Professor David Seidman will speak about Northwestern University’s Center of Atom Probe Tomography.

He will explain what is an atom-probe tomograph and then describe two examples of its use: (1) determination of the ratio of carbon 12 (99%) to carbon 13 (1%) in nanodiamonds extracted from a famous meteorite, Allende, which was thought to have been formed before our solar system was created, that is, greater than 4.5 billion years old. (2) the formation of silicon nanowires using aluminum as a catalyst and their complete chemical analysis using our atom-probe tomograph (APT). The APT results are combined with transmission electron microscopy results, which gives a detailed picture of the how the silicon nanowires grow. The need for nanoscale characterization, as in semiconductor chip fabrication which we heard about recently, emphasizes the need for such powerful characterization tools.

David is Walter P. Murphy Professor Emeritus of Materials Science and Engineering and the Founding Director of the Northwestern University Center for Atom-Probe Tomography (NUCAPT). David earned his Ph.D. from the University of Illinois at Urbana-Champaign and M.S., and B.S. from New York University, all in Physical Metallurgy. He joined the Northwestern University faculty in1985. He is a member of the National Academy of Engineering, His current interests center on three high-temperature superalloys: aluminum-based, cobalt-based, and nickel-based. He is specifically interested in understanding the first-order phase transformations (precipitation) that occur in these alloys on an atomic scale utilizing atom-probe tomography (APT) and correlative instruments, which provide information at larger length scales: transmission electron microscopy, scanning electron microscopy and optical microscopy. In the case of Nickel-based alloys he employs vacancy-mediated lattice kinetic Monte Carlo (LKMC) simulations, which complement and supplement the APT experiments and help to elucidate the mechanisms for nucleation, growth and coarsening.