Dept. of Materials Science and
National University of Singapore
Stephen J. Pennycook is a Professor in the Materials Science and Engineering Dept., National University of Singapore, an Adjunct Professor in the University of Tennessee and Adjoint Professor in Vanderbilt University, USA. Previously, he was Corporate Fellow in the Materials Science and Technology Division of Oak Ridge National Laboratory and leader of the Scanning Transmission Electron Microscopy Group. He completed his PhD in physics at the Cavendish Laboratory, University of Cambridge in 1978. Pennycook is a Fellow of the American Physical Society, the American Association for the Advancement of Science, the Microscopy Society of America, the Institute of Physics and the Materials Research Society. He has received the Microbeam Analysis Society Heinrich Award, the Materials Research Society Medal, the Institute of Physics Thomas J. Young Medal and Award and the Materials Research Society Innovation in Characterization Award. He has 38 books and book chapters, over 400 publications in refereed journals and has given over 200 invited presentations on the development and application of atomic resolution Z-contrast microscopy and electron energy loss spectroscopy. His latest book is “Scanning Transmission Electron Microscopy.”
The aberration-corrected scanning transmission electron microscope (STEM) provides real space imaging and spectroscopy with unprecedented sensitivity down to the single atom level. Coupled with first-principles theory, we can now unravel what controls the functionality of materials, the key to the design of new materials with improved properties. For example, in Nb@C catalysts, we find that single atoms are the active sites, not the numerous nanocrystals that are also present . In BiFeO3 films grown on La0.5Sr0.5MnO3-x the precise interface termination determines ferroelectric properties , and in CdTe solar cells, grain boundaries, long supposed detrimental to properties, are actually found to be beneficial . We can understand the origin of colossal ionic conductivity in strained yttria-stabilized zirconia , and the formation of flexible metallic nanowires by electron beam sculpting . In the future we may even be able to determine materials structure and bonding at atomic resolution in three dimensions .
 X. Zhang, et al., "Catalytically active single-atom niobium in graphitic layers," Nature Communications, 4, 1924–1927 (2013).
 Y.-M. Kim, et al., "Interplay of Octahedral Tilts and Polar Order in BiFeO3 Films," Adv Mater, 25, 2497–2504 (2013).
 C. Li, et al., "Grain-Boundary-Enhanced Carrier Collection in CdTe Solar Cells," Phys Rev Lett, 112, 156103 (2014).
 T. J. Pennycook, et al., Origin of Colossal Ionic Conductivity in Oxide Multilayers: Interface Induced Sublattice Disorder, Phys Rev Lett. 104 (2010) 115901.
 J. Lin, et al., “Flexible metallic nanowires with self-adaptive contacts to semiconducting transition-metal dichalcogenide monolayers,” Nature Nanotechnology, 9(6), 436–442.
 R. Ishikawa, R., Pennycook, S. J., Lupini, A. R., Findlay, S. D., Shibata, N., & Ikuhara, Y. (2016). Single atom visibility in STEM optical depth sectioning. Applied Physics Letters, 109, 163102.