Electron spectroscopic diffraction

Investigation of the Structure of Amorphous Substances by Means of Electron Diffraction

“…Compared to the ex perimental facility as used in a previous work [1] we describe in the present paper the use of a commercial electron microscope equipped with a so-called omegafilter. Useful energy filtering has earlier been applied to the study of amorphous materials by Cockayne et al [2] and Reimer et al [3]. In the present study for the first time an imaging omega filter and a slow scan CCD-camera as detector was applied.…”

Thermal vibrations in convergent-beam electron diffraction

“…However, there is more diffuse scattering spreading the intensity in the experimental patterns at low angles than can be accounted for by thermal vibrations. The extra lowangle diffuse scattering can be attributed to scattering by plasmons (Reimer, Fromm & Naundorf, 1990) and possibly a thin oxide or contamination layer on the specimen, neither of which was included in the calculations. The faint broad bands running perpendicular to the Kikuchi bands in the experimental patterns may be the result of correlations between the vibrations of neighboring atoms (Honjo, Kodera & Kitamura, 1964;Komatsu & Teramoto, 1966), * See Note added in proof on p. 277. which are neglected in the simple Einstein model used here.…”

Energy-filtering transmission electron microscopy in materials science

“…-The diffraction patterns of amorphous specimens show diffuse diffraction maxima and minima. A Fourier transform of the oscillations around the averaged decrease of elastic scattering expected without interference results in the radial density distribution 47rr2p(r)dr of atoms with distances r, r+dr [68,69] [70][71][72] is handicapped by the superposition of inelastic small-angle scattering which shows no diffraction for periods larger than the diameter of the excitation volume of plasmon losses of the order of 1 nm [73]. Therefore, zero-loss filtering has successfully been applied to decrease the inelastic background [74,75] in small-angle diffraction patterns of evaporated films.…”

“…4.4 SINGLE-CRYSTAL DIFFRACTION PATTERNS. -Energy filtering of single-crystal diffraction patterns [18,19,21,73,[77][78][79][80][81][82] can be used for a contrast enhancement of Bragg spots, thermaldiffuse streaks caused by electron-phonon scattering and Kikuchi lines and bands by zero-loss filtering and for a separation of the contributions of plasmon scattering to Kikuchi lines and ba.ids and inner-shell ionization processes. Figure lb shows the unfiltered (left) and zero-loss diffraction patterns of a 111-oriented Si foil and Figure 9 shows a series of (a) unfiltered and (bf) energy-filtered diffraction patterns of an 100-oriented GaAs-foil.…”

“…The Bragg spots are increasingly blurred with increasing energy loss by a convolution with the angular distribution of inelastically scattered electrons and disappear at energy losses of a few hundreds of eV However, excess and/or defect Kikuchis bands can be observed up to energy losses of a few thousands of eV When the contribution to the observed high energy loss in the EELS is predominately caused by a single ionization loss from the plasmon-loss region to an energy loss beyond the Ga and As L23 edges at 1115 eV and 1323 eV, excess Kikuchi bands are observed, because the probability for scattering into a distinct direction of the diffraction pattern is proportional to the probability density of a Bloch wave at the nuclei ( [85]. For foils with medium thickness the contrast of Kikuchi bands change from defect at low to excess at high energy losses [21,73]. The angular distribution of inelastic scattering due to interband transitions, plasmon losses and Compton scattering results in special contrast effects in energy-filtered diffraction patterns.…”