『Abstract
Using high intensity beams of fast electrons, the transmission
electron microscope (TEM) and scanning transmission electron microscope
(STEM) enable comprehensive characterization of rocks and minerals
at micrometre to sub-nanometre scales. This review outlines the
ways in which samples of Earth and planetary materials can be
rendered sufficiently thin for TEM and STEM work, and highlights
the significant advances in site-specific preparation enabled
by the focused ion beam (FIB) technique. Descriptions of the various
modes of TEM and STEM imaging, electron diffraction and X-ray
and electron spectroscopy are outlined, with an emphasis on new
technologies that are of particular relevance to geoscientists.
These include atomic-resolution Z-contrast imaging by high-angle
annular dark-field STEM, electron crystallography by precession
electron diffraction, spectrum mapping using X-rays and electrons,
chemical imaging by energy-filtered TEM and true atomic-resolution
imaging with the new generation of aberration-corrected microscopes.
Despite the sophistication of modern instruments, the spatial
resolution of imaging, diffraction and X-ray and electron spectroscopy
work on many natural materials is likely to remain limited by
structural and chemical damage to the thin samples during TEM
and STEM.
Keywords: transmission electron microscopy; electron diffraction;
electron energy loss spectroscopy; focused ion beam.』
Introduction
Which method of sample preparation?
Mechanical and chemical comminution
Ultramicrotome
Ion milling
Focused ion beam (FIB) technique
Sample preparation summary
TEM and STEM instruments
(S)TEM amplitude-contrast imaging
Mass-thickness contrast
Diffraction contrast
TEM phase-contrast imaging
(STEM electron diffraction
Limitations to (S)TEM work by electron beam damage
Compositional analysis by (S)TEM
X-ray analysis
Electron energy loss spectroscopy (EELS)
Energy-filtered TEM (EFTEM) imaging
Low voltage and wet STEM
Conclusions
Acknowledgements
References
Glossary