Energy-filtered TEM (EFTEM)
Energy-filtered TEM uses a post-column Gatan Image Filter (GIF) or in-column Omega Filter to form images from the inelastically-scattered electrons of the EEL spectrum. By imaging with electrons over selected energy ranges (“energy windows”) above and below ionization edges, elemental maps can be made. Compared to STEM-EDX or STEM-EELS mapping, these maps typically have a more photographic appearance. However, mapping at very high spatial resolution can be difficult, and maps can be subject to artefacts from diffraction contrast. Energy filtering can also be used during BF imaging and SAED pattern acquisition to eliminate intensity from incoherently, inelastically scattered electrons, improving image contrast and definition, and thickness maps can be easily made.