Transmission Electron Microscopy
Transmission Electron Microscopy (TEM) is an optical probe technique which utilizes the wave nature of electrons to image specimens.
It operates under much the same principles as an optical microscope using visible light in that image is made by wave transmission, diffraction, and reflection. However, because of the small de Broglie wavelength of electrons, specimens can be imaged on a much smaller scale (several thousand times smaller) than with light microscopes: visible light wavelength is on the order of several hundred nanometers while the electrons in a TEM have wavelenth on the order of tens to hundreds of picometers. This small wavelength is achieved and utilized through a relatively simple apparatus, shown and described below.
Electrons are accelerated by an accelerating voltage, typically 10s~100s kV, and fired from an electron gun. The electron beam then passes through the specimen, interacting with it. Magnetic lenses guide the electrons which are directed toward the viewing screen, creating the image. All of this is done in a vaccuum environment to prevent the possibility of electrons interacting with anything besides the specimen.