A Transmission Electron Microscope (TEM) utilizes energetic electrons to provide morphologic, compositional and crystallographic information on samples.
At a maximum potential magnification of 1 nanometer, TEMs are the most powerful microscopes. TEMs produce high-resolution, two-dimensional images, allowing for a wide range of educational, science and industry applications.
Ernst Ruska developed the first electron microscope, a TEM, with the assistance of Max Knolls in 1931. After significant improvements to the quality of magnification, Ruska joined the Sieman’s Company in the late 1930s as an electrical engineer, where he assisted in the manufacturing of his TEM.
TEMs consist of the following components:
An electron source
Phosphor or fluorescent screen
A Transmission Electron Microscope functions under the same basic principles as an optical microscope.
In a TEM, electrons replace photons, electromagnetic lenses replace glass lenses and images are viewed on a screen rather than through an eyepiece.
A Transmission Electron Microscope produces a high-resolution, black and white image from the interaction that takes place between prepared samples and energetic electrons in the vacuum chamber.
Air needs to be pumped out of the vacuum chamber, creating a space where electrons are able to move.
The electrons then pass through multiple electromagnetic lenses. These solenoids are tubes with coil wrapped around them.
The beam passes through the solenoids, down the column, makes contact with the screen where the electrons are converted to light and form an image.
The image can be manipulated by adjusting the voltage of the gun to accelerate or decrease the speed of electrons as well as changing the electromagnetic wavelength via the solenoids.
The coils focus images onto a screen or photographic plate.
During transmission, the speed of electrons directly correlates to electron wavelength; the faster electrons move, the shorter wavelength and the greater the quality and detail of the image.
The lighter areas of the image represent the places where a greater number of electrons were able to pass through the sample and the darker areas reflect the dense areas of the object.
These differences provide information on the structure, texture, shape and size of the sample.
To obtain a TEM analysis, samples need to have certain properties. They need to be sliced thin enough for electrons to pass through, a property known as electron transparency.
Samples need to be able to withstand the vacuum chamber and often require special preparation before viewing.
Types of preparation include dehydration, sputter coating of non-conductive materials, cryofixation, sectioning and staining.
A Transmission Electron Microscope is ideal for a number of different fields such as:
Scanning (SEM) - Learn about the SEMs high-resolution, three-dimensional images which provide topographical, morphological and compositional information making them invaluable in a variety of science and industry applications.
Cryo-Electron - is a type of transmission electron microscopy that allows for the specimen of interest to be viewed at cryogenic temperatures. Check it out.
Virtual - provides a simulated microscope experience via a computer program or Internet website for both educational and industrial applications and are easily operated and accessible.
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