Interfacial Segregation and Concentration Profiles by Energy-Filtered Transmission Electron Microscopy: Issues and Guidelines

Abstract

Over the several years that imaging energy filters have been available commercially, numerous and wide-ranging applications have demonstrated elemental mapping at resolutions approaching 1 nm. From reviewing applications of energy-filtered transmission electron microscopy (EFTEM) to interfacial segregation and concentration profiles in metals and ceramics, some guidelines and issues may be identified. The work has been performed with a Gatan imaging filter (GIF) interfaced to a Philips CM30 operated at 300 kV with a LaB6 cathode.For quantitative elemental mapping by EFTEM a number of interrelated parameters [field of view, resolution, collection angle (β), slit width (Δ), incident beam divergence (α), illumination uniformity, probe current (i), drift rate, exposure time (T), and local specimen thickness (t)] have always to be properly selected and controlled. For example, the collection angle should be large enough for a strong signal, but not so large that the signal/background (S/B) and chromatic-aberration-limited spatial resolution (δ) are both degraded.