Physics and Astronomy Colloquium
Progress Towards Atomic-Scale Analytical Tomography
Presented by Dr. Thomas F. Kelly has been active in the fields of analytical electron microscopy, atom probe microscopy, and superconducting materials since 1977. He co-authored a book on Local Electrode Atom Probe (LEAP) technology in 2012 and just completed a foundational book on atomic-scale analytical tomography. His work has been recognized by professional colleagues including the Innovation in Materials Characterization Award from the Materials Research Society, the prestigious Nelson W. Taylor Lecture at the Pennsylvania State University, the MAS Peter Ouncumb Award for Excellence in Microanalysis, and Fellowship in the Microscopy Society of America, the Microanalysis Society, the International Field Emission Society, and the Korean Society for Microscopy. He has won three R&D 100 Awards. He was elected member of the US National Academy of Engineering in 2021. Dr. Kelly earned a B.S. in Mechanical Engineering with Highest Honors from Northeastern University in 1977 and a Ph.D. in Materials Science and Engineering from the Massachusetts Institute of Technology in 1982 where he studied rapidly solidified stainless steel using analytical electron microscopy. He was a tenured professor of Materials Science and Engineering at the University of Wisconsin-Madison from 1983 to 2002. In 1999 he founded Imago Scientific Instruments where he created the first LEAP whose successors have become the commercial atomic-scale tomographic instrument in worldwide use today. Imago was acquired by CAMECA Instruments in 2010. In 2018, he founded Steam Instruments and is currently its President and CEO.
Atomic-Scale Analytical Tomography (ASA T) has been defined as the documentation of the correct (isotopic) identity of every atom and its precise three-dimensional (3-0) location in a structure for large volumes (> 106 nm3) of material. ASAT should also be able to determine the local electronic structure of these atoms which makes true 3-D atomic-structure / electronic-property relationships possible. No single technique that exists today has achieved or can achieve ASA T. However, combining transmission electron microscopy (TEM) and atom probe tomography with improved (100% quantum detection efficiency) detector technology has been identified as a path toward ASAT. Atom Probe Tomography (APT) provides mass spectral identification for each individual atom and atom positions; but lacks information about the specimen that limits the spatial resolution. The TEM provides precise information about the atom positions. This combination should achieve ASAT. As an illustration of ASAT's promise, ASAT images of semiconductor nanostructures will reveal the 3-D position of individual dopant atoms with pm spatial resolution, the 3-D position of nuclear spin isotopes, nanometer-scale changes in strain due to structural defects and lattice mismatch, the 3-D position of point defects such as vacancies, and any electronic band structure changes at all these atomic-scale features. Within the next five years, it is expected that ASAT will be achieved through integration of 100% efficiency ion detectors, improved data handling algorithms, and integration of TEM and APT into a single instrument.
3:30 pm, Friday, October 28, 2022
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