Transmission Electron Microscopy (TEM) and Scanning Transmission Electron Microscopy (STEM) are the ideal techniques to use if you need sub-nm imaging resolution. In addition to imaging, it is possible to obtain crystallographic phase and orientation (using electron diffraction), generate elemental maps (by using EDS or EELS), and acquire images highlighting elemental contrast (Z-contrast or HAADF-STEM mode).
How TEM/STEM works — High energy electrons (80keV-300keV) are transmitted through electron transparent samples (~100nm thick) and measured. TEM and STEM have higher spatial resolution than SEM but require more complex and time consuming sample preparation methods.
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Instrumentation Available
Key Attributes
- Signals Detected: Transmitted electrons, back-scattered electrons, secondary electrons, x-rays
- Elements Detected: B-U (EDS)
- Detection Limits: 0.1-1at% with EDS and EELS
- Imaging/Mapping: Yes (EDS, EELS)
- Ultimate Lateral Resolution: <0.2nm
Strengths
- The highest spatial resolution elemental mapping of any analytical technique
- Sub 0.2nm image resolution
- Small area crystallographic information
- Strong contrast between crystalline vs amorphous materials without chemical staining
Limitations
- Time consuming sample preparation (1-4hrs)
- Small sampling volumes that may not be indicative of the sample bulk
- Potential for electron beam damage of delicate materials
Applications
- Metrology at 0.2nm resolution
- Crystallographic phase measurement at the nanometer scale
- Characterization of nanoparticles
- Studies of catalyst materials
- nm-sized defects identification
- Elemental mapping at the nanoscale
- III-V semiconductors super lattice characterization
- Characterization of crystalline defects (dislocations, grain boundaries, voids, stacking faults)
Additional Reading
- Wikipedia
- Australian Microscopy & Microanalysis Research Facility MyScope training tool – a very good interactive training tool for TEM
- Video of TEM – 2:30 video explaining how a TEM works
