Energy-Filtering Imaging and Diffraction

Abstract

Energy-filtering transmission electron microscopy (EFTEM) can combine the modes of electron spectroscopic imaging (ESI) and electron spectroscopic diffraction (ESD), and different modes can be used to record an energy-loss spectrum. ESI allows to remove the inelastically scattered electron in the zero-loss mode and to investigate thicker foils. Plasmon-loss filtering can be used to separate different phases which differ in their position of the plasmon losses, for example. Elemental maps can be calculated with micrographs taken below and beyond an ionization edge. The modes of contrast tuning or most-probable-loss imaging at higher energy losses of a few hundreds of electronvolts can be applied to very thick foils which cannot be investigated in a conventional TEM. ESD also allows to remove the background of inelastically scattered electrons in diffraction patterns of amorphous, polycrystalline and single-crystalline materials by zero-loss filtering. Increasing the selected energy loss can separate the different contributions by thermal-diffuse scattering, inelastically scattered electrons and Kikuchi bands. The filtering of convergent-beam electron diffraction patterns allows a much better determination of the Fourier coefficients of the lattice potential and a calculation of charge-distribution maps. This review summarizes the possibilities of EFTEM for applications in materials science.