Atom Probe Tomography


Development of atom probe tomography at Oak Ridge National Laboratory (ORNL)




Atom probe tomography has developed into one of the most powerful techniques available for the characterization of the atomic scale variations in solute concentration in materials. This technique produces three-dimensional images of the internal structure of metals and semiconductors by the reconstruction of thousands of two-dimensional slices, each containing a few atoms. The resulting data are the spatial coordinates and the mass-to-charge ratios and hence the elemental identities of the atoms in the sampled volume. In modern instruments, the sampled volumes may contain between 105 and 108 atoms. The technique is routinely used by laboratories around the world to investigate many areas of materials science, including phase transformations, solute clustering, ordering and segregation, radiation damage, and alloy design. Atom probe tomography has been applied to a wide range of materials including steels, superalloys, intermetallics, aluminum alloys, bulk metallic glasses, and thin films.






ORNL research efforts — comprising the development of hardware, software, applications, and textbook monographs — have played critical roles in the transformation of atom probe from a one-dimensional profiling technique to a powerful tomographic technique for the three-dimensional reconstruction of atomic scale compositional variations in materials that could not otherwise be measured. The concept for atom probe tomography was discussed at ORNL in the spring of 1983. This concept was first implemented in 1985 by the addition of a second time-of-flight mass spectrometer equipped with a position-sensitive detector to a Vacuum Generator’s FIM 100 atom probe field ion microscope. The first preliminary atom probe tomography results from this prototype "optical" atom probe were presented at the Microscopy Society of America meeting in Albuquerque in 1986. The prototype instrument’s use of a CCD video camera to encode the impact positions of atoms on the single atom detector has since been adopted by commercial manufacturers of atom probe instrumentation — Kindbrisk Ltd, England in their optical position-sensitive atom probe and CAMECA, France in their optical tomographic atom probe — and variants of position-sensitive detectors have been implemented by other atom probe research groups. In parallel with hardware development, ORNL pioneered the development of comprehensive suites of software for the on-line control of the instrument and the statistical analysis of atom probe data. A series of three textbooks on atom probe field ion microscopy have been written, the most recent providing the only currently available monograph dedicated to atom probe tomography [1].

[1] M. K. Miller, Atom Probe Tomography, Kluwer Academic/Plenum Press, 2000.

SHaRE collaborative research by M. K. Miller and K. F. Russell (ORNL).







 Oak Ridge National Laboratory