Characterization of SiGe thin films using a laboratory X-ray instrument

The technique of reciprocal space mapping using X-rays is a recognized tool for the nondestructive characterization of epitaxial films. X-ray scattering from epitaxial Si0.4Ge0.6 films on Si(100) substrates using a laboratory X-ray source was investigated. It is shown that a laboratory source with a rotating anode makes it possible to investigate the material parameters of the super-thin 2–6 nm layers. For another set of partially relaxed layers, 50–200 nm thick, it is shown that from a high-resolution reciprocal space map, conditioned from diffuse scattering on dislocations, it is possible to determine quantitatively from the shape of a diffraction peak (possessing no thickness fringes) additional parameters such as misfit dislocation density and layer thickness as well as concentration and relaxation

A Novel Inexpensive Camera-based Photoelectric Barrier System for Accurate Flying Sprint Time Measurement

Electronic photoelectric barriers are established devices to time subjects in experiments or athletes in sports. The systems are reliable and precise, but also expensive. We propose a novel, affordable photoelectric barrier system based on consumer grade camera hardware and show how to build such a system with common electronic components and a smartphone. In two experiments with track and field athletes, we show that our novel system has similar accuracy than a professional photoelectric barrier system, but for a fraction of the costs.:1. Introduction 1.1 Motivation 1.2 Commercial Photoelectric Barriers 1.3 Image-based Change Detection 1.4 Existing Camera-based Systems 2. Novel Photoelectric Virtual Barriers System 2.1 Virtual Image-based Photoelectric Barriers 2.2 Mobile Image-based Photoelectric Virtual Barrier System 3. Experiments 4. Conclusion & Future Wor

Psychologie, Öffentlichkeit und Alltagsverständnis

Die Probleme, welche Menschen im Alltag beschäftigen, decken sich nur äußerst wenig mit den Themen und Problemstellungen der akademischen Psychologie. Umgekehrt kann die Psychologie nur sehr schwer die Relevanz ihrer Forschungsergebnisse für die lebenspraktischen Probleme im Alltag geltend machen. Im Beitrag werden einige Gründe für die besonderen Vermittlungsschwierigkeiten der Psychologen benannt. Die Überlegungen beziehen sich auf den klinischen, insbesondere psychiatrischen Bereich. Dabei wird auch auf die in den USA zu beobachtende, zunehmende Biologisierung klinischer Problemstellungen eingegangen. Alternativ dazu wird ein Diskursmodell (sog. Psychoseseminare) vorgestellt. Dabei wird im Trialog zwischen Psychoseerfahrenen, Angehörigen und Professionellen das subjektive Erleben der Psychoseerfahrenen thematisiert und darauf aufbauend der offene Austausch von Konflikten zwischen den Beteiligten gefördert

A Hands-On Guide to Shear Force Mixing of Single-Walled Carbon Nanotubes with Conjugated Polymers

This guide provides a detailed step-by-step procedure for the dispersion of (6,5) single-walled carbon nanotubes by shear force mixing with the conjugated polymer PFO-BPy in organic solvents. All processes presented here were developed in the Zaumseil group at Heidelberg University since 2015 and represent best practices to the best of our knowledge. In addition to the detailed instructions, we discuss potential pitfalls and problems, that we have encountered over eight years of operation and show how to solve them. This also includes a detailed description of how to maintain and service a shear force mixer to ensure long operation lifetime. Finally, we show how to expand our process to the dispersion other nanotube chiralities in electronic-grade quality and how to treat dispersions for subsequent processing (e.g., thin film deposition or functionalization)

Near-infrared exciton-polaritons in strongly coupled single-walled carbon nanotube microcavities

This research was financially supported by the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement No. 306298 (EN-LUMINATE) and under the European Union’s Horizon 2020 Framework Programme (FP/2014-2020)/ERC Grant Agreement No. 640012 (ABLASE), by EPSRC through the CM-DTC (EP/L015110/1) and by the Scottish Funding Council through SUPA. J.Z. thanks the Alfried Krupp von Bohlen und Halbach-Stiftung via the “Alfried Krupp Förderpreis für junge Hochschullehrer” for general support.Exciton-polaritons form upon strong coupling between electronic excitations of a material and photonic states of a surrounding microcavity. In organic semiconductors the special nature of excited states leads to particularly strong coupling and facilitates condensation of exciton-polaritons at room temperature, which may lead to electrically pumped organic polariton lasers. However, charge carrier mobility and photo-stability in currently used materials is limited and exciton-polariton emission so far has been restricted to visible wavelengths. Here, we demonstrate strong light-matter coupling in the near infrared using single-walled carbon nanotubes (SWCNTs) in a polymer matrix in a planar metal-clad cavity. By exploiting the exceptional oscillator strength and sharp excitonic transition of (6,5) SWCNTs, we achieve large Rabi splitting (> 110 meV), efficient polariton relaxation and narrow band emission (< 15 meV). Given their high charge carrier mobility and excellent photostability, SWCNTs represent a promising new avenue towards practical exciton-polariton devices operating at telecommunication wavelengths. Publisher PDFPublisher PDFPeer reviewe

Tuning Electroluminescence from Functionalized SWCNT Networks further into the Near-Infrared

Near-infrared electroluminescence from carbon-based emitters, especially in the second biological window (NIR-II) or at telecommunication wavelengths, is difficult to achieve. Single-walled carbon nanotubes (SWCNTs) have been proposed as a possible solution due to their tunable and narrowband emission in the near-infrared and high charge carrier mobilities. Furthermore, the covalent functionalization of SWCNTs with a controlled number of luminescent sp$^{3}$ defects leads to even more red-shifted photoluminescence with enhanced quantum yields. Here, we demonstrate that by tailoring the binding configuration of the introduced sp$^{3}$ defects and hence tuning their optical trap depth we can generate emission from polymer-sorted (6,5) and (7,5) nanotubes that is mainly occurring in the telecommunication O-band (1260-1360 nm). Networks of these functionalized nanotubes are integrated in ambipolar, light-emitting field-effect transistors to yield the corresponding narrowband near-infrared electroluminescence. Further investigation of the current and carrier density-dependent electro- and photoluminescence spectra enable insights into the impact of different sp$^{3}$ defects on charge transport in networks of functionalized SWCNTs

Impact of Dielectric Environment on Trion Emission from Single-Walled Carbon Nanotube Networks

Trions are charged excitons that form upon optical or electrical excitation of low-dimensional semiconductors in the presence of charge carriers (holes or electrons). Trion emission from semiconducting single-walled carbon nanotubes (SWCNTs) occurs in the near-infrared and at lower energies compared to the respective exciton. It can be used as an indicator for the presence of excess charge carriers in SWCNT samples and devices. Both excitons and trions are highly sensitive to the surrounding dielectric medium of the nanotubes, having an impact on their application in optoelectronic devices. Here, the influence of different dielectric materials on exciton and trion emission from electrostatically doped networks of polymer-sorted (6,5) SWCNTs in top-gate field-effect transistors is investigated. The observed differences of trion and exciton emission energies and intensities for hole and electron accumulation cannot be explained with the polarizability or screening characteristics of the different dielectric materials, but they show a clear dependence on the charge trapping properties of the dielectrics. Charge localization (trapping of holes or electrons by the dielectric) reduces exciton quenching, emission blue-shift and trion formation. Based on the observed carrier type and dielectric material dependent variations, the ratio of trion to exciton emission and the exciton blue-shift are not suitable as quantitative metrics for doping levels of carbon nanotubes

A Rapidly Stabilizing Water-Gated Field-Effect Transistor Based on Printed Single-Walled Carbon Nanotubes for Biosensing Applications

Biosensors are expected to revolutionize disease management through provision of low-cost diagnostic platforms for molecular and pathogenic detection with high sensitivity and short response time. In this context, there has been an ever-increasing interest in using electrolyte-gated field-effect transistors (EG-FETs) for biosensing applications owing to their expanding potential of being employed for label-free detection of a broad range of biomarkers with high selectivity and sensitivity while operating at sub-volt working potentials. Although organic semiconductors have been widely utilized as the channel in EGFETs, primarily due to their compatibility with cost-effective low-temperature solution-processing fabrication techniques, alternative carbon-based platforms have the potential to provide similar advantages with improved electronic performances. Here, we propose the use of inkjet-printed polymer-wrapped monochiral singlewalled carbon nanotubes (s-SWCNTs) for the channel of EG-FETs in an aqueous environment. In particular, we show that our EG-CNTFETs require only an hour of stabilization before producing a highly stable response suitable for biosensing, with a drastic time reduction with respect to the most exploited organic semiconductor for biosensors. As a proof-of-principle, we successfully employed our water-gated device to detect the well-known biotin-streptavidin binding event

Multi-Physics and Multi-Scale Interactions in High-Intensity Turbulent Premixed Reacting Flows

Improved understanding of the coupled interactions between advective, diffusive, thermodynamic, and chemical processes is required for the development of more accurate models of subgrid-scale (SGS) dynamics in large eddy simulations (LES) of high-intensity turbulent premixed reacting flows. These interactions can be leading-order dynamical processes that may violate principal assumptions of classical theories of non-reacting turbulence and laminar combustion. Processes that occur at subgrid scales but that affect the resolved scales of simulations are particularly important to understand, since they can only be accounted for by SGS modeling. For example, kinetic energy transfer in premixed reacting flows may dominantly occur from small to large scales as a result of both transient and statistically-stationary chemical heat release, contrary to the net transfer of energy from large to small scales found in many non-reacting flows. Turbulence-chemistry interactions, including spontaneous autoignition and deflagration-to-detonation transition of turbulent reacting flows, play a significant role in the reliability and sustainability of high-speed combustion systems such as scramjet engines, as well as air-breathing and rocket-mode pulsed and rotating detonation engines. In high-speed reacting flows, defined by turbulent velocity fluctuations larger than the relevant laminar flame speed, the reactants are often partially or fully premixed and the turbulence can be nonlinearly compressible, wherein turbulent velocity fluctuations directly generate localized shock waves known as eddy shocklets. In order to develop improved SGS turbulence models that can accurately realize turbulence-chemistry interaction phenomena in high-speed turbulent premixed reacting flows, the coupled, nonlinear effects of both premixed flames on turbulent advection and of turbulent advection on premixed flames need to be dynamically quantified and explained. This dissertation examines kinetic energy transfer by advective processes in a turbulent premixed flame in spectral space using data from a direct numerical simulation of a statistically-stationary turbulent premixed flame. Two-dimensional turbulence kinetic energy spectra conditioned on the planar-averaged reactant mass fraction are computed through the flame brush and variations in the spectra are connected to terms in the spectral kinetic energy transport equation. Conditional kinetic energy spectra show that turbulent small-scale motions are suppressed in the burnt combustion products, while the energy content of the mean flow increases. An analysis of spectral kinetic energy transfer further indicates that, contrary to the net down-scale transfer of energy found in the unburnt reactants, advective processes transfer energy from small to large scales in the flame brush close to the products. Triadic interactions calculated through the flame brush show that this net up-scale transfer of energy occurs primarily at spatial scales near the laminar flame thermal width. The present results thus indicate that advective processes in premixed reacting flows contribute to energy backscatter near the scale of the flame. This dissertation also examines the effects of compressible turbulence thermodynamics on the modes of reaction front propagation under autoignitive conditions, and particularly the conditions required for the localized direct initiation of, or transition to, detonations. Direct numerical simulations of homogeneous isotropic turbulence with both single-step and detailed chemical kinetics models are performed at several target turbulence Mach numbers, Mat, spanning a range of turbulence compressibility regimes. Increasingly broad probability distributions of temperature, dilatation, fuel mass-fraction, and scalar reaction rate are found as Mat increases, indicating that intermittency of quantities relevant to reaction initiation</p