The diagram in Figure 1 shows the major components of an SEM. These components are part of seven primary operational systems: vacuum, beam generation, beam manipulation, beam interaction, detection, signal
processing, and display and record. These systems function together tode termine the results and qualities of a
micrograph such as magnification, resolution, depth of field, contrast, and brightness. The majority of the course is spent discussing these seven systems.
A brief description of each system follows:
- Vacuum system. A vacuum is required when using an electron beam because electrons will quickly disperse or scatter due to collisions with other molecules.
- Electron beam generation system. This system is found at the top of the microscope column (Fig. 1). This system generates the "illuminating" beam of electrons known as the primary (1o) electron beam.
- Electron beam manipulation system. This system consists of electromagnetic lenses and coils located in the microscope column and control the size, shape, and position of the electron beam on the specimen surface.
- Beam specimen interaction system. This system involves the interaction of the electron beam with the specimen and the types of signals that can be detected.
- Detection system. This system can consist of several different detectors, each sensitive to different energy / particle emissions that occur on the sample.
- Signal processing system. This system is an electronic system that processes the signal generated by the detection system and allows additional electronic manipulation of the image.
- Display and recording system. This system allows visualization of an electronic signal using a cathode ray tube and permits recording of the results using photographic or magnetic media.
In the following chapters these systems will be describe in greater detail. These systems are interactive and work together and operators of an SEM need to learn how to control each system to obtain the desired results Changing any control in one system may effect one or more of the other systems. References are provided so students can obtain a more in depth discussions on specific subjects presented in this course. People are encouraged to ask for assistance from the laboratory staff.
