EELS in the TEM : nanometer resolution without a nanoprobe

Abstract
With many TEMs, the resolution of electron energy loss spectrometry (EELS) is limited to ~ 100 nm since a finer probe cannot be positioned and maintained accurately enough for the long dwell times necessary. The alternative TEM image mode (i. e. projecting the area of interest onto the spectrometer aperture) suffers from the energy dependent chromatic blurring, limiting the resolution also to several 100 nm. Due to inevitable misalignment of post specimen lenses (PSLs), electrons that have suffered a characteristic loss will hit the screen at a different position than the elastically scattered ones, even when the chromatic blurring is compensated by objective lens defocus. We describe a correction method for both the chromatic blurring and the chromatic image shift. It is shown by example that quantitative EELS analysis can be done on a scale of better than 10 nm with spots of arbitrary size in regular TEM image-mode.