Abstract
In TEM and STEM, the magnification (M) of images is ordinarily several million or tens of million for observing atomic columns with spacing less than 0.2 nm. The electron intensity (number of electrons onto films or detectors) is reduced by \( M^{2} \). From the viewpoint of irradiation damage of specimens, we cannot illuminate excessive electrons onto a specimen. The signal-to-noise ratio (\( = n/\sqrt n \), where n is the number of electrons) of the images is reduced in higher magnification.
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Notes
- 1.
Derivation of a 3D electrostatic potential V (x, y, z) from the wave field at the exit surface is a kind of “inverse problem ” of electron diffraction, which cannot be solved in most cases. To avoid the difficulty, we use the image simulation method where we calculate first the project potential from V (x, y, z); second, obtain exit wave field; and third, calculate image wave field and then image intensity, in the normal direction along a wave propagation .
- 2.
See a paper by Zemlin et al. (Zemlin et al. 1978).
- 3.
See Kimoto et al. (2012).
References
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Tanaka, N. (2017). What are Image Processing Methods?. In: Electron Nano-Imaging. Springer, Tokyo. https://doi.org/10.1007/978-4-431-56502-4_21
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DOI: https://doi.org/10.1007/978-4-431-56502-4_21
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