Interfacial Segregation Studied With Modern AEM Techniques

Abstract For more than 20 years interfacial segregation has been studied by analytical electron microscopy (AEM). Two recent commercial developments should allow more widespread application of 1 nm resolution AEM studies of interfacial segregation. The first is a system for integrated acquisition that in its most sophisticated form allows spectrum imaging [a full spectrum recorded at every pixel of an image (e.g. STEM)] for simultaneous multiple spectroscopies (e.g., EDS and PEELS). A field emission gun (FEG) is necessary for sufficient sensitivity at high spatial resolution. The second commercial development has been imaging energy filters that allow the production of elemental maps from a series of energy-filtered TEM (EFTEM) images at inner shell ionization edges. Resolutions of ∼1 nm can be achieved without an FEG, but analysis is limited to the electron energy-loss signal. Although complex microstructures may require full two-dimensional mapping, for many planar interfaces a one-dimensional profile of composition or chemistry normal to the interface plane is sufficient.