What is transmission electron microscopy?
Transmission electron microscopy (TEM) is a imaging technology in which electron beams pass through very sparse -divided samples. Since the electrons are transmitted by a sample and interact with its structure, it solves a picture that is enlarged and focused on imaging media, such as a photographic film or fluorescent screen or captured by a special CCD camera. Because the electrons used in transmission electron microscopy have a very small wavelength, the TEM can imagine much higher resolution than conventional optical microscopes that depend on the light rays. Due to their higher strength, Tem plays an important role in virology, cancer research, material studies and research and microelectronics development.
The first prototype Tem was built in 1931, and by 1933 a unit with a resolution greater than light was shown using cotton fiber images as a test sample. Over the next decadeYLY improved transmission electron microscopy, which makes technology useful in the study of biological specimens. After the introduction of the first electron microscope in Germany in 1939, further development was delayed by World War II, in which a key laboratory was bombed and two scientists died. After the war, the first electron microscope was introduced with an enlargement of 100K. Its basic multi -stage construction can still be found in modern transmission electron microscopy.
As the Technology of TEM matured, related technology, transmission electron microscopy (STEM), was specified in the 70s. The development of the emission gun in the field and improved lenses allowed to display atoms using stems. Most of the development of STEM technology was the result of progress in transmission electron microscopy.
Tems usually include three lenses: condensing lens, lens lens and projector lens. PrimaryThe electron beam consists of a condensing lens, while the lens lens focuses a beam that passes through the sample. The protruding lens expands the beam and projects it on display devices such as an electronic screen or a film sheet. Other specialized lenses are used to repair the beam. Energy filtering is also used to repair chromatic aberration, which is a form of distortion caused by the inability of the lens to focus all the colors of the spectrum at the same point of convergence.
While different transmission electron microscopy systems differ in their specific designs, they have several common components and phases. The first is a vacuum system that generates electron current and includes electrostatic plates and lenses with which the operator can direct the beam. The stages of the sample include an air device that allows you to insert an object to be studied into the current.Mechanisms at this stage allow the sample to be placed for optimal view. Electron pistol with a bondIt brings an "drawing" of electron current through the Tem. Finally, it reproduces an electron lens, similar to an optical lens.