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Strain and screening: Optical properties of a small-diameter carbon nanotube from first principles

Physical Review B 2019年第7期99卷 075140-075140页

作者： Christian Wagner Jörg Schuster André Schleife Technische Universität Chemnitz Center for Microtechnologies Reichenhainer Straße 70 09126 Chemnitz Germany Department of Materials Science and Engineering University of Illinois at Urbana-Champaign Urbana Illinois 61801 USA Fraunhofer Institute for Electronic Nano Systems (ENAS) Technologiecampus 3 09126 Chemnitz Germany Dresden Center for Computational Materials Science (DCMS) Technische Universität Dresden 01062 Dresden Germany Frederick Seitz Materials Research Laboratory University of Illinois at Urbana-Champaign Urbana Illinois 61801 USA National Center for Supercomputing Applications University of Illinois at Urbana-Champaign Urbana Illinois 61801 USA

Carbon nanotubes (CNTs) are a one-dimensional material system with intriguing physical properties that lead to emerging applications. While CNTs are unusually strain resistant compared to bulk materials, their optical-absorption spectrum is highly strain dependent. It is an open question, as to what extent this is attributed to strain-dependent (i) electronic single-particle transitions, (ii) dielectric screening, or (iii) atomic geometries including CNT radii. We use cutting-edge theoretical spectroscopy to explain strain-dependent electronic structure and optical properties of an (8,0) CNT. Quasiparticle effects are taken into account using Hedin's GW approximation and excitonic effects are described by solving a Bethe-Salpeter-equation for the optical polarization function. This accurate first-principles approach allows us to identify an influence of strain on screening of the Coulomb electron-electron interaction and to quantify the impact on electronic structure and optical absorption of one-dimensional systems. We interpret our thoroughly converged results using an existing scaling relation and extend the use of this relation to strained CNTs. We show that it captures optical absorption with satisfactory accuracy, as long as screening, quasiparticle gap, and effective electron and hole masses of the strained CNT are known.

关键词： Band gap Molecular spectra Strain Nanotubes GW method Many-body techniques

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Cover Feature: Spruce Hard Carbon Anodes for Lithium-Ion Batteries (ChemElectroChem 24/2021)

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ChemElectroChem 2021年第24期8卷

作者： Mathias Drews Jan Büttner Manuel Bauer Junaid Ahmed Dr. Rajib Sahu Prof. Christina Scheu Dr. Severin Vierrath Prof. Anna Fischer Dr. Daniel Biro Fraunhofer Institute for Solar Energy Systems ISE Heidenhofstraße 2 79110 Freiburg Germany Institute for Inorganic and Analytical Chemistry University of Freiburg Albertstraße 21 79104 Freiburg Germany Freiburg Center for Interactive Materials and Bioinspired Technologies FIT University of Freiburg Georges-Köhler-Allee 105 79110 Freiburg Germany Cluster of Excellence livMatS University of Freiburg 79104 Freiburg Germany Max Planck Institute for Iron Research Max-Planck-Straße 1 40237 Düsseldorf Germany Materials Analytics RWTH University of Aachen Kopernikusstraße 10 52074 Aachen Germany Electrochemical Energy Systems IMTEK - Department of Microsystems Engineering University of Freiburg Georges-Köhler-Allee 103 79110 Freiburg Germany Freiburg Materials Research Center FMF University of Freiburg Stefan-Meier-Straße 21 79104 Freiburg Germany

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A side-wall spacer process for releasing and sealing of post-CMOS MEMS pressure sensor membranes

A side-wall spacer process for releasing and sealing of post...

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MikroSystemTechnik Kongress 2017: MEMS, Mikroelektronik, Systeme - MikroSystemTechnik Conference 2017: MEMS, Microelectronics, systems

作者： Walk, C. Görtz, M. Mokwa, W. Vogt, H. Fraunhofer Institute for Microelectronic Circuits and Systems Duisburg Germany Institute for Materials in Electrical Engineering I RWTH Aachen University Germany University of Duisburg-Essen Department of Electronic Components and Circuits Germany

ISBN: (纸本)9783800744916

In this work a sub-step of the fabrication of an absolute capacitive pressure sensor MEMS on top of a CMOS substrate is discussed. For low pressure applications membrane diameters of more than 100 µm are required. To apply an isotropic HF-vapour phase etching process for successful release of MEMS structures, an access to the sacrificial layer is required. Since vapour phase etching of a sacrificial layer by side openings is shown to be inappropriate due to the addressed diameters, vertically arranged openings in the structural layer of the MEMS-structure have been utilised. Different designs of possible etch accesses are simulated regarding their impact on stress. It is shown that a diameter minimisation of vertical etch-access tunnels is beneficial with respect to stress (under an applied pressure of 1500 hPa) and regarding the conditions for sealing the cavity. Therefore, a side-wall spacer process, which minimises the diameters of vertical etch-access tunnels was developed and discussed. By the use of two applied hardmasks the diameter of lithographically structured tunnels is reduced by about 260 nm (40%). © 2017 *** right reserved.

关键词： Etching

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Systematic Development of Smart Factory using CONSENS

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Procedia Manufacturing 2018年 24卷 278-283页

作者： Ubaidullah Mohammad Cheng Yee Low Ramhuzaini Abd Rahman Laban Asmar Martin Rabe Roman Dumitrescu Noor Ayuni Che Zakaria Advanced Technology Training Center (ADTEC) Shah Alam 40460 Shah Alam Selangor Malaysia Faculty of Mechanical and Manufacturing Engineering Universiti Tun Hussein Onn Malaysia 86400 Parit Raja Johor Malaysia Fraunhofer Institute for Mechatronic Systems Design Zukunftsmeile 1 33102 Paderborn Germany Faculty of Mechanical Engineering Universiti Teknologi MARA Shah Alam Selangor Malaysia

Industry 4.0 is changing design and manufacturing methodologies because future production lines will manufacture customized products for the mass market. As for that, Automated machines and systems in such a production line need to communicate with each other. In this context, data exchange takes place between different kind of systems or platforms. Therefore a system level approach clarifying the interactions between the manufacturing devices in heterogeneous environments addressing highly dynamic and often loosely coupled production processes is required. This paper describes a model-based systems engineering approach of which the system integration of a smart factory is systematically managed right from the conception design phase. During the conception phase, the communication flows between the system elements is specified using CONSENS (Conceptual Design Specification Technique for the engineering of Complex systems). Based on the system level design specifications, a working prototype of a mini production line deploying Supervisory Control and Data Acquisition (SCADA) technology has been developed. The SCADA software acts as a human-machine interface and provides a gateway to access data of the production line either locally or through the internet. Multi-role users could access the system locally or remotely for monitoring, controlling, analyzing and ordering using SCADA as the interface.

关键词： systems engineering CONSENS Industry 4.0 Integrated factory SCADA

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Farming in the Era of Industrie 4.0

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Procedia CIRP 2018年 72卷 979-984页

作者： Anja-Tatjana Braun Eduardo Colangelo Thilo Steckel Reutlingen University Alteburgstraße 150 Reutlingen 72762 Germany Fraunhofer Institute for Manufacturing Engineering and Automation IPA Nobelst. 12 Stuttgart 70569 Germany CLAAS E-Systems KGaA mbH & Co KG Sommerkämpen 11 Gütersloh 49201 Dissen a.T.W.

Consistent supply chain management across all levels of value creation is a common approach in the industrial sector. The implementation in agricultural processes requires rethinking the supply chain concept. The reasons are the heuristic characterised processes, the stochastic environmental conditions, the mobility of the production facilities and the low division of work. In this paper we deal with how concepts of innovative supply chain management in the era of Industrie 4.0 could not only deliver a way to overcome said problems but also provide the foundation for the development of new forms of work and business models for Farming 4.0.

关键词： Supply Chain Management Industrie 4.0 Smart Farming Farming 4.0 Landwirtschaft 4.0

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Table-top high-energy 7µm OPCPA and 260mJ Ho:ylf pump laser

arXiv

引用

arXiv 2019年

作者： Elu, U. Steinle, T. Sánchez, D. Maidment, L. Zawilski, K. Schunemann, P. Zeitner, U.D. Simon-Boisson, C. Biegert, J. ICFO - Institut de Ciencies Fotoniques Barcelona Institute of Science and Technology Castelldefels Barcelona08860 Spain BAE Systems MER15-1813 P.O. Box 868 NashuaNH03061 United States Fraunhofer Institute of Applied Optics and Precision Engineering A.-Einstein-Str. 7 Jena07745 Germany THALES Optronique S.A.S. Laser Solutions Unit 2 avenue Gay-Lussac Elancourt Cedex78995 France ICREA Pg. Lluis Companys 23 Barcelona08010 Spain

We present the state of the art of a compact high-energy mid-infrared laser system for TW-level 8-cycle pulses at 7 µm. This system consists of an Er:Tm:Ho:fiber MOPA which serves as the seeder for a ZGP-based OPCPA chain in addition to a Ho:YLF amplifier which is Tm:fiber pumped. Featuring all-optical synchronization, the system delivers 260-mJ pump energy at 2052 nm, 16-ps duration at 100 Hz with a stability of 0.8 % rms over 20 min. We show that chirp inversion in the OPCPA chain leads to excellent energy extraction and aids in compression of the 7-µm pulses to 8 optical cycles (188 fs) in bulk BaF2 with 93.5 % efficiency. Using 21.7 mJ of the available pump energy, we generate 0.75-mJ-energy pulses at 7 µm due to increased efficiency with a chirp-inversion scheme. The pulse quality of the system’s output is shown by generating high harmonics in ZnSe which span up to harmonic order 13 with excellent contrast. The combination of the passive carrier-envelope phase stable mid-infrared seed pulses and the high-energy 2052 nm picosecond pulses makes this compact system a key enabling tool for the next generation of studies on extreme photonics, strong field physics and table-top coherent X-ray science. Copyright © 2019, The Authors. All rights reserved.

关键词： Infrared devices

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Micro-Doppler based human-robot classification using ensemble and deep learning approaches

arXiv

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arXiv 2017年

作者： Abdulatif, Sherif Wei, Qian Aziz, Fady Kleiner, Bernhard Schneider, Urs Department of Biomechatronic Systems Fraunhofer Institute for Manufacturing Engineering and Automation IPA

Radar sensors can be used for analyzing the induced frequency shifts due to micro-motions in both range and velocity dimensions identified as micro-Doppler (µ-D) and micro-Range (µ-R), respectively. Different moving targets will have unique µ-D and µ-R signatures that can be used for target classification. Such classification can be used in numerous fields, such as gait recognition, safety and surveillance. In this paper, a 25 GHz FMCW Single-Input Single-Output (SISO) radar is used in industrial safety for real-time human-robot identification. Due to the real-time constraint, joint Range-Doppler (R-D) maps are directly analyzed for our classification problem. Furthermore, a comparison between the conventional classical learning approaches with handcrafted extracted features, ensemble classifiers and deep learning approaches is presented. For ensemble classifiers, restructured range and velocity profiles are passed directly to ensemble trees, such as gradient boosting and random forest without feature extraction. Finally, a Deep Convolutional Neural Network (DCNN) is used and raw R-D images are directly fed into the constructed network. DCNN shows a superior performance of 99% accuracy in identifying humans from robots on a single R-D map.68T10 (Primary), 68T40 (Secondary) Copyright © 2017, The Authors. All rights reserved.

关键词： Deep neural networks

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Edge recombination analysis of silicon solar cells using photoluminescence measurements

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AIP Conference Proceedings 2019年第1期2147卷

作者： Hannah Stolzenburg Andreas Fell Florian Schindler Wolfram Kwapil Armin Richter Puzant Baliozian Martin C. Schubert 1Fraunhofer Institute for Solar Energy Systems ISE Heidenhofstraße 2 79110 Freiburg Germany 2University Freiburg Department of Sustainable Systems Engineering (INATECH) Emmy-Noether-Str. 2 79110 Freiburg Germany

Edge losses in silicon solar cells are becoming more important in current photovoltaic research, especially in shingled cell modules with high perimeter to area ratios. Hence, in this study a new approach is presented to quantify edge recombination losses by using photoluminescence (PL) measurements combined with device modelling. The main focus of this work is to determine and separate the contribution of the two relevant edge recombination losses: (i) recombination at the bulk edge, described by an effective surface recombination velocity Seff,edge, and (ii) recombination at the pn-junction edge, described by an edge-length specific non-ideal recombination parameter J02,edge. For this purpose, the PL gradient towards the edge at different illumination intensities is fitted by Quokka3 simulations. The developed method is applied for differently separated unpassivated edges, namely by thermal laser separation (TLS) and by mechanical cleaving. Additionally, an emitter window for the TLS edge is introduced where no pn-junction at the edge is present. It was found that the emitter window results in less edge recombination while having the same bulk-edge recombination properties as without. As a result, J02,edge = 3 nA/cm and Seff,edge = 105 cm/s are determined for the TLS edge without emitter window while the mechanically cleaved edge showed higher edge recombination.

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A WR3-band reflective-type phase shifter MMIC with integrated amplifier for error- and loss compensation 12

A WR3-band reflective-type phase shifter MMIC with integrate...

引用

12th European Microwave Integrated Circuits Conference, EuMIC 2017

作者： Muller, D. Beck, A. Massler, H. Tessmann, A. Leuther, A. Zwick, T. Kallfass, I. Institute of Radio Frequency Engineering and Electronics Karlsruhe Institute of Technology Karlsruhe76131 Germany Fraunhofer Institute for Applied Solid State Physics Freiburg79108 Germany Institute of Robust Power Semiconductor Systems University of Stuttgart Stuttgart70569 Germany

ISBN: (纸本)9782874870484

To enable beamsteering capabilities for millimeter-wave radar and communication systems, phase shifters are key components. In this paper a WR3-band (220-325 GHz) phase shifter MMIC is presented, which is based on reflective-type phase shifters and enhanced with an integrated variable gain amplifier for loss-compensation, RMS error optimization and antenna tapering. The circuit has an average loss of only 1.6 dB and a 3 dB bandwidth ranging from 218 to 268 GHz. In this frequency range the maximum phase shift is 247° with phase and amplitude RMS errors below 10.4° and 1.5 dB, respectively. The MMIC was processed in a 50 nm InGaAs metamorphic HEMT technology and has a chip size of only 0.75 × 0.75 mm2. © 2017 European Microwave Association.

关键词： Monolithic microwave integrated circuits

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High repetition rate and high photon flux HHG source enabled by ultrafast fiber laser

High repetition rate and high photon flux HHG source enabled...

引用

Ultrafast Optics 2017

作者： Hädrich, S. Eidam, T. Hoffmann, A. Wunderlich, S. Jansen, F. Steil, D. Mathias, S. Limpert, J. Active Fiber Systems GmbH Wildenbruchstr. 15 Jena07745 Germany Georg-August-Universität Göttingen I. Physikalisches Institut Friedrich-Hund-Platz 1 Göttingen37077 Germany Friedrich-Schiller-Universität Jena Abbe Center of Photonics Institute of Applied Physics Albert-Einstein-Straße 15 Jena07745 Germany Helmholtz-Institute Jena Fröbelstieg 3 Jena07743 Germany Fraunhofer Institute for Applied Optics and Precision Engineering Albert-Einstein-Straße 7 Jena07745 Germany

A commercial 100W turn-key fiber-laser system is used for HHG at 0.5MHz. The source offers record-high photon flux of >4.5·1010 photons/s (68.6eV) or a narrowband harmonic with 8.6·1011 photons/s (26.6eV)... 详细信息

ISBN: (纸本)9781510617162

关键词： Photons

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