Obtaining diffraction patterns from annular dark-field STEM-in-SEM images: Towards a better understanding of image contrast.

This contribution demonstrates experimentally how a series of annular dark-field transmission images collected in a scanning electron microscope (SEM) with a basic solid-state detector can be used to quantify electron scattering distributions (i.e., diffraction patterns). The technique is demonstrated at different primary electron energies with a polycrystalline aluminum sample and two amorphous samples comprising vastly different mass-thicknesses. Contrast reversal is demonstrated in both amorphous samples, suggesting that intuitive image contrast interpretation is not always straightforward even for ultrathin, low atomic number samples. We briefly address how the scattering distributions obtained here can be used as an aid to interpret contrast in annular dark-field images, and how to set up imaging conditions to obtain intuitively interpretable contrast from samples with regions of significantly different thickness.