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  • Articles  (168)
  • 2015-2019  (168)
  • 2016  (168)
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  • Articles  (168)
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  • 2015-2019  (168)
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  • 1
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    Design and commissioning of an aberration-corrected ultrafast spin-polarized low energy electron microscope with multiple electron sources (2016)
    Elsevier
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    Publication Date: 2016-12-28
    Description: Publication date: Available online 27 December 2016 Source: Ultramicroscopy Author(s): Weishi Wan, Lei Yu, Lin Zhu, Xiaodong Yang, Zheng Wei, Jefferson Zhe Liu, Jun Feng, Kai Kunze, Oliver Schaff, Ruud Tromp, Wen-Xin Tang We describe the design and commissioning of a novel aberration-corrected low energy electron microscope (AC-LEEM). A third magnetic prism array (MPA) is added to the standard AC-LEEM with two prism arrays, allowing the incorporation of an ultrafast spin-polarized electron source alongside the standard cold field emission electron source, without degrading spatial resolution. The high degree of symmetries of the AC-LEEM are utilized while we design the electron optics of the ultrafast spin-polarized electron source, so as to minimize the deleterious effect of time broadening, while maintaining full control of electron spin. A spatial resolution of 2 nm and temporal resolution of 10 ps (ps) are expected in the future time resolved aberration-corrected spin-polarized LEEM (TR-AC-SPLEEM). The commissioning of the three-prism AC-LEEM has been successfully finished with the cold field emission source, with a spatial resolution below 2 nm.
    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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    Non-iterative phase retrieval by phase modulation through a single parameter (2016)
    Elsevier
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    Publication Date: 2016-12-28
    Description: Publication date: Available online 26 December 2016 Source: Ultramicroscopy Author(s): A.P. Konijnenberg, W.M.J. Coene, H.P. Urbach We report on a novel non-iterative phase retrieval method with which the complex-valued transmission function of an object can be retrieved with a non-iterative computation, with a limited number of intensity measurements. The measurements are taken in either real space or Fourier space, and for each measurement the phase in its dual space is modulated according to a single optical parameter. The requirement found for the phase modulation function is a general one, which therefore allows for plenty of customization in this method. It is shown that quantitative Zernike phase contrast imaging is one special case of this general method. With simulations we investigate the sampling requirements for a microscopy setup and for a Coherent Diffraction Imaging (CDI) setup.
    Print ISSN: 0304-3991
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 3
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    High-resolution scanning precession electron diffraction: alignment and spatial resolution (2016)
    Elsevier
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    Publication Date: 2016-12-27
    Description: Publication date: Available online 25 December 2016 Source: Ultramicroscopy Author(s): Jonathan S. Barnard, Duncan N. Johnstone, Paul A. Midgley Methods are presented for aligning the pivot point of a precessing electron probe in the scanning transmission electron microscope (STEM) and for assessing the spatial resolution in scanning precession electron diffraction (SPED) experiments. The alignment procedure is performed entirely in diffraction mode, minimising probe wander within the bright-field (BF) convergent beam electron diffraction (CBED) disk and is used to obtain high spatial resolution SPED maps. Through analysis of the power spectra of virtual bright-field images extracted from the SPED data, the precession-induced blur was measured as a function of precession angle. At low precession angles, SPED spatial resolution was limited by electronic noise in the scan coils; whereas at high precession angles SPED spatial resolution was limited by tilt-induced two-fold astigmatism caused by the positive spherical aberration of the probe-forming lens.
    Print ISSN: 0304-3991
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 4
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    Investigation of tip-depletion-induced fail in scanning capacitance microscopy for the determination of carrier type (2016)
    Elsevier
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    Publication Date: 2016-12-25
    Description: Publication date: Available online 23 December 2016 Source: Ultramicroscopy Author(s): Lin Wang, Brice Gautier, Andrei Sabac, Georges Bremond Scanning capacitance microscopy (SCM) was performed on an n -type Si multilayer structure doped by phosphorus whose concentration ranges from 2×10 17 to 2×10 19 cm −3 . Three types of tips were used, i.e. fresh Pt/Ir coated tip, worn Pt/Ir coated tip and non-coated commercial Si tip. The use of fresh Pt/Ir coated tips produces SCM result in good agreement with the doping profile including the correct identification of the carrier type. In contrast, a worn Pt/Ir coated tip which has lost its metal coating and a non-coated tip will fail to recognize successfully the carrier type for phosphorus dopant concentration above 8×10 18 cm −3 (identifying as p instead of n ) due to the tip depletion effect. These results alert us to carefully interpret the SCM results, especially in the case for identification of carrier type inside the sample of interest which is unknown.
    Print ISSN: 0304-3991
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 5
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    Calibrating conservative and dissipative response of electrically-driven quartz tuning forks (2016)
    Elsevier
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    Publication Date: 2016-12-25
    Description: Publication date: Available online 23 December 2016 Source: Ultramicroscopy Author(s): Lifeng Hao, Qi Wang, Ping Peng, Zhenxing Cao, Weicheng Jiao, Fan Yang, Wenbo Liu, Rongguo Wang, Xiaodong He Determining sensor parameters is a prerequisite for quantitative force measurement. Here we report a direct, high-precision calibration method for quartz tuning fork(TF) sensors that are popular in the field of nanomechanical measurement. In the method, conservative and dissipative forces with controlled amplitudes are applied to one prong of TF directly to mimic the tip-sample interaction, and the responses of the sensor are measured at the same time to extract sensor parameters. The method, for the first time, allows force gradient and damping coefficient which correspond to the conservative and dissipative interactions to be measured simultaneously. The calibration result shows surprisingly that, unlike cantilevers, the frequency shift for TFs depends on both the conservative and dissipative forces, which may be ascribed to the complex dynamics. The effectiveness of the method is testified by force spectrum measurement with a calibrated TF. The method is generic for all kinds of sensors used for non-contact atomic force microscopy(NC-AFM) and is an important improvement for quantitative nanomechanical measurement.
    Print ISSN: 0304-3991
    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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  • 6
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    Challenges in quantitative crystallographic characterization of 3D thin films by ACOM-TEM (2016)
    Elsevier
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    Publication Date: 2016-12-23
    Description: Publication date: February 2017 Source: Ultramicroscopy, Volume 173 Author(s): A. Kobler, C. Kübel Automated crystal orientation mapping for transmission electron microscopy (ACOM-TEM) has become an easy to use method for the investigation of crystalline materials and complements other TEM methods by adding local crystallographic information over large areas. It fills the gap between high resolution electron microscopy and electron back scatter diffraction in terms of spatial resolution. Recent investigations showed that spot diffraction ACOM-TEM is a quantitative method with respect to sample parameters like grain size, twin density, orientation density and others. It can even be used in combination with in-situ tensile or thermal testing. However, there are limitations of the current method. In this paper we discuss some of the challenges and discuss solutions, e.g. we present an ambiguity filter that reduces the number of pixels with a ‘180° ambiguity problem’. For that an ACOM-TEM tilt series of nanocrystalline Pd thin films with overlapping crystallites was acquired and analyzed.
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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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    Cathodoluminescence in the scanning transmission electron microscope (2016)
    Elsevier
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    Publication Date: 2016-12-21
    Description: Publication date: Available online 19 December 2016 Source: Ultramicroscopy Author(s): M. Kociak, L.F. Zagonel Cathodoluminescence (CL) is a powerful tool for the investigation of optical properties of materials. In recent years, its combination with scanning transmission electron microscopy (STEM) has demonstrated great success in unveiling new physics in the field of plasmonics and quantum emitters. Most of these results were not imaginable even twenty years ago, due to conceptual and technical limitations. The purpose of this review is to present the recent advances that broke these limitations, and the new possibilities offered by the modern STEM-CL technique. We first introduce the different STEM-CL operating modes and the technical specificities in STEM-CL instrumentation. Two main classes of optical excitations, namely the coherent one (typically plasmons) and the incoherent one (typically light emission from quantum emitters) are investigated with STEM-CL. For these two main classes, we describe both the physics of light production under electron beam irradiation and the physical basis for interpreting STEM-CL experiments. We then compare STEM-CL with its better known sister techniques: scanning electron microscope CL, photoluminescence, and electron energy-loss spectroscopy. We finish by comprehensively reviewing recent STEM-CL applications.
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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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    Analysis of Electron Energy Loss Spectroscopy Data using Geometric Extraction Methods (2016)
    Elsevier
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    Publication Date: 2016-12-18
    Description: Publication date: Available online 16 December 2016 Source: Ultramicroscopy Author(s): Jakob Spiegelberg, Ján Rusz, Thomas Thersleff, Kristiaan Pelckmans A set of geometric data decomposition methods is discussed. In particular, randomized vertex component analysis (RVCA), an extension of vertex component analysis (VCA) for the application to noisy data is established. Minimum volume simplex analysis (MVSA), a recent technique for the extraction of endmembers in the absence of pure pixels, is presented. A comparison between MVSA and the previously presented technique of Bayesian Linear Unmixing (BLU) is drawn. Lastly, the efficiency of these methods for high-dimensional data is examined. Improvement on the extracted source components spectral signatures are achieved by establishing Gaussian mixture modeling as extraction technique.
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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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    IFC (Editorial Board) (2016)
    Elsevier
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    Publication Date: 2016-12-17
    Description: Publication date: January 2017 Source: Ultramicroscopy, Volume 172
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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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    How precise can atoms of a nanocluster be located in 3D using a tilt series of scanning transmission electron microscopy images? (2016)
    Elsevier
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    Publication Date: 2016-12-17
    Description: Publication date: Available online 15 December 2016 Source: Ultramicroscopy Author(s): M. Alania, A. De Backer, I. Lobato, F.F. Krause, D. Van Dyck, A. Rosenauer, S. Van Aert In this paper, we investigate how precise atoms of a small nanocluster can ultimately be located in three dimensions (3D) from a tilt series of images acquired using annular dark field (ADF) scanning transmission electron microscopy (STEM). Therefore, we derive an expression for the statistical precision with which the 3D atomic position coordinates can be estimated in a quantitative analysis. Evaluating this statistical precision as a function of the microscope settings also allows us to derive the optimal experimental design. In this manner, the optimal angular tilt range, required electron dose, optimal detector angles, and number of projection images can be determined.
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    Topics: Electrical Engineering, Measurement and Control Technology , Natural Sciences in General , Physics
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