University of Siegen
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Publication Access status: Open Access , X-ray diffraction with micrometre spatial resolution for highly absorbing samplesX-ray diffraction with high spatial resolution is commonly used to characterize (poly)crystalline samples with, for example, respect to local strain, residual stress, grain boundaries and texture. However, the investigation of highly absorbing samples or the simultaneous assessment of high-Z materials by X-ray fluorescence have been limited due to the utilization of low photon energies. Here, a goniometer-based setup implemented at the P06 beamline of PETRA III that allows for micrometre spatial resolution with a photon energy of 35 keV and above is reported. A highly focused beam was achieved by using compound refractive lenses, and high-precision sample manipulation was enabled by a goniometer that allows up to 5D scans (three rotations and two translations). As experimental examples, the determination of local strain variations in martensitic steel samples with micrometre spatial resolution, as well as the simultaneous elemental distribution for high-Z materials in a thin-film solar cell, are demonstrated. The proposed approach allows users from the materialsscience community to determine micro-structural properties even in highly absorbing samples.Source Type:Article3 10 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , In situ coupling applied voltage and synchrotron radiation: operando characterization of transistorsA compact voltage application setup has been developed for in situ electrical testing of organic field effect transistors in combination with X-ray scattering studies at a synchrotron beamlines. Challenges faced during real condition in-operando test of newly developed OFETs originated an idea of creation of a new setup which excludes number of factors that make experiments complicated. The application of the setup is demonstrated on a prototype of an organic transistors based on α,ω-dihexyl-α-quaterthiophene molecules. The new setup allows to monitor material structural changes by X-ray scattering under applied voltage conditions and their direct correlations. The versatile setup eliminates possible shadowing effects and short circuits due to misalignment of the contacts. The electrical stability of the prototypes was characterized by the application of different voltage values. Corresponding structural changes were monitored by grazing X-ray scattering technique before, during and after the voltage was applied. The selected oligothiophene material with proved transistor properties shows high stability and directional anisotropy under applied voltage conditions. Thanks to a compact and flexible design of the setup, different type of small dimension devices could be studied under external voltage conditions at various synchrotron beamlines.Source Type:Article2 12 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Symmetries in quantum networks lead to no-go theorems for entanglement distribution and to verification techniquesQuantum networks are promising tools for the implementation of long-range quantum communication. The characterization of quantum correlations in networks and their usefulness for information processing is therefore central for the progress of the field, but so far only results for small basic network structures or pure quantum states are known. Here we show that symmetries provide a versatile tool for the analysis of correlations in quantum networks. We provide an analytical approach to characterize correlations in large network structures with arbitrary topologies. As examples, we show that entangled quantum states with a bosonic or fermionic symmetry can not be generated in networks; moreover, cluster and graph states are not accessible. Our methods can be used to design certification methods for the functionality of specific links in a network and have implications for the design of future network structures.Source Type:Article1 7 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , Biosensing with a scanning planar Yagi-Uda antennaWe investigate a model bioassay in a liquid environment using a z-scanning planar Yagi-Uda antenna, focusing on the fluorescence collection enhancement of ATTO-647N dye conjugated to DNA (deoxyribonucleic acid) molecules. The antenna changes the excitation and the decay rates and, more importantly, the emission pattern of ATTO-647N, resulting in a narrow emission angle (41°) and improved collection efficiency. We efficiently detect immobilized fluorescently-labeled DNA molecules, originating from solutions with DNA concentrations down to 1 nM. In practice, this corresponds to an ensemble of fewer than 10 ATTO-647N labeled DNA molecules in the focal area. Even though we use only one type of biomolecule and one immobilization technique to establish the procedure, our method is versatile and applicable to any immobilized, dye-labeled biomolecule in a transparent solid, air, or liquid environment.Source Type:Article2 8 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , F-number and focal length of light field systems: a comparative study of field of view, light efficiency, signal to noise ratio, and depth of field(2022)The paper discusses the light efficiency and signal-to-noise ratio (SNR) of light field imaging systems in comparison to classical 2D imaging, which necessitates the definition of focal length and f-number. A comparison framework between 2D imaging and arbitrary light field imaging systems is developed and exemplified for the kaleidoscopic and the afocal light field imaging architectures. Since the f-number, in addition to the light efficiency of the system, is conceptually linked to the depth-of-field, an appropriate depth-of-field interpretation for light field systems is discussed as well.Source Type:Article7 7 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Open Access , State-independent quantum contextuality with projectors of nonunit rankVirtually all of the analysis of quantum contextuality is restricted to the case where events are represented by rank-one projectors. This restriction is arbitrary and not motivated by physical considerations. We show here that loosening the rank constraint opens a new realm of quantum contextuality and we demonstrate that state-independent contextuality (SIC) can even require projectors of nonunit rank. This enables the possibility of SIC with less than 13 projectors, which is the established minimum for the case of rank one. We prove that for any rank, at least 9 projectors are required. Furthermore, in an exhaustive numerical search we find that 13 projectors are also minimal for the cases where all projectors are uniformly of rank two or uniformly of rank three.Source Type:Article300 225
