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@ARTICLE{Leidl:1028899,
author = {Leidl, Max Leo and Diederichs, Benedikt and Sachse, Carsten
and Müller-Caspary, Knut},
title = {{I}nfluence of loss function and electron dose on
ptychography of 2{D} materials using the {W}irtinger flow},
journal = {Micron},
volume = {185},
issn = {0047-7206},
address = {New York, NY [u.a.]},
publisher = {Elsevier},
reportid = {FZJ-2024-04860},
pages = {103688 -},
year = {2024},
abstract = {Iterative phase retrieval is based on minimising a loss
function as a measure of the consistency of an initial guess
and underlying experimental data. Under ideal experimental
conditions, real data contains Poissonian noise due to
counting statistics. In this work, we use the Wirtinger Flow
concept in combination with four common loss functions,
being the L1 loss, the mean-squared error (MSE), the
amplitude loss and the Poisson loss. Since only the latter
reflects the counting statistics as an asymmetric Poisson
distribution correctly, our simulation study focuses on two
main cases. Firstly, high-dose momentum-resolved scanning
transmission electron microscopy (STEM) of an MoS2 monolayer
is considered for phase retrieval. In this case, it is found
that the four losses perform differently with respect to
chemical sensitivity and frequency transfer, which we
interprete in terms of the substantially different signal
level in the bright and dark field part of diffraction
patterns. Remedies are discussed using further simulations,
addressing the use of virtual ring detectors for the dark
field, or restricting loss calculation to the bright field.
Secondly, a dose series is presented down to 100 electrons
per diffraction pattern. It is found that all losses yield
qualitatively reasonable structural data in the phase,
whereas only MSE and Poisson loss range at the correct
amplitude level. Chemical contrast is, in general, reliably
obtained using the Poisson concept, which also provides the
most continuous spatial frequency transfer as to the
reconstructed object transmission function.},
cin = {ER-C-3},
ddc = {570},
cid = {I:(DE-Juel1)ER-C-3-20170113},
pnm = {5352 - Understanding the Functionality of Soft Matter and
Biomolecular Systems (POF4-535) / 5241 - Molecular
Information Processing in Cellular Systems (POF4-524) /
4D-BioSTEM (DE002325)},
pid = {G:(DE-HGF)POF4-5352 / G:(DE-HGF)POF4-5241 /
G:(DE-Juel-1)DE002325},
typ = {PUB:(DE-HGF)16},
pubmed = {38991624},
UT = {WOS:001267955000001},
doi = {10.1016/j.micron.2024.103688},
url = {https://juser.fz-juelich.de/record/1028899},
}