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  • Articles  (876)
  • 2010-2014  (876)
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  • Articles  (876)
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  • 1
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    In quest of perfection in electron optics-A biographical sketch of Harald Rose on the occasion of his 80th birthday (2014)
    Elsevier
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    Publication Date: 2014-12-26
    Description: Publication date: Available online 24 December 2014 Source: Ultramicroscopy Author(s): Knut W. Urban This brief biographical sketch of Harald Rose on occasion of his 80th birthday describes some of the key events in an extraordinarily successful scientific life. Many of the theoretical concepts developed by him over the last fifty years have been fundamental for electron optics. Indeed, some of them have changed the whole complexion of this field and are fundamental to modern electron microscopy, both in TEM and in STEM mode. With this dedicated issue of Ultramicroscopy, the members of the electron microscopy community would like to thank Harald Rose for dedicating his professional life to their field and thereby enriching the life of those active in it.
    Print ISSN: 0304-3991
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 2
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    Observation of lens aberrations for high resolution electron microscopy II: Simple expressions for optimal estimates (2014)
    Elsevier
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    Publication Date: 2014-12-25
    Description: Publication date: Available online 23 December 2014 Source: Ultramicroscopy Author(s): W.O. Saxton This paper lists simple closed-form expressions estimating aberration coefficients (defocus, astigmatism, three-fold astigmatism, coma / misalignment, spherical aberration) on the basis of image shift or diffractogram shape measurements as a function of injected beam tilt. Simple estimators are given for a large number of injected tilt configurations, optimal in the sense of least-squares fitting of all the measurements, and so better than most reported previously. Standard errors are given for most, allowing different approaches to be compared. Special attention is given to the measurement of the spherical aberration, for which several simple procedures are given, and the effect of foreknowledge of this on other aberration estimates is noted. Details and optimal expressions are also given for a new and simple method of analysis, requiring measurements of the diffractogram mirror axis direction only, which are simpler to make than the focus and astigmatism measurements otherwise required.
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    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 3
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    Towards a full retrieval of the deformation tensor F using Convergent Beam Electron Diffraction (2014)
    Elsevier
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    Publication Date: 2014-12-22
    Description: Publication date: Available online 19 December 2014 Source: Ultramicroscopy Author(s): Y. Martin , J.L. Rouvière , J.M. Zuo , V. Favre-Nicolin A new method to retrieve the local lattice parameters and rotations in a crystal from off-axis Convergent Beam Electron Diffraction (CBED) patterns is presented and validated using Bloch wave dynamical simulations. The originality of the method is to use both the diffracted and transmitted beams and to use kinematical approximations in the fitting algorithm. The study is based on the deformation gradient tensor F which includes rotation and strain. Working on simulated images it is shown that (i) from a single direction of observation, 7 parameters out of the 9 parameters of F can be determined with an an accuracy of 3×10 −4 for the normal strain parameters ε xx , ε yy , ε zz , (ii) the unit cell volume can only be retrieved if the diffracted and transmitted beams are both included in the fitting and (iii) all the 9 parameters of F can be determined by combining two directions of observation separated by about 20 degrees.
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    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 4
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    Adaptive and robust statistical methods for processing near-field scanning microwave microscopy images (2014)
    Elsevier
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    Publication Date: 2014-12-19
    Description: Publication date: March 2015 Source: Ultramicroscopy, Volume 150 Author(s): K.J. Coakley , A. Imtiaz , T.M. Wallis , J.C. Weber , S. Berweger , P. Kabos Near-field scanning microwave microscopy offers great potential to facilitate characterization, development and modeling of materials. By acquiring microwave images at multiple frequencies and amplitudes (along with the other modalities) one can study material and device physics at different lateral and depth scales. Images are typically noisy and contaminated by artifacts that can vary from scan line to scan line and planar-like trends due to sample tilt errors. Here, we level images based on an estimate of a smooth 2-d trend determined with a robust implementation of a local regression method. In this robust approach, features and outliers which are not due to the trend are automatically downweighted. We denoise images with the Adaptive Weights Smoothing method. This method smooths out additive noise while preserving edge-like features in images. We demonstrate the feasibility of our methods on topography images and microwave | S 11 | images. For one challenging test case, we demonstrate that our method outperforms alternative methods from the scanning probe microscopy data analysis software package Gwyddion. Our methods should be useful for massive image data sets where manual selection of landmarks or image subsets by a user is impractical.
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    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 5
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    Simultaneous orientation and thickness mapping in transmission electron microscopy (2014)
    Elsevier
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    Publication Date: 2014-12-19
    Description: Publication date: March 2015 Source: Ultramicroscopy, Volume 150 Author(s): Dmitry Tyutyunnikov , V. Burak Özdöl , Christoph T. Koch In this paper we introduce an approach for simultaneous thickness and orientation mapping of crystalline samples by means of transmission electron microscopy. We show that local thickness and orientation values can be extracted from experimental dark-field (DF) image data acquired at different specimen tilts. The method has been implemented to automatically acquire the necessary data and then map thickness and crystal orientation for a given region of interest. We have applied this technique to a specimen prepared from a commercial semiconductor device, containing multiple 22 nm technology transistor structures. The performance and limitations of our method are discussed and compared to those of other techniques available.
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    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 6
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    Quantitative investigation of SiGeC layers using atom probe tomography (2014)
    Elsevier
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    Publication Date: 2014-12-19
    Description: Publication date: March 2015 Source: Ultramicroscopy, Volume 150 Author(s): Robert Estivill , Adeline Grenier , Sébastien Duguay , François Vurpillot , Tanguy Terlier , Jean-Paul Barnes , Jean-Michel Hartmann , Didier Blavette The quantification of carbon and germanium in a Si/SiGeC multilayer structure using atom probe tomography has been investigated as a function of analysis conditions. The best conditions for quantitative results are obtained using an intermediate electric field and laser power. Carbon evaporation shows strong spatial and temporal correlation. By using multi-ion event analysis, an evaporation mechanism is put forward to explain the modification of mass spectra as a function of electric field and laser power.
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    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 7
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    Prospects of linear reconstruction in atomic resolution electron holographic tomography (2014)
    Elsevier
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    Publication Date: 2014-12-19
    Description: Publication date: March 2015 Source: Ultramicroscopy, Volume 150 Author(s): Jonas Krehl , Axel Lubk Tomography commonly requires a linear relation between the measured signal and the underlying specimen property; for Electron Holographic Tomography this is given by the Phase Grating Approximation (PGA). While largely valid at medium resolution, discrepancies arise at high resolution imaging conditions. We set out to investigate the artefacts that are produced if the reconstruction still assumes the PGA even with an atomic resolution tilt series. To forego experimental difficulties the holographic tilt series was simulated. The reconstructed electric potential clearly shows peaks at the positions of the atoms. These peaks have characterisitic deformations, which can be traced back to the defocus a particular atom has in the holograms of the tilt series. Exchanging an atom for one of a different atomic number results in a significant change in the reconstructed potential that is well contained within the atom's peak.
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    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 8
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    3D image reconstruction of fiber systems using electron tomography (2014)
    Elsevier
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    Publication Date: 2014-12-19
    Description: Publication date: February 2015 Source: Ultramicroscopy, Volume 149 Author(s): Osama M. Fakron , David P. Field Over the past several years, electron microscopists and materials researchers have shown increased interest in electron tomography (reconstruction of three-dimensional information from a tilt series of bright field images obtained in a transmission electron microscope (TEM)). In this research, electron tomography has been used to reconstruct a three-dimensional image for fiber structures from secondary electron images in a scanning electron microscope (SEM). The implementation of this technique is used to examine the structure of fiber system before and after deformation. A test sample of steel wool was tilted around a single axis from −10° to 60° by one-degree steps with images taken at every degree; three-dimensional images were reconstructed for the specimen of fine steel fibers. This method is capable of reconstructing the three-dimensional morphology of this type of lineal structure, and to obtain features such as tortuosity, contact points, and linear density that are of importance in defining the mechanical properties of these materials.
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    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 9
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    Spectrum imaging of complex nanostructures using DualEELS: I. digital extraction replicas (2014)
    Elsevier
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    Publication Date: 2014-12-19
    Description: Publication date: February 2015 Source: Ultramicroscopy, Volume 149 Author(s): Joanna Bobynko , Ian MacLaren , Alan J. Craven This paper shows how it is possible to use Dual Electron Energy Loss Spectroscopy (DualEELS) to digitally extract spectrum images for one phase of interest in a complex nanostructured specimen. The specific cases studied here concern Nb or V precipitates, a few nanometres in size, in high manganese steels. The procedures outlined allow the extraction of the precipitate signal from the Fe–Mn matrix, as well as correction for surface oxide and any surface carbon contamination. The resulting precipitate-only spectrum images are then suitable for quantitative analysis of the precipitate chemistry. This procedure results in much improved background shapes under all edges of interest, mainly as a result of the removal of the extended electron loss fine structure (EXELFS) from the elements in the matrix. This allows the reliable extraction of even tiny quantities of elements, such as low levels of nitrogen in some carbide precipitates. As well as being relevant to precipitation in steels, these techniques will be widely applicable to the separation of chemically-distinct phases in complex nanostructured samples, and can be viewed as a digital version of the extraction replica technique.
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    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 10
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    Spectral analysis of the emission current noise exhibited by few layer WS2 nanosheets emitter (2014)
    Elsevier
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    Publication Date: 2014-12-19
    Description: Publication date: February 2015 Source: Ultramicroscopy, Volume 149 Author(s): Sachin R. Suryawanshi , Pankaj S. Kolhe , Chandra S. Rout , Dattatray J. Late , Mahendra A. More Spectral analysis of the field emission (FE) current fluctuations has been carried out at the base pressure ~1×10 −8 mbar. The emission current stability investigated at preset value of 2 µA is characterized by ‘step’ like fluctuation. The spectral analysis performed on a FFT (Fast Fourier Transform) analyzer revealed that the observed noise is of 1/ f α type, with the value of α as ~1.05. The estimated value of α implies that the current fluctuations are mainly due the various processes occurring on atomic scale like adsorption, migration, and/or desorption of the residual gas species on the emitter surface. Graphical abstract
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    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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