Scanning transmission electron microscopy (STEM): high-precision nanometric analysis
Scanning transmission electron microscopy (STEM) is an advanced technique that enables ultra-detailed analysis of the structure and composition of materials at the atomic scale. 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 the fields of nanotechnology, semiconductors, polymer materials, and biology , this technique is essential for characterizing 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 scanning point by point, allowing for extremely detailed chemical and structural mapping.
The main stages of the STEM process:
- Electron beam emission by an electron gun (e.g., FEG source for better resolution).
- Interaction with the sample , allowing the analysis of its crystalline structure and elemental composition.
- Detection of emitted signals (scattered electrons, energy losses), used to generate high-resolution images.
- Data processing to provide accurate information on the morphology, chemical composition and defects of materials.
Technical characteristics of scanning transmission electron microscopy (STEM)
Extreme resolution : down to the atomic scale (< 1 nm).
Multiple imaging modes :
- Clear field (BF-STEM) : observation of the internal structure of materials.
- Annular dark field (HAADF-STEM) : high-contrast imaging based on atomic mass.
- EDX and EELS spectroscopy : identification of chemical elements and atomic bonds.
Specific preparation of samples :
- Ultrathin samples (< 100 nm).
- Preparation techniques such as ultramicrotomy and Focused Ion Beam (FIB).
What samples can be analyzed with scanning transmission electron microscopy (STEM)?
Scanning transmission electron microscopy (STEM) is particularly well-suited to materials requiring detailed analysis of their internal structure. Among the main matrices studied are:
Industrial applications of scanning transmission electron microscopy (STEM)
Léa Géréec
Technical and scientific expert
