Effect of convergent beam semiangle on image intensity in HAADF STEM images

In this study, we experimentally and theoretically show that the intensities of bright spots in a spherical aberration (C_s)-uncorrected high-angle annular dark-field (HAADF) scanning transmission electron microscope (STEM) image of [011]-oriented Co₃O₄, which has two different numbers of Co atoms in the projected atomic columns, are reversed with increasing sample thickness. However, C_s-corrected HAADF STEM images produce intensities that correctly depend on the average number of atoms in the projected atomic columns. From an analysis based on the Bloch-wave theorem, it is found that an insufficient semiangle of the incident convergent beam yields intensities that do not depend on the average atomic number in the atomic columns.