Thickness effects in ADF STEM zone axis images

Quantitative measurements of intensities in annular dark field scanning transmission electron microscope images of (100) indium phosphide are reported. Fourier analysis of the experimental images gives the lattice fringe intensities which are related to the intensities of individual atomic columns. Electron energy loss measurements of the plasmon intensities provide a thickness. Analysis of simulated images for the same instrumental conditions provides a comparison that is consistent with an earlier prediction that electrons channel for considerably different distances along atomic columns of differing atomic number. This effect has considerable implications for image interpretation and analytical studies. The measurements indicate that reasonable partial coherence effects give rise to serious limitations on imaging at the highest resolution levels.