This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.
 

=================================================================================

In HAADF Z (atomic-number)-contrast imaging mode, the intensity of electron scattering by the atoms depends on the atomic number Z. For the superlattice structure consisting of LaTiO₃ and SrTiO₃ layers, the brightest features are columns of La ions, the second brightest features are columns of Sr ions, and the Ti ions are weakly visible in between the LaTiO₃ and SrTiO₃ layers as shown in Figure 3513a. Even though the Z contrasts of La, Sr, and Ti are clear, the oxygen ions are still not visible due to their much lower atomic number. Note that the number of the LaTiO₃ and SrTiO₃ layers is determined by the deposition recipe.

Figure 3513a. HAADF image of superlattice structures consisting of LaTiO₃ and SrTiO₃ layers. The imaging optical axis is the [100] zone axis of the crystals. Adapted from [1].

Figure 3513b shows high-resolution HAADF Z-contrast STEM images presenting the interface between Si₃N₄ matrix (on the top of each image) and the mixtures (at the bottom of each image) of  Yb₂O₃ and Al₂O₃ (a) and  Yb₂O₃ and SiO₂ (b). The Yb atoms, visible here as bright spots due to enhanced electron scattering (giving higher Z-contrast), are located periodically along the interface. The images are oriented along the low-index zone axis [0001] of Si₃N₄.

Figure 3513b. High-resolution STEM images showing the atomic interface between a Si₃N₄ matrix
grain and two different mixtures. Adapted from [2]

[1] A. Ohtomo, D. A. Muller, J. L. Grazul and H. Y. Hwang, Artificial charge-modulation in atomic-scale perovskite titanate superlattices, Nature 419, 378-380.
[2] A. Ziegler, M. K. Cinibulk, C. Kisielowski, and R. O. Ritchie, Atomic-scale observation of the grain-boundary structure of Yb-doped and heat-treated silicon nitride ceramics, Appl. Phys. Lett. 91, 141906 (2007).