electron microscopy



Scanning Transmission Electron Microscopy (STEM)

In STEM, a tiny, convergent electron beam is scanned over a defined area of the sample. At each spot, the generated signal is simultaneously recorded by selected detectors, building up an image. Furthermore, such a convergent beam is used to gain a highly localized signal from the specimen in analytical TEM (e.g., EDXS, EELS), and thus the combination of STEM with analytical methods is a main application in practical work. As the resolution of a STEM is limited by the diameter of the electron beam, the correction of the spherical aberration of the probe-forming lens leads to substantial improvements of the imaging properties and gives access to the sub Angstrom regime (see here).

Utilized signals: elastically scattered electrons - direct and diffracted beams (BF/DF) and incoherent scattering (Z contrast)

Methods Information
BF/ADF-STEM Detection of crystalline areas, defects and grain boundaries, phase analysis, particle size
HAADF-STEM Detection of small clusters or even single atoms of a heavy metal in a matrix of light elements (Z-contrast), direct visualisation of structures and defects

An introduction into theory and practice of STEM is given by Rodenburg.


ETH Zürich | ETH chemistry department | ETH inorganic chemistry

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