TY - INPR A1 - Steffens, Oliver T1 - Leibniz, Llull and the Logic of Truth: Precursors of Artificial Intelligence N2 - Mankind has always been confronted with limited knowledge about Nature and many people devoted their lives and intellects to the very question: How to gain knowledge, confirm ideas and theories, and understand the world we live in? Religion was one fundamental base for explanations and existential questions. Philosophy and Science were the other. Nowadays, science and technology dominate our daily lives, religion and metaphysics have lost their former dominance, while our thoughts and factual knowledge are increasingly governed by the digitised versions of conversation and discussion, filtered and guided by the algorithms of social networks. Today, "artificial intelligence" is a phenomenon in information technology which takes over everyday routines. A new ideal, a new promise, and at the same time used as a stratagem by political and economic systems to guide and manipulate our thinking, values, and behaviour. But nothing is so new that one could not find its precursors in earlier times. Science and mathematics has kindled many brilliant ideas. Can we describe the world by numbers, find truth and explanation in mathematical structures? This essay is devoted to early ideas by the medieval philosopher Ramón Llull, the great rationalist G.W. Leibniz, and early approaches to combinations, number theory. and information processing. Llull's thinking machine and subsequent endeavours to find methods of mechanical reasoning and inference paved the way to modern-day concepts of artificial intelligence. KW - artificial intelligence KW - Leibniz KW - Ramón Llull KW - thinking machine KW - combinatorics KW - number theory KW - Giordano Bruno KW - Turing machine KW - Ars Magna KW - logic Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-58399 CY - Regensburg ER - TY - INPR A1 - Steffens, Oliver T1 - The Media Revolution in the 19th Century: How Sound Recording, Motion Pictures and Writing Machines affected human perception, thinking, and our society until today N2 - Which influence had the sudden appearance of sound recording, film, and typewriters at the end of the 19th century on the human perception of and our thinking about what we consider “reality”? How did our society change with these technological innovations? After millennia of speech and the culture of writing, a fundamental disruption occurred when Thomas Alva Edison introduced his “phonograph” in 1877. In his book “Grammophon, Film, Typewriter” (Brinkmann & Bose, Berlin 1986), Friedrich Kittler (1943-2011) discusses this question from his perspective as literary scholar and media theorist, reviewing contemporary authors to let them bear witness to their experiences and impressions of the then-new media. This essay intends to be a short extract of Kittler’s book, meandering between additional sources of historians, writers, commentators, yet always coming back to Kittler’s fascinating panopticon. KW - History of technology KW - cultural impact KW - film KW - sound recording KW - typewriter KW - gramophone KW - motion picture KW - media KW - literature Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-58376 CY - Regensburg ER - TY - CHAP A1 - Melekhov, Evgeny A1 - Abb, Valerius A1 - Lechner, Alfred A1 - Kammler, Martin ED - Ivanov, Artem ED - Bicker, Marc ED - Patzelt, Peter T1 - Development of a glass-fiber-based spectrometer for the determination of drug residues in groundwater T2 - Tagungsband 2. Symposium Elektronik und Systemintegration ESI 2020 "Intelligente Systeme und ihre Komponenten: Forschung und industrielle Anwendung" N2 - Within the scope of this project, a portable measuring device has been developed which enables a cost-effective analysis of organic substances from ppm to sub-ppm range, such as drug residues in groundwater. The measurement is carried out by means of a surface-enhanced Raman scattering effect (SERS effect) and an exchangeable sensor head. The sensor head used is a nanostructured optical glass fiber glued into a fiber cannula. The tip of the fiber has been processed to act as a SERS cell. The fiber cannula is connected to a freely movable patch cable by using an adapter. Para-thiocresol is used to characterize the SERS cells. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:860-opus4-2174 SN - 978-3-9818439-4-1 SP - 101 EP - 109 ER - TY - CHAP A1 - Höller, Christoph A1 - Zeitler, Berndt A1 - Schneider, M. A1 - Schanda, Ulrich T1 - Tieffrequenter Trittschall – Stand der Wissenschaft und Technik T2 - Fortschritte der Akustik - DAGA 2020 : 46. Deutsche Jahrestagung für Akustik Y1 - 2020 UR - https://www.dega-akustik.de/publikationen/online-proceedings PB - Deutsche Gesellschaft für Akustik e.V. ER - TY - CHAP A1 - Silberbauer, Theodor A1 - Lindner, Matthias A1 - Schreiner, Rupert T1 - Charakterisierung der dielektrischen Barrierenentladung von Mikroplasmaaktuatoren in Abhängigkeit der Substratdicke T2 - Intelligente Systeme und ihre Komponenten: Forschung und industrielle Anwendung : Fachbeiträge 2. Symposium Elektronik und Systemintegration ESI 2020 Y1 - 2020 UR - https://nbn-resolving.org/urn:nbn:de:bvb:860-opus4-2130 N1 - Die Fachtagung, geplant für den 01. April 2020 an der Hochschule Landshut, wurde aufgrund der Corona-Pandemie abgesagt, die eingereichten Fachbeiträge im Tagungsband 2. Symposium Elektronik und Systemintegration ESI 2020: "Intelligente Systeme und ihre Komponenten: Forschung und industrielle Anwendung" veröffentlicht. Hrsg.: Artem Ivanov, Marc Bicker und Peter Patzelt. Hochschule Landshut, 2020, ISBN 978-3-9818439-4-1. SP - 64 EP - 72 CY - Landshut ER - TY - GEN A1 - Ławrowski, Robert Damian A1 - Hausladen, Matthias A1 - Schreiner, Rupert T1 - Individually Addressable Silicon Field Emission Cathodes Fabricated by Laser Micromachining T2 - 7th ITG International Vacuum Electronics Workshop (IVEW) 2020 and 13th International Vacuum Electron Sources Conference (IVeSC) 2020, 26. - 29.5.2020, Bad Honnef Y1 - 2020 ER - TY - GEN A1 - Hausladen, Matthias A1 - Ławrowski, Robert Damian A1 - Schreiner, Rupert T1 - Fast Pulse Source for Field Emission Applications T2 - 7th ITG International Vacuum Electronics Workshop (IVEW) 2020 and 13th International Vacuum Electron Sources Conference (IVeSC) 2020, 26. - 29.5.2020, Bad Honnef Y1 - 2020 ER - TY - GEN A1 - Bresinsky, Markus T1 - Strategic Forecasting with Machine Learning for Geopolitical Analysis Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-25103 ER - TY - CHAP A1 - Bresinsky, Markus A1 - Willner, Sophia ED - Brooks, Anthony L. ED - Brooks, Eva Irene T1 - GLOBE - Digital Literacy and Organizational Learning by Scenario-Driven Exercises T2 - Interactivity, Game Creation, Design, Learning, and Innovation: 8th EAI International Conference, ArtsIT 2019, and 4th EAI International Conference, DLI 2019: Aalborg, Denmark, November 6-8, 2019, Proceedings N2 - Due to rapid technological development and fast-changing working environments, organizations active in such context find themselves facing internal change and adaption processes. Originally prominent among start-up or IT-companies, the use of management concepts to steer such change processes and to increase efficiency also spread among humanitarian organizations preoccupied with crisis management. In this regard, concepts retrieved from the domain of Organization Development offer a great potential to facilitate change processes and to enhance learning among practitioners. The notions of Learning Organization and Quality Management are combined with the theory of Argyris and Schön’s Levels of Learning. This combination then serves as a theoretical decision-making base used in a simulation game at the University of Applied Sciences OTH Regensburg. Within this scenario-driven exercise, Quality Management, virtual collaboration and digital skills are trained. During the simulation game, participants are encouraged to think critically, to utilize new technologies and to apply their problem-solving skills to real-life examples, which ultimately aims at preparing students for a dynamic working environment within the era of digitization. KW - Deming cycle KW - Learning organization KW - Organization development KW - Simulation games KW - Situational awareness KW - Virtual Collaboration Y1 - 2020 SN - 978-3-030-53293-2 U6 - https://doi.org/10.1007/978-3-030-53294-9_51 SP - 671 EP - 682 PB - Springer International Publishing CY - Cham ER - TY - JOUR A1 - Bachmann, Michael A1 - Düsberg, Felix A1 - Langer, Christoph A1 - Herdl, Florian A1 - Bergbreiter, Lukas A1 - Dams, Florian A1 - Miyakawa, Natuski A1 - Eggert, Tobias A1 - Pahlke, Andreas A1 - Edler, Simon A1 - Prommesberger, Christian A1 - Ławrowski, Robert Damian A1 - Hausladen, Matthias A1 - Schreiner, Rupert T1 - Vacuum-sealed field emission electron gun JF - Journal of Vacuum Science & Technology B N2 - A compact vacuum-sealed field emission electron gun with an operation voltage below 5 kV is presented. With a 150 nm thick pyrolytic carbon membrane, a transmission of 40% at 5 kV is obtained. For more than 2500 h of continuous operation at an emission current of 100 nA, no significant increase (<50V ) and almost no degradation were found. From this measurement, a lifetime of more than 10 000 h at continuous operation with approximately a linear increase of the extraction voltage from about 545 V to about 730 V is predicted. This electron source enables application of field emitter arrays in poor vacuum or even ambient pressure. ACKNOWLEDGMENT This work was supported by the German Federal Ministry for Economic Affairs and Energy under Project No. ZF4081502GM8. C.P., R.L., M.H., and R.S. were supported by Grant No. ZF4562901GM8. Y1 - 2020 U6 - https://doi.org/10.1116/1.5139316 VL - 38 IS - 2 PB - AIP Publishing ER - TY - CHAP A1 - Bresinsky, Markus A1 - Schroeder, Johanna A1 - Viscardi, Valerio T1 - Strategic Forecasting with Machine Learning for Regional Geopolitical Analysis T2 - Η Περιφερειακή Επιστήμη, το μέλλον της και οι προκλήσεις στα πεδία της έρευνας και της εφαρμογής : 21ο Επιστημονικό Συνέδριο του Συνδέσμου Ελλήνων Περιφερειολόγων Ελληνικό Μεσογειακό Πανεπιστήμιο, Ηράκλειο Κρήτης, 16-17 Οκτωβρίου 2020 - Challenges for the Future of Regional Science: Research and Applications; 21st Conference: Heraklion, Crete, Oktober 2020 N2 - Strategic forecasting of regional geopolitical development is important for early warning and contingency planning. Open source data and machine learning can help to identify indicators for effective scenario development. Using data of the Bertelsmann Transformation Index (BTI) and the machine learning software Waikato Environment for Knowledge Analysis (WEKA), this paper gives an insight into the generation of a decision tree to provide indicators for forecasting regional development across parts of Northern and Western Africa. Results show that machine learning with open source data can support redefining indicator development but does not replace critical thinking. Y1 - 2020 UR - https://drive.google.com/file/d/1o2qAxcnq5srRr8r8okibHWwb4O0c69Oz/view SN - 978-618-00-2351-0 SP - 267 EP - 276 ER - TY - CHAP A1 - Koenig, Eric A1 - Guertler, Katherine A1 - Żarnowska, Dorota A1 - Horbačauskienė, Jolita T1 - Developing English language competence for global engineers T2 - 2020 IEEE Global Engineering Education Conference (EDUCON): 27-30 April 2020, Porto, Portugal N2 - English language skills are essential to professional communication in international engineering environments. Given the concomitant degree of specialization, university-level coursework in English for Specific Purposes is an essential component of engineering student preparation. This large-scale survey of university students of engineering in three European countries provides important insight into the most relevant language skills, with the goal of informing communicative, task-based curricula for Technical English courses. KW - English as a foreign language KW - English for engineers KW - English for specific purposes KW - professional communication KW - technical English Y1 - 2020 U6 - https://doi.org/10.1109/EDUCON45650.2020.9125208 SP - 242 EP - 249 ER - TY - CHAP A1 - Bresinsky, Markus A1 - Schroeder, Johanna A1 - Viscardi, Valerio T1 - Asymmetry in Trust Building – different perspectives in gains and losses explained via Prospect Theory T2 - Common Effort Conference, The Hague: 19 – 22 October 2020 N2 - Building trust within conflicts situations is a required process to establish a suitable environment for peace keeping and state building processes. However, it remains unclear what are the best ways to foster trusts between actors in a conflict environment. This study draws insights from the literature on trust and from Kahneman’s Prospect Theory to analyse the decision-making dynamics of the actors involved in a conflict and how these dynamics could affect the trust levels between those actors. To this purpose, the fourfold pattern of preferences I applied to a thought experiments where opposing actors in a conflict in the Sahel face the decision to accept or refuse a peace agreement when either one of the two actors face huge gains or catastrophic losses. The main findings is that, in those extreme situations, the actors involved tend to take unnational decisions that undermine the trust building process in the country. Therefore, it would be recommendable to boost situations where actors are negotiating in a more balanced environment. To this purpose, further research should be conducted on the ways to create such suitable environment for trust building. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-24778 SP - 1 EP - 9 ER - TY - PAT A1 - Olbrich, Florian A1 - Pongratz, Christian A1 - Bierl, Rudolf A1 - Ehrlich, Ingo T1 - Method and System for Evaluating a Structural Integrity of an Aerial Vehicle T2 - Europäisches Patentblatt (09.12.2020) zur Anmeldung: OTH Regensburg, Anmeldenummer: 19179054.2, Patentnummer 1001/3748327, Veröffentlichungsnummer: 3 748 327 Y1 - 2020 SP - 395 EP - 396 ER - TY - CHAP A1 - Lang, Christian A1 - Steinborn, Florian A1 - Steffens, Oliver A1 - Lang, Elmar Wolfgang ED - Valenzuela, O. ED - Rojas, F. ED - Herrera, L.J. ED - Pomares, H. ED - Rojas, I. T1 - Applying a 1D-CNN Network to Electricity Load Forecasting T2 - Theory and Applications of Time Series Analysis N2 - This paper presents a convolutional neural network (CNN) which can be used for forecasting electricity load profiles 36 hours into the future. In contrast to well established CNN architectures, the input data is one-dimensional. A parameter scanning of network parameters is conducted in order to gain information about the influence of the kernel size, number of filters and number of nodes. Furthermore, different dropout methods are applied to the CNN and are evaluated. The results show that a good forecast quality can already be achieved with basic CNN architectures, the dropout improves the forecast. The method works not only for smooth sum loads of many hundred consumers, but also for the load of single apartment buildings. KW - Energy load forecasting KW - STLF KW - Neural networks KW - CNN KW - Convolutional networks Y1 - 2020 U6 - https://doi.org/10.1007/978-3-030-56219-9_14 SP - 205 EP - 218 PB - Springer ER - TY - JOUR A1 - Malz, Sebastian A1 - Krenkel, Walter A1 - Steffens, Oliver T1 - Infrared Reflective Wall Paint in Buildings: Energy Saving Potentials and Thermal Comfort JF - Energy and Buildings N2 - The reduction of the energy demand of existing buildings is the main objective of building refurbishment. Managing the heat radiation properties of the wall construction is a possible way to develop highly effective and resource efficient insulation materials and concepts. The application of infrared reflective wall paints and coatings has been studied since the latter half of the 20th century. A brief review of the literature gives an account of the current research status. One has to realise that the conclusions are not uniformly consistent but depend strongly on the specific boundary conditions and investigated parameters. The study presented here discusses the usage of infrared reflective wall paint in conjunction with heat insulation for historic brick masonry. The possible energy savings are linked to the resulting thermal comfort. We identify critical parameters that must be taken into account when using infrared reflective wall paint and derive recommended design rules for the refurbishment of such building types. The findings prove that infrared reflective wall paint can decrease heat losses by 18% and up to 22% if comfort conditions are considered. Increasing energy savings can also cause the negative effect of high radiative asymmetry. Thus, each configuration must be observed in detail. KW - Infrared-reflective KW - Wall paint KW - Coating KW - Existing buildings KW - Radiative asymmetry KW - Energy efficiency Y1 - 2020 U6 - https://doi.org/10.1016/j.enbuild.2020.110212 SN - 0378-7788 VL - 224 IS - October PB - Elsevier ER - TY - CHAP A1 - Ławrowski, Robert Damian A1 - Schreiner, Rupert A1 - Linghu, Shuangyi A1 - Gu, Fuxing T1 - Field Emission Behaviour of Single-Crystal Pd Nanowires T2 - 33rd International Vacuum Nanoelectronics Conference (IVNC): 6-10 July 2020, Lyon, France N2 - Single-crystal Pd nanowires with typically 100 nm diameters and lengths from several micrometers to tens of micrometers were grown on Al 2 O 3 substrates in a furnace with Ar atmosphere. Integral field emission measurements of such samples after Pd coating (~10 nm) were performed in a diode configuration with a 50 μm mica spacer in a vacuum chamber at pressures of about 10 -9 mbar. The IV measurement of the sample shows an integral emission current up to 2 μA at a voltage of 500 V (10 MV/m) and an onset voltage for a current of 1 nA of about 275 V. The corresponding Fowler-Nordheim plot show a linear behavior, like expected for a metal needle. Y1 - 2020 SN - 978-1-7281-9454-7 U6 - https://doi.org/10.1109/IVNC49440.2020.9203510 SP - 1 EP - 2 PB - IEEE ER - TY - CHAP A1 - Ławrowski, Robert Damian A1 - Hausladen, Matthias A1 - Schreiner, Rupert T1 - Individually Addressable Fully Integrated Field Emission Electron Source Fabricated by Laser Micromachining of Silicon T2 - 33rd International Vacuum Nanoelectronics Conference (IVNC): 6-10 July 2020, Lyon N2 - A cathode with individually addressable Si tips allows the observation of the activation procedure and emission behaviour of each field emission emitter at any time of the measurement. The cathode consists of an array of 2x2 conically shaped emitter structures, which were fabricated by laser micromachining and wet etching of a Si substrate bonded on a glass carrier. Using the same process, a Si extractions grid was fabricated and mounted onto the emitter. Integral field emission measurements were performed in a diode configuration in a vacuum chamber at pressures of about 10- 9 mbar. The emitters show an onset voltage between 200 V and 300 V. The emission current for each emitter on the cathode was regulated to a given value (1.0 μA, 2.5μA, 5.0μA) by an external regulating circuit and was recorded individually during the measurement. With such approach, the relation between the emission behaviour and the geometry of emitters can be studied in detail. In addition, the current stabilization of each emitters of an array can be investigated, which led to a current stability of better than 0.5%. Y1 - 2020 SN - 978-1-7281-9454-7 U6 - https://doi.org/10.1109/IVNC49440.2020.9203470 SP - 1 EP - 2 PB - IEEE ER - TY - CHAP A1 - Lindner, Matthias A1 - Berndt, Dominik A1 - Tschurtschenthal, Karl A1 - Ehrlich, Ingo A1 - Jungbauer, Bastian A1 - Schreiner, Rupert A1 - Pipa, Andrei V. A1 - Hink, Rüdiger A1 - Foest, Rüdiger A1 - Brandenburg, Ronny A1 - Neuwirth, Daniel A1 - Karpen, Norbert A1 - Bonaccurso, Elmar A1 - Weichwald, Robert A1 - Max, Alexander A1 - Caspari, Ralf T1 - Aircraft Icing Mitigation by DBD-based Micro Plasma Actuators T2 - AIAA AVIATION 2020 FORUM: June 15-19, 2020 N2 - We present the application of plasma actuators as a technology for ice prevention at airfoils. The miniaturized dielectric barrier discharge (DBD) plasma actuators (PA) were fabricated by means of microelectromechanical systems (MEMS). We elucidate how to make the actuator samples scalable and applicable to any desired shape by the use of flexible inorganic zirconia substrates. For this purpose, we applied our developed embedding method to integrate the micro actuators in modern carbon/glass fiber reinforced polymer (CFRP/GFRP) materials. Next, the embedded actuator samples were mounted on a mechanical air profile-like fixture and placed in the icing wind tunnel iCORE. The samples were tested in rime ice conditions at temperatures of -15 to -20° C and air speeds up to 30 m/s. Unlike other groups we used a thin film zirconia substrate as dielectric for the plasma actuator. Due to the low substrate thickness of just 150 µm, an operating voltage of 2 kVRMS is already sufficient enough for a stable plasma formation. The experiments show that the operated actuator was able to prevent the ice formation and first indications of a De-icing function were also found. Hence, we show that it is feasible to realize an anti-icing system with zirconia-based plasma actuators operated at lower voltages compared to conventional ones. Y1 - 2020 U6 - https://doi.org/10.2514/6.2020-3243 ER - TY - JOUR A1 - Weigl, Stefan A1 - Feldmeier, Florian A1 - Bierl, Rudolf A1 - Matysik, Frank-Michael T1 - Photoacoustic detection of acetone in N2 and synthetic air using a high power UV LED JF - Sensors Actuators B Chemical N2 - The performance of a photoacoustic trace gas sensor for the detection of acetone in N2 and synthetic air is reported. The sensor system utilises an amplitude modulated UV LED. The light source has an emission maximum at 278 nm and a maximum CW output power of 300 mW according to the datasheet. Three different collimating and focusing approaches have been investigated to guide the highly divergent LED light into the acoustic resonator of the photoacoustic measurement cell. A 3D printed aluminium cell was designed to optimize light coupling by simultaneously minimizing the photoacoustic background signal generation. Hence, the diameter of the resonator was set to a comparable large diameter of 10 mm and the inner walls of the resonator were mirror polished. The additive manufacturing procedure allowed for integration of a spirally formed gas channel, enabling gas heating prior to detection. The sensor performance was investigated by measuring acetone in N2 and synthetic air at different concentrations. The UV LED current was set to 86 % of the maximum value according to the datasheet of the light source in order to increase the lifetime and thermal stability. An Allan-Werle deviation analysis validates a stable sensor performance. The limit of detection (LoD) was determined at a 3σ noise level with a 10 s lock-in amplifier time constant by sampling data points over 20 s with a data acquisition rate of 5 Hz. LoDs of 80.8 ppbV and 19.6 ppbV were obtained for acetone in N2 and synthetic air, respectively. KW - Acetone detection KW - Photoacoustic spectroscopy KW - High power UV LED KW - UV LED collimation system KW - Acetone breath analysis Y1 - 2020 U6 - https://doi.org/10.1016/j.snb.2020.128109 N1 - Corresponding author at: Sensorik-Applikationszentrum (SappZ) der Ostbayerischen Technischen Hochschule Regensburg VL - 316 IS - August SP - 1 EP - 11 PB - Elsevier ER - TY - CHAP A1 - Hausler, Peter A1 - Jobst, Simon A1 - Fischer, Johannes A1 - Roth, Carina A1 - Bierl, Rudolf T1 - Homogeneous Light Source for Surface Plasmon Resonance Imaging T2 - PHOTOPTICS 2020: proceedings of the 8th International Conference on Photonics, Optics and Laser Technology, Valletta, Malta, February 27-29, 2020 N2 - We describe how to build a homogeneous light source for Surface Plasmon Resonance Imaging (SPRi) which mainly finds its applications in pharmaceutical screening and biotechnology so far. SPR spectroscopy is a label-free, non-destructive and highly sensitive measurement principle for detecting changes in the refractive index in close vicinity of a gold surface. A transfer of this technology to a miniaturized sensor will broaden the range of possible applications. Commercial SPR assays are mainly working with a small number of sensing spots. In contrast, the SPR imaging system shown here will allow the use of an array of many sensing spots. In combination with chemical receptors designed as an artificial nose or an electronic tongue, the simultaneous detection of many analytes is envisioned. So far, lasers or other inhomogeneous light sources were used to illuminate the sensing surface, which is decreasing the systems sensitivity. We show a compact ( 300mm2) homogeneous top hat profile. The combination of a high bit-resolution camera with our new light source enables a reflectivity based surface plasmon resonance imaging system with a high refractive index unit (RIU) resolution. KW - Surface Plasmon Resonance Spectroscopy KW - Sensor KW - SPR-imaging KW - Miniaturization KW - Micro-opto-electro-mechanical Systems Y1 - 2020 U6 - https://doi.org/10.5220/0009168701630167 SP - 163 EP - 167 PB - SCITEPRESS - Science and Technology Publications ER - TY - JOUR A1 - Ławrowski, Robert Damian A1 - Pirker, Luka A1 - Kaneko, Keita A1 - Kokubo, Hiroki A1 - Bachmann, Michael A1 - Ikuno, Takashi A1 - Remskar, Maja A1 - Schreiner, Rupert T1 - Field emission from nanotubes and flakes of transition metal dichalcogenides JF - Journal of Vacuum Science and Technology B N2 - Transition metal dichalcogenides such as MoS2 and WS2 are low-dimensional semiconductor materials. MoS2 and WS2 nanotubes and flakes were grown by a chemical transport reaction under a temperature gradient. I2 was used as a transport agent for previously synthesized MoS2 and WS2, respectively. These multilayered nanotubes are indirect bandgap semiconductors with a bandgap depending on their diameter. WS2 flakes were prepared by the sulfurization of thin WOx flakes. To increase the field enhancement of such low-dimensional structures by a higher aspect ratio, two approaches were examined: (a) the MoS2 and WS2 nanotubes were attached individually by a focused ion beam with Pt on dry etched n-type Si pillars and (b) the WS2 flakes were grown directly on the surface of the (n-type and p-type) Si pillars. Integral field emission measurements were performed in a diode configuration with a 50 μm mica spacer in a vacuum chamber at pressures of about 10−9 mbar. At a voltage of 900 V (18 MV/m), the integral emission current from the nanotubes is up to 11 μA for the lateral mounted MoS2 and about 1.3 μA (1.0 μA) for the upright mounted WS2 (MoS2). The onset voltage for a current of 1 nA is about 550 V for MoS2 and 500 V for WS2, respectively. The voltage conversion factor is in the range of 6 × 104–8 × 104 cm−1 for the nanotubes. The mounted MoS2 flakes show a field emission current of about 6 μA at 18 MV/m in contrast to the directly grown WS2 flakes, which show a pronounced saturation regime and, therefore, a lower emission current of about 0.5 μA is reached at 1500 V (25 MV/m). The WS2 flakes show a two times higher (1 × 105 cm−1) voltage conversion factor in comparison to the MoS2 flakes (5 × 104 cm−1). The extracted characteristics of the current-limiting part show a difference in the behavior of the extracted current-limiting characteristics between the lateral (linear) and upright mounted (exponential) nanotubes and the MoS2 flakes. In contrast, the WS2 flakes show charge carrier depletion effects. Y1 - 2020 U6 - https://doi.org/10.1116/1.5140474 VL - 38 IS - 3 SP - 032801 PB - AIP Publishing ER - TY - JOUR A1 - Berndt, Dominik A1 - Muggli, Josef A1 - Wittwer, Franz A1 - Langer, Christoph A1 - Heinrich, Stephan A1 - Knittel, Thorsten A1 - Schreiner, Rupert T1 - MEMS-based thermal conductivity sensor for hydrogen gas detection in automotive applications JF - Sensors and Actuators A: Physical N2 - Accurate detection of hydrogen gas in vehicle interiors is very important for the future of a fuel cell car. Since this type of gas is highly volatile and flammable, the measurement methods have to be very reliable and precise due to safety reasons. In this paper a thermal conductivity sensor for hydrogen gas detection is presented, exhibiting a lower detection limit of 2000 ppm hydrogen in laboratory air. The sensor element is realized by micro-fabrication techniques on silicon wafers. The heated filament is exposed by a selective wet etching process creating a micro-hotplate on a thin membrane. In order to minimize power consumption, the sensor is operated in pulsed mode. Hydrogen gas detection was carried out using a synthetic gas testbench. Measurements of hydrogen contents ranging from 0% to 4% with an increment of 0.5% were successfully performed for ambient gas temperatures between -15°C and 84°C. Including humidity, high moisture contents have the greatest influence on thermal conductivity. This was predicted in theoretical investigations and confirmed in experiments. For evaluation, both the change in resistance ΔR as well as the time constant τ were taken as sensor output. For both quantities, the previously established theoretical relationship with thermal conductivity could be confirmed. Y1 - 2020 U6 - https://doi.org/10.1016/j.sna.2019.111670 VL - 305 IS - April PB - Elsevier ER - TY - JOUR A1 - Langer, Christoph A1 - Bomke, Vitali A1 - Hausladen, Matthias A1 - Ławrowski, Robert Damian A1 - Prommesberger, Christian A1 - Bachmann, Michael A1 - Schreiner, Rupert T1 - Silicon Chip Field Emission Electron Source Fabricated by Laser Micromachining JF - Journal of Vacuum Science & Technology B N2 - The components for a silicon chip electron source were fabricated by laser micromachining using pulsed laser ablation and wet chemical cleaning and etching dips. The field emission electron source consists of a silicon field emission cathode with 4 × 4 conical shaped emitters with a height of 250 μm and a tip radius of about 50 nm, a 50 μm thick laser-structured mica spacer, and a silicon grid electrode with a grid periodicity of 200 μm and a bar width of 50 μm. These three components are combined to a single chip with the size of 14 × 10 mm2 and the thickness of 1 mm to form the electron source. Several of these devices were characterized in ultrahigh vacuum. Onset voltages of about 165 V and cathode currents of about 15 μA for voltages lower than 350 V were observed. Operating the electron source with an anode voltage of 500 V and an extraction grid voltage of 300 V yielded a cathode current of 4.5 μA ± 8.9%, an anode current of 4.0 μA ± 9.6%, and a corresponding grid transmittance of 89%. Regulating the anode current by the extraction grid voltage, an extremely stable anode current of 5.0 μA ± 0.017% was observed. A long-term measurement over 120 h was performed, and no significant degradation or failure was observed. KW - Ultra-high vacuum KW - Field emitter arrays KW - Etching KW - Electrical properties and parameters KW - Electron sources KW - Laser ablation KW - Laser micromachining KW - Silicon chip KW - Triodes Y1 - 2020 U6 - https://doi.org/10.1116/1.5134872 VL - 38 IS - 1 PB - AIP Publishing ER -