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Nanotechnology-Enabled Sensors

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256 Chapter 5: Characterization Techniques for Nanomaterials<br />

lenses and enlarged. Eventually by striking a phosphor or CCD surface it<br />

forms an image.<br />

Fig. 5.35 Schematic diagram of a TEM set-up.<br />

The TEM has the capability to create both electron microscope images<br />

(information in real space) and diffraction patterns (information in reciprocal<br />

space) for the same region by adjusting the strength of the magnetic<br />

lenses. 91 By inserting a selected area aperture and using parallel incident<br />

beam illumination, a selected area electron diffraction pattern from an area<br />

as small as several hundreds to a few nm in diameter is obtained.<br />

Crystal structures can also be investigated by high resolution transmission<br />

electron microscopy (HRTEM) where the images are formed due<br />

to differences in phase of electron waves scattered through a thin<br />

specimen. The emergence of HRTEM has allowed the direct reconstruction<br />

of Bragg differential electron beams to create interference patters, which in

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