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Starting in the 1950s and continuing over the next two decades, field ion microscopy (FIM) became the first true atomic-scale microscopy technique [1], allowing for the direct imaging of individual atom positions on a material's surface with sub-angstrom precision [2]. By controlling the field evaporation of atoms from the surface, a three-dimensional (3D) reconstruction can be achieved through digital processing of a sequence of micrographs [3]. Spatial resolutions, both lateral and in-depth, can reach fractions of an angstrom. Detection efficiency is also improved compared to atom probe tomography (APT), with a global efficiency reaching 85% and a local efficiency nearing 100%. Additionally, contrast differences in the spots observed in FIM images, which reveal the presence of different chemical species, can be used to create a qualitative map of atomic distribution within the sample.
These capabilities allow for the 3D reconstruction of defects such as dislocations, nano-voids, and even vacancies [3][4]. Recent advances in 3D FIM have been applied to characterize various samples, including the orientation of the superlattice of ordered phases in meteorites, the evolution of amorphous glasses after annealing, and small defects created by irradiation damage. Despite these capabilities which allow the analysis of the finest crystalline defects, 3D FIM remains limited in its ability to identify chemical elements. It is generally necessary to complement these analyses with other instruments, such as APT.
Future developments involving time-resolved cameras could lead to the creation of an instrument that combines the mass resolution of APT with the spatial resolution of 3D FIM, thereby merging the best features of both instruments into one.
[1] E.W. Müller et al. 1956 Phys. Rev. 102 624–31
[2] E.W. Muller 1965 Science 149 591–601
[3] B. Klaes et al., 2021. Microsc Microanal. 27 365-384
[4] S. Katnagallu et al. 2019 New J. Phys. 21 123020
