Dark field imaging transmission electron microscop

Figure 9.3. Characterization of mesoporous Ti02 films templated by Pluronics block copolymers using diverse characterization techniques XRD pattern (a), transmission electron microscope (TEM) image (b), dark-field TEM image (c), and isotherms of Kr adsorption (d).The Pluronic-templated Ti02 films were calcined at 400°C (solid points) and 600°C (open points). The films were prepared according to Alberius et al. (Ref. 14).

Figure 45. Scanning transmission electron microscopy Top Schematic representation of the essential components of a scanning transmission electron microscope (ADF annular dark field BF bright field FEG field image gun)...

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...

Transmission electron microscopy is able to identify the orientation of molecules within thin films of those thermotropic polymers which are sufficiently resistant to the necessary intense electron beam. The high resolution possible in TEM enables fine scale structures to be characterized which are invisible in a light microscope. Diffraction data can be recorded from the same area as bright and dark field images. However it must be recognised that the requirement for thin specimens can produce structures not necessarily typical of the bulk, particularly since surface interactions may be of importance. 

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