On the alignment for precession electron diffraction.
Precession electron diffraction has seen a fast increase in its adoption as a technique for solving crystallographic structures as well as an alternative to conventional selected-area and converged-beam diffraction methods. One of the key issues of precession is the pivot point alignment, as a stationary apparent beam does not guarantee a fixed pivot point. A large precession tilt angle, along with pre-field and post-field misalignment, induces shift in the image plane. We point out here that the beam should be aligned to the pre-field optic axis to keep the electron illumination stationary during the rocking process. A practical alignment procedure is suggested with the focus placed on minimizing the beam wandering on the specimen, and is demonstrated for a (110)-oriented silicon single crystal and for a carbide phase (∼20nm in size) within a cast cobalt-chromium-molybdenum alloy.
Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208, USA. yifeng-liao@northwestern.edu
Yifeng
Y
Liao
Laurence D
LD
Marks
D002858:Chromium Alloys / Q000737:chemistry; D003035:Cobalt / Q000737:chemistry; D003460:Crystallization; D004583:Electrons; D004867:Equipment Design; D046529:Microscopy, Electron, Transmission; D008982:Molybdenum / Q000737:chemistry; D049329:Nanostructures / Q000032:analysis; D012825:Silicon / Q000032:analysis*; D014961:X-Ray Diffraction / Q000379:methods*
D002858:Chromium Alloys; D003035:Cobalt; D008982:Molybdenum; D012825:Silicon