annular dark-field scanning transmission electron microscopy Microscopy where a finely focused (<10 nm diameter) electron beam with an acceleration voltage 50–150 kV is scanned across an electron-transparent specimen under vacuum. The beam of electrons is scattered or diffracted before reaching the specimen, and the image results from a weakening of the beam by its interaction with the sample. An annular aperture is used to select electrons that have passed through given symmetric zones within the objective lens of the microscope. ADF-STEM CHMO:0000729 dark-field scanning transmission electron microscopy