Back scattered electrons

HEED High-energy electron diffraction [104] Diffraction of elastically back-scattered electrons (-20 keV, grazing incidence) Surface structure... 

Electron Beam Techniques. One of the most powerful tools in VLSI technology is the scanning electron microscope (sem) (see Microscopy). A sem is typically used in three modes secondary electron detection, back-scattered electron detection, and x-ray fluorescence (xrf). AH three techniques can be used for nondestmctive analysis of a VLSI wafer, where the sample does not have to be destroyed for sample preparation or by analysis, if the sem is equipped to accept large wafer-sized samples and the electron beam is used at low (ca 1 keV) energy to preserve the functional integrity of the circuitry. Samples that do not diffuse the charge produced by the electron beam, such as insulators, require special sample preparation. 

REELS will continue to be an important surface analytical tool having special features, such as very high surface sensitivity over lateral distances of the order of a few pm and a lateral resolution that is uniquely immune from back scattered electron effects that degrade the lateral resolution of SAM, SEM and EDS. Its universal availability on all types of electron-excited Auger spectrometers is appealing. However in its high-intensity VEELS-form spectral overlap problems prevent widespread application of REELS. 

Future trends will include studies of grain-dependent surface adsorption phenomena, such as gas-solid reactions and surface segregation. More frequent use of the element-specific CEELS version of REELM to complement SAM in probing the conduction-band density of states should occur. As commercially available SAM instruments improve their spot sizes, especially at low Eq with field emission sources, REELM will be possible at lateral resolutions approaching 10 nm without back scattered electron problems. 

Older experimental arrangements used Earaday cups with small apertures mounted on goniometers, which could be moved around the sample to collect the back-scattered electron current directly, or spot photometers, which were directed at one dif-... 

Since the wavelength is of the order of lattice distances, electrons that are scattered elastically undergo constructive and destructive interference (as with X-rays in XRD). The back-scattered electrons form a pattern of spots on a fluorescent screen from which the symmetry and structure of the surface may be deduced. 

Figure 4 is a back-scattered electron image of the sintered platinum-doped tungsten oxide photocat yst (the bri t spheres are platinum). Analysis of the sintered platinum-doped tungsten oxide by ESCA reveal that the platinum the surface is Pt. ... 

The surface analysis for morphology and average particle size was carried out with JEOL JSM 6301 F scanning electron microscope (SEM). The micrographs of the samples were observed at different magnifications under different detection modes (secondary or back-scattered electrons). 

Figure 2 The SEM pictures of Pd/C type 1 catalyst a)secondary mode, b) back scattered electron.

Backscattered electrons, however, do give some elemental information about the sample because they are more energetic than secondary electrons and escape from farther within the sample [45,46], On the molecular level, the electron beam can interact with the nucleus of an atom and be scattered with minimal loss of energy. These incident electrons may be scattered more than once and then ejected from the sample as backscattered electrons. The back-scattered electrons originate from a greater depth within the sample and are... 

X-Ray Mapping and the Use of Back-Scattered Electrons in the SEM, Amray Technical Bulletin 106-274, Amray, Bedford, Mass., 1976, pp. 11-13. 

Figure 14. (a) Three-dimensional assay of volume of new bone growth by back-scattered electron... 

Backscattered electron images, 24 76-77 Backscattered primary ions, 24 106 Back-scatter electron detectors, in fine art examination/conservation, 11 406 Backstaining, 10 303 Backus process, 4 810 Backward approach, to qualitative reliability analysis, 26 984 Backwash, 11 323... 

Fig. 2.55 Scanning electron micrographs (SEM) in the back scattered electron (BSE) mode at 100,000x of the ABCR MgH + 5 wt.% n-Ni mixtures ball- S milled powder under 700 kPa hydrogen with varying SSA (see the insets in the pictures)...

Fig. 2. Back-scattered electron image of a euhedral, zoned sulfarsenide hosted in pentlandite (Pn). Inner core (white) is irarsite (IrAsS), outer core (pale grey) is hollingworthite (RhAsS), rim (dark grey) is Rh-bearing Ni-cobaltite.

Fig. 2. EPMA back-scattered electron images of a polished section from Chelehkureh deposit, a) carbonate in a mineralized vein with chalcopyrite b) larger image of carbonate grain marked by + in previous image, c), d) and e) are in turn compositional Mg, Fe and Ca images of that grain.

To enable detection of fine mineral particles (<20pm),back-scattered electron imaging was used. Once the minerals were detected, EDS was used for analysis. Selected lignite particles were scanned to determine the distribution of minerals. Mineral types were then differentiated by variation in back scatter intensity and identified using EDS. The relative proportions (major, minor) and size and spatial distributions of the minerals were recorded. The overall surface of the polished section was viewed and massive minerals were analyzed and their distribution and size recorded. 

Fig. 2. Back scattered electron images of glass-ceramics containing various amounts of MSWI bottom ash ...

Figure 2.4 Different types of interactions of electrons with a solid 1, X-ray or optical photons 2, back-scattered electrons 3, secondary electrons 4, coherent elastic scattering 5, inelastic scattering 6, incoherent elastic scattering.

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