Kikuchi lines

Image of a silicon single crystal with a 300keV electron beam tilted 7.9 ° from the [100] plane

Kikuchi lines are characteristic lines that arise during electron diffraction in transmission electron microscopes or during diffraction of backscattered electrons in scanning electron microscopes .

Its name goes back to its description by Seishi Kikuchi in 1928.

Emergence

The Kikuchi lines arise from multiple scattering of the electrons. When a material is bombarded with electrons, they have a defined kinetic energy. Now it can happen that the electrons are not only scattered once on the sample, but after the first scattering they fly isotropically and with a random wave vector and are scattered again. The energy loss during the first scattering must be small compared to the electron energy. The double spread is very important. The first inelastic collision causes the electron beam to be deflected slightly around the direction of incidence. The scattered electrons are then elastically bent by lattice planes .

Using a crystal lattice, this can be easily explained with the help of kinematic scattering theory , although this is a dynamic phenomenon:

After the Laue condition applies: . In contrast to the Ewald construction , the vector is applied to a grid center. It forms a sphere around this point. Every point of intersection of this sphere with the Brillouin zone edge results in a reflex. While in the Ewald construction, individual points are hit and the diffraction pattern is also point-shaped, here the sphere and surface intersect (depending on the Brillouin zone) and this creates a line pattern. ${\ displaystyle {\ vec {k}} - {\ vec {k}} '= {\ vec {G}}}$ ${\ displaystyle {\ vec {k}}}$

application

The Kikuchi lines can be observed with electron transmission as well as with electron backscatter. A frequent application is in connection with the RHEED method (from English reflection high energy electron diffraction ). The crystal can be analyzed with the method described there as well as with the help of the Kikuchi lines, which can also be observed. Another application is in the EBSD process ( electron backscatter diffraction ), in which Kikuchi lines of the electrons backscattered in the scanning electron microscope (with the appropriate geometry) are recorded in order to determine the crystal structure and orientation.

literature

H. Alexander: Physical basics of electron microscopy . Teubner study books, Stuttgart 1997, ISBN 978-3-519-03221-2 .

Web links

Commons : Kikuchi lines - collection of images, videos and audio files

Individual evidence

↑ S. Kikuchi: Diffraction of Cathode Rays by Mica . In: Proceedings of the Imperial Academy . tape 4 , 1928, pp. 354-356 .
^ S. Nishikawa , S. Kikuchi: The Diffraction of Cathode Rays by Calcite . In: Proceedings of the Imperial Academy . tape 4 , 1928, pp. 475-477 .
^ S. Nishikawa, S. Kikuchi: Diffraction of Cathode Rays by Mica . In: Nature . tape 121 , June 30, 1928, pp. 1019-1020 , doi : 10.1038 / 1211019a0 .

[1] S. Kikuchi: Diffraction of Cathode Rays by Mica . In: Proceedings of the Imperial Academy . tape 4 , 1928, pp. 354-356 .

[2] S. Nishikawa , S. Kikuchi: The Diffraction of Cathode Rays by Calcite . In: Proceedings of the Imperial Academy . tape 4 , 1928, pp. 475-477 .

[3] S. Nishikawa, S. Kikuchi: Diffraction of Cathode Rays by Mica . In: Nature . tape 121 , June 30, 1928, pp. 1019-1020 , doi : 10.1038 / 1211019a0 .