Calcul de l'influence de la diffusion inélastique des électrons sur les images de monocristaux

Duval, Hélène; Henry, L.

doi:10.1080/14786437708232960

Cited by 17 publications

(6 citation statements)

References 4 publications

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“…Therefore, this approximation will be useful only for non-localized inelastic scattering processes. This concept of incoherent partial inelastic waves with different k, has also been used to explain the blurring of Bragg contrast of edge and bend contours (Duval &Henry, 1977;Doniach & Sommers, 1985;Bakenfelder et al, 1990).…”

Section: Phase Contrastmentioning

confidence: 99%

Contrast in the electron spectroscopic imaging mode of a TEM

Reimer

Ross-Messemer

1990

Journal of Microscopy

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SUMMARY The ratio of inelastic‐to‐elastic total cross‐sections has been measured in an energy‐filtering electron microscope for different elements. Formulae for the transmission of elastically and inelastically scattered electrons in part I were used to calculate the optimum conditions for a Z‐ratio contrast in the electron spectroscopic imaging mode. Structure‐sensitive contrast can be observed for all non‐carbon atoms in biological sections when filtering with an energy loss at ΔE ∼ 250 eV below the carbon K edge. Model experiments with evaporated layers of different elements on a carbon film allow measurement of the contrast increase. Filtering with the carbon plasmon loss shows a lower phase contrast than with zero‐loss filtering. This can be explained by calculating contrast transfer functions for inelastically scattered electrons.

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Section: Phase Contrastmentioning

confidence: 99%

Contrast in the electron spectroscopic imaging mode of a TEM

Reimer

Ross-Messemer

1990

Journal of Microscopy

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“…This blurring can be explained by the assumption that the angular distribution of inelastic scattering results in an incoherent superposition (Metherell, 1967;Duval & Henry, 1977; Rossouw & Mhelan, 1981; Doniach & Sommers, 1985) of imagcs with a spectrum of excitation errors s = so + e/dh,l, where dhkr denotes the lattice plane distance. The spectral distribution is proportional to the inelastic cross-section do,/dR a (e2 + d;)-* where the square bracket contains the convolution of Z,(t, w ) with as the normalized angular distribution of inelastically scattered electrons (1) with the scattering angle O = (Ox, 6)) which is projected on the x-axis parallel to g and with w = &flx/dhkl.…”

Section: E P E N D E N C E O F B R a G G Contrast O N E N E R G Y Lossmentioning

confidence: 99%

“…We know from theory (Howie, 1963; Humphreys & Whelan, 1969) and experiments (Watanabe, 1964;Castaing et al, 1967;Cundy et al, 1967Cundy et al, , 1969 Kuwabara & Uefuji, 1975;Craven et al, 1978) that the Bragg contrast is preserved in inelastic scattering processes exciting plasmons or inner-shell ionizations of low ionization energy. However, the angular distribution of inelastically scattered electrons results in a spectrum of excitation errors and finally a blurring of edge and bend contours with increasing energy loss (Duval & Henry, 1977; Doniach & Sommers, 1985) analogous to an incoherent illumination with an increased illumination aperture as in the STEM mode (Reimer & Hagemann, 1976), for example. The electron energy-loss spectrum (EELS) results in a chromatic aberration which also contributes to a blurring at high magnification.…”

Section: Introductionmentioning

confidence: 99%

Contrast in the electron spectroscopic imaging mode of a TEM

Bakenfelder

Fromm

Reimer

et al. 1990

Journal of Microscopy

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SUMMARY An energy‐filtering microscope working at 80 keV is used for the investigation of the effect of inelastic scattering on Bragg contrast. Inelastic scattering results in a preservation of Bragg contrast but edge and bend contours are blurred by a spectrum of excitation errors due to the angular distribution of inelastic scattering. This blurring and the chromatic aberration results in a decrease of contrast and resolution for thick specimens. Therefore, contrast and resolution can be increased by zero‐loss filtering as shown by evaporated films of increasing thickness below 150 μg/cm2. Up to ∼300 μg/cm2 an energy‐filtered image at the most probable energy shows the best results. The results obtained are extrapolated to energy‐filtered high‐voltage electron microscopy.

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“…Filtering in the range up to 100 eV energy loss showed that the Bragg contrast of crystalline silver halide matter is also preserved in inelastic scattering processes exciting plasmons, excitons, and low intensity inner ionization edges. Furthermore, the blurring of bend and edge contours by a spectrum of excitation errors due to the angular distribution of inelastic scattering considered by Duval and Henry (1977), Doniach and Sommers (1985,) and then by Bakenfelder et al (1990) was found insignificant in the range of selected energy losses. So, tuning the energy loss allowed an optimization of the conditions, in which microcrystals could be imaged with comparable contrast and intensity within the range of available grey levels.…”

Section: Results and Discussion Energy-filtering Transmission Electronmentioning

confidence: 89%

Combined characterization of composite tabular silver halide microcrystals by cryo-EFTEM/EELS and cryo-STEM/EDX techniques

Oleshko

Gijbels

Daele

et al. 1998

Microsc. Res. Tech.

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The combination of cryo‐energy filtering transmission electron microscopy (EFTEM)/electron spectroscopic diffraction (ESD)/electron energy‐loss spectroscopy (EELS) and cryo‐energy‐dispersive X‐ray (EDX) analysis in the scanning transmission (STEM) and scanning (SEM) modes was applied for the characterization of composite tabular Ag(Br,I) microcrystals. A low‐loss fine structure in EEL spectra between 4 and 26 eV was attributed to excitons and plasmons possibly superimposed with interband transitions and many‐electron effects. The contrast tuning under the energy‐filtering in the low‐loss region was used to image the crystal morphology, defect structure (random dislocations and {111―} stacking faults) and bend and edge contours as well as electron excitations in the microcrystals. Sharp extra reflections at commensurate positions in between the main Bragg reflections and diffuse honeycomb contours in ESD patterns of the microcrystals taken near the [111] zone were assigned to the number of defects in the shell region parallel to the grain edges and polyhedral clusters of interstitial silver cations, respectively. The imaginary part of the energy‐loss function, Im (‐1/ϵ), and the real and imaginary parts, ϵ1and ϵ2, of the dielectric permittivity were determined by means of a Kramers‐Kronig analysis. An assignment of exciton peaks based on calculations of electronic band structure of silver bromide is proposed. Inner‐shell excitation bands of silver halide were detected in line with EDX‐analyses. The energy‐loss near‐edge structure (ELNES) of the AgM4,5‐edge governed by spin‐orbital splitting between the 3d3/2‐ and 3d5/2‐states has been evaluated. Combined silver and halide distributions were obtained by a three‐window method (EFTEM) and by EDX/STEM including area mapping and line profiling of iodide. Microsc. Res. Tech. 42:108–122, 1998. © 1998 Wiley‐Liss, Inc.

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Calcul de l'influence de la diffusion inélastique des électrons sur les images de monocristaux

Cited by 17 publications

References 4 publications

Contrast in the electron spectroscopic imaging mode of a TEM

Contrast in the electron spectroscopic imaging mode of a TEM

Contrast in the electron spectroscopic imaging mode of a TEM

Combined characterization of composite tabular silver halide microcrystals by cryo-EFTEM/EELS and cryo-STEM/EDX techniques

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