Scanning Transmission Electron Microscopy (STEM): High-precision nanometric analysis
Scanning transmission electron microscopy (STEM) is an advanced technique for the ultra-detailed analysis of the structure and composition of materials at the atomic level. Combining the principles of transmission electron microscopy ( TEM ) and scanning electron microscopy ( SEM ), it offers high-resolution imaging and advanced chemical analysis capabilities. Widely used in nanotechnology , semiconductors, polymer materials, and biology , this technique is essential for the characterization of complex structures.
How does scanning transmission electron microscopy (STEM) work?
Scanning transmission electron microscopy (STEM) relies on a focused electron beam passing through an ultrathin sample (< 100 nm thick). Unlike conventional TEM, the image is obtained by point-by-point scanning, which allows for extremely detailed chemical and structural mapping.
The main steps of the STEM process:
- Emission of the electron beam by an electron gun (e.g. FEG source for better resolution).
- Interaction with the sample , allowing the analysis of its crystalline structure and its elemental composition.
- Detection of emitted signals (scattered electrons, energy losses), used to generate high-resolution images.
- Data processing to provide accurate information on material morphology, chemical composition and defects.
Technical characteristics of scanning transmission electron microscopy (STEM)
Extreme resolution : down to the atomic scale (< 1 nm).
Multiple imaging modes :
- Bright field (BF-STEM) : observation of the internal structure of materials.
- Annular dark field (HAADF-STEM) : atomic mass-based contrast imaging.
- EDX and EELS spectroscopy : identification of chemical elements and atomic bonds.
Specific sample preparation :
- Ultra-thin samples (< 100 nm).
- Preparation techniques such as ultramicrotomy and Focused Ion Beam (FIB).
Which samples should be analyzed with scanning transmission electron microscopy (STEM)?
Scanning transmission electron microscopy (STEM) is particularly suited to materials requiring detailed analysis of their internal structure. Among the main matrices studied:
Industrial applications of scanning transmission electron microscopy (STEM)
Léa Géréec
Technical and scientific advisor
