Electron Microscope Invention and History
Electron microscopes operation is based on imaging backscattered/interacted electrons incident on a surface. These microscopes work on the basis of de Broglie particle-wave duality, where electrons have replaced photons to obtain a resolution 5000 times greater than optical microscopes. Since the first prototype of electron microscope made by German scientists in 1931, nowadays, electron microscopes are capable of two-million-power magnification.
Who Invented the Electron Microscope?
The first prototype of electron microscope was invented by two German scientists, physicist Ernst Ruska and electric engineer Max Knoll, in 1931 in Technical University of Berlin, which brought 1986 Noble Prize for Ruska. This microscope worked based on imaging transmitted electrons from the sample with 400 power magnification (Figure 1).
The First scanning-tunneling electron microscope was first produced by Manfred Von Ardenne in 1937 (Figure 2). Subsequently, the first commercial transmission electron microscope (TEM) was made by Ruska and Bodo von Borries in Siemens in 1938. In the 1940s, Ruska developed a scanning electron microscope by focusing a scanning electron beam utilizing electromagnetic lenses and collecting scattered electrons, which contained information on the sample topography and structure.
Developments of EMs
Afterward, electron microscopes improved rapidly in the 1950s, when developing scanning electron microscope in Charles Oatley’s laboratory at Cambridge University led to the first commercial scanning electron microscope by Cambridge Instruments in 1965.
In 1973, John Venable made the first backscattered electron diffraction pattern (EBDS) by scanning electron microscopy. In 2000, imaging was revolutionized by the introduction of aberration-corrected lenses.
The development of different kinds of electron microscopes continues persistently to obtain higher resolution and accuracy and overcome existing challenges in the way of producing high-quality images from different samples.
Samples of Electron Microscopes
The samples investigated by electron microscopy mainly should be conductive, so there will be no charging effect on the sample surface while imaging. One of the common methods for imaging non-conductive samples is to deposit a conductive coating on their surface. Thus, vacuum coating systems are the best choices for deposition of electron microscopes samples.
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Also, high vacuum magnetron sputter coater (DST1) and sputter and carbon coater (DSCT), equipped with turbomolecular pump, are favorable deposition systems for SEM/FESEM sample preparation and deposition of different targets, provided by optional thermal evaporation and plasma cleaning, which is used for making hydrophilic surfaces and TEM grids cleaning.
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