Kikuchi Diffraction Patterns: Crystal structure seen from the inside
Aimo Winkelmann (Laser Zentrum Hannover)

The polycrystalline microstructure of many technological, geological, and even biological materials calls for suitable microcrystallographic analysis methods. In this context, Kikuchi diffraction patterns observed in the Scanning Electron Microscope (SEM) are a powerful tool to investigate a wide variety of samples on length scales ranging from centimeters down to the nanometer region. Because Kikuchi patterns are formed by electrons which are emitted from incoherent sources inside crystals, it is instructive to discuss the beautiful geometry and interesting physics of Kikuchi pattern formation by adopting the perspective of an atom in a crystal. The physics of Kikuchi pattern formation can be visualized by a Bloch wave approach, which also highlights the close relationship between the concepts of electronic band structure and the mechanism of electron diffraction in crystals. A selection of applications will be discussed, which show how quantitative Kikuchi pattern simulations make it possible to improve the orientation determination and phase discrimination in important materials on the sub-micron scale.