Publication
Title
On central focusing for contrast optimization in direct electron ptychography of thick samples
Author
Abstract
Ptychography provides high dose efficiency images that can reveal light elements next to heavy atoms. However, despite ptychography having an otherwise single signed contrast transfer function, contrast reversals can occur when the projected potential becomes strong for both direct and iterative inversion ptychography methods. It has recently been shown that these reversals can often be counteracted in direct ptychography methods by adapting the focus. Here we provide an explanation of why the best contrast is often found with the probe focused to the middle of the sample. The phase contribution due to defocus at each sample slice above and below the central plane in this configuration effectively cancels out, which can prevent contrast reversals when dynamical scattering effects are not overly strong. In addition we show that the convergence angle can be an important consideration for removal of contrast reversals in relatively thin samples.
Language
English
Source (journal)
Ultramicroscopy. - Amsterdam
Publication
Amsterdam : 2024
ISSN
0304-3991
DOI
10.1016/J.ULTRAMIC.2023.113879
Volume/pages
256 (2024) , p. 1-7
Article Reference
113879
ISI
001112166400001
Pubmed ID
37944427
Full text (Publisher's DOI)
Full text (open access)
UAntwerpen
Faculty/Department
Research group
Project info
High Definition Electron Microscopy: Greater clarity via multidimensionality (HDEM).
Advancing 4D STEM for atomic scale structure property correlation in 2D materials.
Publication type
Subject
Affiliation
Publications with a UAntwerp address
External links
Web of Science
Record
Identifier
Creation 09.01.2024
Last edited 11.01.2024
To cite this reference