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Incoming links: Scanning transmission electron microscope
Ondrej Krivanek Created 2026-10-24 Updated 2026-11-05
Ondrej Krivanek develops electron microscopy methods that connect atomic structure with chemical identity. A 2010 coauthored experiment used an aberration-corrected scanning transmission electron microscope to distinguish individual boron, nitrogen, carbon and oxygen atoms in a single sheet of hexagonal boron nitride. Collecting electrons scattered through large angles made the image intensity sensitive to atomic identity: the same measurement located atoms and identified substitutional impurities, rather than merely showing an unresolved average composition.[ref]
Atom-by-atom structural and chemical analysis by annular dark-field electron microscopy by O. L. Krivanek and others. Nature 464, 571–574 (2010), abstract and atomic identification in a monolayer
Portrait of Ondrej Krivanek
. Thomas Barstad Eckhoff, credited as Thomas Eckhoff, via The Kavliprize; Oslo, 5 September 2022; existing individual Krivanek crop. CC BY-SA 2.0, via Wikimedia Commons. Source.A scanning transmission electron microscope makes an image by assigning a transmitted-electron signal to each position of a scanned probe. Its essential chain is electron source, probe-forming optics, scan system, thin specimen, transmitted-electron detectors and synchronized acquisition.
An electron gun and accelerating supply provide a stable beam of the chosen kinetic energy. Condenser lens optics and an aperture control probe current and convergence; the probe-forming objective lens focuses a small spot on the specimen. Alignment, focusing and astigmatism correction keep the probe usable across the field.
Scan coils deflect the probe in a raster. A stable specimen holder positions an electron-transparent region, and a high-vacuum column limits gas scattering and contamination. A bright-field transmission electron microscopy detector collects the central transmitted beam; an annular detector can select annular dark-field electron imaging, including high-angle annular dark-field imaging. Different angular selections give different contrasts, rather than a universal map of height.
Detector electronics, scan timing and a computer assign the collected signal to the corresponding image pixel. Spectrometers are useful additions but not essential to basic image formation. The post-specimen optics can adjust detector collection geometry; they do not set scan-image magnification in the same way as the projection lenses of conventional transmission imaging.
