On the visibility of "heavy" atoms in dark-field STEM

One of the most useful and apparently straightforward attributes of annular dark-field (ADF) STEM imaging is the ability to image heavy atoms on relatively light substrates using Z-contrast (High-Angle ADF) imaging. From multislice calculations, however, some isolated heavy atoms, e.g. Re, can go un...

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Bibliographic Details
Published in:Journal of physics. Conference series 2012-01, Vol.371 (1), p.12055-4
Main Authors: Shannon, M D, Nellist, P D, Nicolosi, V, Shannon, G B, Shmeliov, A
Format: Article
Language:English
Subjects:
Aberration
Adatoms
Cobalt
Image contrast
Imaging
Mathematical analysis
Nanoparticles
Physics
Simulation
Sodium
Substrates
Visibility
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Summary:One of the most useful and apparently straightforward attributes of annular dark-field (ADF) STEM imaging is the ability to image heavy atoms on relatively light substrates using Z-contrast (High-Angle ADF) imaging. From multislice calculations, however, some isolated heavy atoms, e.g. Re, can go undetected in a thin Co matrix in standard aberration-corrected HAADF-STEM imaging of catalyst nanoparticles oriented accurately on a zone-axis [2]. More recently simultaneous Medium-Angle and High-Angle ADF imaging of a few layers of BN has shown experimentally that some adatoms are invisible in MAADF whilst exhibiting very strong contrast in HAADF. Simulations confirm that this can occur for atoms such as sodium. In both situations HOLZ ring imaging can be used to extract additional information.
ISSN:1742-6596
1742-6588
1742-6596
DOI:10.1088/1742-6596/371/1/012055