Strong Optical Coupling of Lattice Resonances in a Top-down Fabricated Hybrid Metal-Dielectric Al/Si/Ge Metasurface

Optical metasurfaces enable the manipulation of the light-matter interaction in ultrathin layers. Compared with their metal or dielectric counterparts, hybrid metasurfaces resulting from the combination of dielectric and metallic nanostructures can offer increased possibilities for interactions between modes present in the system. Here, we investigate the interaction between lattice resonances in a hybrid metal-dielectric metasurface obtained from a single-step nanofabrication process. Finite-difference time domain simulations show the avoided crossing of the modes appearing in the wavelength-dependent absorptance inside the Ge upon variations in a selected geometry parameter as evidence for strong optical coupling. We find good agreement between the measured and simulated absorptance and reflectance spectra. Our metasurface design can be easily incorporated into a top-down optoelectronic device fabrication process with possible applications ranging from on-chip spectroscopy to sensing.

Chemical and Morphological Characterization of Magnetron Sputtered at Different Bias Voltages Cr-Al-C Coatings

MAX phases (M = transition metal, A = A-group element, and X = C/N) are of special interest because they possess a unique combination of the advantages of both metals and ceramics. Most attention is attracted to the ternary carbide Cr₂AlC because of its excellent high-temperature oxidation, as well as hot corrosion resistance. Despite lots of publications, up to now the influence of bias voltage on the chemical bonding structure, surface morphology, and mechanical properties of the film is still not well understood. In the current study, Cr-Al-C films were deposited on silicon wafers (100) and Inconel 718 super alloy by dc magnetron sputtering with different substrate bias voltages and investigated using Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), and nanoindentation. Transmission Electron Microscopy (TEM) was used to analyze the correlation between the growth of the films and the coating microstructure. The XPS results confirm the presence of Cr₂AlC MAX phase due to a negative shift of 0.6–0.9 eV of the Al2p to pure aluminum carbide peak. The XRD results reveal the presence of Cr₂AlC MAX Phase and carbide phases, as well as intermetallic AlCr₂. The film thickness decreases from 8.95 to 6.98 µm with increasing bias voltage. The coatings deposited at 90 V exhibit the lowest roughness (33 nm) and granular size (76 nm) combined with the highest hardness (15.9 GPa). The ratio of Al carbide to carbide-like carbon state changes from 0.12 to 0.22 and correlates with the mechanical properties of the coatings. TEM confirms the columnar structure, with a nanocrystalline substructure, of the films.

Genesis of femtosecond-induced nanostructures on solid surfaces

The start and evolution of the formation of laser-induced periodic surface structures (LIPSS, ripples) are investigated. The important role of irradiation dose (fluence×number of pulses) for the properties of the generated structures is demonstrated. It is shown how, with an increasing dose, the structures evolve from random surface modification to regular sub-wavelength ripples, then coalesce to broader LIPSS and finally form more complex shapes when ablation produces deep craters. First experiments are presented following this evolution in one single irradiated spot.

Vergleich von zwei Plasma-Gewinnungssystemen beim Pferd

Gegenstand und Ziel: Vergleich zweier kommerziell erhältlicher Plasma-Gewinnungssysteme, die nach dem Sedimentationsprinzip arbeiten, hinsichtlich Qualität des gewonnenen Plasmas und Funktionalität bezogen auf die Tierart Pferd. Material und Methoden: Folgende Gewinnungssysteme wurden verglichen: System 1 (S1): Baxter Fenwal®, Maurepas, Frankreich, System 2 (S2): „Plasma Collection Kit“, Arnolds, Shropshire UK. Die Blutentnahme wurde in zufälliger Reihenfolge bei denselben fünf Warmblutpferden durchgeführt. Im Anschluss erfolgte die Herstellung von Plasma. Festgehalten wurden die Dauer der Blutentnahme, das Gewicht des gewonnenen Plasmas sowie Erythrozytenverunreinigung und Bakteriengehalt des Plasmas. Weitere Vergleichsparameter waren Kosten und Anwenderfreundlichkeit. Ergebnisse: Methodisch bedingt ergab sich für System 1 eine kürzere Dauer der Blutentnahme sowie eine geringere Menge gewonnenen Plasmas. Der Erythrozytengehalt betrug 0,11 ± 0,02 T/l für System 1 und 0,18 ± 0,04 T/l für System 2. In einer der mit System 1 gewonnenen Plasmaproben ließ sich ein geringgradiger Keimgehalt nachweisen. Schlussfolgerung: Beide Systeme eignen sich grundsätzlich zur Gewinnung von Plasma. Klinische Relevanz: Die relativ kurze Entnahmedauer bei Verwendung von System 1 führt zu einer guten Duldung durch die Pferde. Allerdings ist das maximal erhältliche Plasmavolumen pro Entnahmevorgang verglichen mit System 2 deutlich geringer.