A novel method of Z-contrast imaging in STEM applied to double-labelling

Summary A novel method of Z-contrast imaging in the scanning transmission electron microscope (STEM) is presented. The technique relies on the element dependence of the angular distribution of the scattered electrons, and is realized with a detector consisting of a set of concentric rings. It is possible to discriminate 9-nm colloidal gold and silver specifically distributed on thin sections. In addition to this practical work, numerical evaluations are used to assess the method. With two smaller markers, this approach will be useful in discriminating closely spaced antigenic sites when steric hindrance occurs with double-labelling using probes of different sizes.