An Atom-Probe Tomography Primer
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David N. Seidman and Krystyna Stiller, Guest Editors Abstract Atom-probe tomography (APT) is in the midst of a dynamic renaissance as a result of the development of well-engineered commercial instruments that are both robust and ergonomic and capable of collecting large data sets, hundreds of millions of atoms, in short time periods compared to their predecessor instruments. An APT setup involves a field-ion microscope coupled directly to a special time-of-flight (TOF) mass spectrometer that permits one to determine the mass-to-charge states of individual field-evaporated ions plus their x-, y-, and z-coordinates in a specimen in direct space with subnanoscale resolution. The three-dimensional (3D) data sets acquired are analyzed using increasingly sophisticated software programs that utilize high-end workstations, which permit one to handle continuously increasing large data sets. APT has the unique ability to dissect a lattice, with subnanometer-scale spatial resolution, using either voltage or laser pulses, on an atom-by-atom and atomic planeby-plane basis and to reconstruct it in 3D with the chemical identity of each detected atom identified by TOF mass spectrometry. Employing pico- or femtosecond laser pulses using visible (green or blue light) to ultraviolet light makes the analysis of metallic, semiconducting, ceramic, and organic materials practical to different degrees of success. The utilization of dual-beam focused ion-beam microscopy for the preparation of microtip specimens from multilayer and surface films, semiconductor devices, and for producing site-specific specimens greatly extends the capabilities of APT to a wider range of scientific and engineering problems than could previously be studied for a wide range of materials: metals, semiconductors, ceramics, biominerals, and organic materials.
Introduction Nothing tends so much to the advancement of knowledge as the application of a new instrument. The native intellectual powers of men in different times are not so much the causes of the different success of their labours, as the peculiar nature of the means and artificial resources in their possession. (Sir Humphry Davy, 1778–1829) This profound observation is pertinent to this issue of MRS Bulletin on atom-probe tomography (APT) and its many applications to an ever-widening range of material classes that involve important scientific and technological problems in materials science and engineering. APT is coming of age, after a long gestation
period,1 because of the availability of reliable and well-engineered commercial instruments and data analysis software that are both robust and ergonomic. In this article, we first describe the basic physical principles of APT commencing with the field ion microscope (FIM), invented by E.W. Müller, which provided the first images of atoms in direct space, 54 years ago, on the surfaces of crystalline tungsten specimens. After explaining the basic physics of field-ion microscopy, field ionization, and field evaporation, we discuss the physical concepts of mode
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