Comparison of Images of Crystalline Specimens by Energy-Filtering TEM at 80 keV and CTEM at 200 keV

Abstract

One advantage of energy-filtering electron microscopy (EFEM) is to avoid the chromatic aberration of conventional transmission electron microscopy (CTEM) by the mode of electron spectroscopic imaging (ESI) using either zero-loss filtering of unscattered and elastically scattered electrons or a narrow selected energy window at the most probable loss of the electron-energy-loss spectrum (EELS). Chromatic aberration can also be reduced by high-voltage electron microscopy (HVEM). Comparisons of ESI at 80 keV and CTEM at 200 keV have already been reported for biological tissues. In this contribution we compare the imaging of evaporated crystalline films with ESI at 80 keV in a ZEISS EM902 and with CTEM at 200 keV in a Hitachi H800/NA.Zero-loss filtering at 80 keV can be applied for maximum mass-thicknesses of x=ρt≃150 μg/cm2 where the zero-loss transmission falls below 0.001 and an energy window at the most-probable energy loss can be used below ≃300 μg/cm2. Inelastic scattering preserves the Bragg contrast.