High-angle annular dark field HAADF

Fig. 12. Schematic of the information from HRSTEM, DF, and high-angle annular dark-field (HAADF) microscopy.

This chapter includes a review of the recent literature on polymer microscopy. The basic principles and current challenges of the techniques, as well as the experimental aspects of sample preparation and observation are reviewed elsewhere [1-8]. Specific techniques are surveyed in other reviews for instance TEM [9], SEM [10], Field emission SEM [11], and high angle annular dark field (HAADF)-STEM [12]. 

Fig. 3.14 Schematic set-up of an electron microscope in the transmission (TEM) (a) and combined (TEM and STEM) (b) modes. Note how the dark field detector is off the central axis, as the dark field image is based on scattered electrons. The HAADF-STEM operation mode with bright— (on the central axis) and dark-field detectors (of the central axis) is shown in (c). Two different modes are available for dark field imaging, i.e. annular dark field (ADF) high-angle annular dark field (HAADF). Figures modified after [37]. J. W Niemantsverdriet Spectroscopy in Catalysis An Introduction, pages 182 and 187. 2007. Copyright Wiley-VCH Verlag GmbH Co. KGoA. Reproduced with permission...

Fig. 6 — STEM imaging (200 kV Osiris STEM) combined with energy dispersive x-ray spectroscopy (EDX) of Pt-Pd catalytic nanoparticles. Unlike the high angle annular dark field (HAADF) image, EDX elemental mapping reveals the core shell structure of the nanoparticles. The high efficiency EDX system and high brightness electron source allows quickly obtaining elemental maps and statistically significant data within a realistic time frame. Total acquisition time was less than 12 minutes for (a) and less than 10 minutes for (b). The author would like to thank Dominique Delille (FEI company).

---