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Moharam Habibnejad Korayem, Maniya B Saraie, Mahdieh B Saraee
An important challenge when using an atomic force microscope (AFM) is to be able to control the force exerted by the AFM for performing various tasks. Nevertheless, the exerted force is proportional to the deflection of the AFM cantilever, which itself is affected by a cantilever's stiffness coefficient. Many papers have been published so far on the methods of obtaining the stiffness coefficients of AFM cantilevers in 2D; however, a comprehensive model is yet to be presented on 3D cantilever motion. The discrepancies between the equations of the 2D and 3D analysis are due to the number and direction of forces and moments that are applied to a cantilever...
January 13, 2017: Ultramicroscopy
Bernard Legrand, Jean-Paul Salvetat, Benjamin Walter, Marc Faucher, Didier Théron, Jean-Pierre Aimé
Silicon ring-shaped micro-electro-mechanical resonators have been fabricated and used as probes for dynamic atomic force microscopy (AFM) experiments. They offer resotnance frequency above 10MHz, which is notably greater than that of usual cantilevers and quartz-based AFM probes. On-chip electrical actuation and readout of the tip oscillation are obtained by means of built-in capacitive transducers. Displacement and force resolutions have been determined from noise analysis at 1.5fm/√Hz and 0.4 pN/√Hz, respectively...
January 12, 2017: Ultramicroscopy
Jakob Spiegelberg, Ján Rusz, Kristiaan Pelckmans
A selection of tensor decomposition techniques is presented for the detection of weak signals in electron energy loss spectroscopy (EELS) data. The focus of the analysis lies on the correct representation of the simulated spatial structure. An analysis scheme for EEL spectra combining two-dimensional and n-way decomposition methods is proposed. In particular, the performance of robust principal component analysis (ROBPCA), Tucker Decompositions using orthogonality constraints (Multilinear Singular Value Decomposition (MLSVD)) and Tucker decomposition without imposed constraints, canonical polyadic decomposition (CPD) and block term decompositions (BTD) on synthetic as well as experimental data is examined...
January 11, 2017: Ultramicroscopy
Robert Sinclair, Sang Chul Lee, Yezhou Shi, William C Chueh
We have applied aberration-corrected transmission electron microscopy (TEM) imaging and electron energy loss spectroscopy (EELS) to study the structure and chemistry of epitaxial ceria thin films, grown by pulsed laser deposition onto (001) yttria-stabilized zirconia (YSZ) substrates. There are few observable defects apart from the expected mismatch interfacial dislocations and so the films would be expected to have good potential for applications. Under high electron beam dose rate (above about 6000 e(-)/Å(2)s) domains of an ordered structure appear and these are interpreted as being created by oxygen vacancy ordering...
January 6, 2017: Ultramicroscopy
Toby Sanders, Anne Gelb, Rodrigo B Platte, Ilke Arslan, Kai Landskron
Over the last decade or so, reconstruction methods using ℓ1 regularization, often categorized as compressed sensing (CS) algorithms, have significantly improved the capabilities of high fidelity imaging in electron tomography. The most popular ℓ1 regularization approach within electron tomography has been total variation (TV) regularization. In addition to reducing unwanted noise, TV regularization encourages a piecewise constant solution with sparse boundary regions. In this paper we propose an alternative ℓ1 regularization approach for electron tomography based on higher order total variation (HOTV)...
January 3, 2017: Ultramicroscopy
Z C Wang, X Y Zhong, L Jin, X F Chen, Y Moritomo, J Mayer
Electron energy-loss magnetic chiral dichroism (EMCD) spectroscopy, which is similar to the well-established X-ray magnetic circular dichroism spectroscopy (XMCD), can determine the quantitative magnetic parameters of materials with high spatial resolution. One of the major obstacles in quantitative analysis using the EMCD technique is the relatively poor signal-to-noise ratio (SNR), compared to XMCD. Here, in the example of a double perovskite Sr2FeMoO6, we predicted the optimal dynamical diffraction conditions such as sample thickness, crystallographic orientation and detection aperture position by theoretical simulations...
December 30, 2016: Ultramicroscopy
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...
December 27, 2016: Ultramicroscopy
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...
December 26, 2016: Ultramicroscopy
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...
December 25, 2016: Ultramicroscopy
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...
December 23, 2016: Ultramicroscopy
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...
December 23, 2016: Ultramicroscopy
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...
December 19, 2016: Ultramicroscopy
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...
December 16, 2016: Ultramicroscopy
Daniel Knez, Philipp Thaler, Alexander Volk, Gerald Kothleitner, Wolfgang E Ernst, Ferdinand Hofer
We report the transformation of nickel clusters into NiO rings by an electron beam induced nanoscale Kirkendall effect. High-purity nickel clusters consisting of a few thousand atoms have been used as precursors and were synthesized with the superfluid helium droplet technique. Aberration-corrected, analytical scanning transmission electron microscopy was applied to oxidise and simultaneously analyse the nanostructures. The transient dynamics of the oxidation could be documented by time lapse series using high-angle annular dark-field imaging and electron energy-loss spectroscopy...
December 13, 2016: Ultramicroscopy
Hasan Ali, Johan Eriksson, Hu Li, S Hassan M Jafri, M S Sharath Kumar, Jim Ögren, Volker Ziemann, Klaus Leifer
We propose an experimental setup based on a streak camera approach inside an energy filter to measure time resolved properties of materials in the transmission electron microscope (TEM). In order to put in place the streak camera, a beam sweeper was built inside an energy filter. After exciting the TEM sample, the beam is swept across the CCD camera of the filter. We describe different parts of the setup at the example of a magnetic measurement. This setup is capable to acquire time resolved diffraction patterns, electron energy loss spectra (EELS) and images with total streaking times in the range between 100ns and 10μs...
December 11, 2016: Ultramicroscopy
Rafal E Dunin-Borkowski, Joachim Mayer, Karsten Tillmann
No abstract text is available yet for this article.
December 11, 2016: Ultramicroscopy
Zhichao Zhong, Bart Goris, Remco Schoenmakers, Sara Bals, K Joost Batenburg
A three-dimensional (3D) chemical characterization of nanomaterials can be obtained using tomography based on high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) or energy dispersive X-ray spectroscopy (EDS) STEM. These two complementary techniques have both advantages and disadvantages. The Z-contrast images have good image quality but lack robustness in the compositional analysis, while the elemental maps give more element-specific information, but at a low signal-to-noise ratio and a longer exposure time...
December 11, 2016: Ultramicroscopy
U Bangert, A Stewart, E O'Connell, E Courtney, Q Ramasse, D Kepatsoglou, H Hofsäss, J Amani, J-S Tu, B Kardynal
Functionalisation of two-dimensional (2-D) materials via low energy ion implantation could open possibilities for fabrication of devices based on such materials. Nanoscale patterning and/or electronically doping can thus be achieved, compatible with large scale integrated semiconductor technologies. Using atomic resolution High Angle Annular Dark Field (HAADF) scanning transmission electron microscopy supported by image simulation, we show that sites and chemical nature of individual implants/ dopants in graphene, as well as impurities in hBN, can uniquely and directly be identified on grounds of their position and their image intensity in accordance with predictions from Z-contrast theories...
December 11, 2016: Ultramicroscopy
James E Wittig, James Bentley, Lawrence F Allard
In situ high-resolution electron microscopy was used to reveal information at the atomic level for the disordered-to-ordered phase transformation of equiatomic FePt nanoparticles that can exhibit outstanding magnetic properties after transforming from disordered face-centered-cubic into the tetragonal L10 ordered structure. High-angle annular dark-field imaging in the scanning transmission electron microscope provided sufficient contrast between the Fe and Pt atoms to readily monitor the ordering of the atoms during in situ heating experiments...
December 11, 2016: Ultramicroscopy
Ai Leen Koh, Robert Sinclair
In this work, we examine how the imaging electron beam can induce damage in carbon nanotubes (CNTs) at varying oxygen gas pressures and electron dose rates using environmental transmission electron microscopy (ETEM). Our studies show that there is a threshold cumulative electron dose which brings about damage in CNTs in oxygen - through removal of their graphitic walls - which is dependent on O2 pressure, with a 4-5 fold decrease in total electron dose per decade increase at a lower pressure range (10(-6) to 10(-5)mbar) and approximately 1...
December 10, 2016: Ultramicroscopy
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