@article{47982, abstract = {{Spontaneous Raman spectroscopy (SR) is a versatile method for analysis and visualization of ferroelectric crystal structures, including domain walls. Nevertheless, the necessary acquisition time makes SR impractical for in situ analysis and large scale imaging. In this work, we introduce broadband coherent anti-Stokes Raman spectroscopy (B-CARS) as a high-speed alternative to conventional Raman techniques and demonstrate its benefits for ferroelectric domain wall analysis. Using the example of poled lithium niobate, we compare the spectral output of both techniques in terms of domain wall signatures and imaging capabilities. We extract the Raman-like resonant part of the coherent anti-Stokes signal via a Kramers–Kronig-based phase retrieval algorithm and compare the raw and phase-retrieved signals to SR characteristics. Finally, we propose a mechanism for the observed domain wall signal strength that resembles a Čerenkov-like behavior, in close analogy to domain wall signatures obtained by second-harmonic generation imaging. We, thus, lay here the foundations for future investigations on other poled ferroelectric crystals using B-CARS.}}, author = {{Reitzig, Sven and Hempel, Franz and Ratzenberger, Julius and Hegarty, Peter A. and Amber, Zeeshan H. and Buschbeck, Robin and Rüsing, Michael and Eng, Lukas M.}}, issn = {{0003-6951}}, journal = {{Applied Physics Letters}}, keywords = {{Physics and Astronomy (miscellaneous)}}, number = {{16}}, publisher = {{AIP Publishing}}, title = {{{High-speed hyperspectral imaging of ferroelectric domain walls using broadband coherent anti-Stokes Raman scattering}}}, doi = {{10.1063/5.0086029}}, volume = {{120}}, year = {{2022}}, } @article{47986, abstract = {{Conductive domain walls (DWs) in insulating ferroelectrics have recently attracted considerable attention due to their unique topological, optical, and electronic properties, and offer potential applications such as in memory devices or rewritable circuitry. The electronic properties of DWs can be tuned by the application of strain, hence controlling the charge carrier density at DWs. In this paper, we study the influence of uniaxial stress on the conductivity of DWs in the bulk single crystal lithium niobate (LiNbO3). Using conductive atomic force microscopy, we observe a large asymmetry in the conductivity of DWs, where only negatively screened walls, so called head-to-head DWs, are becoming increasingly conductive, while positively screened, tail-to-tails DWs, show a decrease in conductivity. This asymmetry of DW conductivity agrees with our theoretical model based on the piezoelectric effect. In addition, we observed that the current in the DW increases up to an order of magnitude for smaller compressive stresses of 100 MPa. This response of DWs remained intact for multiple stress cycles over two months, opening a path for future applications.}}, author = {{Singh, Ekta and Beccard, Henrik and Amber, Zeeshan H. and Ratzenberger, Julius and Hicks, Clifford W. and Rüsing, Michael and Eng, Lukas M.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{14}}, publisher = {{American Physical Society (APS)}}, title = {{{Tuning domain wall conductivity in bulk lithium niobate by uniaxial stress}}}, doi = {{10.1103/physrevb.106.144103}}, volume = {{106}}, year = {{2022}}, } @article{47985, abstract = {{Strongly charged head-to-head domain walls that are purposely engineered along the [110] crystallographic orientation into ferroelectric BaTiO3 single crystals have been proposed as intrinsically nanoscaled two-dimensional electron gases (2DEGs) because of their significant conductivity. Here, we quantify these 2DEG properties through dedicated Hall transport measurements in van der Pauw 4-point geometry, finding the electron mobility to reach around 400 cm2 (V s)^{−1}, while the two-dimensional charge density amounts to 7 × 103 cm^{–2}. We underline the necessity to take into account the thermal and geometrical misalignment offset voltages by evaluating the Hall resistance under magnetic field sweeps; otherwise, errors of several hundred percent in the derived transport parameters can occur.}}, author = {{Beccard, Henrik and Kirbus, Benjamin and Beyreuther, Elke and Rüsing, Michael and Bednyakov, Petr and Hlinka, Jiří and Eng, Lukas M.}}, issn = {{2574-0970}}, journal = {{ACS Applied Nano Materials}}, keywords = {{General Materials Science}}, number = {{7}}, pages = {{8717--8722}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Nanoscale Conductive Sheets in Ferroelectric BaTiO3: Large Hall Electron Mobilities at Head-to-Head Domain Walls}}}, doi = {{10.1021/acsanm.2c01919}}, volume = {{5}}, year = {{2022}}, } @inproceedings{47981, author = {{Golde, Jonas and Rüsing, Michael and Kindler, Richard and Steuer, Svea and Rix, Jan and Eng, Lukas M. and Koch, Edmund}}, booktitle = {{Optical Components and Materials XIX}}, editor = {{Digonnet, Michel J. and Jiang, Shibin}}, location = {{San Francisco, California, United States}}, publisher = {{SPIE}}, title = {{{Investigation of ferroelectric domain walls in periodically-poled LiNbO3 single crystals by polarization-sensitive optical coherence tomography}}}, doi = {{10.1117/12.2608470}}, year = {{2022}}, } @article{47989, abstract = {{Thin-film materials from μm thickness down to single-atomic-layered 2D materials play a central role in many novel electronic and optical applications. Coherent, nonlinear optical (NLO) μ-spectroscopy offers insight into the local thickness, stacking order, symmetry, or electronic and vibrational properties. Thin films and 2D materials are usually supported on multi-layered substrates leading to (multi-)reflections, interference, or phase jumps at interfaces during μ-spectroscopy, which all can make the interpretation of experiments particularly challenging. The disentanglement of the influence parameters can be achieved via rigorous theoretical analysis. In this work, we compare two self-developed modeling approaches, a semi-analytical and a fully vectorial model, to experiments carried out in thin-film geometry for two archetypal NLO processes, second-harmonic and third-harmonic generation. In particular, we demonstrate that thin-film interference and phase matching do heavily influence the signal strength. Furthermore, we work out key differences between three and four photon processes, such as the role of the Gouy-phase shift and the focal position. Last, we can show that a relatively simple semi-analytical model, despite its limitations, is able to accurately describe experiments at a significantly lower computational cost as compared to a full vectorial modeling. This study lays the groundwork for performing quantitative NLO μ-spectroscopy on thin films and 2D materials, as it identifies and quantifies the impact of the corresponding sample and setup parameters on the NLO signal, in order to distinguish them from genuine material properties.<}}, author = {{Amber, Zeeshan H. and Spychala, Kai J. and Eng, Lukas M. and Rüsing, Michael}}, issn = {{0021-8979}}, journal = {{Journal of Applied Physics}}, keywords = {{General Physics and Astronomy}}, number = {{21}}, publisher = {{AIP Publishing}}, title = {{{Nonlinear optical interactions in focused beams and nanosized structures}}}, doi = {{10.1063/5.0125926}}, volume = {{132}}, year = {{2022}}, } @article{47987, abstract = {{AbstractPure samples of colorless, air‐stable Ba(BO2OH) crystals were obtained from Ba(NO3)2 and H3BO3 under the ultra‐alkaline conditions of a KOH hydroflux at about 250 °C. The product formation depends on the water‐base molar ratio and the molar ratio of the starting materials. B(OH)3 acts as a proton donor (Brønsted acid) rather than a hydroxide acceptor (Lewis acid). Ba(BO2OH) crystallizes in the non‐centrosymmetric orthorhombic space group P212121. Hydrogen bonds connect the almost planar (BO2OH)2− anions, which are isostructural to HCO3−, into a syndiotactic chain. IR and Raman spectroscopy confirm the presence of hydroxide groups, which are involved in weak hydrogen bonds. Upon heating in air to about 450 °C, Ba(BO2OH) dehydrates to Ba2B2O5. Moreover, the non‐centrosymmetric structure of Ba(BO2OH) crystals was verified with power‐dependent confocal Second Harmonic Generation (SHG) microscopy indicating large conversion efficiencies in ambient atmosphere.}}, author = {{Li, Yuxi and Hegarty, Peter A. and Rüsing, Michael and Eng, Lukas M. and Ruck, Michael}}, issn = {{0044-2313}}, journal = {{Zeitschrift für anorganische und allgemeine Chemie}}, keywords = {{Inorganic Chemistry}}, number = {{21}}, publisher = {{Wiley}}, title = {{{Ba(BO2OH) – A Monoprotonated Monoborate from Hydroflux Showing Intense Second Harmonic Generation}}}, doi = {{10.1002/zaac.202200193}}, volume = {{648}}, year = {{2022}}, } @article{47988, abstract = {{Second harmonic (SH) microscopy represents a powerful tool for the investigation of crystalline systems, such as ferroelectrics and their domain walls (DWs). Under the condition of normal dispersion, i.e., the refractive index at the SH wavelength is larger as compared to the refractive index at the fundamental wavelength, n(2ω)>n(ω), bulk crystals will generate no SH signal. Should the bulk, however, contain DWs, an appreciable SH signal will still be detectable at the location of DWs stemming from the Čerenkov mechanism. In this work, we demonstrate both how SH signals are generated in bulk media and how the Čerenkov mechanism can be inhibited by using anomalous dispersion, i.e., n(ω)The concept of ‘ornamental constellations’ introduced in the following article highlights the structural relationships of decorative elements and miscellaneous content in magazines and the importance of the reader’s perspective for their interpretation. ‘Ornamental constellations’ are considered one of the most important media devices of emerging aesthetic capitalism, as they produce economies of attention and affect and establish a visual connection between the basic concept of a magazine, its individual contributions, and the readership addressed, thus promoting a specific aesthetic lifestyle. Their respective staging value is illustrated by analysing two complementary magazines and their constellation techniques: the elitist art magazine Blätter für die Kunst with its ‘strategic arrangement’ of literary and programmatic contributions and the creation of ‘resonances’ between them and the popular sports and society magazine Sport im Bild with its hybridizing flow of texts, images, and advertisements. Despite all the differences, it becomes clear that these are two quite compatible projects within the framework of an emerging aesthetic capitalism: whereas the Blätter für die Kunst staged and materialized the idea of pure art as an exclusive aesthetic lifestyle, the Sport im Bild made the desired aesthetic way of life also attainable by non-artists (with enough money) by associating it with the idea of an aesthetic capitalism.}}, author = {{Gretz, Daniela and Krause, Marcus}}, issn = {{2506-6587}}, journal = {{Periodical Formats in the Market}}, keywords = {{General Medicine}}, number = {{2}}, publisher = {{Ghent University}}, title = {{{From Pure Art to Sheer Luxury: Magazines as Ornamental Constellations and the Emergence of Aesthetic Capitalism in the Early Twentieth Century}}}, doi = {{10.21825/jeps.84789}}, volume = {{7}}, year = {{2022}}, } @article{33373, author = {{Hahn, Charlotte Anna and Mindt, Ilka}}, issn = {{0947-0034}}, journal = {{Anglistik}}, keywords = {{General Medicine}}, number = {{2}}, pages = {{11--14}}, publisher = {{Universitatverlag WINTER Heidelberg}}, title = {{{Introduction: English Linguistics, Learners and the Classroom}}}, doi = {{10.33675/angl/2022/2/5}}, volume = {{33}}, year = {{2022}}, } @inbook{48050, author = {{Gretz, Daniela}}, booktitle = {{Kellers Erzählen}}, publisher = {{De Gruyter}}, title = {{{Aufwärtsstreben als Niedergang oder Variationen des Immergleichen. Zur Ästhetik der Serialität in Gottfried Kellers "Martin Salander" in der "Deutschen Rundschau"}}}, doi = {{10.1515/9783110722819-014}}, year = {{2022}}, } @inbook{48049, author = {{Gretz, Daniela}}, booktitle = {{Fontanes Medien}}, isbn = {{9783110733235}}, publisher = {{De Gruyter}}, title = {{{Medieneffekte und -reflexionen im Erstdruck von Theodor Fontanes "Stechlin" in "Über Land und Meer"}}}, doi = {{10.1515/9783110733235-017}}, year = {{2022}}, } @misc{48017, author = {{Albers, Timm and Hoeft, Maike and Abendroth, Sonja and Meusel, Sarah}}, title = {{{Ein Blick auf: Verstetigung und Transfer im Bundesprogramm „Kita-Einstieg: Brücken bauen in frühe Bildung“}}}, year = {{2022}}, } @misc{48016, author = {{Abendroth, Sonja and Hoeft, Maike and Meusel, Sarah}}, title = {{{Erkenntnisse zu Verstetigung und Transfer im Bundesprogramm "Kita-Einstieg: Brücken bauen in frühe Bildung"}}}, year = {{2022}}, } @unpublished{34079, abstract = {{Data collection and aggregation by online services happens to an extent that is often beyond awareness and comprehension of its users. Transparency tools become crucial to inform people, though it is unclear how well they work. To investigate this matter, we conducted a user study focusing on Facebook, which has recently released the "Off-Facebook Activity" transparency dashboard that informs about personal data collection from third parties. We exposed a group of n = 100 participants to the dashboard and surveyed their level of awareness and reactions to understand how transparency impacts users' privacy attitudes and intended behavior. Our participants were surprised about the massive amount of collected data, became significantly less comfortable with data collection, and more likely to take protective measures. Collaterally, we observed that current consent schemes are inadequate. Based on the survey findings, we make recommendations for more usable transparency and highlight the need to raise awareness about transparency tools and to provide easily actionable privacy controls.}}, author = {{Arias Cabarcos, Patricia and Khalili, Saina and Strufe, Thorsten}}, booktitle = {{arXiv:2209.08048}}, title = {{{'Surprised, Shocked, Worried': User Reactions to Facebook Data Collection from Third Parties}}}, year = {{2022}}, }