TY - CHAP A1 - Steglich, Patrick A1 - Mai, Christian A1 - Stolarek, David A1 - Lischke, Stefan A1 - Kupijai, Sebastian A1 - Villringer, Claus A1 - Pulwer, Silvio A1 - Heinrich, Friedhelm A1 - Bauer, Joachim A1 - Meister, Stefan A1 - Knoll, Dieter A1 - Casalboni, Mauro A1 - Schrader, Sigurd T1 - Partially slotted silicon ring resonator covered with electro-optical polymer T2 - Proceedings of SPIE N2 - 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. Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13771 SN - 1996-756X ER - TY - JOUR A1 - Gerhard, Christoph A1 - Letien, Emilie A1 - Cressent, Thomas A1 - Hofmann, Mandy T1 - Inline monitoring of hydrogenous plasma-induced defect formation within fused silica via plasma emission spectroscopy JF - Applied Physics A: Materials Science and Processing N2 - In this paper, the indirect monitoring of plasma-induced defect formation within fused silica via plasma emission spectroscopy is presented. It is shown that low-pressure plasma treatment with hydrogen as process gas leads to a decrease in UV transmission of fused silica. This decrease can be directly attributed to oxygen vacancy-related defects and the presence of hydrogen within the silicon dioxide glass network. By the analysis of the plasma composition, it was observed that the amount of oxygen within the plasma increases with increasing treatment duration. Hence, oxygen was continuously released from glass network in the course of the plasma treatment. It was further observed that this release is strongly dependent on the applied plasma power where the lowest process efficiency occurs at the highest plasma power. It is shown that an increase in plasma power leads to a remarkable increase in light emission from the working gas, hydrogen. This observation indicates that the higher the degree of excitation and ionisation of the plasma, the lower the efficiency of plasma-induced formation of oxygen deficiency-related defects. This finding is of mentionable relevance for a better understanding of plasma-induced surface modification and coating processes. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13118 SN - 1432-0630 VL - 126 ER - TY - CHAP A1 - N’Tsoukpoe, Kokouvi Edem A1 - Ko, Gaëlle Kafira A1 - Falcoz, Quentin A1 - Coulibaly, Yézouma T1 - Design, construction and experimental investigation of a linear Fresnel concentrator for sustainable energy services in Sub-Saharan Africa T2 - Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo N2 - Concentrating solar power (CSP) is considered as one of the promising ways for future sustainable electricity generation, especially in the Sahel region, which is characterized by high direct solar irradiation, but also severe and acute energy poverty. In this paper, we focus on the linear Fresnel system, which it is probably the simplest CSP technology and presents the lowest investment costs. However, it is the less investigated CSP technology and several authors expect significant cost reduction of this technology. Therefore, deeper knowledge on the technology is required. We aim at investigating the coupling of a linear Fresnel system with various energy processes in order to bring out its interests for the Sahel region and, hence, provide sustainable energy services such as electricity generation for rural areas, cooling and refrigeration via sorption cold production, hot water or steam supply for semi-industrial or industrial processes. We have built a linear Fresnel collector of 7.5 m2. The receiver has been designed as a trapezoidal receiver with multi-tubular absorber; it has been experimentally investigated in order to determine its thermal performance, especially the heat loss coefficients. Jatropha curcas oil, a locally produced non-edible vegetable oil is used as heat transfer fluid. The concentrator has been characterised in order to find its optical, thermal and global efficiencies. Paths for the prototype performance improvement have been identified and examined. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13194 SP - 7 EP - 16 ER - TY - CHAP A1 - Reiff-Stephan, Jörg T1 - Implementation approaches for distributed energy management systems in production T2 - Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo N2 - The energy management of manufacturing facilities must be taken increasing account for an efficient operation within a production process. Future efforts and solutions will focus on improvement of the process stability and on cost reduction to meet the needs of successfully compete in local and global markets especially for SME. The paper describes an approach for manufacturing facilities using an example for thermoprocessing equipment. For this purpose, the TPS-principle Jidōka is used, the mechanism of self-adapting limit setting as well as an implementation is presented prototypically. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13220 SP - 116 EP - 124 ER - TY - CHAP A1 - Reiff-Stephan, Jörg T1 - Solar power in product development T2 - Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo N2 - The availability of electrical energy is one of the essential basic elements for economic growth and humanitarian living conditions. In one of the poorest regions of Western Africa - in the savannah region of northern Togo - the central expansion of electricity grids has not taken place. Decentralized solutions based on renewable energy systems can help here and promote the region's development. In the presented paper, the various renewable energy carrier systems were examined with regard to their use in the savannah region of Western Africa. The solar energy carrier system could be used as a power supplier in the secondary conversion process to mechanical power. Subsequently, a prototype for a clay brick production machine was designed and a digital mock-up was developed. Together with the partners in Togo, the prototype is built and tested in the field. Experiences are being gathered in cooperation with Bonita-Haus and will be incorporated into the educational content in Togo as well as at the Technical University of Wildau. This will make a significant contribution to the utilization of the technology at the site and to improving the living conditions in Western Africa. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13206 SP - 55 EP - 65 ER - TY - CHAP A1 - Giese, Lutz B. A1 - Fürkus, Stefan T1 - A Short Approximation Method to Pre-estimate the Electric Yield of Wind Farms T2 - Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo N2 - Amongst the Renewable Energy Sources (RES) contributing to the worldwide electricity production, wind energy became very important. Germany and several other countries own significant wind potentials. 2% of a country’s area can be used for wind farms, thus Germany could produce easily up to 200 TWhel yearly just onshore. However, often legal and especially financial aspects decide about the speed of development. Careful project preparation guaranteed by professional management is obligatory. Beside factors such as (i) rights to the property and (ii) electric grid connection, (iii) the sufficiency of the wind and peripheral conditions need to be known. A proper wind forecast and yield prognoses are important items. To solve these tasks, professional programs are sold on the markets. To offer a convenient alternative, authors will present software based on Excel named as WindCalc 1.5, which is still under development. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13256 SP - 34 EP - 40 ER - TY - CHAP A1 - Giese, Lutz B. T1 - Turnaround in Energy Policy – Measures to Reduce the Carbon Dioxide Emission from the Private Sector T2 - Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo N2 - The greenhouse gases (GHG) carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) are considered mainly to be responsible for the additional anthropogenic greenhouse effect, the so-called “global warming”. In the private sector, the “Rational Use of Energy” can be a very effective tool (i) to reduce the greenhouse gas emissions, (ii) to decrease the annual energy costs and furthermore (iii) it prepares the integration of Renewable Energy Sources by saving conventional, mostly fossil energy. Aim of this paper is (i) to show that by applying energy saving measures, the primary energy demand and thus the individual (direct) carbon dioxide emission can be reduced in a relevant scale. (ii) It is to give laterally information about (ii.i) the energy market structure and (ii.ii) the legal backgrounds in the EU. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13248 SP - 81 EP - 86 ER - TY - CHAP A1 - Afenyiveh, Serge Dzo Mawuefa A1 - Adanlete Adjanoh, Assiongbon A1 - Douti, Dam-Be Lardja T1 - Optical simulation of a parabolic solar concentrator T2 - Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo N2 - This work presents a 3D ray tracing approach for the optical simulation of a parabolic solar concentrator for a thermo-magnetic (Curie motor) experiment. An approach based on Snell's law of reflection (geometrical optics) in vector form is used in this study. We consider the solid angle of the sun through a rotation of the concentrator around an axis. This paper aims to set up a digital technical tool as flexible as possible for applications in the field of renewable energy.Mathematical modelling as well as numerical simulation in Python environment are presented. The aim of the proposed algorithm is to be used for the concentration of light rays on any optical system, symmetrical or not. Better yet, offers a solar tracking model. KW - solar parabolic concentrator KW - optical modelling KW - ray tracing simulation Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13238 SP - 66 EP - 72 ER - TY - CHAP A1 - Steglich, Patrick A1 - Paul, Martin A1 - Mai, Christian A1 - Böhme, Andrea A1 - Bondarenko, Siegfried A1 - Weller, Michael G. A1 - Mai, Andreas T1 - A monolithically integrated micro fluidic channel in a silicon-based photonic-integrated-circuit technology for biochemical sensing T2 - Proc. SPIE 11772, Optical Sensors 2021 N2 - 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. Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13925 ER - TY - CHAP ED - Amouzou, Kou 'santa ED - Adanlete Adjanoh, Assiongbon ED - Reiff-Stephan, Jörg T1 - Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo N2 - Conference Proceedings of the 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes. 1st July 2020 - Kara, Togo. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13424 SN - 978-3-9819225-5-4 ER - TY - CHAP A1 - N’Gobi, Gabin Koto A1 - Donnou, Hagninou E. V. A1 - Agbazo, Médard A1 - Akpo, Aristide. B. A1 - Kounouhewa, Basile B. T1 - Estimation of the Global Solar Radiation Received on the Soil in Nalohou and Natitingou (Northern Benin) T2 - Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo N2 - The design of solar energy systems requires knowledge of the global solar radiation received by solar panels on the ground. However, for many developing countries such as the Benin Republic, there is a serious lack of radiometric stations everywhere in the country. The unavailability of these data, therefore, limits knowledge regarding the optimal functioning of solar installations. To cope with these difficulties, a method for estimating the global irradiation is developed at Nalohou AMMA CATCH station and Natintingou synoptic station, two sites in North-West Benin. This model depends on meteorological and astronomical parameters. Meteorological data such as sunshine duration, relative humidity, and air temperature have been collected on the synoptic station of Natitingou, and observed data of irradiation are collected from Nalohou. They are used to validate the model. The results show that the estimation of the mean square deviation value is around 10 -2 . Overall solar radiation is significant in this region and its annual average value varies between 9.80 kWh/m2 and 10.50 kWh/m2. This model can, therefore, be used by solar system operators to optimize energy production in the region. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13376 SP - 41 EP - 54 ER - TY - CHAP A1 - van de Sand, Ron A1 - Corasaniti, Sandra A1 - Reiff-Stephan, Jörg T1 - Review of Condition Based Maintenance approaches for vapor compression refrigeration systems T2 - Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo N2 - Vapor compression refrigeration systems are subject to performance degradation over time due to the presence of faults. However, latest work in the field of condition-based maintenance shows promising results in the automatic early detection of anomalous behaviour as well as in accurate machine diagnostics and can, therefore, increase the overall system reliability by simultaneously preventing machine downtimes. In this paper, the latest research works carried out within the last decade are reviewed and the approaches are classified regarding their working principles. Furthermore, the work at hand depicts the current research trend in this field and outlines current obstacles. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13369 SP - 24 EP - 33 ER - TY - CHAP A1 - Smajic, H. A1 - Duspara, T. T1 - Design and manufacturing of an unmanned aerial vehicle with air quality control system T2 - Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo N2 - Within the scope of this project, a fully functional model of an unmanned aerial vehicle with an air control system was developed and implemented as a prototype. By using the mobile measuring stations, it is feasible to measure the air quality in any part of the city, independent of the measuring altitude. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13396 SP - 87 EP - 93 ER - TY - CHAP A1 - Dable, Etienne T1 - Construction of PV Systems for Elementary Schools in the Savannah of Togo BT - Light for Education and Culture T2 - Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo N2 - The savannah region in northern Togo borders on Ghana, Burkina Faso and Benin (Figure 1). It covers 8,596 km2, which is 15% of the total area of Togo. The regional capital Dapaong has about 100,000 inhabitants. The savannah region consists of 5 prefectures, 70 cantons, 1,073 villages and 451 hamlets. The number of inhabitants is growing rapidly. The population figures were 828,224 in 2010 and 890,403 in 2013, a growth rate of 8.2% in only 3 years. With 105 inhabitants per km2 the savannah region is more densely populated than German Mecklenburg-Vorpommern (69 inhabitants per km2). The savannah region is the poorest region in the country. In the villages, subsistence farming prevails. Surpluses are sold at village markets or nearby city markets with little profit, since raw products are rarely processed and certainly not processed and the purchasing power in the region is low. The sensitive savannah floors are overused. During the long dry season (October to May) there is a lack of artificial irrigation. The climate change affects the savannah region through shorter and irregular rainy seasons. Deforestation leads to further drying out of the soil. The population is increasing, becoming poorer and poorer and uses almost exclusively wood for cooking in the villages. This leads to further deterioration of the arable land. Harvest yields are falling because improved seeds and fertilisers are also lacking. The infrastructure in the region is at an extremely low level. There are no industrial enterprises in the savannah region. There is an almost complete lack of companies that process and refine agricultural products. There is a lack of storage facilities and cold chains for agricultural products. Only for wood and charcoal there are transport routes from the international highway to regions with better purchasing power. A major obstacle to the establishment of small businesses is the lack of electricity. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13415 SP - 111 EP - 115 ER - TY - CHAP A1 - Krou, Nitale M'Balikine A1 - Baba, Gnon A1 - Segbeaya, Kwamivi N. A1 - Akpaki, Ogouvidé T1 - Energy recovery from sewage sludge and fermentable fractions of solid waste from the city of Sokode by co-digestion T2 - Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo N2 - One of the consequences of the improvement of the living conditions of the populations is the strong demand in thermal energy for the households whereas in the developing countries, the cost of living is a brake with all the social layers to reach supply of butane gas for their energy needs. This study takes place in the context of energy, environmental and sanitation challenges in the city of Sokodé. Indeed, we are witnessing more and more growing needs for butane gas, firewood or charcoal for cooking or lighting in the city of Sokodé as everywhere in other cities of the same size. Thus by the production of energy in situ, the condition of the populations will be able to improve significantly thanks to the recovery of sludge and fermentable fractions of solid waste into biogas. The objective of this work is to produce and recover methane from fermentable waste produced in the city of Sokodé. The methane or biogas recovered will be used as fuel to fuel kitchens in households. The resulting digestate will serve as an organic amendment to agricultural soils in the commune of Sokodé. Laboratory scale tests have been carried out to validate the value of co-digestion of sewage sludge with fermentable solid waste. The results obtained have shown that the methanogenic potential of sewage sludge is low compared to that of fermentable solid waste. The co-digestion of the two products allows a greater production of methane representing an energy gain compared to the methanisation of the sewage sludge alone. This study shows that waste (sludge from public septic tanks, waste from markets, hotels and fermentable households) can be considered an appreciable energy resource. Their Co-treatment would, while reducing the nuisance associated with this waste, produce valuable energy. KW - renewable energy KW - anaerobic co-digestion KW - organic solid waste KW - drain sludge Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13262 SP - 94 EP - 101 ER - TY - CHAP A1 - Lisker, Roberto A1 - Nowitzki, Mario A1 - Hellwig, Udo A1 - Wildenauer, Franz-Xaver T1 - Comparable numerical study on different working fluids for micro scale power cycle integrated into a pellet fired boiler BT - Numerical Simulation of the Tesla Turbine Efficiency T2 - Conference Proceedings : 1st German-West African Conference on Sustainable, Renewable Energy Systems SusRes : 1st July 2020 - Kara, Togo N2 - A cost-effective power cycle shall be developed to supply heat and electricity (co-generation). The aim of this study is to find an appropriate power cycle and working fluid for a friction turbine application. Due to its low production costs, better scalability and low-maintenance requirements, a friction turbine, also known as Tesla turbine, shall be used. In order to find a proper working fluid and estimate the efficiency and power output,a numerical study was performed on five promising working fluids namely Xenon, Argon, Helium, Air and superheated Steam. The simulation model consists of three disks with a diameter of 0,25 m and an outlet diameter of 0,12 mm rotating at constant 10.000 rpm.It is tried to keep the Gap Reynolds number at a constant 73, to ensure a laminar flow regime between the disks. The outcome of the numerical study showed that all working fluids are suitable. The highest efficiency (shaft power / technical power) has been achieved with steam (96%) and a power output of 126 W/gap. The least efficiency with 89% has been realized with air and a Power output of 118 W/gap. The noble gases are in between these fluids. By comparing the simulation data and taken into account numerical and estimation errors,all five working fluids are at par. Thus, the choice of the working fluid and the power cycle is an economical. While a hot gas air turbine is not as efficient as the steam turbine, the invest and maintenance costs are lower due to less heat exchangers and necessaries like water reconditioningand a phase separator. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13383 SP - 73 EP - 80 ER - TY - CHAP ED - Reiff-Stephan, Jörg ED - Amouzou, Kou 'santa ED - Adanlete Adjanoh, Assiongbon T1 - 2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021) : 6th April 2021 – Kara, Togo : Conference Proceedings N2 - 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. Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-14093 SN - 2748-8829 PB - TIB Open Publishing CY - Hannover ER - TY - JOUR A1 - Lukose, R. A1 - Lisker, Marco A1 - Akhtar, Fatima A1 - Fraschke, Mirko A1 - Grabolla, T. A1 - Mai, Andreas A1 - Lukosius, Mindaugas T1 - Influence of plasma treatment on SiO2/Si and Si3N4/Si substrates for large-scale transfer of graphene JF - Scientific Reports N2 - 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. Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-14179 SN - 2045-2322 VL - 11 ER - TY - JOUR A1 - Steglich, Patrick A1 - Bondarenko, Siegfried A1 - Mai, Christian A1 - Paul, Martin A1 - Weller, Michael G. A1 - Mai, Andreas T1 - CMOS-Compatible Silicon Photonic Sensor for Refractive Index Sensing Using Local Back-Side Release JF - IEEE Photonics Technology Letters N2 - Silicon photonic sensors are promising candidates for lab-on-a-chip solutions with versatile applications and scalable production prospects using complementary metal-oxide semiconductor (CMOS) fabrication methods. However, the widespread use has been hindered because the sensing area adjoins optical and electrical components making packaging and sensor handling challenging. In this work, a local back-side release of the photonic sensor is employed, enabling a separation of the sensing area from the rest of the chip. This approach allows preserving the compatibility of photonic integrated circuits in the front-end of line and metal interconnects in the back-end of line. The sensor is based on a micro-ring resonator and is fabricated on wafer-level using a CMOS technology. We revealed a ring resonator sensitivity for homogeneous sensing of 106 nm/RIU. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13649 SN - 1941-0174 VL - 32 IS - 19 SP - 1241 EP - 1244 ER - TY - BOOK ED - Steglich, Patrick T1 - Electromagnetic Propagation and Waveguides in Photonics and Microwave Engineering N2 - 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. KW - Wellenleiter KW - Simulation KW - Optik Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-18063 UR - https://www.intechopen.com/books/10093 SN - 978-1-83968-190-5 PB - IntechOpen CY - London ER - TY - JOUR A1 - Sopinskyy, Mykola A1 - Grytsenko, Kostyantyn A1 - Villringer, Claus A1 - Kolomzarov, Yurii A1 - Schrader, Sigurd T1 - Determination of scattering and Urbach absorption contributions to the light extinction in PTFE films by using graphical representation technique and numerical solution of the inverse problem JF - Semiconductor Physics, Quantum Electronics & Optoelectronics N2 - 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. KW - Rayleigh scattering KW - Urbach tail KW - absorption coefficient KW - scattering coefficient KW - graphical method KW - ellipsometry KW - polytetrafluoroethylene Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-18035 SN - 1605-6582 VL - 26 IS - 3 SP - 303 EP - 314 PB - National Academy of Sciences of Ukraine. Institute for Semiconductor Physics CY - Kyiv ER - TY - JOUR A1 - Roos, Andreas Hult A1 - Hoque, Ziaul A1 - Klimešová, Eva A1 - Ben Ltaief, Ltaief A1 - Medina, Cristian A1 - Jurkovič, Matej A1 - Albrecht, Martin A1 - Finke, Ondřej A1 - Hort, Ondřej A1 - Nejdl, Jaroslav A1 - Mudrich, Marcel A1 - Andreasson, Jakob A1 - Krikunova, Maria T1 - Electron correlation dynamics in atomic Kr excited by XUV pulses and controlled by NIR laser pulses of variable intensity JF - New Journal of Physics N2 - 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. KW - electron correlation KW - control ionization dynamics KW - krypton satellite states KW - XUV/NIR pump-probe KW - HHG KW - quantum beating oscillation KW - doubly excited states Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-16987 VL - 25 PB - Institute of Physics Publishing (IOP) ER - TY - CHAP A1 - Steglich, Patrick A1 - Mai, Andreas T1 - Analysis of BTO-on-Si-waveguides for energy-efficient electro-optical modulators T2 - Proc. SPIE 11775, Integrated Optics: Design, Devices, Systems and Applications VI N2 - 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. Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13934 ER - TY - JOUR A1 - Yeshchenko, Oleg A. A1 - Dmitruk, Igor M. A1 - Grytsenko, Kostyantyn A1 - Prokopets, Vadym M. A1 - Kotko, Andriy V. A1 - Schrader, Sigurd T1 - Influence of interparticle interaction on melting of gold nanoparticles in Au/polytetrafluoroethylene nanocomposites JF - Journal of Applied Physics N2 - The temperature dependence of the surface plasmon resonance energy and width in 5 nm spherical gold nanoparticles embedded in a polymer polytetrafluoroethylene matrix has been studied using absorption spectroscopy. The jumplike features have been observed in these dependences indicating the melting of gold nanoparticles at temperatures considerably lower than the bulk melting point. The interaction between gold nanoparticles sufficiently affects the melting of nanoparticles. The increase in the filling factor of the particles leads to a decrease in the melting temperature of gold nanoparticles. Y1 - 2009 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-9759 SN - 1089-7550 VL - 105 IS - 9 ER - TY - BOOK ED - Steglich, Patrick ED - De Matteis, Fabio T1 - Fiber Optics - From Fundamentals to Industrial Applications N2 - 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. Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-18093 UR - https://www.intechopen.com/books/7294 SN - 978-1-83881-157-0 PB - IntechOpen CY - London ER - TY - BOOK ED - Steglich, Patrick T1 - Plasmonic Nanostructures - Basic Concepts, Optimization and Applications N2 - 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. KW - Plasmonik KW - Simulation KW - Biomedizinische Technik KW - Nanotechnologie Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-18084 UR - https://www.intechopen.com/books/11147 SN - 978-1-80356-004-5 PB - IntechOpen CY - London ER - TY - JOUR A1 - Bauer, Joachim A1 - Gutke, Marko A1 - Heinrich, Friedhelm A1 - Edling, Matthias A1 - Stoycheva, Vesela A1 - Kaltenbach, Alexander A1 - Burkhardt, Martin A1 - Gruenefeld, Martin A1 - Gamp, Matthias A1 - Gerhard, Christoph A1 - Steglich, Patrick A1 - Steffen, Sebastian A1 - Herzog, Michael A1 - Dreyer, Christian A1 - Schrader, Sigurd T1 - Novel UV-transparent 2-component polyurethane resin for chip-on-board LED micro lenses JF - Optical Materials Express N2 - In this work we present a novel optical polymer system based on polyurethane elastomer components, which combines excellent UV transparency with high thermal stability, good hardness, high surface tension and long pot life. The material looks very promising for encapsulation and microlensing applications for chip-on-board (CoB) light-emitting diodes (LED). The extinction coefficient k, refractive index n, and bandgap parameters were derived from transmission and reflection measurements in a wavelength range of 200-890 nm. Thermogravimetry and differential scanning calorimetry were used to provide glass transition and degradation temperatures. The surface tension was determined by means of contact angle measurements. As proof of concept, a commercial InGaN-CoB-LED is used to demonstrate the suitability of the new material for the production of microlenses. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13472 SN - 2159-3930 VL - 10 IS - 9 SP - 2085 EP - 2099 ER - TY - JOUR A1 - Goldenberg, Leonid A1 - Köhler, Mathias A1 - Kahle, Olaf A1 - Dreyer, Christian T1 - Impact of inorganic nanoparticles on optical properties of low refractive index waveguiding polymers JF - Optical Materials Express N2 - The objective of this work is to improve the optical properties of low refractive index polymers used for waveguide by introduction of inorganic nanoparticles. Copolymers of fluorinated monomers and glycidyl methacrylate are used. Introduction of SiO2 nanoparticles into polymer matrix is performed by direct mixing; copolymerization with SiO2 nanoparticles modified by monomer, and in situ sol-gel formation of SiO2 during photochemical cross-linking and annealing catalyzed by photoacid generator. It is demonstrated that nanoparticles are able to decrease thermo-optic coefficient. It is also possible to fabricate waveguiding layers by direct introduction of nanoparticles without compromising of optical propagation losses. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-13521 SN - 2159-3930 VL - 10 IS - 11 SP - 2987 EP - 2997 ER - TY - JOUR A1 - Felke, Florens A1 - Groth, Anne A1 - Hempel, Martin A1 - Czerny, Bernhard A1 - Khatibi, Golta A1 - Döhler, Torsten A1 - Geißler, Ute T1 - Effect of the loop forming process on the lifetime of aluminum heavy wire bonds under accelerated mechanical testing JF - Microelectronics Reliability N2 - 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. KW - aluminum heavy wire bonding KW - mechanical accelerated lifetime testing method KW - heel crack KW - loop forming process KW - wrinkling Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-18631 VL - 154 PB - Elsevier ER - TY - CHAP A1 - Sievers, Jan A1 - Villringer, Claus A1 - Lebek, Werner A1 - Gilani, Taravat Saeb A1 - Laufer, Jan T1 - Photoacoustic tomography using a Fabry-Perot sensor with homogeneous optical thickness and wide-field camera-based detection T2 - Opto-Acoustic Methods and Applications in Biophotonics VI N2 - 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. KW - photoacoustic tomograph KW - Fabry-Perot sensor KW - camera-based setup KW - photopolymer KW - polyvinyl cinnamate KW - interferometer transfer function KW - acoustic sensitivity KW - detection aperture Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-17850 ER - TY - JOUR A1 - Dubrovinskaia, Natalia A1 - Dubrovinsky, Leonid A1 - Crichton, Wilson A1 - Langenhorst, Falko A1 - Richter, Asta T1 - Aggregated diamond nanorods, the densest and least compressible form of carbon JF - Applied Physics Letters N2 - We report the synthesis of aggregated diamondnanorods (ADNRs) from fullerene C60C60 at 20(1) GPa and 2200  °C using a multianvil apparatus. Individual diamond nanoroads are of 5–20 nm in diameter and longer than 1μm1μm. The x-ray and measured density of ADNRs is ∼0.2%–0.4%∼0.2%–0.4% higher than that of usual diamond. The extremely high isothermal bulk modulusKT=491(3)GPaKT=491(3)GPa [compare to KT=442(4)GPaKT=442(4)GPa of diamond] was obtained by in situx-ray diffraction study. Thus, ADNRs is the densest among all carbonmaterials and it has the lowest so far experimentally determined compressibility. Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-5646 SN - 0003-6951 VL - 87 IS - 8 ER - TY - GEN A1 - Bräske, Jörn A1 - Klohs, Steffen A1 - Mirre, Thomas T1 - Untersuchung zum Ausfall der Strangführungsrollen in der horizontalen Zone einer Brammenstranggussanlage T2 - Wissenschaftliche Beiträge 2016 N2 - Es besteht ein Problem durch den häufigen Ausfall der Strangführungsrollen und die resultierenden erheblichen Verluste durch den Produktionsausfall, welcher beim Ersetzen der Rolleneinheiten entsteht. Um die Ursachen zu ergründen wurden, zunächst die Randbedingungen und das Schadensbild analysiert. Daraus entstand die Hypothese, dass allgemein eine zu hohe Temperaturbelastung für die Schädigung der Lagerkomponenten verantwortlich ist und dies die grundlegende Ursache für die weitere Zerstörung darstellt. Folglich musste eine Messeinrichtung installiert werden, um genauere Erkenntnisse über den Überhitzungsvorgang zu erlangen. Zu diesem Zweck wurden mehrere Verfahren zur Temperaturmessung miteinander verglichen, woraufhin eine Auswahl anhand einer Nutzwertanalyse erfolgte. Die Auswertung der gewonnenen Messdaten zeigte, dass die Charakteristik der aufgezeichneten Überhitzungen sehr variabel ist. Weiterhin konnte keine Abhängigkeit von einem Prozessparameter ermittelt werden. Die genauer betrachteten Vorgänge konnten nicht oder nur eingeschränkt als Ursache für die Überhitzung nachgewiesen werden. Wenngleich somit weitere Untersuchungen erforderlich sind, wurden mögliche Maßnahmen zur Lösung des Problems vorgeschlagen. N2 - The problem deals with the frequent malfunction of the guide rolls and the following serious loss through the lost output, which develops because of the replacement of the rolls. First of all, the boundary conditions and the failure mode were analyzed to fathom the possible causes. Hence, the assumption arose that the general reason for the damage of the bearing components is that the temperature stress is too high, which is the reason for the further destruction. Consequently, a system of measurements has to be installed to get detailed insights about overheating. For this purpose, different methods of temperature detections were compared, whereupon a choice occurred on the basis of a utility analysis. The evaluation of the achieved measurement data showed that the characteristic of the recorded overheating is very different. Furthermore, a dependence on a process parameter cannot be proved. It was not possible, or just restricted, to verify the eyed instances as a cause of the high temperature. Although more researches are necessary, possible actions to solve the problem were proposed. Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-5346 SN - 0949-8214 VL - 20 SP - 49 EP - 58 ER - TY - JOUR A1 - Ou, Xin A1 - Anwand, Wolfgang A1 - Kögler, Reinhard A1 - Zhou, Hong-Bo A1 - Richter, Asta T1 - The role of helium implantation induced vacancy defect on hardening of tungsten JF - Journal of Applied Physics N2 - Vacancy-type defects created by helium implantation in tungsten and their impact on the nano-hardness characteristics were investigated by correlating the results from the positron annihilation spectroscopy and the nano-indentation technique. Helium implantation was performed at room temperature (RT) and at an elevated temperate of 600 °C. Also, the effect of post-annealing of the RT implanted sample was studied. The S parameter characterizing the open volume in the material was found to increase after helium irradiation and is significantly enhanced for the samples thermally treated at 600 °C either by irradiation at high temperature or by post-annealing. Two types of helium-vacancy defects were detected after helium irradiation; small defects with high helium-to-vacancy ratio (low S parameter) for RT irradiation and large defects with low helium-to-vacancy ratio (high S parameter) for thermally treated tungsten. The hardness of the heat treated tungsten coincides with the S parameter, and hence is controlled by the large helium-vacancy defects. The hardness of tungsten irradiated at RT without thermal treatment is dominated by manufacturing related defects such as dislocation loops and impurity clusters and additionally by trapped He atoms from irradiation effects, which enhance hardness. He-stabilized dislocation loops mainly cause the very high hardness values in RT irradiated samples without post-annealing. Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-5623 SN - 1089-7550 VL - 115 IS - 12 ER - TY - JOUR A1 - Rogge, Christian A1 - Zinn, Steffen A1 - Prosposito, Paolo A1 - Francini, Roberto A1 - Foitzik, Andreas T1 - Transmitted light pH optode for small sample volumes JF - Journal of Sensors and Sensor Systems N2 - An innovative concept of a low-cost pH optode with working volumes of less than 150 µL is presented. The pH monitoring is based on the color changing effect of pH indicators. The optode includes an RGB color sensor patch TCS34725 from Adafruit, a controllable LED and reactor slides and is addressed by a self-written LabVIEW© software. Utilizing the hue value of the HSV color model, it is possible to analyze the color change of the indicator and estimate the pH value of the analyzed samples by exploiting sigmoidal fit models. Measurements carried out with phenol red and DMEM (Dulbecco's Modified Eagle's Medium) reported a standard error of calibration in the physiologic pH range (6.5–7.5) of ±0.04 pH units. Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-10093 SN - 2194-878X VL - 6 IS - 2 SP - 351 EP - 359 ER - TY - JOUR A1 - Maier, Petra A1 - Clausius, Benjamin A1 - Richter, Asta A1 - Bittner, Benjamin A1 - Hort, Norbert A1 - Menze, Roman T1 - Crack Propagation in As-Extruded and Heat-Treated Mg-Dy-Nd-Zn-Zr Alloy Explained by the Effect of LPSO Structures and Their Micro- and Nanohardness JF - Materials N2 - 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. KW - magnesium KW - Mg-Dy-Nd-Zn-Zr KW - RESOLOY® KW - LPSO phases KW - crack propagation KW - hardness KW - nanoindentation Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-14194 SN - 1996-1944 VL - 14 IS - 13 PB - MDPI ER - TY - JOUR A1 - Smith, Roger A1 - Christopher, D. A1 - Kenny, S. D. A1 - Richter, Asta A1 - Wolf, Bodo T1 - Defect generation and pileup of atoms during nanoindentation of Fe single crystals JF - Physical Review B N2 - 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. Y1 - 2003 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-14855 VL - 67 IS - 24 ER - TY - JOUR A1 - Gerhard, Christoph A1 - Dobis, Alexander T1 - Manufacturing-induced surface contaminations JF - Vakuum in Forschung und Praxis N2 - 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. Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-15656 VL - 33 IS - 1 SP - 33 EP - 37 PB - Wiley ER - TY - JOUR A1 - Tarabrin, Mikhail K. A1 - Bushunov, Andrey A. A1 - Teslenko, Andrei A. A1 - Sakharova, Tatiana A1 - Hinkel, Jonas A1 - Usenov, Iskander A1 - Döhler, Torsten A1 - Geißler, Ute A1 - Artyushenko, Viacheslav A1 - Lazarev, Vladimir A. T1 - Fabrication of an antireflection microstructure on AgClBr polycrystalline fiber by single pulse femtosecond laser ablation JF - Optical Materials Express N2 - 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. Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-15384 VL - 11 IS - 2 SP - 487 EP - 496 PB - Optical Society of America ER - TY - CHAP A1 - Dietrich, Alexander A1 - van de Sand, Ron A1 - Reiff-Stephan, Jörg T1 - Implementation of a Machine Tool Retrofit System T2 - 2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021) N2 - 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. KW - retrofitting KW - CPS KW - machine tool KW - software architecture Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-15004 SP - 239 EP - 247 PB - TIB Open Publishing CY - Hannover ER - TY - CHAP A1 - Giese, Lutz B. A1 - Reiff-Stephan, Jörg T1 - Hydrogen and Usability of Hydrogen Storage Technologies T2 - 2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021) N2 - 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. KW - hydrogen storage KW - LOHC KW - climate-neutral mobility Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-14937 SP - 97 EP - 106 PB - TIB Open Publishing CY - Hannover ER - TY - CHAP A1 - van de Sand, Ron A1 - Corasaniti, Sandra A1 - Reiff-Stephan, Jörg T1 - Positive-Unlabelled Learning based Novelty Detection for Industrial Chillers BT - A Data-Driven Approach to Avoid Energy Wastage T2 - 2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021) N2 - 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. KW - chiller CBM KW - machine learning KW - energy efficiency Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-14965 VL - 1 SP - 155 EP - 164 PB - TIB Open Publishing CY - Hannover ER - TY - CHAP A1 - Falk, Constantin A1 - van de Sand, Ron A1 - Corasaniti, Sandra A1 - Reiff-Stephan, Jörg T1 - A Comparison Study of Data-Driven Anomaly Detection Approaches for Industrial Chillers T2 - 2nd German-West African Conference on Sustainable, Renewable Energy Systems (SusRES2021) N2 - 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. KW - fault detection KW - refrigeration system KW - data-driven machine-learning Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-14970 SP - 165 EP - 174 PB - TIB Open Publishing CY - Hannover ER - TY - INPR A1 - Steglich, Patrick A1 - Rabus, Dominik G. A1 - Sada, Cinzia A1 - Paul, Martin A1 - Weller, Michael G. A1 - Mai, Christian A1 - Mai, Andreas T1 - Silicon Photonic Micro-Ring Resonators for Chemical and Biological Sensing: A Tutorial T2 - TechRxiv N2 - 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. Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-16840 ER - TY - JOUR A1 - Alber, J A1 - Assfalg, L A1 - Nayeri, C N A1 - Paschereit, C O A1 - Lahr, Markus A1 - Semmler, L A1 - Twele, J A1 - Fortmann, J A1 - Fischer, J A1 - Latoufis, K A1 - Dorn, I T1 - 3D printed rotor blades for a research wind turbine: Aerodynamic and structural design and testing JF - Journal of Physics: Conference Series N2 - 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. Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-16314 VL - 2265 PB - Institute of Physics Publishing (IOP) ER - TY - JOUR A1 - Hermann, Jörg A1 - Grojo, David A1 - Axente, Emanuel A1 - Gerhard, Christoph A1 - Burger, Miloš A1 - Craciun, Valentin T1 - Ideal radiation source for plasma spectroscopy generated by laser ablation JF - Physical Review E N2 - 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. Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-16132 VL - 96 IS - 5 PB - American Physical Society (APS) ER - TY - GEN A1 - Gerhard, Christoph A1 - Letien, Emilie A1 - Cressent, Thomas A1 - Hofmann, Mandy T1 - Impact of the plasma power on plasma-induced increase in absorption of fused silica T2 - Wissenschaftliche Beiträge 2019 N2 - In the last decades, laser machining of fused silica has gained in importance where the main challenge is to overcome the high transmission of this medium in order to achieve surface absorption. One approach is plasma treatment using hydrogenous process gases. In doing so, a near-surface glass layer is chemically modified by a removal of oxygen and an implantation of hydrogen, resulting in the formation of optically active defects and an increase in absorption. Against this background, the impact of the plasma power on plasma-induced increase in absorption of fused silica was investigated in the present work. Here, the highest efficiency of the plasma treatment process was found at the lowest applied plasma power whereas for higher plasma powers, a notably lower increase in absorption was observed. This effect is attributed to the decomposition of plasma species required for initiating the formation of optically active defects within the glass. Such decomposition increases with rising power due to the corresponding increase in electric field strength within the plasma. This finding is of substantial interest for an extensive understanding of plasma-glass interactions. N2 - Die Laserbearbeitung von Quarzglas hat in den letzten Jahrzehnten an Bedeutung gewonnen. Dabei besteht die Herausforderung darin, die hohe Transmission dieses Mediums zu überwinden. Hierzu stellt eine Plasmabehandlung mittels wasserstoffhaltigen Prozessgasen einen Ansatz dar. Dabei wird eine oberflächennahe Glasschicht durch Entfernung von Sauerstoff und Implantation von Wasserstoff chemisch modifiziert, woraus die Ausbildung optisch aktiver Defekte und ein Anstieg der Absorption resultieren. Vor diesem Hintergrund wurde in dieser Arbeit der Einfluss der Plasmaleistung auf die plasmainduzierte Absorptionssteigerung untersucht. Die höchste Effizienz der Plasmabehandlung wurde bei der geringsten applizierten Leistung erzielt, wohingegen bei höheren Plasmaleistungen nennenswert geringere Absorptionssteigerungen beobachtet wurden. Dieser Effekt wird auf den Zerfall von Plasmaspezies, die für eine Ausbildung optisch aktiver Defekte benötigt werden, zurückgeführt, welcher mit ansteigender Leistung und dem damit einhergehenden Anstieg der elektrischen Feldstärke im Plasma anwächst. Diese Erkenntnis ist von hohem Interesse für ein umfassendes Verständnis von Plasma-Glas-Wechselwirkungen. N2 - Ces dernières décennies, les applications laser en usine composées de silice fondue ont gagné en importance, l'enjeu consistant à surmonter le problème de la transmission élevée de ce milieu dans le but d’obtenir l’absorption de surface. Une façon d’aborder le problème est d’appliquer le traitement au plasma en utilisant des procédés au gaz de dihydrogène. En agissant ainsi, une couche de verre proche de la surface est modifiée chimiquement par l’ablation d’oxygène et l’implantation d’hydrogène, ce qui provoque la formation de défauts optiquement actifs et l’augmentation de l’absorption. Dans ce contexte, l’impact de la puissance du plasma sur l’augmentation de l’absorption de silice fondue induite par le plasma a été étudié dans cet article. Ici, la meilleure efficacité du traitement au plasma a été constatée à la puissance de plasma la plus faible tandis que pour de plus fortes puissances, une augmentation bien plus faible en absorption a été observée. Cet effet est attribué à la décomposition des espèces de plasma requises dans la formation des défauts optiquement actifs à l’intérieur du verre. Une telle décomposition augmente avec la montée de puissance due à l'augmentation de force du champ électrique dans le plasma. Cette découverte est d’un intérêt considérable pour une compréhension plus poussée des interactions plasma-verre. Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-10802 SN - 0949-8214 VL - 23 SP - 33 EP - 37 ER - TY - CHAP A1 - Prelipceanu, Marius A1 - Cojocariu, Lucian A1 - Graur, Adrian A1 - Schrader, Sigurd T1 - Analysis of thermally stimulated processes in new phenanthroline derivatives suitable for optoelectronic devices T2 - Journal of Physics: Conference Series (JPCONF) N2 - Thermally stimulated processes have been studied in thin films of phenanthroline derives to describe the states that had been localized. Ultraviolet Photoelectron Spectroscopy had checked out before thin films of new pyrrolo[l,2-a][l,10] phenanthroline derivatives [1], in order to further applications in optoelectronic devices. The investigated compounds have an electronic band structure which is due to the substituent (R=NO2, Cl) induced transformations of molecular orbitals. Thermally stimulated discharge currents (TSDC) attested dipolar and charge transport mechanisms. Each TSDC peak has been assigned to elementary processes that are different utilizing in addition dielectric spectroscopy (DES), and the mean trap depths have been approximated from thermally stimulated luminescence (TSL) curves. Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-12050 SN - 1742-6596 VL - 585 ER - TY - JOUR A1 - Ksianzou, Viachaslau A1 - Velagapudi, R. K. A1 - Grimm, Bernd A1 - Schrader, Sigurd T1 - Polarization-dependent optical characterization of poly(phenylquinoxaline) thin films JF - Journal of Applied Physics N2 - Linear optical properties of two types of poly(phenylquinoxaline) (PPQ) are studied by multiwavelength prism coupling technique and optical absorption spectroscopy. Surface roughness measurements are done using atomic force microscopy. PPQs form smooth films of high optical quality having refractive indices above 1.7 in the visible and near infrared spectral ranges. Enhanced birefringence of Δn∼0.04Δn∼0.04 has been observed in both PPQ films prepared by spin coating. Sellmeier coefficients are derived for the wavelength range starting from 0.532to1.064μm0.532to1.064μm for both TE and TM polarizations. Quantum chemical calculations both on the semiempirical and on the ab initio level are carried out in order to calculate the first-order molecular polarizability tensors of the polymer repeat units. From the obtained tensor elements, theoretical values for both the average refractive indices and the maximum expectable birefringence are calculated. Based on these values a more detailed interpretation of the experimental findings is carried out. The dispersion of refractive index is quantified by the value of Abbe’s constant (νd)(νd). In our case the value νd≈11νd≈11 indicates high dispersion in the visible spectral range. The imaginary part kk of the complex refractive index n∗=n−ikn*=n−ik reaches values of k⩽10−3k⩽10−3 in the wavelength range from 0.5to1μm0.5to1μm. Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-9761 SN - 1089-7550 VL - 100 IS - 6 ER - TY - JOUR A1 - Minaev, Boris A1 - Jansson, Emil A1 - Ågren, Hans A1 - Schrader, Sigurd T1 - Theoretical study of phosphorescence in dye doped light emitting diodes JF - The Journal of Chemical Physics N2 - Phosphorescence of platinum(II) octaethyl porphyrin (PtOEP), which has been used in organic light emitting diodes to overcome the efficiency limit imposed by the formation of triplet excitons, is studied by time-dependent (TD) density functional theory (DFT). Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-9775 SN - 1089-7690 VL - 125 IS - 23 ER - TY - JOUR A1 - Gerhard, Christoph A1 - Gimpel, Thomas A1 - Tasche, Daniel A1 - Koch, Jennifer A1 - Brückner, Stephan A1 - Flachenecker, Günter A1 - Wieneke, Stephan A1 - Schade, Wolfgang A1 - Viöl, Wolfgang T1 - Atmospheric pressure plasma-assisted femtosecond laser engraving of aluminium JF - Journal of Physics D: Applied Physics N2 - In this contribution, we report on the impact of direct dielectric barrier discharge argon plasma at atmospheric pressure on femtosecond laser engraving of aluminium. It is shown that the assisting plasma strongly affects the surface geometry and formation of spikes of both laser-engraved single lines and patterns of adjacent lines with an appropriate overlap. Further, it was observed that the overall ablation depth is significantly increased in case of large-scale patterning whereas no notable differences in ablation depth are found for single lines. Several possible mechanisms and underlying effects of this behaviour are suggested. The increase in ablation depth is supposed to be due to a plasma-induced removal of debris particles from the cutting point via charging and oxidation as supported by EDX analysis of the re-solidified debris. Furthermore, the impact of a higher degree of surface wrinkling as well as direct interactions of plasma species with the aluminium surface on the ablation process are discussed. Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:526-opus4-10521 SN - 1361-6463 VL - 51 SP - 1 EP - 7 ER -