The Different Observation Modes in Electron Microscopy (SEM, TEM, STEM) - Sample Preparation Topic for Transmission Electron Microscopy - page 34

Signals Emitted by
The Surface X-Rays

Characteristic X-Rays Emission
X-Rays Background Emission

Bulk
Sample

Secondary X-Rays Fluorescent Emission

Primary Emission
Secondary
Backscattered
X-Rays

Spatial Resolution

Fig. 3.1 Signals derived from the electron-material interaction within a bulk sample and emitted
by the surface

Number of Electrons

Elastic Electrons

Inelastic Electrons

Electrons

Secondary Electrons Backscattered Electrons

Fig. 3.2 Energy diagram of the different electrons emitted during the electron-matter interaction

Figure 3.1 shows the different signals derived from the electron-matter inter-
action. The information contained in these signals can be used to characterize
materials.
When the sample is thick (Fig. 3.1) , the electron beam ends up being absorbed
after multiple interactions. Depending on their energy, the primary electrons more
or less penetrate the material and gradually lose their energy (through scattering) on
the atoms that they encounter and ionize. The result is that other electrons liberated
by the sample will in turn ionize other atoms and then scatter in a certain volume
called the “excited volume.” For example, in nickel, the X-rays emitted come from