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Dissertation
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Validation of a generalized model for the description of polycrystalline exchange-biased magnetic thin films
(2022)
Applications based on nano- and microscaled systems have become indispensable in many aspects in everyday life, industry, research and medicine. In this regard, thin film technology plays a crucial role with the physical properties of solids changing significantly when they are reduced to thin layers with thicknesses in the nanometer range. In this regime, a solid’s microstructure as well as boundary and surface effects start to dominate. A prominent example is the exchange bias effect, which results due to the ...
Dissertation
Chiral recognition in the gas phase using femtosecond to nanosecond photoelectron circular dichroism
(2020-05)
Diese Arbeit konzentriert sich auf die chirale Erkennung in der Gasphase unter Verwendung der resonant verstärkten Multi-Photonen-Ionisation. Gasphasentechniken bieten die Möglichkeit, die Chiralität von Molekülen innerhalb einer nahezu interaktionsfreien Umgebung zu untersuchen. Photoionisation von chiralen Molekülen mit zirkular polarisiertem Licht führt zu einer Asymmetrie in der Photoelektronenemission bezüglich der Ausbreitungsrichtung des ionisierenden Lichts. Diese Asymmetrie ist bekannt als Photoelektronenz ...
Dissertation
A new perspective to strongly-interacting lattice fermions in the framework of density functional theory
(2020)
Die in dieser Arbeit formulierte Theorie betrachtet das Vielteilchenproblem wechselwirkender Fermionen auf einem Gitter aus einem neuen Blickwinkel.
Dissertation
High temperature-stable InGaAs QDs for the monolithic integration in external-cavity surface-emitting lasers
(2021)
Optically pumped vertical external-cavity surface-emitting lasers (VECSELs), also called semiconductor disk lasers (SDLs), benefit from the flexibility and versatility of the semiconductor material. With a simple cavity layout, fundamental transverse mode operation with a circular output beam and high beam quality is possible. They have excellent heat-sink properties and only require inexpensive multimode diode lasers for pumping. The complete VECSEL structure is only a few micrometers thick which leads to a strong ...
Dissertation
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Analysis of near-substrate magnetic particle transport for Lab-on-a-chip applications: stray field modulations, influence of particle properties and three-dimensional trajectories
(2022)
Die Entwicklung schneller und zuverlässiger Diagnostik ist ein wichtiges Ziel für die Früherkennung von Krankheiten. Standardisierte Labormethoden sind heutzutage meist langsam und mit hohen Kosten verbunden. Innerhalb der Lab-on-a-chip (LOC)-Technologie kann der Nachweis eines pathogenen Organismus auf die Größe eines kleinen Chips miniaturisiert werden, indem magnetische Partikel als Fängerobjekte integriert werden. Die Kombination einer statischen Magnetfeldlandschaft (MFL) mit zeitlich variierenden externen ...
Dissertation
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Magnetic Textures and Magnetization Reversal Processes in Arrays of Ferromagnetic and Exchange-Biased Hollow Hemispheres
(2022)
The main objective of this thesis is to investigate hemispherical caps prepared by thin film deposition of magnetic material compositions on top of nano- and micrometer sized silica spheres. When compared to flat magnetic discs, these microcaps differ in their magnetic properties due to the curved and therefore three-dimensional shape. However, under certain conditions, both microstructures have previously been proven to express the famous magnetic vortex texture because of the confinement into a circular shape. ...
Dissertation
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Electronic Theory of the Magnetic Order, Anisotropy and Reversal Processes in Rolled-Up Stripes and Thin Films
(2022)
A comprehensive multiscale approach consisting of a combination of state of the art, first principles quantum theory and the flexible statistical methodologies of complex systems is applied in order to achieve a detailed microscopic understanding of the magnetic properties of rolled-up transition-metal [TM] ultrathin films and stripes. A quantum electronic investigations of the effective interactions between the local magnetic moments is performed as a function of composition and rolling radius R including the limit ...
Dissertation
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Investigations on Diamond Thin Films as Implant Coating and Biosensing Platform
(2021)
Diamond is researched in biological context for decades. Fundamental research has established diamond as a material that combines a pronounced compatibility with biological entities and resilience against even the harshest chemical and physical conditions. The present dissertation strives to improve the abilities of diamond in this matter even further by utilizing methods of nanostructuring and biochemical functionalization. Numerous characterization methods are used to monitor each step in detail and to evaluate the ...
Dissertation
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Optimal Control of Quantum Information Tasks in Open Quantum Systems
(2020-07-30)
Every quantum system inevitably interacts with its environment. This is a fundamental requirement that allows us to control, measure and, in general, interact with quantum systems. In that respect, a quantum system's openness can be interpreted as prerequisite that enables quantum technologies in the first place. The latter are built to harness the intrinsic quantum mechanical behavior of quantum devices in order to build new, powerful technologies. However, a quantum system's openness also causes it to interact ...
Dissertation
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Development of Carrier-Envelope-Phase-Stabilized, mJ-Class Laser Sources Generating Intense, Few-Cycle Laser Pulses
(2020-05-19)
Over a decade ago the frontiers of ultrashort physics and nonlinear optics have reached the attosecond timescale ($1 as = 10 ^ {-18} s$) . Currently, in order to generate isolated attosecond pulses, an intense femtosecond pulse is focused in a jet of a noble gas. Given the sufficient intensity, this leads to high harmonic generation (HHG), which can be filtered (gated) to create a single isolated attosecond pulse. The laser source for the driver pulses has to fulfill two requirements: the pulses need to be limited ...