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Compressed sensing and electron microscopy
- Modeling Nanoscale Imaging in Electron Microscopy, Nanostructure Science and Technology
, 2012
"... Abstract Compressed Sensing (CS) is a relatively new approach to signal acquisition which has as its goal to minimize the number of measurements needed of the signal in order to guarantee that it is captured to a prescribed accuracy. It is natural to inquire whether this new subject has a role to p ..."
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Abstract Compressed Sensing (CS) is a relatively new approach to signal acquisition which has as its goal to minimize the number of measurements needed of the signal in order to guarantee that it is captured to a prescribed accuracy. It is natural to inquire whether this new subject has a role to play in Electron Microscopy (EM). In this paper, we shall describe the foundations of Compressed Sensing and then examine which parts of this new theory may be useful in EM.
Structure Determination Through Z-Contrast Microscopy Abstract
"... The technique of Z-contrast scanning transmission electron microscopy (STEM) provides an incoherent image of crystals at atomic resolution. There are no phases in an incoherent image, therefore, no phase problem for structure determination. Location of atom column positions in an image is greatly si ..."
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The technique of Z-contrast scanning transmission electron microscopy (STEM) provides an incoherent image of crystals at atomic resolution. There are no phases in an incoherent image, therefore, no phase problem for structure determination. Location of atom column positions in an image is greatly simplified. In addition, the resolution is a factor of two higher than in a coherent image, the information is more highly localized, the intensity of atom columns directly reflects their mean square atomic number (Z), and there are no contrast reversals with crystal thickness. It is also the only means to achieve spectroscopy from individual atomic columns. Here we give a simple but quantum mechanically correct description of this imaging technique. The value of the method lies in providing an approximate starting model which can then be refined by other techniques such as X-ray or electron crystallography or density-functional calculations. 1.
Chin-Kang Ken ShihCharacterization of Nanomaterials by Transmission Electron Microscopy and Related Techniques
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Compressed Sensing and Electron Microscopy
"... Compressed Sensing (CS) is a relatively new approach to signal acquisition which has as its goal to minimize the number of measurements needed of the signal in order to guarantee that it is captured to a prescribed accuracy. It is natural to inquire whether this new subject has a role to play in Ele ..."
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Compressed Sensing (CS) is a relatively new approach to signal acquisition which has as its goal to minimize the number of measurements needed of the signal in order to guarantee that it is captured to a prescribed accuracy. It is natural to inquire whether this new subject has a role to play in Electron Microscopy (EM). In this paper, we shall describe the foundations of Compressed Sensing and then examine which parts of this new theory may be useful in EM.
Understanding the Role of NH4F and Al2O3 Surface Co-modification on Lithium-Excess Layered Oxide Li1.2Ni0.2Mn0.6O2
"... ABSTRACT: In this work we prepared Li1.2Ni0.2Mn0.6O2 (LNMO) using a hydroxide co-precipitation method and investigated the effect of co-modification with NH4F and Al2O3. After surface co-modification, the first cycle Coulombic efficiency of Li1.2Ni0.2Mn0.6O2 improved from 82.7 % to 87.5%, and the re ..."
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ABSTRACT: In this work we prepared Li1.2Ni0.2Mn0.6O2 (LNMO) using a hydroxide co-precipitation method and investigated the effect of co-modification with NH4F and Al2O3. After surface co-modification, the first cycle Coulombic efficiency of Li1.2Ni0.2Mn0.6O2 improved from 82.7 % to 87.5%, and the reversible discharge capacity improved from 253 to 287 mAh g−1 at C/20. Moreover, the rate capability also increased significantly. A combination of neutron diffraction (ND), high-resolution transmission electron microscopy (HRTEM), aberration-corrected scanning transmission electron microscopy (a-STEM)/electron energy loss spectroscopy (EELS), and X-ray photoelectron spectroscopy (XPS) revealed the changes of surface structure and chemistry after NH4F and Al2O3 surface co-modification while the bulk properties showed relatively no changes. These complex changes on the material’s surface include the formation of an amorphous Al2O3 coating, the transformation of layered material to a spinel-like phase on the surface, the formation of nanoislands of active material, and the partial chemical reduction of surface Mn4+. Such enhanced discharge capacity of the modified material can be primarily assigned to three aspects: decreased irreversible oxygen loss, the activation of cathode material facilitated with preactivated Mn3+ on the surface, and stabilization of the Ni-redox pair. These insights will provide guidance for the surface modification in high-voltage-cathode battery materials of the future.
