**3. General features**

In scanning electron microscope image formation, electrons accelerated by high voltage are focused onto the sample. This focused beam of electrons scans the sample surface. During scanning, various interferences occur between electron and sample atoms. Signals resulting from this interference are collected by appropriate sensors. The signals passed through the signal amplifiers are then transferred to the screen of a cathode ray tube. Thus, a surface image is obtained [3]. In modern systems, the signals obtained from the sensors are easily converted into digital signals and transferred to the monitor. In newly developed devices, it expands the usage area by combining separation power, depth of focus and imaging. For example, while the optical microscope is 0.1 μm at 1000X magnification, this focal depth reaches 30 μm in the scanning electron microscope. This situation is compared in more detail in **Table 1**.


#### **Table 1.**

*Differences in optical and electron microscope.*

Today, the discrimination power of modern scanning electron microscopes can be as low as 0.05 nm.

The Quanta FEG 450 model, shown in **Figure 1** [7], provides an advantage in imaging biological and metallic samples at high resolution and effectively, thanks to its high and low vacuum mode.
