A transmission electron microscope works like a light microscope but uses electrons. Light microscopes are limited by their magnification because they use light as a medium. Because TEMs use electrons, which have a lower wavelength, they can get resolutions much higher than a light microscope. TEMs are tools used for medical and biological research. However, they are also extremely useful for nanotechnology research because they can view structural information smaller than a nanometer.
Purpose
In terms of topography, TEM microscopes are good for observing the surface features of objects and how they relate to the sample's properties. In terms of morphology, they look at the shape and size of particles and see how they relate to material properties like strength and reactivity. TEM microscopes also check the composition of the sample and study melting point and hardness factor. Last, TEM microscopes can obtain crystallographic information, the arrangement of the sample's atoms in relation to conductivity and electrical properties.
History
The Royal Swedish Academy of Sciences awarded the 1986 Nobel Prize in Physics to Professor Ernst Ruska for his work in electron optics, and Dr. Gerd Binning and Dr. Heinrick Rohrer for their design in the scanning tunneling microscope. Ruska also designed the first electron microscope. The electron microscope helped the advancement of science fields like biology, medicine and nanotechnology.
Function
A TEM can magnify a sample up to 50 million times its size. Additional component attachments also give TEMs the ability to study crystal structure, electronic structure and chemical structure. TEMs also come with energy filters, X-ray energy dispersive spectrometers, electron energy-loss spectrometers and digital recording systems. TEMs can have holograph technology to improve chemical mapping resolution.
Usage
When a TEM is in use, a light source at the top of the unit emits electrons. These electrons travel through a vacuum at the center of the microscope column. The TEM's electromagnetic lenses focus the electrons into a thin beam that passes through the sample. The electrons that are scattered because of the sample's density end up at the bottom of the microscope, where it passes through a fluorescent screen. The darkness of the images relates to the sample's density.
Disadvantages
Although TEMs are powerful and make research and studying easy, the sample to examine can be difficult to collect. Samples must be "electron transparent" thin. This means that they have to be sliced so thin the electrons can properly pass over them. Processing these samples can be time consuming and very difficult. It is possible for the samples to be damaged in the process. In cases of biological specimens, there is scrutiny over the accuracy of TEMs because of the possibility of damage to the specimen from electron bombardment.
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