A script-based method for achieving distortion-free selected area electron diffraction.

Autor: Mitchell DRG; Electron Microscopy Centre, AIIM Building, Innovation Campus, University of Wollongong, Fairy Meadow, New South Wales, Australia.
Jazyk: angličtina
Zdroj: Microscopy research and technique [Microsc Res Tech] 2022 Jul; Vol. 85 (7), pp. 2708-2713. Date of Electronic Publication: 2022 Apr 09.
DOI: 10.1002/jemt.24124
Abstrakt: Electron diffraction patterns obtained on a TEM contain elliptical distortion resulting from column defects. This distortion can be corrected by applying offsets to the objective lens stigmators to cancel distortions occurring further down the column. In this work, a DigitalMicrographTM script-based method has been developed to identify the optimum objective stigmator settings which produce a distortion minimum in diffraction. Initially, a manual (by eye) correction is used to determine the stigmator values necessary to bring the pattern distortion below the threshold at which it is no longer visible to the naked eye (<1%). Thereafter, an automated acquisition script is used to acquire matrices of diffraction patterns while varying the stigmator values about the values which were identified as producing a distortion minimum in the preceding step. This analysis can be applied iteratively to refine the location of the distortion minimum, using progressively finer step changes in objective stigmator values. The optimum stigmator values producing the distortion minimum in diffraction are very different to those in imaging. These imaging and diffraction stigmator values can be saved to script and subsequently recalled at the click of a button, making their application very simple. Using this method, diffraction pattern elliptical distortion in a newly installed TEM was reduced from 1.6% to 0.3%, on a measurement precision of 0.3%, effectively producing distortion-free diffraction. The relevant scripts can be freely downloaded from the internet. RESEARCH HIGHLIGHTS: This paper reports a DigitalMicrograph script-based method to identify and subsequently apply optimized objective stigmator values in diffraction mode. These effectively eliminate elliptical distortion inherent to this diffraction technique.
(© 2022 The Author. Microscopy Research and Technique published by Wiley Periodicals LLC.)
Databáze: MEDLINE
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