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Now showing 1 - 10 of 236
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    Fast scatterometric measurement of periodic surface structures plasma-etching processes
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2018) Klesse, Wolfgang Matthias; Rathsfeld, Andreas; Groß, Claudine; Malguth, Enno; Skibitzki, Oliver; Zealouk, Lahbib
    To satisfy the continuous demand of ever smaller feature sizes, plasma etching technologies in microelectronics processing enable the fabrication of device structures with dimensions in the nanometer range. In a typical plasma etching system a plasma phase of a selected etching gas is activated, thereby generating highly energetic and reactive gas species which ultimately etch the substrate surface. Such dry etching processes are highly complex and require careful adjustment of many process parameters to meet the high technology requirements on the structure geometry. In this context, real-time access of the structures dimensions during the actual plasma process would be of great benefit by providing full dimension control and film integrity in real-time. In this paper, we evaluate the feasibility of reconstructing the etched dimensions with nanometer precision from reflectivity spectra of the etched surface, which are measured in real-time throughout the entire etch process. We develop and test a novel and fast reconstruction algorithm, using experimental reflection spectra taken about every second during the etch process of a periodic 2D model structure etched into a silicon substrate. Unfortunately, the numerical simulation of the reflectivity by Maxwell solvers is time consuming since it requires separate time-harmonic computations for each wavelength of the spectrum. To reduce the computing time, we propose that a library of spectra should be generated before the etching process. Each spectrum should correspond to a vector of geometry parameters s.t. the vector components scan the possible range of parameter values for the geometrical dimensions. We demonstrate that by replacing the numerically simulated spectra in the reconstruction algorithm by spectra interpolated from the library, it is possible to compute the geometry parameters in times less than a second. Finally, to also reduce memory size and computing time for the library, we reduce the scanning of the parameter values to a sparse grid.
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    VPN Seat - drahtloses virtuelles Netzwerk für die Kommunikation durch den Passagier : Abschlußbericht für Verbundprojekt VPN Seat
    (Hannover : Technische Informationsbibliothek (TIB), 2010) Langendörfer, Peter; Maye, Oliver
    [no abstract available]
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    Separation, characterization, and handling of microalgae by dielectrophoresis
    (Basel : MDPI, 2020) Abt, Vinzenz; Gringel, Fabian; Han, Arum; Neubauer, Peter; Birkholz, Mario
    Microalgae biotechnology has a high potential for sustainable bioproduction of diverse highvalue biomolecules. Some of the main bottlenecks in cell-based bioproduction, and more specifically in microalgae-based bioproduction, are due to insufficient methods for rapid and efficient cell characterization, which contributes to having only a few industrially established microalgal species in commercial use. Dielectrophoresis-based microfluidic devices have been long established as promising tools for label-free handling, characterization, and separation of broad ranges of cells. The technique is based on differences in dielectric properties and sizes, which results in different degrees of cell movement under an applied inhomogeneous electrical field. The method has also earned interest for separating microalgae based on their intrinsic properties, since their dielectric properties may significantly change during bioproduction, in particular for lipid-producing species. Here, we provide a comprehensive review of dielectrophoresis-based microfluidic devices that are used for handling, characterization, and separation of microalgae. Additionally, we provide a perspective on related areas of research in cell-based bioproduction that can benefit from dielectrophoresis-based microdevices. This work provides key information that will be useful for microalgae researchers to decide whether dielectrophoresis and which method is most suitable for their particular application. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
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    Support for a long lifetime and short end-to-end delays with TDMA protocols in sensor networks
    (London : Hindawi, 2012) Brzozowski, Marcin; Salomon, Hendrik; Langendoerfer, Peter
    This work addresses a tough challenge of achieving two opposing goals: ensuring long lifetimes and supporting short end-to-end delays in sensor networks. Obviously, sensor nodes must wake up often to support short delays in multi-hop networks. As event occurs seldom in common applications, most wake-up are useless: nodes waste energy due to idle listening. We introduce a set of solutions, referred to as LETED (limiting end-to-end delays), which shorten the wake-up periods, reduce idle listening, and save energy. We exploit hardware features of available transceivers that allow early detection of idle wake-up periods. This feature is introduced on top of our approach to reduce idle listening stemming from clock drift owing to the estimation of run-time drift. To evaluate LETED and other MAC protocols that support short end-to-end delays we present an analytical model, which considers almost 30 hardware and software parameters. Our evaluation revealed that LETED reduces idle listening by 15x and more against similar solutions. Also, LETED outperforms other protocols and provides significant longer lifetimes. For example, nodes with LETED work 8x longer than those with a common TDMA and 2x-3x longer than with protocols based on preamble sampling, like B-MAC.
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    Entwicklung, Umsetzung und Professionalisierung eines Verwertungskonzeptes am Leibniz-Institut für innovative Mikroelektronik (IHP)
    (Hannover : Technische Informationsbibliothek (TIB), 2014) Kissinger, Wolfgang
    [no abstract available]
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    Charge pump design in 130 nm SiGe BiCMOS technology for low-noise fractional-N PLLs
    (München : European Geopyhsical Union, 2015) Kucharski, M.; Herzel, F.
    This paper presents a numerical comparison of charge pumps (CP) designed for a high linearity and a low noise to be used in a fractional-N phase-locked loop (PLL). We consider a PLL architecture, where two parallel CPs with DC offset are used. The CP for VCO fine tuning is biased at the output to keep the VCO gain constant. For this specific architecture, only one transistor per CP is relevant for phase detector linearity. This can be an nMOSFET, a pMOSFET or a SiGe HBT, depending on the design. The HBT-based CP shows the highest linearity, whereas all charge pumps show similar device noise. An internal supply regulator with low intrinsic device noise is included in the design optimization.
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    A survey on Bluetooth multi-hop networks
    (Amsterdam [u.a.] : Elsevier Science, 2019) Todtenberg, Nicole; Kraemer, Rolf
    Bluetooth was firstly announced in 1998. Originally designed as cable replacement connecting devices in a point-to-point fashion its high penetration arouses interest in its ad-hoc networking potential. This ad-hoc networking potential of Bluetooth is advertised for years - but until recently no actual products were available and less than a handful of real Bluetooth multi-hop network deployments were reported. The turnaround was triggered by the release of the Bluetooth Low Energy Mesh Profile which is unquestionable a great achievement but not well suited for all use cases of multi-hop networks. This paper surveys the tremendous work done on Bluetooth multi-hop networks during the last 20 years. All aspects are discussed with demands for a real world Bluetooth multi-hop operation in mind. Relationships and side effects of different topics for a real world implementation are explained. This unique focus distinguishes this survey from existing ones. Furthermore, to the best of the authors’ knowledge this is the first survey consolidating the work on Bluetooth multi-hop networks for classic Bluetooth technology as well as for Bluetooth Low Energy. Another individual characteristic of this survey is a synopsis of real world Bluetooth multi-hop network deployment efforts. In fact, there are only four reports of a successful establishment of a Bluetooth multi-hop network with more than 30 nodes and only one of them was integrated in a real world application - namely a photovoltaic power plant. © 2019 The Authors
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    Effectiveness of myAirCoach: A mHealth Self-Management System in Asthma
    (Amsterdam [u.a.] : Elsevier, 2020) Khusial, Rishi J.; Honkoop, Persijn J.; Usmani, Omar; Soares, Marcia; Simpson, Andrew; Biddiscombe, Martyn; Meah, Sally; Bonini, Matteo; Lalas, Antonios; Polychronidou, Eleftheria; Koopmans, Julia G.; Moustakas, Konstantinos; Snoeck-Stroband, Jiska B.; Ortmann, Steffen; Votis, Konstantinos; Tzovaras, Dimitrios; Chung, Kian Fan; Fowler, Stephen; Sont, Jacob K.
    Background: Self-management programs have beneficial effects on asthma control, but their implementation in clinical practice is poor. Mobile health (mHealth) could play an important role in enhancing self-management. Objective: To assess the clinical effectiveness and technology acceptance of myAirCoach-supported self-management on top of usual care in patients with asthma using inhalation medication. Methods: Patients were recruited in 2 separate studies. The myAirCoach system consisted of an inhaler adapter, an indoor air-quality monitor, a physical activity tracker, a portable spirometer, a fraction exhaled nitric oxide device, and an app. The primary outcome was asthma control; secondary outcomes were exacerbations, quality of life, and technology acceptance. In study 1, 30 participants were randomized to either usual care or myAirCoach support for 3 to 6 months; in study 2, 12 participants were provided with the myAirCoach system in a 3-month before-after study. Results: In study 1, asthma control improved in the intervention group compared with controls (Asthma Control Questionnaire difference, 0.70; P = .006). A total of 6 exacerbations occurred in the intervention group compared with 12 in the control group (hazard ratio, 0.31; P = .06). Asthma-related quality of life improved (mini Asthma-related Quality of Life Questionnaire difference, 0.53; P = .04), but forced expiratory volume in 1 second was unchanged. In study 2, asthma control improved by 0.86 compared with baseline (P = .007) and quality of life by 0.16 (P = .64). Participants reported positive attitudes toward the system. Discussion: Using the myAirCoach support system improves asthma control and quality of life, with a reduction in severe asthma exacerbations. Well-validated mHealth technologies should therefore be further studied. © 2020 The Authors
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    A QPSK 110-Gb/s Polarization-Diversity MIMO Wireless Link with a 220-255 GHz Tunable LO in a SiGe HBT Technology
    (New York, NY : IEEE, 2020) Rodríguez-Vázquez, Pedro; Grzyb, Janusz; Heinemann, Bernd; Pfeiffer, Ullrich R.
    In this article, a polarization-diversity technique multiple-input multiple-output (MIMO) is demonstrated to double the spectral efficiency of a line-of-sight quadrature phase-shift keying (QPSK) wireless link at 220-255 GHz with a pair of highly integrated single-chip transmitter (TX) and receiver (RX) front-end modules in 0.13-µ {m SiGe HBT technology ( fTmax=350 /550 GHz) exploiting only a low-cost wire-bonded chip-on-board packaging solution for high-speed baseband (BB) signals. Both TX and RX chips accommodate two independent fundamentally operated direct-conversion in-phase and quadrature (IQ) paths with separately tunable on-chip multiplier-based ( × 16 ) local oscillator (LO) generation paths driven from a single external highly stable 13.75-16-GHz frequency synthesizer. On the RX side, a mixer-first architecture is implemented to improve the symmetry between upper and lower sidebands (USB and LSB) at the cost of an increased noise figure (NF), whereas, on the TX chip, each upconversion mixer is followed by a gain-bandwidth (BW)-limited four-stage power amplifier (PA) to support the link budget at a meter distance. Next, two independent IQ data streams from the upconversion/downconversion paths on each chip are directed to a common lens-coupled broadband on-chip slot antenna system. This way, two orthogonal circular polarizations [left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP)] can be transmitted with sufficient isolation for link operation without the need for a high-speed depolarizer in the BB for any relative orientation between TX and RX modules. The antenna combined with a 9-mm diameter Si-lens provides a directivity of 23.5-27 dBi at 210-270 GHz for each of the modules. This, along with a peak radiated power of 7.5 dBm/ch from the TX module, and the cascaded conversion gain (CG)/single sideband (SSB) NF of 18/18 dB/ch for the RX module followed by a broadband amplifier (PSPL5882) from Tektronix allowed successful transmission of two independent QPSK data streams with an aggregate speed of 110 and 80 Gb/s over 1 and 2 m, respectively, at 230 GHz with a board-level limited channel BB bandwidth (BW) of 13.5 GHz. © 1963-2012 IEEE.
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    Subnanometer Control of the Heteroepitaxial Growth of Multimicrometer-Thick Ge /(Si, Ge) Quantum Cascade Structures
    (College Park, Md. [u.a.] : American Physical Society, 2023) Talamas Simola, Enrico; Montanari, Michele; Corley-Wiciak, Cedric; Di Gaspare, Luciana; Persichetti, Luca; Zöllner, Marvin H.; Schubert, Markus A.; Venanzi, Tommaso; Trouche, Marina Cagnon; Ortolani, Michele; Mattioli, Francesco; Sfuncia, Gianfranco; Nicotra, Giuseppe; Capellini, Giovanni; Virgilio, Michele; De Seta, Monica
    The fabrication of complex low-dimensional quantum devices requires the control of the heteroepitaxial growth at the subnanometer scale. This is particularly challenging when the total thickness of stacked layers of device-active material becomes extremely large and exceeds the multi-μm limit, as in the case of quantum cascade structures. Here, we use the ultrahigh-vacuum chemical vapor deposition technique for the growth of multi-μm-thick stacks of high Ge content strain-balanced Ge/SiGe tunneling heterostructures on Si substrates, designed to serve as the active material in a THz quantum cascade laser. By combining thorough structural investigation with THz spectroscopy absorption experiments and numerical simulations we show that the optimized deposition process can produce state-of-the-art threading dislocation density, ultrasharp interfaces, control of dopant atom position at the nanoscale, and reproducibility within 1% of the layer thickness and composition within the whole multilayer. We show that by using ultrahigh-vacuum chemical vapor deposition one achieves simultaneously a control of the epitaxy down to the sub-nm scale typical of the molecular beam epitaxy, and the high growth rate and technological relevance of chemical vapor deposition. Thus, this technique is a key enabler for the deposition of integrated THz devices and other complex quantum structures based on the Ge/SiGe material system.