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Ultramicroscopy

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https://read.qxmd.com/read/31005023/pattern-matching-analysis-of-electron-backscatter-diffraction-patterns-for-pattern-centre-crystal-orientation-and-absolute-elastic-strain-determination-accuracy-and-precision-assessment
#1
Tomohito Tanaka, Angus J Wilkinson
Pattern matching between target electron backscatter patterns (EBSPs) and dynamically simulated EBSPs was used to determine the pattern centre (PC) and crystal orientation, using a global optimisation algorithm. Systematic analysis of error and precision with this approach was carried out using dynamically simulated target EBSPs with known PC positions and orientations. Results showed that the error in determining the PC and orientation was <10-5 of pattern width and <0.01° respectively for the undistorted full resolution images (956 × 956 pixels)...
April 15, 2019: Ultramicroscopy
https://read.qxmd.com/read/31005819/an-in-situ-approach-for-preparing-atom-probe-tomography-specimens-by-xenon-plasma-focussed-ion-beam
#2
J E Halpin, R W H Webster, H Gardner, M P Moody, P A J Bagot, D A MacLaren
A method for the rapid preparation of atom probe tomography (APT) needles using a xenon plasma-focussed ion beam (FIB) instrument is presented and demonstrated on a test sample of Ti-6Al-4V alloy. The method requires significantly less operator input than the standard lift-out protocol, is site-specific and produces needles with minimal ion-beam damage; electron microscopy indicated the needle's surface amorphised/oxidised region to be less than 2 nm thick. The resulting needles were routinely analysable by APT, confirming the expected microstructure and showing negligible Xe contamination...
April 12, 2019: Ultramicroscopy
https://read.qxmd.com/read/31005818/calatom-a-software-for-quantitatively-analysing-atomic-columns-in-a-transmission-electron-microscope-image
#3
Q Zhang, L Y Zhang, C H Jin, Y M Wang, F Lin
We developed a software tool named CalAtom in MATLAB™ for quantitative analyses of atomic columns in (scanning) transmission electron microscopy, (S)TEM, images. This software provides three algorithms to determine the position of an atomic column with high precision: the moment method, the model-based method and the multiple-ellipse fitting method. Based on the measured positions, the software offers several options for further analyses, such as in-plane scale local environments of the atomic columns, local elementary composition and real-space averaging of image motifs...
April 12, 2019: Ultramicroscopy
https://read.qxmd.com/read/31003162/a-method-of-z-tomography-using-high-aperture-soft-x-ray-microscopy
#4
Ilya V Malyshev, Nikolay I Chkhalo
Multilayer normal-incidence mirrors allow the numerical aperture (NA=0.3-0.5) of a projection lens to be significantly increased in the spectral ranges of the water (λ = 2.3-4.4 nm) and carbon (λ = 4.4-7 nm) windows, in comparison with the Fresnel zone plates. The low depth of focus of high-aperture optics (tens of nm) makes it possible to use z-tomography to reconstruct the structure of samples in soft X-ray microscopy. The presence of strong absorption prevents the direct use of a powerful deconvolution apparatus developed for fluorescence optical microscopy to improve the clarity of the image...
April 12, 2019: Ultramicroscopy
https://read.qxmd.com/read/31005817/beam-brightness-and-its-reduction-in-a-1-2-mv-cold-field-emission-transmission-electron-microscope
#5
Takeshi Kawasaki, Tetsuya Akashi, Keigo Kasuya, Hiroyuki Shinada
In this paper we discuss probe properties in terms of probe currents, probe sizes, energy spread, virtual source sizes, and brightness in a 1.2-MV cold field-emission (cold FE) transmission electron microscope (TEM) equipped with a magnetic gun lens. The probe size increased gradually in proportion to the (3/8)th power of the probe current, very unusual behavior in cold FE guns but typical behavior in thermionic guns. This is due to the magnetic gun lens, which caused large emission angles for electron beams in the probe before being limited by aberrations at the gun and acceleration tube...
April 11, 2019: Ultramicroscopy
https://read.qxmd.com/read/30953993/quantitative-stem-imaging-of-electron-beam-induced-mass-loss-of-epoxy-resin-sections
#6
Radim Skoupy, Jana Nebesarova, Miroslav Slouf, Vladislav Krzyzanek
In sample preparation of biological samples for electron microscopy, many types of embedding media are widely used. Unfortunately, none of them is perfectly resistant to beam induced damage. The article is focused on mass loss measuring of pure epoxy resin EMbed 812 that replaced Epon - the most widely used embedding resin for biological electron microscopy, in a form of ultrathin sections with thicknesses ranging from 30 to 100 nm. The STEM imaging was performed in a quantitative way which allowed us to estimate the mass loss directly up to the total dose of 3000 e- /nm2 ...
March 30, 2019: Ultramicroscopy
https://read.qxmd.com/read/30933741/high-throughput-crystal-structure-and-composition-mapping-of-crystalline-nanoprecipitates-in-alloys-by-transmission-kikuchi-diffraction-and-analytical-electron-microscopy
#7
Arunodaya Bhattacharya, Chad M Parish, Jean Henry, Yutai Katoh
Statistically significant crystal structure and composition identification of nanocrystalline features such as nanoparticles/nanoprecipitates in materials chemistry and alloy designing using electron microscopy remains a grand challenge. In this paper, we reveal that differing crystallographic phases of nanoprecipitates in alloys can be mapped with unprecedented statistics using transmission Kikuchi diffraction (TKD), on typical carbon-based electron-transparent samples. Using a case of multiphase, multicomponent nanoprecipitates extracted from an improved version of 9% chromium Eurofer-97 reduced-activation ferritic-martensitic steel we show that TKD successfully identified more than thousand M23 C6 , MX, M7 C3, and M2 X (M=Fe, Cr, W, V, Ta; X = C, N) nanoprecipitates in a single scan, something that is currently unachievable using a transmission electron microscope (TEM) without incorporating a precision electron diffraction (PED) system...
March 28, 2019: Ultramicroscopy
https://read.qxmd.com/read/30959241/conduction-mechanisms-and-voltage-drop-during-field-electron-emission-from-diamond-needles
#8
Olivier Torresin, Mario Borz, Julien Mauchain, Ivan Blum, Victor I Kleshch, Alexander N Obraztsov, Angela Vella, Benoit Chalopin
We report results of experimental investigation of field electron emission from diamond nanoemitters. The measurements were performed with single crystal diamond needles fixed at tungsten tips. The voltage drop along diamond needles during emission was revealed and measured using electron energy spectroscopy. The observed linear dependence of the voltage drop in diamond on voltage applied to the tungsten tip is explained in the frame of a simple macroscopic electrical model combining Poole-Frenkel conduction along the diamond tip and Fowler-Nordheim tunneling at the diamond-vacuum junction...
March 27, 2019: Ultramicroscopy
https://read.qxmd.com/read/30933740/optimization-of-off-axis-electron-holography-performed-with-femtosecond-electron-pulses
#9
F Houdellier, G M Caruso, S Weber, M J Hÿtch, C Gatel, A Arbouet
We report on electron holography experiments performed with femtosecond electron pulses in an ultrafast coherent Transmission Electron Microscope based on a laser-driven cold field emission gun. We first discuss the experimental requirements related to the long acquisition times imposed by the low emission/probe current available in these instruments. The experimental parameters are first optimized and electron holograms are then acquired in vacuum and on a nano-object showing that useful physical properties can nevertheless be extracted from the hologram phase in pulsed condition...
March 26, 2019: Ultramicroscopy
https://read.qxmd.com/read/30928639/improving-electron-micrograph-signal-to-noise-with-an-atrous-convolutional-encoder-decoder
#10
Jeffrey M Ede, Richard Beanland
We present an atrous convolutional encoder-decoder trained to denoise electron micrographs. It consists of a modified Xception backbone, atrous convoltional spatial pyramid pooling module and a multi-stage decoder. Our neural network was trained end-to-end using 512  ×  512 micrographs created from a large dataset of high-dose ( > 2500 counts per pixel) micrographs with added Poisson noise to emulate low-dose ( ≪  300 counts per pixel) data. It was then fine-tuned for high dose data (200-2500 counts per pixel)...
March 26, 2019: Ultramicroscopy
https://read.qxmd.com/read/30925298/low-energy-electron-properties-electron-inelastic-mean-free-path-energy-loss-function-and-the-dielectric-function-recent-measurements-applications-and-the-plasmon-coupling-theory
#11
C T Chantler, J D Bourke
We review new self-consistent models of inelastic electron scattering in condensed matter systems for accurate calculations of low-energy electron inelastic mean free paths (IMFPs) for XAFS and low energy diffraction. The accuracy of theoretical determinations of the electron IMFP at low energies is one of the key limiting factors in current XAFS modeling and Monte Carlo transport. Recent breakthroughs in XAFS analysis show that there exist significant discrepancies between theoretical and experimental IMFP values, and that this can significantly impact upon extraction of other key structural parameters from both XANES and XAFS...
March 26, 2019: Ultramicroscopy
https://read.qxmd.com/read/30927610/effect-of-tip-shape-on-nanomechanical-properties-measurements-using-afm
#12
Quang Dang Nguyen, Koo-Hyun Chung
Atomic force microscopy (AFM)-based indentation has been widely used to understand mechanical properties in conjunction with surface topography and structure at the nano-scale. In this work, nanomechanical properties of three different specimens were determined using four different AFM probes with spherical and flat-ended tips and conical tips with rounded apexes, to provide useful information for probe selection and for better interpretation of force-indentation data. These probes were modeled as a sphere, flat punch, and hyperboloid, respectively, after careful characterization to determine the elastic modulus based on contact models...
March 22, 2019: Ultramicroscopy
https://read.qxmd.com/read/30925297/tip-wear-and-tip-breakage-in-high-speed-atomic-force-microscopes
#13
Timo Strahlendorff, Gaoliang Dai, Detlef Bergmann, Rainer Tutsch
Tip abrasion is a critical issue particularly for high-speed atomic force microscopy (AFM). In this paper, a quantitative investigation on the tip abrasion of diamond-like-carbon (DLC) coated tips in a high-speed metrological large range AFM device has been detailed. Wear tests are conducted on four different surfaces made of silicon, niobium, aluminum and steel. During the tests, different scanning speeds up to 1 mm/s and different vertical load forces up to approximately 33.2 nN are applied. Various tip characterization techniques such as scanning electron microscopy (SEM) and AFM tip characterizers have been jointly applied to measure the tip form change precisely...
March 22, 2019: Ultramicroscopy
https://read.qxmd.com/read/30928781/experimental-steering-of-electron-microscopy-studies-using-prior-x-ray-computed-tomography
#14
Tobias Starborg, James D B O'Sullivan, Claudia Martins Carneiro, Julia Behnsen, Kathryn J Else, Richard K Grencis, Philip J Withers
Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) can provide unrivalled high-resolution images of specific features and volumes of interest. However, the regions interrogated are typically very small, and sample preparation is both time-consuming and destructive. Here we consider how prior X-ray micro-computed tomography (microCT) presents an opportunity to increase the efficiency of electron microscopy in biology. We demonstrate how it can be used to; select the most promising samples and target site-specific locations; provide a wider context of the location being interrogated (multiscale correlative imaging); guide sample preparation and 3D imaging schemes; as well as quantify the effects of destructive sample preparation and staining procedures...
March 20, 2019: Ultramicroscopy
https://read.qxmd.com/read/30991264/angular-resolution-expected-from-ichord-orientation-maps-through-a-revisited-ion-channeling-model
#15
C Langlois, T Douillard, S Dubail, C Lafond, S Cazottes, J Silvent, A Delobbe, P Steyer
Crystalline orientation maps are obtained in a Focused Ion Beam (FIB) microscope using the ion CHanneling ORientation Determination (iCHORD) method, which relies on the channeling phenomenon observed in ion-induced secondary electron images. The current paper focuses on the angular resolution that can be expected from such orientation maps, obtained using a revisited ion channeling model. A specific procedure was developed to evaluate the angular resolution, based on the distribution of orientation errors when evaluating controlled sample disorientation...
March 19, 2019: Ultramicroscopy
https://read.qxmd.com/read/30986656/microed-data-collection-with-serialem
#16
M Jason de la Cruz, Michael W Martynowycz, Johan Hattne, Tamir Gonen
The cryoEM method Microcrystal Electron Diffraction (MicroED) involves transmission electron microscope (TEM) and electron detector working in synchrony to collect electron diffraction data by continuous rotation. We previously reported several protein, peptide, and small molecule structures by MicroED using manual control of the microscope and detector to collect data. Here we present a procedure to automate this process using a script developed for the popular open-source software package SerialEM. With this approach, SerialEM coordinates stage rotation, microscope operation, and camera functions for automated continuous-rotation MicroED data collection...
March 19, 2019: Ultramicroscopy
https://read.qxmd.com/read/30928638/pulse-picking-in-synchrotron-based-xpeem
#17
Lucia Aballe, Michael Foerster, Meritxell Cabrejo, Jordi Prat, Paolo Pittana, Rudi Sergo, Matteo Lucian, Maurizio Barnaba, Tevfik Onur Menteş, Andrea Locatelli
We report on a simple and cost-effective device for high-speed gating in photoemission electron microscopy (PEEM) with pulsed photon sources. This device is based on miniaturized electrode plates, which deflect the photoelectron beam inside the imaging column of the microscope so that it is either accepted or blocked in its path towards the detector. The gating device is optimized for installation on the Elmitec SPELEEM III microscope. Due to the compact design, it can be driven by voltage pulses of low amplitude (few volts), delivered by commercially available signal generators...
March 19, 2019: Ultramicroscopy
https://read.qxmd.com/read/30913478/fast-mechanical-model-for-probe-sample-elastic-deformation-estimation-in-scanning-probe-microscopy
#18
Petr Klapetek, Anna Charvátová Campbell, Vilma Buršíková
We present a numerical approach for estimation of the probe-sample elastic deformation for higher contact forces and/or smaller probe apex radii in Scanning Probe Microscopy (SPM) measurements. It is based on a mass-spring model implemented on a graphics card in order to perform very high numbers of individual force-distance curves calculations in reasonable time, forming virtual profiles or virtual SPM images. The model is suitable for predicting the mechanical response of the probe and sample in SPM mechanical properties mapping regimes and for estimating the uncertainty sources related to probe-sample elastic deformation in dimensional nanometrology...
March 19, 2019: Ultramicroscopy
https://read.qxmd.com/read/30904784/magnetic-measurement-by-electron-magnetic-circular-dichroism-in-the-transmission-electron-microscope
#19
Dongsheng Song, Ziqiang Wang, Jing Zhu
Magnetic measurement by transmitted electrons at nanometer or even atomic scale is always an attractive and challenging issue in the transmission electron microscope. Electron magnetic circular dichroism, proposed in 2003 and realized in 2006, opens a new insight into the measurement of local magnetic properties. Later, it is developed into a powerful technique for quantitative magnetic measurement with site specificity and element specificity at high spatial resolution over years of efforts, both in the aspect of theory and experiments...
March 19, 2019: Ultramicroscopy
https://read.qxmd.com/read/31005022/a-hybrid-genetic-levenberg-marquardt-algorithm-for-automated-spectrometer-design-optimization
#20
Kang Hao Cheong, Jin Ming Koh
Advancements in computational tools have driven increasingly automated, simulation-centric approaches in the design and optimization of spectroscopic electron-optical systems. These augmented methodologies accelerate the optimization process, and can yield better-performing instruments. While classical gradient-based methods had been explored, modern alternatives such as genetic algorithms have rarely been applied. In this paper, we propose a novel fully-automated hybrid optimization method for use on electron-optical systems...
March 15, 2019: Ultramicroscopy
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