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Using a Modular Aperture System to Obtain Annular Dark-Field Image Intensity Distributions as a Function of Scattering Angle.



Jason D. Holm


In this contribution, 10 nm-thick non-stoichiometric silicon nitride films were examined in a scanning electron microscope (SEM) using a zero-dimensional solid-state transmission electron detector equipped with a modular aperture system. Effects of several parameters on annular dark-field image intensity distributions as a function of detector acceptance angle were investigated, including primary electron energy, transmission detector acceptance angle and span, and beam convergence angle. Results showed that intensity distributions varied significantly with STEM detector acceptance angle span, and that even a modestly wide aperture integrates over a large signal range and can hide distribution details. Distributions collected with narrow apertures and normalized to acceptance angle span exhibited distinct broad peaks that shifted to greater angles with decreasing primary electron energy. Beam convergence angle had a smaller effect on the distributions, but sample charging was problematic when large primary electron beam apertures were used.


STEM-in-SEM, transmission-SEM, aperture, image intensity distribution
Created June 15, 2018, Updated August 28, 2019