Transmission electron microscopy (TEM): principle, applications and laboratory analyses
Transmission electron microscopy (TEM) is an advanced analytical technique that allows the observation of nanoscale structures with a resolution far superior to that of conventional optical microscopes. By using an electron beam passing through an ultra-thin sample, TEM is essential for the study of materials, biological structures, nanoparticles, and polymers. This method is widely used in various industrial and scientific sectors, including nanotechnology research, cell biology, metal characterization, and food analysis.
What is transmission electron microscopy?
Definition of transmission electron microscopy
Transmission electron microscopy is an analytical method that uses an electron beam to image an extremely thin sample. Unlike scanning electron microscopy (SEM), which provides surface images, TEM allows the study of the internal structure of samples based on how electrons are transmitted through the material.
This technique is particularly valuable for analyzing the morphology, crystal structure and chemical composition of materials at a nanometric or even atomic scale.
How does transmission electron microscopy work?
The operation of MET is based on several key steps:
- Sample preparation
- The sample must be extremely thin (on the order of 50 to 100 nanometers thick).
- Ultra-thin cutting (ultramicrotomy) or thin film deposition techniques are used.
- In the case of biological samples, cryo-preparation may be necessary.
- Interaction with the electron beam
- An electron gun generates a beam that passes through the sample.
- Some electrons are absorbed, others are scattered or transmitted without interaction.
- The image is formed from variations in absorption and scattering of electrons.
- Image acquisition and processing
- The transmitted electrons are collected by a detector and converted into a high-resolution image.
- Advanced techniques, such as electron diffraction and EDX spectroscopy, provide additional information on the chemical composition of samples.
Technical characteristics of transmission electron microscopy
- Resolution : Up to 0.1 nm, allowing the observation of atomic structures.
- Electron source : Thermionic emission (tungsten filament) or field emission.
- Analysis modes :
- Conventional imaging (transmission contrast)
- Electron diffraction for the study of crystal structures
- Electron Energy Loss Spectroscopy (EELS)
- Energy-dispersive X-ray spectroscopy (EDX) for elemental analysis
- Sample preparation :
- Ultra-thin microtomes for biological samples
- Chemical or physical deposition of thin layers for materials
- Cryopreparation techniques to avoid alteration of sensitive samples
What types of samples can be analyzed with transmission electron microscopy?
TEM is ideal for analyzing solid materials and ultra-thin biological samples
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Applications of transmission electron microscopy in industry and research
Transmission electron microscopy is an essential technique for many industrial and scientific sectors.
Léa Géréec
Technical and scientific advisor
