The first electron microscope prototype was built in 1933 by the German engineers Ernst Ruska and Max Knoll. It was based on the ideas and discoveries of French physicist Louis de Broglie. Although it was primitive and not fit for practical use, the instrument was still capable of magnifying objects by four hundred times. Siemens director Reinhold Rudenburg had patented the electron microscope in 1931, and by the year 1937 Siemens began developing the electron microscope, even though he has no research on electron microscope, with the help of funding Ruska and Bondo von Borries to develop the instrument, he also employed Ruska’s brother Helmut to work on applications, particularly with biological materials. The first TEM was built by Siemens in 1939, and the first practical microscope was built at the University of Toronto in 1938, by Eli Franklin Burton and students Cecil Hall, James Hillier and Albert Prebus. Although modern microscopes like electron microscopes can magnify objects up to two million times, they are still based upon Ruska’s prototype and his correlation between wavelength and resolution. The modern electron microscope is an integral part of many laboratories. Researchers use it to examine biological materials such as cell and microorganism, a variety of large molecules, metals and crystalline structures, medical biopsy samples, and the characteristic of various surfaces.

“Types of Electron Microscopes” - the TEM Transmission Electron Microscopy, the SEM Scanning Electron Microscope, the REM Reflection Electron Microscope, and the STEM Scanning Transmission Electron Microscope.

The TEM involves a high VOLTAGE electron beam emitted by a CATHODE and formed by magnetic lenses. The electron beam that has been partially transmitted through the very thin and so semitransparent for electrons specimen carries information about the inner structure of the specimen. The image is then magnified by a series of magnetic lenses until it is recorded by hitting a fluorescent screen, photographic plate, or light sensitive sensor such as a CCD charge coupled camera. The image detected by the CCD may be displayed in real time on a monitor or computer. The high-resolution TEM-HRTEM is limited by spherical aberration and chromatic aberration, but a new generation of aberration correctors has been able to overcome spherical aberration. Spherical aberration has allowed the production of images with sufficient resolution to show carbon atoms in diamond separated by only 0.89 angstrom-89 Pico meters and atoms in silicon 0.78 angstrom-78 Pico meters at magnification of 50 million times. SEM Scanning Electron Microscope produces images by detecting secondary electrons which are emitted from the surface due to excitation by the primary electron beam. In the SEM, the electron beam is rastered across the sample, with detectors building up an image by mapping the detected signals with beam position. Generally, the TEM resolution is about an order of magnitude better than the SEM resolution, however, because the SEM image relies on surface processes rather than transmission it is able to image bulk samples and has a much greater depth of view, and so can produce images that are a good representation of the 3D structure of the sample. The REM Reflection Electron Microscope like the TEM this technique involves electron beams incident on a surface, but instead of using the transmission TEM or secondary electrons SEM, the reflected beam is detected. This technique is typically coupled with Reflection High energy Electron Diffraction and Reflection high-energy loss spectrum RHELS. Another variation is Spin-Polarized Low-Energy Electron Microscopy SPLEEM, which is used for looking at the microstructure of magnetic domains.