Scanning beam-specimen interactions

Figure 2 The primary electron beam-specimen interaction in a scanning electron microscope.

Scanning electron microscopy (SEM) is a useful technique for the analysis of plastic surfaces. It involves a finely collimated beam of electrons that sweeps across the surface of the specimen being analyzed. The beam is focused into a small probe that scans across the surface of a specimen. The beam s interactions with the material results in the emission of electrons and photons as the electrons penetrate the surface. The emitted particles are collected with the appropriate detector to yield information about the surface. The final product of the electron beam collision with the sample surface topology is an image (Fig. 10.18). 

Figure 1 Signals generated when the focussed electron beam interacts with a thin specimen in a scanning transmission electron microscope (STEM).

The electron microprobe is similar to the scanning electron microscope however, its primary function is to detect characteristic X-rays produced by the electron beam interaction with the specimen. The X-ray emissions can be used to determine the elemental composition of the specimen quantitatively and the location of a particular element within the morphology or topological structure of the specimen. 

The scanning electron microscope (SEM) forms an image by scanning a probe across the specimen, and in the SEM the probe is a focused electron beam. The probe interacts with a thin surface layer of the specimen, a few micrometers thick at most. The detected signal commonly used to form the TV-type image is the number of low energy secondary electrons emitted from the sample surface. Scanning electron microscopy is fully described in several texts [22-26], and its use with polymers has been reviewed by White and Thomas [27]. 

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