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@PHDTHESIS{Flatten:875393,
author = {Flatten, Tim},
title = {{D}irect measurement of anisotropic resistivity in thin
films using a 4-probe {STM}},
volume = {213},
school = {Universität Köln},
type = {Dr.},
address = {Jülich},
publisher = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
reportid = {FZJ-2020-02002},
isbn = {978-3-95806-460-7},
series = {Schriften des Forschungszentrums Jülich. Reihe
Schlüsseltechnologien / Key Technologies},
pages = {VIII, 129 S.},
year = {2020},
note = {Universität Köln, 2019},
abstract = {Four-point electronic transport measurements have proven to
be the best choice for determining the resistance of a
sample and thus the resistivity properties, because the
contact resistances are negligibly small. Various techniques
using the 4-point method have been explored, whereby the
4-probe scanning tunneling microscope is a powerful
experimental tool to measure the sample resistance on small
length scales including the possibility to vary probe
spacings. Nowadays, layered materials are in the focus of
interest due to their intriguing fundamental properties and
their high potential in a variety of applications. In
addition, they are also possible parenting materials for
so-called 2D materials due to a typically weaker chemical
bonding along one crystalline axis. Beside the famous
parent-materials such as graphite, hexagonal boron nitride,
and transition metal dichalcogenides, there is a further
class of layered materials, namely the so-called MAX phases
comprising both metal as well as ceramic properties. This
unique combination stems from a complex, anisotropic bonding
scheme that leads to an anisotropic conductivity. Growing
those layered materials as thin-film samples, they comprise
usually a bonding anisotropy perpendicular to the surface.
Thus, an anisotropy between the in-plane and out-of-plane
conductivities is expected. Such anisotropic electronic
transport properties are characterized by introducing the
resistivity as a second rank tensor. The resistivity is then
expressed by a symmetry-dependent number of independent
components that can be determined from resistance
measurements along different directions of the sample. The
in-plane resistivity components can be easily characterized
using several well-known methods, while up to now the
out-of-plane resistivity cannot be determined without any
additional sample treatment or modication, if a material can
only be prepared in thin-film form. Therefore, a novel
direct and parameter-free method is developed in this thesis
for the accurate determination of the out-of-plane
resistivity without any further treatment of the sample. A
multi-probe scanning tunneling microscope is used to carry
out 4-probe transport measurements with variable probe
spacings. The observation of the crossover from the 3D
electronic transport regime for small spacings between the
probesto the 2D regime for large spacings enables the
determination of both in-plane and perpendicular-to-plane
resistivities. After working out the analytical description
of the method, the experimental procedures for measuring
electronic transport properties witha multi-probe scanning
tunneling microscope are described, in particular the
influences of sample size and shape, surface morphology and
grain size, probe-sample contact sizeand as well as the main
experimental error sources. [...]},
cin = {PGI-6},
cid = {I:(DE-Juel1)PGI-6-20110106},
pnm = {899 - ohne Topic (POF3-899)},
pid = {G:(DE-HGF)POF3-899},
typ = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
url = {https://juser.fz-juelich.de/record/875393},
}