![]() ![]() For comparison, the d-spacing for silicon (022) is about 192 picometres while the d-spacing for silicon (004) is about 136 picometres. The Kikuchi band widths themselves (roughly λL/d where λ/d is approximately twice the Bragg angle for the corresponding plane) are well under 1°, because the wavelength λ of electrons (about 1.97 picometres in this case) is much less than the lattice plane d-spacing itself. This image subtends an angular range of over 10° and required use of a shorter than usual camera length L. Fully quantitative work on such diffraction features is therefore assisted by the large linear dynamic range of CCD detectors. Kikuchi lines are much easier to follow with dark-adapted eyes on a fluorescent screen, than they are to capture unmoving on paper or film, even though eyes and photographic media both have a roughly logarithmic response to illumination intensity. The dynamic range in the image is so large that only portions of the film are not overexposed. The figure at left shows the Kikuchi lines leading to a silicon zone, taken with the beam direction approximately 7.9° away from the zone along the (004) Kikuchi band. Recording experimental Kikuchi patterns and maps Kikuchi lines in a convergent beam diffraction pattern of single crystal silicon taken with a 300 keV electron beam In x-ray scattering, these lines are referred to as Kossel lines (named after Walther Kossel). The main features of their geometry can be deduced from a simple elastic mechanism proposed in 1928 by Seishi Kikuchi, although the dynamical theory of diffuse inelastic scattering is needed to understand them quantitatively. Kikuchi lines are formed in diffraction patterns by diffusely scattered electrons, e.g. indices which represent integer multiples of the lattice basis vectors a, b and c. ![]() Kikuchi band intersections, or zones, on the other hand are indexed with direct-lattice indices i.e. ![]() Because each Kikuchi line is associated with Bragg diffraction from one side of a single set of lattice planes, these lines can be labeled with the same Miller or reciprocal-lattice indices that are used to identify individual diffraction spots. bend contours, electron channeling patterns, and fringe visibility maps are increasingly useful tools in electron microscopy of crystalline and nanocrystalline materials. Unlike diffraction spots, which blink on and off as one tilts the crystal, Kikuchi bands mark orientation space with well-defined intersections (called zones or poles) as well as paths connecting one intersection to the next.Įxperimental and theoretical maps of Kikuchi band geometry, as well as their direct-space analogs e.g. In transmission electron microscopes, they are easily seen in diffraction from regions of the specimen thick enough for multiple scattering. They pair up to form bands in electron diffraction from single crystal specimens, there to serve as "roads in orientation-space" for microscopists uncertain of what they are looking at. Kikuchi lines are patterns of electrons formed by scattering. Patterns formed by scattering Map of Kikuchi line pairs down to 1/1Å for 300 keV electrons in hexagonal sapphire (Al 2O 3), with some intersections labeled ![]()
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