Transmission electron microscope

1. Introduction
• Transmission electron microscopy (TEM) is an analytical technique used to visualize
the smallest structures in matter.
• Unlike optical microscopes, which rely on light in the visible spectrum, TEM can
reveal stunning detail at the atomic scale by magnifying nanometer structures up to
50 million times.
• This is because electrons can have a significantly shorter wavelength (about 100,000
times smaller) than that of visible light when accelerated through a strong
electromagnetic field, thus increasing the microscope resolution by several orders of
magnitude.
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2. Introduction (Contd…)
• To form a TEM image, a high energy electron beam is accelerated through an
extremely thin “electron transparent” sample, typically thinner than 100 nm.
• A series of electromagnetic lenses and apertures are placed throughout the
microscope’s column to focus the beam on the sample, minimize distortions, and
magnify the resulting image onto a phosphor screen or a specialized camera.
• A TEM comes in many different forms, but all share the same fundamental
principles and components.
• The two major types of TEM instruments are the conventional TEM (also referred to
simply as TEM) and the STEM (scanning transmission electron microscope).
• Other variations of TEMs include the AC-S/TEM (where AC stands for “aberration
corrected”) and the E-S/TEM (where E stands for “environmental”).
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3. What is Transmission Electron Microscopy Used For?
• Countless discoveries and innovations have been driven by applying TEM to the
world around us.
• The ability to “see” atoms enable scientists to understand materials and biological
systems at the most fundamental level.
• TEM images not only hold immense scientific value but are forms of art on their
own.
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4. TEM
• Zooming into the atomic scale allows scientists to view
the fundamental building blocks of functional materials
like catalyst nanoparticles, batteries, and
semiconductor devices.
• Focused electron beams can also be used to manipulate
materials in situ, allowing “nanofabrication” and novel
phenomena to be studied and discovered.
• The level of detail on this scale is nothing short of
stunning and provides a way for understanding the
connections between structure, property, and
performance, allowing engineers to design
nanomaterials from the bottom up.
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TEM image of nanoparticle
showing atomic resolution

5. aa
• The world of biology is full of fascinating and dynamic yet
invisible phenomena.
• Cryogenic TEM allows structural biologists to visualize the
architecture of macromolecular assemblies like proteins,
viruses, and intracellular structures at near atomic resolution.
• Recent technological advancements such as the use of direct
electron detectors, automation, and data processing have
propelled the technique into the mainstream.
• Using a method known as single particle analysis, scientists
have been able to determine the structure of the novel
coronavirus spike protein, which allows the virus to bind to
host cells, allowing targeted vaccines to be developed.
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TEM micrograph of apoferritin particles and the 3D reconstruction, at a calculated resolution of 2.5 Å, generated by
cryo-EM analysis using a vitrified sample prepared with the Vitrojet

6. Principle of Transmission Electron Microscope (TEM)
• The working principle of the Transmission Electron Microscope (TEM) is similar to the light
microscope.
• The major difference is that light microscopes use light rays to focus and produce an image
while the TEM uses a beam of electrons to focus on the specimen, to produce an image.
• Electrons have a shorter wavelength in comparison to light which has a long wavelength.
The mechanism of a light microscope is that an increase in resolution power decreases the
wavelength of the light, but in the TEM, when the electron illuminates the specimen, the
resolution power increases increasing the wavelength of the electron transmission.
• The wavelength of the electrons is about 0.005nm which is 100,000X shorter than that of
light, hence TEM has better resolution than that of the light microscope, of about
1000times.
• This can accurately be stated that the TEM can be used to detail the internal structures of
the smallest particles like a virion particle.
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7. Components of the TEM
• TEMs are composed of five key
components:
– High voltage source
– Vacuum system
– Microscope column
– Detectors (e.g., imaging cameras,
spectrometers)
– Control computers and software
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