STEM Detectors

Scanning transmission electron microscopy (STEM) is the capability of a microscope for combining the principles used in Transmission Electron Microscopes (TEMs) and SEM. STEM is a popular technique for laboratories without transmission electron microscopy (TEM) capabilities. STEM detectors extend the imaging capabilities and analytical power of SEM and FIB-SEM systems by providing unique information that is carried by transmitted electrons. Specimens analysed with this technique need to be prepared in the form of thin lamellae with thicknesses of < 100 nm. This technique can be used in combination with elemental analysis such as EDX and transmission-mode EBSD to provide high-resolution microanalysis of specimens.
 
Transmitted electrons scattered in different angles provide different information from the specimen. 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.
 
Applications: The STEM detector enables investigation of ultrastructure in biological specimens, failure analysis in semiconductors devices and characterisation of materials.
 
TESCAN has developed two types of STEM detectors that can be installed into our SEM or FIB-SEM systems. This enhances the analytical power of FIB-SEM systems; high-quality lamellae can be prepared and in-situ analysed.
 

TESCAN STEM detectors:

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.
  • Colour STEM: The BF, DF and HADF signals can be colour-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

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.
STEM Detectors
The HADF R-STEM detector enhances the SEM analysis (SE, BSE, EDX, EBSD) that can be performed on thin-sliced samples by adding the unique information that only transmitted electrons can provide.

Related Application Notes

High resolution analysis of thin foils using the STEM Detector with HADF
Performing scanning transmission electron microscopy (STEM) in a scanning electron microscope (SEM) is a popular technique for laboratories without transmission electron microscopy (TEM) capabilities. The new option for TESCAN STEM detector extends the imaging capabilities by simultaneous acquisition of multiple signals from transmitted and diffracted electrons including bright field, dark field and high angle dark field. The STEM analysis can be further supplemented with transmission EDX or EBSD microanalysis for receiving higher resolution, utilizing the available analytical techniques of the SEM.
pdf – 1.7 MB