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Minimizing Transmission Electron Microscopy Beam Damage during the Study of Surface Reactions on Sodium Chloride

Published online by Cambridge University Press:  28 July 2005

Heather C. Allen
Affiliation:
Department of Chemistry, University of California, Irvine, CA 92697
Martha L. Mecartney
Affiliation:
Department of Chemical and Biochemical Engineering and Materials Science, University of California, Irvine, Irvine, CA 92697
John C. Hemminger
Affiliation:
Department of Chemistry, University of California, Irvine, CA 92697
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Abstract

Electron beam damage is a significant limitation for transmission electron microscopy (TEM) studies of beam-sensitive samples. An approach for studying surface reactions on alkali halide crystals using 200 kV TEM is presented. Experiments were designed to monitor the reaction of NaCl crystals with HNO3 gas followed by water vapor to form solid NaNO3. During beam damage experiments, TEM micrographs record structural changes to both NaCl and NaNO3, including dislocation loops, void formation, and decomposition. Sample decomposition can be successfully minimized by a combination of commonly used techniques: (1) focusing the beam adjacent to the area of interest, (2) lowering the electron density, (3) choosing to image larger (micrometer- versus submicrometer-sized) alkali halide crystals, and (4) lowering temperature by the use of a liquid nitrogen cooling stage. From these results, additional studies were designed that monitored sequential experiments. Sensitive micrometer-sized sodium chloride single crystals before and after exposure to nitric acid vapor and water vapor and the subsequent growth of submicrometer-sized sodium nitrate single crystals could then be successfully imaged using TEM.

Type
Research Article
Copyright
© 2005 Microscopy Society of America

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