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@PHDTHESIS{Winkler:860248,
author = {Winkler, Florian},
title = {{A}bsolute scale off-axis electron holography of thin
dichalcogenide crystals at atomic resolution},
volume = {191},
school = {RWTH Aachen},
type = {Dr.},
address = {Jülich},
publisher = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
reportid = {FZJ-2019-01032},
isbn = {978-3-95806-383-9},
series = {Schriften des Forschungszentrums Jülich. Reihe
Schlüsseltechnologien / Key Technologies},
pages = {XXIII, 187 S.},
year = {2019},
note = {RWTH Aachen, Diss., 2018},
abstract = {High-resolution transmission electron microscopy (HRTEM) is
an enormously powerful technique for the investigation of
material structures at atomic resolution. In addition,
off-axis electron holography allows information to be
obtained about electromagnetic fields inside and around the
object. However, due to electron diffraction in the sample
and subsequent electron optical imaging, the extraction of
quantitative information from recorded images is by no means
a trivial task, as information related to the object
structure, electromagnetic fields and microscope properties
are encoded in the recorded signal in a highly complex
manner. The comparison of experimental data with accurate
simulations, ideally on the same absolute scale, is a common
approach in HRTEM to extract pure information about objects
and fields. Prior to this work, absolute scale agreements
had only been achieved manually in a few cases for HRTEM,
but had not been demonstrated for off-axis electron
holography. In this work, an automated optimization
procedure is developed that enables the determination of
unknown or only partially known experimental parameters
directly from high-resolution electron wave functions
measured using off-axis electron holography. The procedure
is applied to the study of two-dimensional WSe$_{2}$,
yielding one of the most precise local specimen orientation
measurements that has been achieved in TEM for ultra-thin
samples. Extensive tests on simulated data reveal that
diffraction-related parameters, such as specimen tilt or
absorption, can be determined unambiguously with extremely
high accuracy and precision, even in the presence of
realistic recording noise. In contrast, coherent aberration
coefficients cannot be determined unambiguously from
electron wavefunctions of periodic objects. By applying the
procedure to a recorded off-axis electron hologram of
five-layer-thick WSe$_{2}$, absolute scale agreement between
experiment and simulation is achieved, which is limited
primarily by the experimental recording noise. The automated
procedure developed in this work is fast and computationally
cheap. In comparison to previous manual optimizations, it is
less prone to human error and bias. This work represents a
significant advance for quantitative electron microscopy in
general, as the procedure is not limited to off-axis
electron holography, but can also be applied to HRTEM and
other techniques.},
cin = {PGI-5 / ER-C-1},
cid = {I:(DE-Juel1)PGI-5-20110106 / I:(DE-Juel1)ER-C-1-20170209},
pnm = {143 - Controlling Configuration-Based Phenomena (POF3-143)},
pid = {G:(DE-HGF)POF3-143},
typ = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
url = {https://juser.fz-juelich.de/record/860248},
}