Chapter Twelve - Performing EELS at higher energy losses at both 80 and 200 kV

An overview of recent progress in high loss electron energy loss spectroscopy is presented. This covers the instrumental aspects of how to best set up a scanning transmission electron microscope and post-column spectrometer combination to provide best performance, a survey of a range of results that are possible in EELS with a good setup, and a brief investigation of the current limitations imposed by the current mainstream detector technology. In the first section, detailed consideration is given to the coupling optics between microscope and spectrometer, the effects on the EELS spectrum, the need for spectrometer refocusing, and the problems with gun anodes in some field emission gun designs. In the second section, a survey of the absolute cross sections for the L edges of 4d transition elements is set out, these are used for absolute quantification in two cases, and the extended energy loss fine structure beyond the Si–K edge is used for atomic structure investigation. The final section comprises an investigation of noise levels on the Rh L3 edge with a standard CCD detector in the spectrometer with a comparison to simulated shot noise, and shows that in this case, RMS noise was 7 times worse than the fundamental limit, illustrating clearly how much improvement would be possible with electron counting detectors.