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[en] This contribution aims at reporting, from the subjective point of view of a witness based in Orsay, the fundamental role of Ondrej Krivanek in the spectacular emergence of EELS (Electron Energy-Loss Spectroscopy) as a key tool in analytical electron microscopy. In this regard, he has successively designed and built while he was at Gatan, serial EELS spectrometers, parallel EELS spectrometers and post-column energy filters which have been fitted to many different (S)TEM columns installed around the world. More recently the implementation of monochromators on the NION dedicated STEM together with the realization and performance of aberration correctors (which lie out of the scope of the present review), have placed the most advanced instrumental tool in the hands of continuously increasing populations of users in many domains of materials science and in life sciences. Furthermore, the impact of Ondrej Krivanek has spread widely beyond his technical achievements into that of a highly respected organizer of workshops, bringing together at regular intervals, all the experts from around the world and building up a real community of scientists.
[en] 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. - Highlights: • Limitations of VCA for application to noisy data are discussed. • RVCA is introduced for analysis of grossly noise corrupted data. • MVSA and BLU are compared based on performance and computational costs. • Clustering methods are demonstrated for feature extraction from EEL spectra.
[en] Highlights: • Titanium carbide derived carbons were obtained from hydrochlorination reaction. • Spectroscopy studies provided evidence of formation of sp3 hybridized carbon. • The Raman bands located at ≈ 680, 838 and 1060 cm−1, revealed diamonoid clusters. • Electron energy loss spectroscopy data yield sp2 carbon bonding from 82 to 100%.
[en] High-resolution electron energy-loss measurements at off-specular directions on a clean Cu(100) surface (Gamma-bar-X-bar direction) demonstrate the presence of both surface and bulk phonon excitations. We present what we believe to be the first detailed cross-section analysis of surface and bulk phonon excitations on the Cu(100) surface. The data are shown to be in very good agreement with calculations based on the multiple-scattering slab method. The achievement of experimental phonon intensities one to two orders of magnitude higher than previously obtained is also demonstrated
[en] In this work we present a theoretical study of EELS (electron-energy-loss spectroscopy) experiments on the C60 molecule. Our treatment of the problem is based on the simple two-fluid model originally proposed for the description of plasma oscillations in graphite and fullerenes [J. Cazaux, Solid State Commun. 8 (1970) 545; Opt. Commun. 2 (1970) 173; G. Barton and C. Eberlein, J. Chem. Phys. 95 (1991) 1512]. It is shown that in spite of the simplicity of the model the calculated intensities of the EELS peaks are in good agreement with experimental data which may indicate that the model can be used as a simple and effective tool for the investigation of the collective behaviour of electrons in fullerene systems. (orig.)
[en] Compared to other methods of analysis, the imaging electron energy-loss spectroscopy is characterized by a high detection sensitivity of light elements such as B, C, N and O. With this method, the provable concentrations lie at 0.1 to 1 volume percent. The minimum detectable masses are 10-21 grams. This high detection sensitivity, too, is combined with a high lateral resolution of about 1 nm. Therefore, this method is particularly appropriate for the analysis of microsized structures. (orig.)
[de]Die abbildende Elektronenenergieverlustspektroskopie zeichnet sich gegenueber anderen Analyseverfahren durch eine hohe Nachweisempfindlichkeit von leichten Elementen wie z.B. B, C, N und O aus. Die nachweisbaren Konzentrationen liegen mit diesem Verfahren bei 0.1 bis 1 Volumenprozent. Die kleinsten nachweisbaren Massen liegen in der Groessenordnung von 10-21 g. Diese hohe Nachweisempfindlichkeit ist ebenfalls mit einer hohen lateralen Aufloesung von ca. 1 nm verbunden. Daher ist dieses Verfahren besonders fuer die Analyse kleinster Strukturen geeignet. (orig.)
[en] We propose a new theoretical interpretation of the electron energy loss spectroscopy results of Pichler et al on bulk carbon nanotube samples. The origin of the nondispersive modes found experimentally has been controversial, and at least three different interpretations have been offered in the literature. From our theoretical results of the loss functions for individual carbon nanotubes based on a tight-binding model, we find that the nondispersive modes could be due to collective electronic modes in chiral carbon nanotubes, while the observed dispersive mode should be due to collective electronic modes in armchair and zigzag carbon nanotubes. (letter to the editor)
[en] The functionalization with amine groups was developed on the SBA-15, and its effect in the laccase immobilization was compared with that of a Periodic Mesoporous Aminosilica. A method to encapsulate the laccase in situ has now been developed. In this work, spherical aberration (Cs) corrected scanning transmission electron microscopy combined with high angle annular dark field detector and electron energy loss spectroscopy were applied to identify the exact location of the enzyme in the matrix formed by the ordered mesoporous solids
[en] Some features of the anticipated improvements in microanalysis by electron energy loss spectroscopy (EELS) at 300 kV compared to opeation at 100kV have been studied with the use of a Philips EM430T equipped with Gatan 607 EELS and EDAX 9100/70 systems. Detailed measurements have been made on a range of specimens, with emphasis on boron nitride and silicon carbide