 6, 2017: Ultramicroscopy
Hidetaka Sawada, Christopher S Allen, Shanshan Wang, Jamie H Warner, Angus I Kirkland
The geometric and chromatic aberration coefficients of the probe-forming system in an aberration corrected transmission electron microscope have been measured using a Ronchigram recorded from monolayer graphene. The geometric deformations within individual local angular sub-regions of the Ronchigram were analysed using an auto-correlation function and the aberration coefficients for the probe forming lens were calculated. This approach only requires the acquisition of a single Ronchigram allowing rapid measurement of the aberration coefficients...
July 5, 2017: Ultramicroscopy
P Eaton, P Quaresma, C Soares, C Neves, M P de Almeida, E Pereira, P West
Nanoparticles have properties that depend critically on their dimensions. There are a large number of methods that are commonly used to characterize these dimensions, but there is no clear consensus on which method is most appropriate for different types of nanoparticles. In this work four different characterization methods that are commonly applied to characterize the dimensions of nanoparticles either in solution or dried from solution are critically compared. Namely, transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), and dynamic light scattering (DLS) are compared with one another...
July 5, 2017: Ultramicroscopy
Hiroki Minoda, Takayuki Tamai, Yuya Ohmori, Hirofumi Iijima
Visualizing materials composed of light elements is difficult, and the development of an imaging method that enhances the phase contrast of such materials has been of much interest. In this study, we demonstrate phase-plate scanning transmission electron microscopy (P-STEM), which we developed recently, and its application to nanomaterials. An amorphous carbon film with a small hole in its center was used to control the phase of incident electron waves, and the phase-contrast transfer function (PCTF) was modified from sine-type to cosine-type...
July 4, 2017: Ultramicroscopy
H G Brown, N Shibata, H Sasaki, T C Petersen, D M Paganin, M J Morgan, S D Findlay
Electric field mapping using segmented detectors in the scanning transmission electron microscope has recently been achieved at the nanometre scale. However, converting these results to quantitative field measurements involves assumptions whose validity is unclear for thick specimens. We consider three approaches to quantitative reconstruction of the projected electric potential using segmented detectors: a segmented detector approximation to differential phase contrast and two variants on ptychographical reconstruction...
July 3, 2017: Ultramicroscopy
J Cui, Y Yao, Y G Wang, X Shen, R C Yu
The effects of the tilt of the crystallographic orientation with respect to an incident electron probe on high-angle annular dark field (HAADF) imaging in aberration-corrected scanning transmission electron microscopy (STEM) have been investigated with experiments and simulations. A small specimen tilt can lead to unequal deviations of different atom species in the HAADF image and result in further relative displacement between anions and cations. Simulated HAADF images also confirm that the crystal tilt causes an artifact in atom polarization as well...
July 3, 2017: Ultramicroscopy
Stephen D House, Yuxiang Chen, Rongchao Jin, Judith C Yang
The adaptation of quantitative STEM techniques to enable atom-counting in supported metal nanoparticles with a modern, conventional (non-aberration-corrected) TEM/STEM (a JEOL JEM2100F) without the need for any modifications or special hardware is presented. No image simulation is required, either. This technique enables the practical analysis of the size, mass, and basic shape information of statistically robust populations of hundreds to thousands of nanoparticles. The methods for performing the necessary calibrations of the microscope and images are detailed...
July 3, 2017: Ultramicroscopy
K C Prabhat, K Aditya Mohan, Charudatta Phatak, Charles Bouman, Marc De Graef
Lorentz transmission electron microscopy (TEM) observations of magnetic nanoparticles contain information on the magnetic and electrostatic potentials. Vector field electron tomography (VFET) can be used to reconstruct electromagnetic potentials of the nanoparticles from their corresponding LTEM images. The VFET approach is based on the conventional filtered back projection approach to tomographic reconstructions and the availability of an incomplete set of measurements due to experimental limitations means that the reconstructed vector fields exhibit significant artifacts...
July 3, 2017: Ultramicroscopy
Felix Börrnert, Heiko Müller, Thomas Riedel, Martin Linck, Angus I Kirkland, Max Haider, Bernd Büchner, Hannes Lichte
No abstract text is available yet for this article.
June 28, 2017: Ultramicroscopy
C J Edgcombe
The image of a simple phase object produced by a round lens with a Foucault or Hilbert phase plate can be determined with Abbe imaging theory and a 2D transform expressed in cylindrical coordinates. The contributions to the image amplitude from a uniform disc object and an azimuthally varying plate can then be distinguished and their phases relative to the incident wave can be compared. It appears that the usual choice of added phase for a Hilbert plate causes the image of a weak disc object to vanish as the plate edge approaches the axis, but a different choice of plate thickness can enable a weak phase object to provide a linear contribution to image intensity...
June 22, 2017: Ultramicroscopy
Philip J B Koeck
No abstract text is available yet for this article.
June 22, 2017: Ultramicroscopy
Konstantin E Mochalov, Anton A Chistyakov, Daria O Solovyeva, Alexey V Mezin, Vladimir A Oleinikov, Ivan S Vaskan, Michael Molinari, Igor I Agapov, Igor Nabiev, Anton E Efimov
In the past decade correlative microscopy, which combines the potentials of different types of high-resolution microscopies with a variety of optical microspectroscopy techniques, has been attracting increasing attention in material science and biological research. One of outstanding solutions in this area is the combination of scanning probe microscopy (SPM), which provides data on not only the topography, but also the spatial distribution of a wide range of physical properties (elasticity, conductivity, etc...
June 21, 2017: Ultramicroscopy
Knud Thomsen, Klaus Mehnert, Patrick W Trimby, Ali Gholinia
The authors of the present work propose a color coding technique using quaternions for the display of crystallographic orientation data such as EBSD maps. The main difference to existing color coding techniques in this field is that it creates a color space, within which the perceived color differences are approximately proportional to Euclidean distances in the corresponding 3D quaternion vector space, and thus approximately proportional to mutual disorientation angles. Since all disorientation parameters (axis and angle pairs, but represented as quaternions) are taken into account, color ambiguities appearing in maps created by other techniques are successfully avoided, and the sub-grain orientation differences within grains can be unambiguously visualized...
June 21, 2017: Ultramicroscopy
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