Precession Electron Diffraction Tomography

Equipment, AAP 2019

Installation of the equipment at the end of 2020.

Team: Center for Nanosciences and Nanotechnologies (C2N), Département Matériaux

Abstract:

High-resolution transmission electron microscopy (HRTEM) can provide direct space information at resolutions of 0.1 nm, but this technique requires high-intensity illumination conditions and a large electron dose on the sample, which result in rapid amorphization. Also, the use of oriented “in-zone” electron diffraction patterns, which demands long exposure times while orienting crystals for data acquisition, gives rise to dynamical effects.

By tilting (manually/automatically) around an arbitrary axis a single nanocrystal in combination with precession electron diffraction (PED), the reciprocal cell can be reconstructed and crystal cell parameters can be evaluated automatically and precisely. Reflection intensities can also be measured automatically to enable the solution of the crystal structure. The spatial resolution is directly related to the size of the electron beam. The nano-beam mode of microscopes equipped with a FEG gun can reach a probe size of 1nm. It is thus possible to make orientation or phase maps using the precession of the nano-beam. The electron beam is scanned in combinaison with beam precession through the sample area of interest. To realize a phase map, a high number of electron diffraction patterns are acquired at high speed using a dedicated fast CCD camera. Electron beam precession diffraction is extremely useful for obtaining patterns with a large number of spots and without dynamical effects (the recommended precession angle is about 0.5 to 1 degree).

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