Instrument
Scanning electron microscopy - Principles and equipment

A scanning electron microscope consists of the following components (figure 1):

• an electron column, comprising an electron gun, a number of electromagnetic lenses ("condensers"), a number of electrical alignment and adjustment coils, and an electron beam scanning device. This column is maintained under vacuum at a minimum level of 10^–3 Pa. In conventional microscopes (SEM-W), the necessary vacuum is obtained by a primary pump (vane or scroll) coupled with a secondary pumping system (oil diffusion pump, or more frequently turbo-molecular pump). More powerful FEG-SEMs require ion pumping at the electron gun;

• an "object" chamber, where the...