Electron backscatter diffraction

What is EBSD analysis used for?

EBSD is used to profile and visualize the complex crystalline structures of solid-state materials, which in turn can have a great influence on their physical and mechanical properties. Hence, EBSD is used in metallurgy to study the physical makeup of metals and alloys, and in geological sciences to investigate the effects of microstructures on rock and ore formation.

As magnetic and electrical properties can also be influenced by the crystal structure, EBSD can be used to help develop materials that are used in manufacturing computers, smart devices, and electrical supply equipment. EBSD is also an effective failure analysis tool that can be used to identify causes of corrosion or fracturing in samples including thin films, metals, and semiconductor devices.

How does electron backscatter diffraction work?

The EBSD detector is connected to a scanning electron microscope (SEM), and a flat crystalline sample is inserted into the sample chamber for analysis. A beam of electrons is then fired at the sample, usually at an angle of 70 degrees. The electrons interact with the sample and are scattered as they come into contact with the atoms within the structure.

These scattered electrons then reach a phosphorescent screen, where they create a pattern that represents the way in which they were diffracted and therefore the crystal structure of the sample itself. This data can be interpreted to make calculations and observations about the nature of the crystal structure, including grain shape, size, and orientation. When combined with data acquired with an EDX detector, the elemental composition can also be determined.

Suitable samples and sample preparation

EBSD can be performed on a range of smooth-surfaced solid crystalline materials, with either single or multi-phase crystal structures, though with the latter additional preparation may be required to achieve optimal results. Samples are generally polished to improve the surface condition before analysis, which can be done mechanically or in some cases electrochemically. Samples may also be treated through ion milling which helps to optimize the surface further.

EBSD vs XRD 

X-ray diffraction (XRD) is another scattering technique with similar applications to EBSD. As X-rays are naturally more penetrating than electrons, this technique allows the user to probe relatively deeply into a crystal structure. The data it produces is most often quantitative and will require further interpretation or modeling to produce a visual form of the crystal structure. Therefore, XRD is most suited to understanding the bulk structure on a more fundamental level.

EBSD instead produces an image of a diffraction pattern and therefore allows the user to see one interpretation of a visual crystal structure. It does not scan deeply but is rather used to analyze local areas of the surface and sub-surface layer, meaning it is more suited to investigating localized microstructures as opposed to the overall structure. For the best possible results, XRD and EBSD can be used as complementary techniques to gather a full set of data.

Advantages and limitations of EBSD analysis

EBSD offers a fast and reliable way of analyzing crystal structures. It works in a visual medium which allows researchers to interpret results by eye as well as mathematically. It can provide data on different planes of symmetry at once, allowing for a solid understanding of a specific region of a crystal structure.

The main limitation of EBSD is that the surface of the sample must be free of damage and other contaminants to achieve accurate results. This means that polishing can be intensive and may require multiple attempts before high-quality results are achieved.