Scanning transmission electron microscopy (STEM) is the capability of a microscope for combining Transmission Electron Microscopes (TEMs) and SEM. STEM is a popular technique for laboratories without transmission electron microscopy (TEM) capabilities. Transmitted electrons which carrying unique information extend the imaging capabilities and analytical power of SEM and FIB-SEM systems. Specimens analysed with this technique need to be prepared in the form of thin lamellae with thicknesses of less than 100 nm. This technique can be combined with elemental analysis such as EDX and transmission-mode EBSD to provide high-resolution microanalysis of specimens.
Different information from the specimen provided by transmitted electrons scattered in different angles. The following signals are available.
- The Bright Field (BF) signal typically represents Bragg-diffraction orientation contrast and absorption contrast in lamellae.
- The Dark Field (DF) contains partly orientation contrast and material contrast on light elements.
- The High Angle Dark Field (HADF) contains maximum information about material contrast and minimum Bragg-diffraction contrast.
The scattering angles depend on the sample material, lamella thickness and energy of the beam.
The STEM detector enables investigation of ultrastructure in biological specimens, failure analysis in semiconductors devices and characterisation of materials.
Two types of STEM detectors developed that can be installed into TESCAN SEM or FIB-SEM systems. This enhances the analytical power of FIB-SEM systems (high-quality lamellas can be prepared and in-situ analysed).
STEM Detector
- STEM detector consists of three semiconductor sensors for bright field and dark field imaging.
- Simultaneous bright field and dark field image acquisition or mixing of the signals is possible.
- Compact design – removable adaptor on stage.
- Standard TEM grid is placed into the specimen holder of the detector.
HADF R-STEM Detector (High-Angle Dark-Field Retractable STEM detector)
- Multiple specimens can be observed without breaking the chamber vacuum
- Simultaneous acquisition of the Bright Field (BF), Dark Field (DF) and High Angle Dark Field (HADF) signals.
· Color STEM: The BF, DF and HADF signals can be color-coded and be combined in a one single image.
- The sample can be moved up and down relative to the detector in order to reach the best imaging conditions
- The sample can be tilted independently of the detector
- Acquisition of larger areas using the Image Snapper is possible
- Exchangeable sample holders for easy grid manipulation
- Two sample holders available: multiple sample holder and TEM lamella holder
- Improved geometry of the sample holders for EDX analysis
