Scanning Electron Microscope (SEM)

In 1942, Zworykin, Hillier, and R.L. Snyder developed another type of an electron microscope called Scanning Electron Microscope (SEM). SEM is another example of an electron microscope and is arguably the most widely used electron beam instrument. In SEM, the electron beam excites the sample and its radiation is detected and photographed. SEM is a mapping device—a beam of electrons scanning across the surface of the sample creates the overall image. SEM also consists of major parts:

1. Electron source (electron gun)
2. System of lenses
3. Collector of electrons
4. System of image production

SEM’s resolution is about 20 nm and its magnification is about 200,000x. SEM cannot be used to study living cells as well since the sample for this process must be very dry.