Direct Detection EELS at High Energy: Elemental Mapping and EXELFS

Electron energy-loss spectroscopy (EELS) is a powerful technique for nanoscale elemental mapping and determination of chemistry, such as oxidation state. One limitation, however, is that the acquisition of high quality high energy edges beyond ~3 keV is difficult. This restriction is problematic for both elemental mapping and oxidation state determination of certain elements. Moreover, extended energy loss fine structure (EXELFS) analysis -which yields an element's radial distribution function (RDF)generally requires measurement of high energy K-edges, making RDF determination challenging with conventional EELS. Recently, progress has been made in optimizing the optical coupling to allow experimental observation of high energy edges out to 10 keV We have previously shown that spectral SNR can be improved through the use of direct detection (DD) technology and electron counting Here, we investigate the use of DD EELS on high energy edges; we demonstrate improved elemental mapping capabilities and show that EXELFS on a high energy K-edge can provide accurate RDF determination within the TEM.