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Micro-Transfer printing (µTP) is a promising technique for hetero-integration of III-V materials into Si-based photonic platforms. To enhance the print yield by increasing the adhesion between the III-V material and Si or SiO2 surface, an adhesion promoter like Benzocyclobutene is typically used as interlayer. In this work, we demonstrate µTP of InP based coupons on SiO2 interlayer without any adhesive interlayer and investigate the mechanism of adhesive free bonding. Source coupons are InP-based coupon stacks on a sacrificial layer that is removed by a chemical wet etch with FeCl3. For the target we fabricated amorphous-Si waveguides on 8” wafer encapsulated by a High Density Plasma SiO2 which was planarized by a chemical mechanical polishing procedure. We used O2 plasma to activate both source and target to increase adhesion between coupon and substrate. To get a better understanding of the bonding mechanism we applied several surface characterization methods. Root mean square roughness of InP and SiO2 was measured by atomic force microscopy before and after plasma activation. The step height of the micro-transfer printed source coupon on the target wafer is estimated by optical step profiler. We used Raman peak position mappings of InP to analyze possible strain and contact angle measurements on SiO2, before and after plasma activation to observe a change in the hydrophilicity of the surface. X-ray Photoelectron Spectroscopy analysis was used to characterize the surface energy states of P2p, In3d, O1s for InP source and Si2p, O1s for SiO2 target. Our results demonstrate direct bonding of InP coupons by means of µTP without the need of a strain-compensation layer. In this way, a promising route towards Complementary Metal-Oxide-Semiconductor compatible use of µTP for the hetero-integration of InP is provided.
The MAC end-station at the ELI Beamlines facility is a multipurpose user's station for atomic, molecular, and optical sciences and coherent diffractive imaging. The technical design of the station, the available instruments, and an overview of the whole beamline have been published in Eur. Phys. J. Spec. Top. 230, 4183 (2021). Here, we address ongoing upgrades of the MAC end-station that will provide users with advanced capabilities for beam manipulation and electron/ion detection. The upgrades include (i) the installation of a beam preparation chamber in front of the MAC chamber, (ii) a magnetic bottle electron spectrometer with high collection and detection efficiency and high energy resolution, and (iii) an event-driven TPX3CAM detector for velocity map imaging spectrometer, which provides both spatial and temporal information for each pixel. We present results from the first commissioning measurements with these instruments, confirming their performance for state-of-the-art experiments in atomic, molecular, and optical sciences.
Heavy wire bonding is one of the most common interconnection technologies in manufacturing of high-power electronics. For industrial applications, the long-term reliability of these connections is crucial. Besides the selection of the wire material and the loop geometry itself, the loop forming process parameters also have an influence on the reliability of the wire bond. In this work, the influence of the backward bond head movement during wire bonding process on the quality of wire bond connections was systematically investigated and qualified by cyclic mechanical lifetime tests, surface roughness measurements of the heel area by laser confocal microscopy and static pull tests. The wire bond loops were fabricated with 300 μm aluminum H11 and H14CR wires with different hardness values. The lifetime at low frequency cycle and high frequency cycle regime was determined by means of two different mechanical cyclic test methods operating at 5 Hz and at 60 kHz respectively. The results have shown, that the surface topology of the heel region caused by the initial plastic deformation during the loop forming process has a significant effect on the wire bond failure due to heel cracking. The number of loading cycles to failure shows an inverse correlation with the degree of surface roughness in a so called wrinkling analysis in the low and high frequency cycle regime. The soft wire exhibits different lifetimes compared to the hard ones depending on the testing conditions, while a significant decrease of the lifetime is observed with >30 % reverse movement during bonding in all cases.
Der technische Fortschritt hat dazu geführt, dass die Kosten für das automatisierte Drucken von Emblemen, Anhängern sowie allgemein gedruckten Prototypen stark gefallen sind. Dies geschah insbesondere auch vor dem Hintergrund eines Wandels der Industrie hin zu einer modernen Industrie 4.0. In dieser Arbeit wird ein neuer Ansatz für das automatische 3D-Drucken eines Logos präsentiert, welches als Pixelgrafik vorliegt. Die vorgeschlagene Prozesskette erzeugt hierbei final den G-code zum Drucken. Dabei sind seitens des Users wenige Eingaben erforderlich.
The rise of Fe magnetic moment, changes in Al electronic structure and a variation of Al magnetic polarization in thin films of transition metal aluminide Fe60Al40 have been probed through the order-disorder phase transition by soft X-ray absorption spectroscopy and X-ray resonant magnetic reflectivity in the extreme ultraviolet regime. In a course of the transition induced by 20 keV Ne+ irradiation with low fluences (1014 ions·cm-2), X-ray magnetic circular dichroism spectra taken at the Fe L2,3 absorption edges at room and low temperatures revealed a pronounced increase of Fe 3d states spin-polarization. X-ray resonant magnetic reflectivity applied to the Al L2,3 and Fe M2,3 edges allowed to detect the magnetic polarization of Al atoms in the films. The changes in Al electronic structure have been seen by alteration of Al K edge X-ray absorption near edge structure. A difference in anisotropy fields for films before and after irradiation has been observed by element-specific hysteresis loops recorded at low temperatures in absorption and reflection geometries at the Fe L2,3 and M2,3 edges, respectively. An attempt to reduce the top oxide layer by an inductively coupled hydrogen plasma has shown a possibility to recover the chemically ordered phase.
Ultrafast electron dynamics drive phenomena such as photochemical reactions, catalysis, and light harvesting. To capture such dynamics in real-time, femtosecond to attosecond light sources are extensively used. However, an exact match between the excitation photon energy and a characteristic resonance is crucial. High-harmonic generation sources are advantageous in terms of pulse duration but limited in spectral tunability in the vacuum ultraviolet range. Here, we present a monochromatic femtosecond source continuously tunable around 21eV photon energy utilizing the second harmonic of an optical parametric chirped pulse amplification laser system to drive high-harmonic generation. The unique tunability of the source is verified in an experiment probing the interatomic Coulombic decay in doped He nanodroplets across the He absorption bands. Moreover, we achieved intensities sufficient for driving collective processes in multiply excited helium nanodroplets, which have been previously observed only at free electron lasers.
Optical fibers in metrology, telecommunications, sensors, manufacturing, and health science have gained massive research interest. The number of applications is increasing at a fast pace. This book aims to present a collection of recent advances in fiber optics, addressing both fundamental and industrial applications. It covers the current progress and latest breakthroughs in emergent applications of fiber optics. The book includes five chapters on recent developments in optical fiber communications and fiber sensors, as well as the design, simulation, and fabrication of novel fiber concepts.
Plasmonics includes the fundamentals of surface plasmon polaritons in metals, and its rapidly increasing applications in biochemistry, nanotechnology, optical communication, sensing, and medicine. Surface plasmon polaritons have become popular because of their ultrasensitive optical measurement capabilities, and in recent years they have also been employed for ultra-high-speed data transfer. This book presents recent advances in the broad field of plasmonics, covering not only current progress and the latest breakthroughs in emergent applications but also geometry optimizations and the fundamentals of physical interactions.
Optical and microwave waveguides have attracted much research interest in both science and industry. The number of potential applications for their use is growing rapidly. This book examines recent advances in the broad field of waveguide technology. It covers current progress and latest breakthroughs in emergent applications in photonics and microwave engineering. The book includes ten contributions on recent developments in waveguide technologies including theory, simulation, and fabrication of novel waveguide concepts as well as reviews on recent advances.
Ellipsometrically obtained spectral dependences of ordinary αxy and extra-ordinary αz extinction/attenuation coefficients within the spectral range λ = 300…980 nm of uniaxially anisotropic polytetrafluoroethylene (PTFE) films were analyzed. We considered the capabilities and specific features of the graphical representation technique for determining the contribution of Rayleigh scattering and Urbach absorption to light attenuation in the spectral range beyond fundamental absorption. It has been shown that the graphical approach enables to estimate these contributions qualitatively, semi-quantitatively or quantitatively, depending on the situation. The conclusions made using the analysis of graphical representation are confirmed by numerical solution of the inverse problem via simulation of the αxy (λ), αz (λ) experimental dependences within the framework of a best-fit procedure. Being based on both of these approaches, we have ascertained that, in the as-prepared PTFE films, the so-called anomalous light scattering (ALS) with the spectral dependence of scattering coefficient αs ≈ as λ–p (p > 4) takes place. Transformation of scattering from ALS to the Rayleigh one with p ≈ 4 due to annealing is accompanied by an increase of Urbach (subband) absorption. Both of these factors cause narrowing the dynamic range of extinction coefficient values. Both scattering and absorption coefficients are higher for the component of light polarized along the normal to the substrate as compared to the component polarized in parallel to it. The relationship between observed behavior of the scattering and absorption coefficients and the film structure has been discussed.
The two main features of the memristive devices which makes them the promising candidates for neuromorphic applications are low power consumption and CMOS compatibility. The monolithic integration of memristive devices with CMOS circuitry paves the way for in-memory computing. This chapter focuses on the factors governing the CMOS integration process. Firstly, the influence of CMOS baseline technology selection on the memristor module is briefly discussed. Secondly, the selection of metal level interconnects and their effect on the memristive device performance is explained. Further, the widely used deposition technique for the CMOS compatible memristive switching layers is presented. Finally, the implementation of the optimized process for the fabrication of the memristive module and its influence on the device performance is presented in terms of electrical characterization results.
Fabry-Pèrot (FP) interferometer sensors enable highly sensitive backward mode acoustic detection in Photoacoustic (PA) imaging. They are transparent to the excitation wavelength, can be placed directly next to the PA source, and offer a broadband frequency response and high acoustic sensitivity. PA tomography using parallelized detection requires high spatial uniformity of the optical and acoustic properties, which can be hampered by contaminations during fabrication that lead to the formation of inhomogeneities and artefacts. The quality and homogeneity of the dielectric and polymer layers have a direct effect on the maximum optical phase sensitivity, and hence acoustic sensitivity. In this study, cross-sectional images of FP sensors were obtained using focused ion beam milling and ultramicrotomy followed by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) to evaluate different fabrication methods.
Fabry-Perot (FP) sensors are typically read out using a raster scan to acquire tomographic Photoacoustic (PA) images. To speed up the recording time, wide-field illumination of the sensor in combination with a camera as detector can be used. In this study, an sCMOS camera and wavelengths around 517 nm are used to interrogate a FP sensor with a homogeneous optical thickness over a 4 cm2 aperture. The recorded time series show PA signals are acquired over the entire area of the interrogation beam. The performance of the system, such as the noise equivalent pressure, is evaluated.
Biomedical photoacoustics is usually used to image absorption-based contrast in soft tissues up to depths of several centimeters and with sub-millimeter resolution. By contrast, measuring Photoacoustic (PA) signals through hard bone tissue shows severe signal degradation due to aberration and high attenuation of high frequency acoustic signal components. This is particularly noticeable when measuring through thicker, human, skull bone. Which is the main reason why transcranial PA imaging in humans has so far proved challenging to implement. To tackle this challenge, we developed an optical resonator sensor based on a previous planar-concave design. This sensor was found to be highly suitable for measuring the low-pressure amplitude and low acoustic frequency signals that are transmitted through human cranial bone. A plano-concave optical resonator sensor was fabricated to provide high sensitivity in the acoustic frequency range of DC to around 2 MHz, a low noise equivalent pressure and a small active element size enabling it to significantly outperform conventional piezoelectric transducers when measuring PA waves transmitted through ex vivo human cranial bones.
We study the dynamics of avalanche ionization of pure helium nanodroplets activated by a weak extreme-ultraviolet (XUV) pulse and driven by an intense near-infrared (NIR) pulse. In addition to a transient enhancement of ignition of a nanoplasma at short delay times ${\sim}200$ fs, long-term activation of the nanodroplets lasting up to a few nanoseconds is observed. Molecular dynamics simulations suggest that the short-term activation is caused by the injection of seed electrons into the droplets by XUV photoemission. Long-term activation appears due to electrons remaining loosely bound to photoions which form stable 'snowball' structures in the droplets. Thus, we show that XUV irradiation can induce long-lasting changes of the strong-field optical properties of nanoparticles, potentially opening new routes to controlling avalanche-ionization phenomena in nanostructures and condensed-phase systems.
Thin polytetrafluoroethylene (PTFE) films are produced by deposition from a gas phase by two methods: electron-enhanced vacuum deposition (EVD) and EVD + low-temperature plasma (LTP). Structure, morphology, and composition of the films are studied by IR spectroscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. They are close to the structure of bulk PTFE. The roughness of the films’ surface is changed with gas pressure and LTP power variations. Films are transparent from UV to near-infrared regions. Refractive and extinction indices and their anisotropy are measured by spectral ellipsometry. They are tuned by variations of deposition conditions. Hardness and Young modulus of the films are increased if EVD + low power LTP is used for film deposition. Use of EVD + LTP also increases thermal stability of the films. Contact angle of the films corresponds to the bulk PTFE. The PTFE molecules oriented are preferentially in perpendicular direction to the substrate surface.
We have investigated the possibility to track and control correlation dynamics of valence electrons in krypton (Kr) initiated by the absorption of one extreme ultraviolet (XUV) photon. In this investigation, pump-probe experiments have been performed where monochromatized single high-harmonics at photon energies 29.6, 32.8, and 35.9 eV have been used as pump to populate different intermediate excited states. A temporally delayed near-infrared (NIR) pulse probes the population of various decay channels via the detection of Kr²⁺ ion yields and its transient profiles. We observe that by varying the NIR pulse intensity within a range from 0.3 x 10¹³ to 2.6 x 10¹³ W cm⁻², the shape of the Kr²+ transient profile changes significantly. We show that by varying the intensity of the NIR pulse, it is possible—(i) to control the ratio between sequential and non-sequential double ionization of Kr; (ii) to selectively probe quantum beating oscillations between Kr+* satellite states that are coherently excited within the bandwidth of the XUV pulse; and (iii) to specifically probe the relaxation dynamics of doubly excited (Kr**) decay channels. Our studies show that the contribution of different ionization and decay channels (i)–(iii) can be altered by the NIR pulse intensity, thus demonstrating an efficient way to control the ionization dynamics in rare gas atoms.
Silicon photonic micro-ring resonators (MRR) developed on the silicon-on-insulator (SOI) platform, owing to their high sensitivity and small footprint, show great potential for many chemical and biological sensing applications such as label-free detection in environmental monitoring, biomedical engineering, and food analysis. In this tutorial, we provide the theoretical background and give design guidelines for SOI-based MRR as well as examples of surface functionalization procedures for label-free detection of molecules.
After introducing the advantages and perspectives of MRR, fundamentals of MRR are described in detail, followed by an introduction to the fabrication methods, which are based on a complementary metal-oxide semiconductor (CMOS) technology. Optimization of MRR for chemical and biological sensing is provided, with special emphasis on the optimization of waveguide geometry. At this point, the difference between chemical bulk sensing and label-free surface sensing is explained, and definitions like waveguide sensitivity, ring sensitivity, overall sensitivity as well as the limit of detection (LoD) of MRR are introduced. Further, we show and explain chemical bulk sensing of sodium chloride (NaCl) in water and provide a recipe for label-free surface sensing.
From Lab-on-chip to Lab-in-App: Challenges towards silicon photonic biosensors product developments
(2022)
This work presents and evaluates different approaches of integrated optical sensors based on photonic integrated circuit (PIC) technologies for refractive index sensing. Bottlenecks in the fabrication flow towards an applicable system are discussed that hinder a cost-effective mass-production for disposable sensor chips. As sensor device, a waveguide coupled micro-ring based approach is chosen which is manufactured in an 8” wafer level process. We will show that the co-integration with a reproducible, scalable and low-cost microfluidic interface is the main challenge which needs to be overcome for future application of silicon technology based PIC sensor chips.
3D printed rotor blades for a research wind turbine: Aerodynamic and structural design and testing
(2022)
This study combines the design, the 3D printing and the testing of a small 3-bladed wind turbine rotor for research and teaching purposes. The objective is the additive manufacturing of a rotor with a radius of one meter, as an alternative to subtractive methods, such as computerized milling. The blade design is developed using freely available software packages. The aerodynamic considerations include the airfoil selection, the calculation of the blade geometry and the simulation of the ultimate load cases. The structural considerations are focussed on the printable materials, the infill structures and the retrofit of a load-carrying spar. The rotor blades are 3D printed with the BigRep One at the maker space of the TH Wildau. The structural integrity of the prototype blade is tested in terms of the ultimate root bending moments and the centrifugal forces at the HTW Berlin. The aerodynamic run-up tests are performed at the large wind tunnel of the TU Berlin measuring the power curves. The successful prototype paves the way for follow-up projects, such as open field tests and the 3D printing of larger rotor blades.
Laboratory plasmas inherently exhibit temperature and density gradients leading to complex investigations. We show that plasmas generated by laser ablation can constitute a robust exception to this. Supported by emission features not observed with other sources, we achieve plasmas of various compositions which are both uniform and in local thermodynamic equilibrium. These properties characterize an ideal radiation source opening multiple perspectives in plasma spectroscopy. The finding also constitutes a breakthrough in the analytical field as fast analyses of complex materials become possible.
Label-free direct-optical biosensors such as surface-plasmon resonance (SPR) spectroscopy has become a gold standard in biochemical analytics in centralized laboratories. Biosensors based on photonic integrated circuits (PIC) are based on the same physical sensing mechanism: evanescent field sensing. PIC-based biosensors can play an important role in healthcare, especially for point-of-care diagnostics, if challenges for a transfer from research laboratory to industrial applications can be overcome. Research is at this threshold, which presents a great opportunity for innovative on-site analyses in the health and environmental sectors. A deeper understanding of the innovative PIC technology is possible by comparing it with the well-established SPR spectroscopy. In this work, we shortly introduce both technologies and reveal similarities and differences. Further, we review some latest advances and compare both technologies in terms of surface functionalization and sensor performance.
Direct optical detection methods such as surface plasmon resonance imaging (SPRi) and photonic-integrated-circuits (PIC)-based biosensors provide a fast label-free detection of COVID-19 antibodies in real-time. Each technology, i.e., SPRi and PIC, has advantages and disadvantages in terms of throughput, miniaturization, multiplexing, system integration, and cost-effective mass production. However, both technologies share similarities in terms of sensing mechanism and both can be used as high-content diagnostics at or near to point of care, where the analyte is not just quantified but comprehensively characterized. This is significant because recent results suggest that not only the antibody concentration of the three isotypes IgM, IgG, and IgA but also the strength of binding (affinity) gives an indication of potential COVID-19 severity. COVID-19 patients with high titers of low affinity antibodies are associated with disease severity. In this perspective, we provide some insights into how SPR and PIC technologies can be effectively combined and complementarily used for a comprehensive COVID-19 severity monitoring. This opens a route toward an immediate therapy decision to provide patients a treatment in an early stage of the infection, which could drastically lowers the risk of a severe disease course.
Summary In the course of classical optics manufacturing glass components are in permanent direct contact with aqueous operating materials. Such contact leads to a certain absorption of water and hydrogenous compounds that may induce severe glass defects. In this contribution, absorption of hydrogen and other contaminants during grinding of glass was observed and qualitatively detected via laser-induced breakdown spectroscopy. It is shown that hydrogen, calcium, magnesium, and carbon are implanted into the glass surface where the contaminant concentration increases over grinding time or contact time of the glass surface with water and the grinding tool, respectively. The contaminants hydrogen, calcium, and magnesium can be attributed to the water used as lubricant. In contrast, carbon most likely originates from wear debris of the used silicon carbide grinding pads. Several possible mechanisms that lead to such surface contamination of glasses during grinding – diffusion, accumulation in micro cracks as well as the formation of hydrated silica – are finally introduced.
Electro-optical properties of doped polymers with high transparency in the visible wavelength range
(2021)
The electro-optical (EO) properties of poly(methyl methacrylate) and the photopolymer poly(vinyl cinnamate) doped with varying concentrations of the EO chromophore 2-Methyl-4-nitroaniline were measured. The EO polymers were embedded in Fabry-Pérot etalons for the simultaneous determination of the Pockels and Kerr coefficients from measurements of the fringe shift induced by an external electric field. It was found that the host polymer has a significant impact on the EO performance and that the undoped host polymers exhibit a significant Pockels effect. Moreover, the Kerr effect provides a substantial contribution of 27% to the total change of the refractive index at relatively high electric field strengths of E = 91.2 MV m−1.
Polycrystalline infrared (PIR) fibers are used for numerous applications, one of those being power delivery for CO2 lasers. However, the fiber tip surface's transmittance cannot be increased with conventional antireflection coatings due to the surface unevenness. Antireflection microstructures (ARMs) offer an alternative way of increasing transmittance. In this work, ARMs were fabricated on the fiber tip surface of an AgClBr fiber by single-pulse femtosecond laser ablation. A single-surface transmittance of 92.8% at 10.6 μm, a CO2 laser operation wavelength, was achieved. The proposed method can help significantly improve the systems' efficiency, where power delivery for CO2 lasers or sources operating in the wide wavelength range is required.
Small and medium-sized companies increasingly turning their attention towards the fourth industrial revolution. In order to increase their own long-term competitiveness, there is a growing desire to make production smarter, more efficient, safer and more sustainable through new technologies. Often, however, existing plants cannot be easily replaced by modern equipment. The reasons for this can be high investment costs, excessive downtimes or the unavailability of an equivalent machine. An alternative solution to the purchase of new equipment is the modernisation or expansion of existing systems, also called retrofitting. Thus, this paper deals with the retrofit process of a machine tool, whereby the software architecture of the control unit is the primary concern of this work.
During the last decade production innovation was mainly focused on connectivity aspects. The vision of smart factories running on software, that uses collected machine data, has become true but foremost for leading industrial companies in highly developed countries. Apart from these, production can also be found in non-industrialized craft professions as well as in less developed countries. As digitalization does not necessarily require an industrial or developed setting the latter could possibly benefit from it as well. Socio-cyber-physical production systems have been used to describe the interdependencies of linked production systems but usually focus on highly developed regions as well as for industrial applications. This paper lines out similarities and differences for each case, introduces the concept of cyber-physical production systems (CPPS) and its extension to socio-CPPS (SCPPS), which emphasizes the role of human workers in the production environment. The relation between industrial, non-industrial production and innovations is examined. Furthermore, the widening of SCCPS concepts for non-industrial production is discussed.
Dermatological in vivo measurements are used for various purposes, e.g. health care, development and testing of skin care products or claim support in marketing. Especially for the last two purposes, in vivo measurements are extensive due to the quantity and repeatability of the measurement series. Furthermore, they are performed manually and therefore represent a nonnegligible time and cost factor. A solution to this is the implementation of collaborative robotics for the measurement execution. Due to various body shapes and surface conditions, common static control procedures are not applicable. To solve this problem, spatial information obtained from a stereoscopic camera can be integrated into the robot control process. However, the designated measurement area has to be detected and the spatial information processed. Therefore the authors propose a concept towards segmenting arm areas through a CNN-based object detector and their further processing to perform robot-based in vivo measurements. The paper gives an overview of the utilization of RGB-D images in 2D object detectors and describes the selection of a suitable model for the application. Furthermore the creation, annotation and augmentation of a custom dataset is presented.
Faults in industrial chiller systems can lead to higher energy consumption, increasing wear of system components and shorten equipment life. While they gradually cause anomalous system operating conditions, modern automatic fault detection models aim to detect them at low severity by using real-time sensor data. Many scientific contributions addressed this topic in the past and presented data-driven approaches to detect faulty system states. Although many promising results were presented to date, there is lack of suitable comparison studies that show the effectiveness of the proposed models by use of data stemming from different chiller systems. Therefore this study aims at detecting a suitable data-driven approach to detect faults reliable in different domains of industrial chillers. Thus, a unified procedure is developed, to train all algorithms in an identical way with same data-basis. Since most of the reviewed papers used only one dataset for training and testing, the selected approaches are trained and validated on two different datasets from real refrigeration systems. The data-driven approaches are evaluated based on their accuracy and true negative rate, from which the most suitable approach is derived as a conclusion.
Chiller systems are used in many different applications in both the industrial and the commercial sector. They are considered major energy consumers and thus contribute a non-negligible factor to environmental pollution as well as to the overall operating cost. In addition, chillers, especially in industrial applications, are often associated with high reliability requirements, as unplanned system downtimes are usually costly. As many studies over the past decades have shown, the presence of faults can lead to significant performance degradation and thus higher energy consumption of these systems. Thus, data-driven fault detection plays an ever-increasing role in terms of energy efficient control strategies. However, labelled data to train associated algorithms are often only available to a limited extent, which consequently inhibits the broad application of such technologies. Therefore, this paper presents an approach that exploits only a small amount of labelled and large amounts of unlabelled data in the training phase in order to detect fault related anomalies. For this, the model utilizes the residual space of the data transformed through principal component analyses in conjunction with a biased support vector machine, which can be ascribed to the concept of semi-supervised learning, or more specifically, positive-unlabelled learning.
To achieve climate goals and contain further global warming, it is inevitable to reduce CO2 emissions especially in energy consumption. A way to do so is by integrating renewable energy sources (RES) into an energy system’s power generation. However, there is no standard procedure to decarbonise a locally restricted system. Therefore, the various local conditions have to be analysed and taken into consideration.
The authors propose a model-based approach to decarbonise the energy system of the island Föhr, Germany. This includes various collected data sets on local conditions such as climate data and heat and power demand. The data is used to represent the island’s energy system and design a model-based solution in a simulation software.
The authors identify potentials by comparing costs and revenues by addressing the deployment of different RES technologies. One finding is that heat generation causes 91 % of CO2 emissions making it the major producer. However, with the designed solution, emissions could be reduced to a third.
The fossil fuels used to provide energy, such as coal, crude oil and natural gas, are largely responsible for carbon dioxide emissions and other so-called greenhouse gases. Hydrogen gas (H2) can make a key contribution to decarbonization. It can be produced using various processes. Several processes are available to produce hydrogen, such as (i) steam reforming, (ii) cracking process or (iii) electrolysis. Depending on the source of origin, there is a distinction made between different “colours”. Gray, blue, turquoise, yellow and green hydrogen is available, the latter made using Renewable Energies. However, items such as (i) possible variants of hydrogen, (ii) leading export countries or (iii) provision paths to be preferred in the future will be discussed in this paper.
Science, technology and politics agree: hydrogen will be the energy carrier of the future. It will replace fossil fuels based on a sufficient supply from sustainable energy. Since the possibilities of storing and transporting hydrogen play a decisive role here, the so-called LOHC (Liquid Organic Hydrogen Carriers) can be used as carrier materials. LOHC carrier materials can reversibly absorb hydrogen, store it without loss and release it again when needed. Since little or no pressure is required, normal containers or tanks can be used. The volume or mass-related energy densities can reach around a quarter of liquid fossil fuels.
This paper is to give an introduction to the field of hydrogen storage and usage of those LOHC, in particular. The developments of the last ten years have been related to the storage and transport of hydrogen with LOHC. These are crucial to meet the future demand for energy carriers e.g. for mobile applications. For this purpose, all transport systems are under consideration as well as the decentralized supply of rural areas with low technological penetration, e.g. regions of Western Africa which are often characterized by a lack of energy supply. Hydrogen bound in LOHC can provide a hazard-free alternative for distribution. The paper provides an overview of the conversion forms as well as the chemical carrier materials. Dibenzyltoluene as well as N-ethylcarbazole - as examples for LOHC - are discussed as well as chemical hydrogen storage materials like ammonia boranes as alternatives to LOHC.
Bi-facial Open-Space Photovoltaic Systems versus Conventional Systems using Mono-facial Modules
(2021)
As part of a scientific work within the solar company Sunfarming GmbH, the aim was to find out whether bi-facial modules on open spaces deliver better results economically than conventional mono-facial solar modules. In this context, an already installed 750 kWp PV system with mono-facial solar modules was compared directly with a structurally identical PV system with bi-facial modules, which, however, does not exist in practice but was only simulated with PV software. The second part of the investigation includes the comparison of four different assembly systems or elevation variants in order to determine the system with the best relationship between system yield and costs.
The final result of the first investigation showed that the use of bi-facial modules reduced the specific costs per kWh by approximately 5 %. In order to improve this effect, the use of compact assembly systems is recommended, e.g. five rows of modules per table with horizontal alignment.
Complementary large scale molecular-dynamics simulations and experiments have been carried out to determine the atomistic mechanisms of the nanoindentation process in single crystal Fe {110}, {100}, and {111}. The defect formation and motion causes the complex mechanisms of plastic and elastic deformation which is reflected in the pileup patterns. The experimental results show distinct patterns of pileup material which are dependent on the individual crystal faces and the superposition of the stress field of the indenter. The highest pileup around the indenter hole occurs on the {100} surface and the shallowest on {111}. The least symmetric surface is {110} which produces an experimental pileup pattern displaying only twofold symmetry with the axially symmetric indenter. The pyramidal indenter produces an asymmetric pattern which changes as the crystal is rotated with respect to the tip but repeats with threefold rotational symmetry. Material displacement occurs primarily in planes of the {110} family. Pileup is formed by cross slip between planes of the same family which intersect in ⟨111⟩ directions. For the {110} surface, dislocation loops propagate in the four in-plane ⟨111⟩ directions and the two inclined
⟨111⟩ directions. The loops that propagate in the in-plane directions are terminated by edge dislocations at the surface. These transport material away from the tip but cannot produce pileup. The loops that propagate in the inclined direction cross slip and cause the observed pileup. The {100} surface has fourfold rotational symmetry and all the ⟨111⟩ directions are inclined. The dislocation loops propagate in these directions and cross slip readily occurs, leading to a large pileup. The {111} face shows the least pileup which is more spread out over the surface. In this case the dislocation loops propagate in shallow slip planes and do not readily cross slip. Experimentally determined force-depth curves show distinct “pop-ins” which correspond to the formation of dislocations. The contact pressure (nanohardness) is not a constant and increases with decreasing indentation depth. It also changes with crystal face. Calculated force-depth curves match the experimental trend but give estimates of the nanohardness and Young’s modulus higher than those values experimentally determined.
C60 and amorphous diamond-like carbon (DLC) films have been grown by thermal evaporation and laser ablation techniques at different substrate temperatures and on various substrates. The elastic modulus and the hardness of the films have been investigated by surface acoustic waves and nanoindentation. Both methods are completely new and designed for investigations of very thin films. For homogeneous C60 films the Young's modulus was found to be 14 GPa and the Poisson's ratio of 0.2. The measured nanohardness of 167 MPa corresponds with the microhardness value of 130 MPa. There is a correlation between deposition techniques and hardness as well as Young's modulus for DLC films.
This work presents a comparison of numerical simulation and experimental data for nanoindentation studies of nanostructural Me-carbonaceous films (where Me = Pd or Ni). Films containing palladium or nickel nanograins embedded in a carbonaceous matrix were synthesized by a PVD process. The topography of films was characterized by AFM and the mechanical properties were analyzed by nanoindentation. Nanoindentation experiments were performed with a tip made of diamond with a shape of a 90° cube corner three-sided pyramid in a Hysitron Triboscope. The finite element method (FEM) was used to simulate the indentation experiment in such heterogeneous material on nanoscale.
Photodynamic therapy (PDT) employs light activation of tissue-localized photosensitizer in an oxygen-dependent process which initiates oxidative stress, inflammation, and cell death. Laser systems, which are mostly used in PDT as light sources can be costly and oversized. light-emitting diodes (LEDs) equipment has a high potential to simplify technical part of phototriggered therapies and to reduce its costs. We develop the LED-based system that includes the control and irradiation units. The system provides the same power density at any irradiation point. Among the advantages of the device is a possibility to change the irradiation area and tune the irradiation dose. PDT experiments with cancer cells in vitro treated with two different photosensitizers demonstrated a possibility to use the developed LED-based system as a low-cost light source in PDT.
Optical-resolution photoacoustic microscopy (OR-PAM) combines high spatial resolution and strong absorption-based contrast in tissue, which has enabled structural and spectroscopic imaging of endogenous chromophores, primarily hemoglobin. Conventional piezoelectric ultrasound transducers are typically placed far away from the photoacoustic source due to their opacity, which reduces acoustic sensitivity. Optical ultrasound sensors are an alternative as their transparency allows them to be positioned close to the sample with minimal source-detector distances. In this work, a backward-mode OR-PAM system based on a planar Fabry-Pérot ultrasound sensor and coaxially aligned excitation and interrogation beams was developed. Two 3D imaging modes, using raster-scanning for enhanced image quality and continuous-scanning for fast imaging, were implemented and tested on a leaf skeleton phantom. In fast imaging mode, a scan-rate of 100,000 A-lines/s was achieved. 3D images of a zebrafish embryo were acquired in vivo in raster-scanning mode. The transparency of the FP sensor in the visible and near-infrared wavelength region makes it suitable for combined functional and molecular imaging applications using OR-PAM and multi-photon fluorescence microscopy.
The investigation of the crack propagation in as-extruded and heat-treated Mg-Dy-Nd-Zn-Zr alloy with a focus on the interaction of long-period stacking-ordered (LPSO) structures is the aim of this study. Solution heat treatment on a hot extruded Mg-Dy-Nd-Zn-Zr (RESOLOY®) was done to change the initial fine-grained microstructure, consisting of grain boundary blocky LPSO and lamellar LPSO structures within the matrix, into coarser grains of less lamellar and blocky LPSO phases. C-ring compression tests in Ringer solution were used to cause a fracture. Crack initiation and propagation is influenced by twin boundaries and LPSO lamellae. The blocky LPSO phases also clearly hinder crack growth, by increasing the energy to pass either through the phase or along its interface. The microstructural features were characterized by micro- and nanohardness as well as the amount and location of LPSO phases in dependence on the heat treatment condition. By applying nanoindentation, blocky LPSO phases show a higher hardness than the grains with or without lamellar LPSO phases and their hardness decreases with heat treatment time. On the other hand, the matrix increases in hardness by solid solution strengthening. The microstructure consisting of a good balance of grain size, matrix and blocky LPSO phases and twins shows the highest fracture energy.
One of the limiting factors of graphene integration into electronic, photonic, or sensing devices is the unavailability of large-scale graphene directly grown on the isolators. Therefore, it is necessary to transfer graphene from the donor growth wafers onto the isolating target wafers. In the present research, graphene was transferred from the chemical vapor deposited 200 mm Germanium/Silicon (Ge/Si) wafers onto isolating (SiO2/Si and Si3N4/Si) wafers by electrochemical delamination procedure, employing poly(methylmethacrylate) as an intermediate support layer. In order to influence the adhesion properties of graphene, the wettability properties of the target substrates were investigated in this study. To increase the adhesion of the graphene on the isolating surfaces, they were pre-treated with oxygen plasma prior the transfer process of graphene. The wetting contact angle measurements revealed the increase of the hydrophilicity after surface interaction with oxygen plasma, leading to improved adhesion of the graphene on 200 mm target wafers and possible proof-of-concept development of graphene-based devices in standard Si technologies.
Renewable energy sources are more important today than ever before, as they represent a key factor in reducing greenhouse emissions and fossil fuel consumption. Avoiding excessive burdens on future generations has now become the declared challenge of this century and justifies the efforts we must undertake to reduce global warming. This can only be achieved by conceiving new technical approaches, exploiting alternative resources and by raising people's awareness of the sustainable use of their own livelihoods. However, this change in awareness is a process that needs to be driven forward, especially in the field of research and education, and is therefore the declared aim of the Joint German-West African Conference on Sustainable, Renewable Energy Systems – SusRES. This annual conference provides a platform for exchange between scientists, students and many other interested parties, with technological progress at the forefront of the event. The SusRES conference is known as an accelerator for an ever-growing international network, not limited to the circumstances of a single country or even continent, which strives to take on and meet the global challenges of the present and future.
This year's guiding theme of the event -Decentralized systems as a key factor in clean energy production for locations with limited infrastructure- of the event is primarily based on the consideration of how the energy supply of the future is to be designed. For some years now, a paradigm shift towards decentralised energy supply has been observed, which opens up new possibilities especially in areas with weak infrastructural supply. This is not just about providing energy from renewable resources, but also about exploiting this energy we have today efficiently and sustainably, whereby intelligent and interconnected systems play an ever-increasing role.
The reader is provided with exciting insights into these topics within this conference proceedings elaborated by stakeholders from twelve time zones and four continents. In their contributions, the authors address important findings, especially from research but also from teaching, which represent an important milestone in their activities and thus make a significant contribution to our declared goals.
In this work, we analyze a horizontal slot waveguide configuration, which evaluates the potential for an integration of barium titanate (BTO) based modulators into a photonic integrated circuit (PIC) technology based on siliconon- insulator (SOI) wafer. The waveguide configuration consists of a doped crystal silicon layer, a Ba0:7Sr0:3TiO3 (BST) template layer, a barium titanate (BTO) layer and a doped poly-silicon layer on top. In contrast to current approaches, we analyze the performance of this waveguide-structure by using a vertical electrode configuration that is formed by the doped silicon layer. In this way, the electric field strength is dramatically increased compared to current horizontal electrode configuration.
In this work, a cost-effective optofluidic system is propossed and preliminary experimental results are presented. A microfluidic channel monolithically integrated into a photonic integrated circuit technology is used in conjunc- tion with a cyclo-olefin copolymer (COC) substrate to provide fluidic in- and output ports. We report on initial experimental results as well as on the simple and cost-effective fabrication of this optofluidic system by means of micro-milling.
Carbon-based functional Materials for Application in Photonics, Optoelectronics and Sensorics
(2015)
In this work, two different processes to deposit Graphene-based transparent conductive films on arbitrary insulting substrates have been developed and examined. The first process is a PE-CVD, based on a gas mixture containing hydrocarbons (e.g. methane) inside a vacuum chamber where the insulating substrates are placed on a temperature controlled heating plate.
The second process uses a pulsed filtered vacuum arc system (Phi-HCA) to homogeneously deposit a small, well defined amount of carbon on heated substrates. The substrates are tilted with respect to the particle beam and placed on a heating plate. A gas atmosphere consisting of Argon or Argon/Hydrogen decreases the particle energy and influences the morphology of the growing film.
For both processes, Scanning Tunneling Microscopy (STM), Transmission Electron Microscopy (TEM) and Raman spectra have been used for a thorough characterization of the samples in order to optimize the growth parameters. Subsequently, the results (sheet resistance, Hall mobility, transmittance) have been compared with respect to the state of the art, reported in literature. The best carbon layers have a surface resistance of 5E3 Ohm_sqr while the optical transparency of the coatings is 88% with an excellent homogeneity over areas of several cm^2. Both for the PE-CVD and the Phi-HCA, the area of deposition is only limited by the respective area of the heated surface. The obtained results and the fact, that the process can be compatible with most semiconductor fabrication processes, makes them promising for various industrial applications.
In this work, we present for the first time a partially slotted silicon ring resonator (PSRR) covered with an electro-optical polymer (Poly[(methyl methacrylate)-co-(Disperse Red 1 acrylate)]). The PSRR takes advantage of both a highly efficient vertical slot waveguide based phase shifter and a low loss strip waveguide in a single ring. The device is realized on 200 mm silicon-on-insulator wafers using 248 nm DUV lithography and covered with the electro-optic polymer in a post process. This silicon-organic hybrid ring resonator has a small footprint, high optical quality factor, and high DC device tunability. A quality factor of up to 105 and a DC device tunability of about 700 pm/V is experimentally demonstrated in the wavelength range of 1540 nm to 1590 nm. Further, we compare our results with state-of-the-art silicon-organic hybrid devices by determining the poling efficiency. It is demonstrated that the active PSRR is a promising candidate for efficient optical switches and tunable filters.
Development of tuneable Fabry-Pérot sensors for parallelised photoacoustic signal acquisition
(2019)
Fabry-Pérot (FP) sensors have enabled high resolution 3D photoacoustic (PA) imaging in backward mode. However, raster-scanning of the interrogation laser beam across the sensor can result in slow 3D image acquisition. To overcome this limitation, parallelized PA signal acquisition can be used for which FP sensors with uniform optical thickness are required. In this work, the optical thickness is tuned a) irreversibly through the use of a photopolymer host matrix and b) actively using embedded electro-optic (EO) chromophores. Polymer spacers (5 μm) were deposited using spin coating and sandwiched between two dielectric mirrors and transparent ITO electrodes. The employed polymer guest-host system consists of an EO chromophore (2-methyl-4-nitroaniline) and poly(vinyl cinnamate). EO tuneability was induced using contact poling and a tuneability of 68 pm was demonstrated. The optical thickness was homogenised by raster scanning a UV beam whilst varying the exposure time across a 4 mm2 detection aperture.
Through Silicon Via (TSV) technology is a key feature of new 3D integration of circuits by creation of interconnections using vias, which go through the silicon wafer. Typically, the highly-selective Bosch Si etch process, characterized by a high etch rate and high aspect ratio and forming of scallops on the sidewalls is used. As presented in this paper, we have developed an experimental setup and a respective evaluation algorithm for the control and monitoring of very high aspect ratio TSV profiles by spectroscopic reflectometry. For this purpose square via arrays with lateral dimension from 3 to 10 μm were fabricated by a Bosch etch process and analyzed by our setup. By exploiting interference and diffraction effects of waves reflected from the top and bottom surfaces as well as from the side walls of the TSV patterns, the measurements provided etch depths, CD values and scallop periods. The results were compared with data obtained by a commercial wafer metrology tool. Aspect ratios of up to 35:1 were safely evaluable by our setup.
Fiber-to-chip light coupling using a graded-index (GRIN) fiber collimator is investigated. Our experiments with grating couplers and strip waveguides fabricated in a photonic integrated circuit technology reveal that the peak coupling efficiency of a GRIN fiber collimator is 7.8 dB lower than that of a single-mode fiber. However, the 3-dB alignment tolerance is improved by a factor of about 5.7 giving rise to pluggable sensor solutions. This work opens a path toward a cost-effective and portable sensor platform based on pluggable photonic biosensors using GRIN fiber collimators.