Reflected light microscopy examples

An example of reflected light microscopy of a polished specimen is shown in Fig. 5.66 which elucidates the complex engineering involved in... 

The mechanism of image formation is different from the light microscopy. It is not absorption, reflection, or fluorescence but scattering of the electrons on the atoms forming the specimen. Elastic scattering on the atomic cores provides information about the specimen structure, morphology, and crystallinity. Inelastic scattering on the atomic shells provides information about its chemical composition and even oxidation state. A comprehensive theory and many examples and practical hints can be found in Refs. 30 and 31. 

Figure 7.14 Experimental set-up for atomic force microscopy. The sample is mounted on a piezoelectric scanner and can be positioned with a precision better than 0.01 nm in the x, y, and z direction. The tip is mounted on a flexible arm the cantilever. When the tip is attracted or repelled by the sample, the deflection of the cantilever/tip assembly is measured as follows. A laser beam is focussed at the end of the cantilever and reflected to two photodiodes, numbered 1 and 2. If the tip bends towards the surface, photodiode 2 receives more light than 1, and the difference in intensity between 1 and 2 is a measure of the deflection of the cantilever and thus of the force between the sample and the tip. With four photodiodes, one can also measure the sideways deflection of the tip, for example at an edge on the sample surface.

Brewster87 angle microscopy is a technique that exploits total reflection of monochromatic visible light at Brewster s angle, Eq. (2.14.31), from an interface Any small adsorbate at the interface—for example, the presence of parts of an adventitious monolayer of different refractive index—can be detected with great sensitivity as a change of reflectivity. 

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