Selected area diffraction

Selected area (electron) diffraction (abbreviated as SAD or SAED), is a crystallographic experimental technique that can be performed inside a transmission electron microscope (TEM).Single spots appear only when the beam is diffracted by a single crystal. In many materials there are many crystals with different orientations. This is the case for typically made metals as well as powders. SAD of polycrystalline materials gives ring patterns analogous to those from X-ray powder diffraction, and can be used to identify texture and discriminate nanocrystalline from amorphous phases.