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3D Scanning Transmission Electron Microscopy for Catalysts: Imaging and Data Analysis

Summary: 3D Scanning Transmission Electron Microscopy for Catalysts: Imaging
and Data Analysis
A. Y. Borisevich,* A.R. Lupini,* A. F. Koschan,** M. Mercimek,** M. A. Abidi,** S. J.
* Materials Science and Technology Division, Oak Ridge National Laboratory, Oak
Ridge, TN 37831
** IRIS Laboratory, EECS Dept, University of Tennessee, 1508, Middle Dr, Knoxville,
TN 37996
Aberration correction has revolutionized electron microscopy, for the first time allowing direct imaging of
sub-angstrom atomic spacings. Using this technique for catalytic materials has been especially beneficial
the improved signal-to-noise ratios now allow for detection of quantities of some elements as small as a
single atom, giving a complete picture of particle size distribution. Wider probe-forming apertures used in
aberration-corrected STEMs also result in reduced depth of field (z = /2
), making it possible to optically
section through a sample, similar to widefield optical microscopy. For modern C3- and C3, C5-corrected
instruments, convergence angles are in the rage of 20 to 35 mrad or more, resulting in the depth of field of
low single nanometers (in amorphous and off-axis media). This makes it possible to examine 3D structure
of realistic heterogeneous catalysts in three dimensions with nanoscale vertical resolution. STEM focal
series can be used to detect single atoms and in suitable cases, determine of their height with sub-
nanometer precision [1, 2]. In the higher end of the currently achievable range of the convergence angles, it


Source: Abidi, Mongi A. - Department of Electrical and Computer Engineering, University of Tennessee


Collections: Computer Technologies and Information Sciences