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Towards Sub-À Resolution Through Incoherent Imaging

Published online by Cambridge University Press:  02 July 2020

S.J. Pennycook ,
M.F. Chisholm  and
P.D. Nellist
S.J. Pennycook
Affiliation:
Solid State Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN37831 -6030
M.F. Chisholm
Affiliation:
Solid State Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN37831 -6030
P.D. Nellist
Affiliation:
Cavendish Laboratory, Madingley Road, Cambridge, CB3 OHE
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Extract

As first pointed out by Lord Rayleigh a century ago, incoherent imaging offers a substantial resolution enhancement compared to coherent imaging, together with freedom from phase contrast interference effects and contrast oscillations. In the STEM configuration, with a high angle annular detector to provide the transverse incoherence, the image also shows strong Z-contrast, sufficient in the case of a 300 kV STEM to image single Pt and Rh atoms on a γ-alumina support. The annular detector provides incoherence by virtue of its large central hole, which is equivalent by Babinet's principle of complementarity to a bright field detector of the same size. For weakly scattering specimens, it shows greater contrast than the incoherent bright field image, and also facilitates EELS analysis at atomic resolution, using the Z-contrast image to locate the probe with sub-À precision. The inner radius of the annular detector can be chosen to reduce the transverse coherence length to well below the spacings needed to resolve the object, a significant advantage compared to light microscopy.

Type
The Limits of Image Resolution: Seeing is Believing
Information
Microscopy and Microanalysis , Volume 3 , Issue S2: Proceedings: Microscopy & Microanalysis '97, Microscopy Society of America 55th Annual Meeting, Microbeam Analysis Society 31st Annual Meeting, Histochemical Society 48th Annual Meeting, Cleveland, Ohio, August 10-14, 1997 , August 1997 , pp. 1167 - 1168
Copyright
Copyright © Microscopy Society of America 1997

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References

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