EBSD | How Does EBSD Work? | Electron Backscatter Diffraction

How does EBSD work?

As anticipated in the previous article explaining electron backscatter diffraction (EBSD), this technique uses the electron beam from the SEM and makes use of the signals that result from the interaction between the electron beam and the surface of the material under study. When the beam enters the sample, some electrons are backscattered from the surface. The energy and angle of these electrons depend on the atomic number of the elements present on the surface and the orientation of the crystal lattice.

When the electrons interact with the crystal lattice of the sample, they undergo diﬀraction. The diﬀraction patterns produced by the electrons are characteristic of the crystal structure and orientation of the material. Each crystallographic plane within the material will produce a unique diﬀraction pattern due to the angles and distances between lattice planes.

The electron diﬀraction patterns are then used to determine the crystallographic orientation and microstructural characteristics. Individual mineral grains can be selected, or data can be acquired on a grid over a selected area of the sample's surface to better understand spatial relations between many grains.

EBSD data acquisition

All the generated diﬀraction patterns produced by the crystal lattice are captured by a detector that records the intensity and direction of the backscattered electrons. The detector is inclined approximately 70° relative to the normal incidence of the electron beam. For this reason, the sample in the SEM chamber is usually tilted to expose the surface of interest to the detector. As with many other SEM detectors, the EBSD detector has a motorized insertion that allows it to get as close as possible to the sample while avoiding the possibility of collision with the sample.

Once the patterns are collected, they are processed by dedicated software that contains known crystallographic data for them to be assigned to speciﬁc crystal structures. This process is called indexing. The data are then translated into maps and processed to get ﬁnal answers about grain size, grain boundary distribution, and texture.

The image shows an EBSD pattern overlaid with simulated bands. It allows for matching the acquired pattern with the expected one.

All the extracted information will give insights into the properties and behavior of materials under various conditions and will serve a wide range of ﬁelds such as materials science, geology, metallurgy, and other ﬁelds where understanding the microstructure and crystallography of materials is important.