The observations of individual atoms have come a long way, from field-ion microscopy (FIM) to atom-probe tomography (APT). A FIM is a lensless point-projection microscope that resolves individual atoms on the surface of a sharply pointed tip at magnifications of greater than 106 times. FIM has also played an important role in many areas of materials research such as in radiation damage in metals FIM proved itself capable of studying in situ point defects, point-defect clusters, and displacement cascades, at temperatures as low as 12 K, in quantitative detail, and to obtain physically important information. The invention of atom-probe tomographs (APT) marks a major advancement in the observation of individual atoms. The commercial APTs have the ability to reconstruct readily a lattice of atoms in 3D with their chemical identities (m/n values) and to analyze the 3D reconstructed structure with sophisticated software programs.
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