Electron backscatter diffraction (EBSD) is a microanalytical technique for SEM. EBSD provides valuable information on crystalline and polycrystalline specimens by studying crystal structure and crystal orientation of sample surface down to nanoscale that help researchers characterise and understand properties of materials. It also provides information about local crystal orientation, phase, characterisation of grain morphology, grain boundary, as well as orientation texture, internal stresses and defects in samples and many others can be determined with this microanalytical technique.
The EBSD principle is based on a Kikuchi-like electron diffraction of focused electron beam. Electrons from the primary beam are diffracted on crystal planes while leaving the sample surface as backscattered electrons
The pattern is captured on a fluorescent screen (that is placed close the sample and almost perpendicular to the beam axis). The electron beam of the SEM or FIB-SEM system impinges a flat polished surface of the 70° tilted sample (to facing the EBSD screen). This high tilt of the sample maximises the yield of diffracted electrons in order to obtain the best contrast of diffraction patterns.
The image of the pattern is synchronized with a beam scanning and further processed by dedicated software, which can automatically detect the orientation according the Kikuchi lines position and width. The results of EBSD measurements are shown crystal orientation maps. Such maps consist of colour-coded points, each colour corresponding to a specific crystal orientation, phase or other parameter. For texture evaluation an orientation distribution function can be calculated out of the map data and shown as orientation density in various diagrams such as pole figures.
The EBSD technique can also be combined with EDS for more precise phase identification (elemental composition and crystallography). Combining EBSD with FIB-SEM serial sectioning (i.e. FIB-slicing followed by EBSD data acquisition of each new surface), a 3D EBSD sample reconstruction can be achieved.
