Physical Principles of Electron Microscopy: An Introduction to TEM ...

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Chapter 1
Figure 1-10. JEOL transmission electron microscopes: (a) model 100B and (b) model 2010.
The TEM has proved invaluable for examining the ultrastructure of
metals. For example, crystalline defects known as dislocations were first
predicted by theorists to account for the fact that metals deform under much
lower forces than calculated for perfect crystalline array of atoms. They were
first seen directly in TEM images of aluminum; one of M.J. Whelan’s
original micrographs is reproduced in Fig. 1-11. Note the increase in
resolution compared to the light-microscope image of Fig. 1-5; detail can
now be seen within each metal crystallite. With a modern TEM (resolution �
0.2 nm), it is even possible to image individual atomic planes or columns of
atoms, as we will discuss in Chapter 4.
Figure 1-11. TEM diffraction-contrast image (M � 10,000) of polycrystalline aluminum.
Individual crystallites (grains) show up with different brightness levels; low-angle boundaries
and dislocations are visible as dark lines within each crystallite. Circular fringes (top-right)
represent local changes in specimen thickness. Courtsey of M.J. Whelan, Oxford University.