*Scanning Electron Microscopy DOI: http://dx.doi.org/10.5772/intechopen.103956*

**Figure 6.**

*Interaction between electron beam and sample.*

scattered electrons are defined as back-scattered electrons. The image formed by these backscattered electrons is called the backscattered image. Here, the amount of backscattered electrons is proportional to the atomic number of the sample. This provides atomic number dependent contrast for polyphase systems in image formation. When the signals are collected (A + B) in the backscattered electron detector, a compositional image depending on the atomic number contrast is obtained [7]. If the image is obtained by taking the difference of the signals here (A-B), a topographic composition image is formed (**Figure 7**) [7].

In summary, **Secondary Electrons:**


#### **Figure 7.**

*Elemental backscatter images (a) backscattered a + B "composition" signal (b) backscattered A-B "topographic" signal.*

#### **Figure 8.**

*Schematic representation of interference patterns of secondary electrons (a) electron interaction (b) production of secondary electrons (c) formation of secondary electrons (d) effect of sloping surface on SE emission [8].*


When **Figure 8** [8] is examined, the interaction of the secondary electron with the sample surface and sample electrons is seen in a and b. Also, in c and d, we see how it interacts with the electrons that make up the sample and then leaves the sample surface.

#### **Backscattered Electrons:**


#### **Figure 9.**

*Schematic representation of the interference patterns of backscattered electrons. (a) Production of backscattered electrons (b) production of backscattered electrons (c) effect of inclined surface to BSE emission (d) effect of atomic number to BSE emission [8].*


When **Figure 9** [8] is examined, the interaction of backscattered electrons with the sample surface and sample electrons can be seen in **Figure 9a-b**. Also, in **Figure 9c-d**, we can see how it interacts with the electrons that make up the sample, and the scattering increases as the atomic number increases.

When the backscattered electron (**Figure 10a**) and the secondary electron image (**Figure 10b**) are examined in **Figure 10** [8], different properties of the same sample surface are clearly seen. From here, it is easy to understand the detection of different phases with the BSE detector. The detection of different phases is mostly used in metallurgical materials science to easily distinguish the structures of the phases in the sample. This shows us that SEM is more than imaging.

**Figure 10.** *Topographic images taken with different detectors (a) BSE image (b) SE image [8].*
