In addition, all samples need to be able to handle the low pressure inside the vacuum chamber. Of the variety of different preparation processes, the two most commonly used prior to SEM analysis are sputter coating for non-conductive samples and dehydration of most biological specimens. Most samples require some preparation before being placed in the vacuum chamber. The beam is focused onto the stage, where a solid sample is placed. The coils are adjusted to focus the incident electron beam onto the sample these adjustments cause fluctuations in the voltage, increasing/decreasing the speed in which the electrons come in contact with the specimen surface.Ĭontrolled via computer, the SEM operator can adjust the beam to control magnification as well as determine the surface area to be scanned. These lenses are tubes, wrapped in coil and referred to as solenoids. The process begins with an electron gun generating a beam of energetic electrons down the column and onto a series of electromagnetic lenses. In addition, SEMs require a stable power supply, vacuum and cooling system, vibration-free space and need to be housed in an area that isolates the instrument from ambient magnetic and electric fields.Ī Scanning Electron Microscope provides details surface information by tracing a sample in a raster pattern with an electron beam. Electromagnetic and/or Electrostatic Lenses.SEMs consist of the following components: Charles Oatlev with the assistance of graduate students in the 1950s, are one of the three types of electron microscopes (EM).Įlectron microscopes utilize the same basic principles as light microscopes, but focus beams of energetic electrons rather than photons, to magnify an object. The Scanning Electron Microscope developed by professor Dr.
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