Annular dark-field imaging

Annular dark-field imaging

Annular dark-field imaging is a method of mapping samples in a scanning transmission electron microscope (STEM). These images are formed by collecting scattered electrons with an annular dark-field detector in scanning transmission electron microscopes.

For dark field imaging, the annular dark field detector collects a much larger number of electrons than conventional dark field imaging in the TEM. This gives advantages in terms of signal collection efficiency and lower electron dose required.

An annular dark field image formed only by very high angle, incoherently scattered electrons - as opposed to Bragg scattered electrons - is highly sensitive to variations in the atomic number of atoms in the sample (Z-contrast images). This technique is also known as High Angle ADF (HAADF).


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