Towards 0.1 EV EELS Using a Beam Monochromator And Maxent Deconvolution

Abstract The resolution in Electron Energy Loss Spectroscopy (EELS) in (S)TEM is presently limited by the instabilities of the high voltage supply (typically 0.2 eV), by the resolution of the spectrometer (typically 0.7 eV), and by the energy spread of the electron source (typically 0.7 eV for a Schottky field emitter). An increase of this resolution to better than 0.1 eV would enable chemical analysis on a nanometer scale. We are presently following hardware as well as software approaches in order to reach this energy resolution in a 200 kV (S)TEM. The hardware side of our project focuses on the three limiting factors mentioned in the previous paragraph. The instabilities of the high voltage supply are mostly noise and drift, which can be reduced significantly by isolating the high voltage tank, thermally as well as acoustically. In addition, Gatan is developing an imaging filter for this project, which has sub-0.1 eV resolution.