What is Forward Scatter Diffraction?

• Forward Scatter Diffraction contrast occurs due to incident electron beam electrons diffracting from the near sample surface, at a sample tilt angle of 70°.
• The scattering characteristics and energies are a function of beam-sample-detector geometry and Bragg's Law of Diffraction.
• The diffraction events are collected by a solid state detector mounted at the 6 o'clock position of the EDSD camera, adjacent to the phosphor screen.
• As forward scattering occurs due to diffraction events, the resulting image is sensitive to the near surface structure of the material

What does the Forward Scatter Detector offer?

• Orientation contrast
• Topographical contrast
• Compositional contrast
• High contrast image with EBSD sample preparation
• No complex signal mixing to combine above contrasts into one image
• Provide new, innovative contrast for imaging your microstructure
• Imaging functionality within OIM software

More Details

FSD imaging effectively captures orientation, topography, texture, and composition variations within the sample and microstructure. Variation of the beam-sample-detector geometry, beam conditions, and camera insertion position can also enhance particular image contrasts.

The FSD displays high structural contrast of the microstructure, relative to the Secondary Electron Image (SEI), at the 70° tilt typically used for EBSD data collection. The FSD image also provides orientation contrast previously only attainable from an OIM scan and the resulting Inverse Pole Figure (IPF) map. Examples of these can be seen in the image below.

The user will find that the SEM is easier to focus at 70° tilt in FSD mode (versus SE) due to the greater structural detail. Best of all, the microstructure can be examined without prior use of chemical etchants or using complex signal mixing between detectors, frequently required for this level of imaging technology. All you need is a good EBSD polish and you will get microstructural information not otherwise attainable with other imaging modes!

The FSD can provide orientation, topographical, and compositional contrast depending on how the user varies working distance, accelerating voltage, beam current, and camera insertion distance. The FSD images below were produced from a poly-phase sulfide ore rock, for which camera insertion distance was varied. Note the different features that are apparent at different insertions.

When the camera is fully inserted, topographical contrast is most dominant, but as the camera is retracted to 12mm, orientation contrast becomes more apparent. With further retraction, compositional contrast appears, approaching the level of detail formerly only achievable with a backscatter detector (BSE). Simply put, the FSD is extremely flexible and can meet most users imaging needs.

The FSD offers high resolution and flexible imaging modes for any microscope application and operates within the OIM Data Collection software version 4.6 (or greater). No additional software is required.