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Energy-Filtering Transmission Electron Microscopy (EFTEM) presents
a summary of the electron optics, the electron-specimen
interactions, and the operation and contrast modes of this new
field of analytical electron microscopy. The electron optics of
filter lenses and the progress in the correction of aberrations are
discussed in detail. An evaluation of our present knowledge of
plasmon losses and inner-shell ionisations is of increasing
interest for a quantitative application of EFTEM in materials and
life sciences. This can be realized not only by filtering the
elastically scattered electrons but mainly by imgaging and
analyzing with inelastically scattered electrons at different
energy losses up to 2000 eV. The strength of EFTEM is the
combination of the modes EELS, ESI, ESD and REM.
Towards the end of the 1960s, a number of quite different
circumstances combined to launch a period of intense activity in
the digital processing of electron micro graphs. First, many years
of work on correcting the resolution-limiting aberrations of
electron microscope objectives had shown that these optical
impediments to very high resolution could indeed be overcome, but
only at the cost of immense exper imental difficulty; thanks
largely to the theoretical work of K. -J. Hanszen and his
colleagues and to the experimental work of F. Thon, the notions of
transfer func tions were beginning to supplant or complement the
concepts of geometrical optics in electron optical thinking; and
finally, large fast computers, capable of manipu lating big image
matrices in a reasonable time, were widely accessible. Thus the
idea that recorded electron microscope images could be improved in
some way or rendered more informative by subsequent computer
processing gradually gained ground. At first, most effort was
concentrated on three-dimensional reconstruction, particu larly of
specimens with natural symmetry that could be exploited, and on
linear operations on weakly scattering specimens (Chap. l). In
1973, however, R. W. Gerchberg and W. O. Saxton described an
iterative algorithm that in principle yielded the phase and
amplitude of the electron wave emerging from a strongly scattering
speci men."
No single volume has been entirely devoted to the properties of
magnetic lenses, so far as I am aware, although of course all the
numerous textbooks on electron optics devote space to them. The
absence of such a volume, bringing together in formation about the
theory and practical design of these lenses, is surprising, for
their introduction some fifty years ago has created an entirely new
family of commercial instruments, ranging from the now traditional
transmission electron microscope, through the reflection and
transmission scanning microscopes, to co lumns for micromachining
and microlithography, not to mention the host of experi mental
devices not available commercially. It therefore seemed useful to
prepare an account of the various aspects of mag netic lens
studies. These divide naturally into the five chapters of this
book: the theoretical background, in which the optical behaviour is
described and formu lae given for the various aberration
coefficients; numerical methods for calculat ing the field
distribution and trajectory tracing; extensive discussion of the
paraxial optical properties and aberration coefficients of
practical lenses, il lustrated with curves from which numerical
information can be obtained; a comple mentary account of the
practical, engineering aspects of lens design, including permanent
magnet lenses and the various types of superconducting lenses; and
final ly, an up-to-date survey of several kinds of highly
unconventional magnetic lens, which may well change the appearance
of future electron optical instruments very considerably after they
cease to be unconventional."
Scanning Electron Microscopy provides a description of the physics
of electron-probe formation and of electron-specimen interactions.
The different imaging and analytical modes using secondary and
backscattered electrons, electron-beam-induced currents, X-ray and
Auger electrons, electron channelling effects, and
cathodoluminescence are discussed to evaluate specific contrasts
and to obtain quantitative information.
Scanning Electron Microscopy provides a description of the physics
of electron-probe formation and of electron-specimen interactions.
The different imaging and analytical modes using secondary and
backscattered electrons, electron-beam-induced currents, X-ray and
Auger electrons, electron channelling effects, and
cathodoluminescence are discussed to evaluate specific contrasts
and to obtain quantitative information.
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