@article{PirkerŁawrowskiSchreineretal., author = {Pirker, Luka and Ławrowski, Robert Damian and Schreiner, Rupert and Remškar, Maja and Višić, Bojana}, title = {MoₓWₓ₋₁S₂ Nanotubes for Advanced Field Emission Application}, series = {Advanced Functional Materials}, journal = {Advanced Functional Materials}, publisher = {Wiley}, issn = {1616-3028}, doi = {10.1002/adfm.202213869}, pages = {1 -- 8}, abstract = {Transition metal dichalcogenide (TMDC) nanotubes complement the field of low-dimensional materials with their quasi-1D morphology and a wide set of intriguing properties. By introducing different transition metals into the crystal structure, their properties can be tailored for specific purpose and applications. Herein, the characterization and a subsequent preparation of single-nanotube field emission devices of MoxWx-1S2 nanotubes prepared via the chemical vapor transport reaction is presented. Energy-dispersive X-ray spectroscopy, Raman spectroscopy, and X-ray diffraction indicate that the molybdenum and tungsten atoms are randomly distributed within the crystal structure and that the material is highly crystalline. High resolution transmission electron microscopy and electron diffraction (ED) patterns further corroborate these findings. A detailed analysis of the ED patterns from an eight-layer nanotube reveal that the nanotubes grow in the 2H structure, with each shell consists of one bilayer. The work function of the nanotubes is comparable to that of pure MoS2 and lower of pure WS2 NTs, making them ideal candidates for field emission applications. Two devices with different geometrical setup are prepared and tested as field emitters, showing promising results for single nanotube field emission applications.}, language = {en} } @unpublished{PangerlMoserMuelleretal., author = {Pangerl, Jonas and Moser, Elisabeth and M{\"u}ller, Max and Weigl, Stefan and Jobst, Simon and R{\"u}ck, Thomas and Bierl, Rudolf and Matysik, Frank-Michael}, title = {A Highly Sensitive Acetone and Ethanol Quantum Cascade Laser Based Photoacoustic Sensor: Characterization and Multi-Component Spectra Recording in Synthetic Breath}, series = {SSRN Electronic Journal}, journal = {SSRN Electronic Journal}, publisher = {Elsevier}, doi = {10.2139/ssrn.4305376}, abstract = {Trace gas analysis in breath is challenging due to the vast number of different components. We present a highly sensitive quantum cascade laser based photoacoustic setup for breath analysis. Scanning the range between 8260 and 8270 nm with a spectral resolution of 48 pm, we are able to quantify acetone and ethanol within a typical breath matrix containing water and CO2. We photoacoustically acquired spectra within this region of mid-infra-red light and prove that those spectra do not suffer from non-spectral interferences. The purely additive behavior of a breath sample spectrum was verified by comparing it with the independently acquired single component spectra using Pearson and Spearman correlation coefficients. A previously presented simulation approach is improved and an error attribution study is presented. With a 3σ detection limit of 6.5 ppbV in terms of ethanol and 250 pptV regarding acetone, our system is among the best performing presented so far.}, language = {en} } @misc{OlbrichPongratzBierletal., author = {Olbrich, Florian and Pongratz, Christian and Bierl, Rudolf and Ehrlich, Ingo}, title = {Method and System for Evaluating a Structural Integrity of an Aerial Vehicle}, language = {en} } @inproceedings{PellerZanklFischeretal., author = {Peller, Sebastian and Zankl, Tobias and Fischer, Christoph and Bierl, Rudolf}, title = {Fast sound field characterization of beamforming capable capacitive micromachined ultrasonic transducer (CMUT) arrays by refracto-vibrometry}, series = {IEEE IUS 2023, International Ultrasonics Symposium, Montr{\´e}al, September 3-8, 2023}, booktitle = {IEEE IUS 2023, International Ultrasonics Symposium, Montr{\´e}al, September 3-8, 2023}, publisher = {IEEE}, isbn = {979-8-3503-4645-9}, issn = {1948-5727}, doi = {10.1109/IUS51837.2023.10308126}, pages = {1 -- 3}, abstract = {We introduce a time-optimized setup based on refracto-vibrometry for the purpose of scanning the sound field of capacitive micromachined ultrasonic transducer (CMUT) arrays primarily for the qualification of their beamforming capability. In comparison to commonly used microphones on a traversing stage the proposed method is substantially faster and consumes only a few minutes of time for a complete two-dimensional sound field containing about 100.000 scan points.}, language = {en} } @inproceedings{HerdlBachmannWohlfartsstaetteretal., author = {Herdl, Florian and Bachmann, Michael and Wohlfartsst{\"a}tter, Dominik and D{\"u}sberg, Felix and Dudeck, Markus and Eder, Magdalena and Meyer, Manuel and Pahlke, Andreas and Edler, Simon and Schels, Andreas and Hansch, Walter and Schreiner, Rupert and Wohlfartsstatter, Dominik and Dusberg, Felix}, title = {A novel current dependent field emission performance test}, series = {2021 34th International Vacuum Nanoelectronics Conference (IVNC): 5-9 July 2021, Lyon, France}, booktitle = {2021 34th International Vacuum Nanoelectronics Conference (IVNC): 5-9 July 2021, Lyon, France}, doi = {10.1109/IVNC52431.2021.9600695}, pages = {1 -- 2}, abstract = {A current dependent performance test for comparison of different field emitter arrays is introduced. Statistical analysis is enabled due to a short measurement time and as a main feature the electric field shift, comparable to the degradation of the emitter is examined. Significance of the test method is shown by a comparison of field emitter arrays with different doping levels.}, language = {en} } @inproceedings{BiekerRoustaieSchlaaketal., author = {Bieker, Johannes and Roustaie, Farough and Schlaak, Helmut F. and Langer, Christoph and Schreiner, Rupert}, title = {Field emission characterization of in-situ deposited metallic nanocones}, series = {2017 30th International Vacuum Nanoelectronics Conference (IVNC), 10-14 July 2017, Regensburg, Germany}, booktitle = {2017 30th International Vacuum Nanoelectronics Conference (IVNC), 10-14 July 2017, Regensburg, Germany}, publisher = {IEEE}, doi = {10.1109/IVNC.2017.8051571}, pages = {120 -- 121}, abstract = {An in-situ fabrication technique based on ion track etched template electrodeposition of metallic nanocones was used for the production of field emitter cathodes. Gold nanocones with a height of 24 microns, a base diameter between 3 to 4 microns and a tip diameter below 300 nanometers were deposited on a circular electrode with a diameter of 2.5 mm. The integral field emission (FE) measurements of samples with cone densities of 6 · 104 cones/cm2 (sample A) and 1 · 106 cones/cm2 (sample B) yielded in a maximum current of 37.5 μA at an applied field of 12.5 V/μm for sample A and 29.1 μA at 9.4 V/μm for sample B. The stability of emission current was investigated for over 48 hours and no degradation was observed.}, language = {en} } @inproceedings{SchelsEdlerHanschetal., author = {Schels, Andreas and Edler, Simon and Hansch, Walter and Bachmann, Michael and Herdl, Florian and Dusberg, F. and Eder, Magdalena and Meyer, Manuel and Dudek, M. and Pahlke, Andreas and Schreiner, Rupert}, title = {Current dependent performance test used on different types of silicon field emitter arrays}, series = {2021 34th International Vacuum Nanoelectronics Conference (IVNC): 5-9 July 2021, Lyon, France}, booktitle = {2021 34th International Vacuum Nanoelectronics Conference (IVNC): 5-9 July 2021, Lyon, France}, editor = {Purcell, Stephen and Mazellier, Jean-Paul}, publisher = {IEEE}, address = {Piscataway, NJ}, isbn = {978-1-6654-2589-6}, doi = {10.1109/IVNC52431.2021.9600787}, pages = {1 -- 2}, abstract = {A current dependent performance test is used to investigate the influence of doping and emitter geometry on the lifetime of silicon field emitter arrays. The measurements reveal an improved performance for lower n-type dopant concentrations. Furthermore, two new types of field emitters are introduced by slightly varying the original fabrication process [1]. The comparison shows superiority of tip like emitters over blade like structures.}, language = {en} } @inproceedings{HoellerQuirtZeitleretal., author = {H{\"o}ller, Christoph and Quirt, David and Zeitler, Berndt and Sabourin, Ivan}, title = {Apparent sound insulation in cold-formed steel-framed buildings}, series = {24th International Congress on Sound and Vibration (ICSV 24), 23-27 July 2017, London, UK}, booktitle = {24th International Congress on Sound and Vibration (ICSV 24), 23-27 July 2017, London, UK}, publisher = {Curran Associates, Inc}, language = {en} } @inproceedings{HoellerZeitlerSchneideretal., author = {H{\"o}ller, Christoph and Zeitler, Berndt and Schneider, M. and Schanda, Ulrich}, title = {Tieffrequenter Trittschall - Stand der Wissenschaft und Technik}, series = {Fortschritte der Akustik - DAGA 2020 : 46. Deutsche Jahrestagung f{\"u}r Akustik}, booktitle = {Fortschritte der Akustik - DAGA 2020 : 46. Deutsche Jahrestagung f{\"u}r Akustik}, publisher = {Deutsche Gesellschaft f{\"u}r Akustik e.V.}, language = {de} } @article{KrenzerHanischBlicharskiSchneideretal., author = {Krenzer, Boris and Hanisch-Blicharski, Anja and Schneider, Paul and Payer, Thomas and M{\"o}llenbeck, Simone and Osmani, O. and Kammler, Martin and Meyer, R. and Horn-von Hoegen, Michael}, title = {Phonon confinement effects in ultrathin epitaxial bismuth films on silicon studied by time-resolved electron diffraction}, series = {Physical Review B}, volume = {80}, journal = {Physical Review B}, number = {2}, publisher = {APS}, doi = {10.1103/PhysRevB.80.024307}, abstract = {The transient temperature evolution of ultrathin bismuth films, epitaxially grown on a silicon single crystal, upon femtosecond laser excitation is studied by time-resolved electron diffraction. The exponential decay of the film temperature is explained by phonon reflection at the interface, which results in a strongly reduced thermal conduction in the cross plane of the layered system. The thermal boundary conductance is found to be as low as 1273 W/(K cm2). Model calculations, including phonon confinement effects, explain the linear relationship between the observed film-temperature decay constant and the film thickness. Even for 2.5 nm thin films the phonon transmission probability across the interface is given by bulk properties. Our simulations show that phonon confinement effects are negligible for bismuth-film thicknesses larger than 1 nm.}, language = {en} } @article{KleinNabbefeldHattabetal., author = {Klein, C. and Nabbefeld, T. and Hattab, H. and Meyer, D. and Jnawali, G. and Kammler, Martin and Meyer zu Heringdorf, Frank-Joachim and Golla-Franz, A. and M{\"u}ller, B. H. and Schmidt, Thomas and Henzler, M. and Horn-von Hoegen, Michael}, title = {Lost in reciprocal space? Determination of the scattering condition in spot profile analysis low-energy electron diffraction}, series = {Review of scientific instruments}, volume = {82}, journal = {Review of scientific instruments}, number = {3}, publisher = {American Institute of Physics}, doi = {10.1063/1.3554305}, abstract = {The precise knowledge of the diffraction condition, i.e., the angle of incidence and electron energy, is crucial for the study of surface morphology through spot profile analysis low-energy electron diffraction (LEED). We demonstrate four different procedures to determine the diffraction condition: employing the distortion of the LEED pattern under large angles of incidence, the layer-by-layer growth oscillations during homoepitaxial growth, a G(S) analysis of a rough surface, and the intersection of facet rods with 3D Bragg conditions.}, language = {en} } @article{SchmidtKroegerClausenetal., author = {Schmidt, Thomas and Kr{\"o}ger, Roland and Clausen, T. and Falta, J. and Janzen, Andreas and Kammler, Martin and Kury, P. and Zahl, P. and Horn-von Hoegen, Michael}, title = {Surfactant-mediated epitaxy of Ge on Si(111): Beyond the surface}, series = {Applied Physics Letters}, volume = {86}, journal = {Applied Physics Letters}, number = {11}, publisher = {AIP}, doi = {10.1063/1.1882760}, abstract = {For a characterization of interface and "bulk" properties of Ge films grown on Si(111) by Sb surfactant-mediated epitaxy, grazing incidence x-ray diffraction and transmission electron microscopy have been used. The interface roughness, defect structure, and strain state have been investigated in dependence of film thickness and growth temperature. For all growth parameters, atomically smooth interfaces are observed. For thin Ge layers, about 75\% of the strain induced by the lattice mismatch is relaxed by misfit dislocations at the Ge/Si interface. Only a slight increase of the degree of relaxation is found for thicker films. At growth temperatures below about 600 °C, the formation of twins is observed, which can be avoided at higher temperatures.}, language = {en} } @article{FriggeWallKrenzeretal., author = {Frigge, Tim and Wall, S. and Krenzer, Boris and Wippermann, St. and Sanna, Simone and Klasing, Friedrich and Hanisch-Blicharski, Anja and Kammler, Martin and Schmidt, Wolf Gero and Horn-von Hoegen, Michael}, title = {Abstract - A Reply to the Comment by H. Shim et al.}, series = {Physical review letters}, volume = {111}, journal = {Physical review letters}, number = {14}, publisher = {American Physical Society}, doi = {10.1103/PhysRevLett.111.149602}, language = {en} } @article{CheeKammlerGrahametal., author = {Chee, See Wee and Kammler, Martin and Graham, Jeremy and Ross, Frances M. and Hull, Robert}, title = {Direct Imaging of Microstructural Changes in Si Induced by FIB-Patterning with Si ++ and Ga + Ions}, series = {Microscopy and Microanalysis}, volume = {17}, journal = {Microscopy and Microanalysis}, number = {S2}, publisher = {Cambridge University Press}, doi = {10.1017/S1431927611004156}, pages = {656 -- 657}, language = {en} } @inproceedings{RothHauslerBierl, author = {Roth, Carina and Hausler, Peter and Bierl, Rudolf}, title = {Einbindung eines 2D-Photodetektors in einen hochintegrierten SPR-Imaging-Sensor}, series = {7. MikroSystemTechnik Kongress "MEMS, Mikroelektronik, Systeme", 23.-25. Oktober 2017, M{\"u}nchen}, booktitle = {7. MikroSystemTechnik Kongress "MEMS, Mikroelektronik, Systeme", 23.-25. Oktober 2017, M{\"u}nchen}, publisher = {VDE-Verlag}, address = {M{\"u}nchen}, isbn = {978-3-8007-4491-6}, pages = {848 -- 850}, abstract = {Die Oberfl{\"a}chenplasmonenresonanzspektroskopie (SPR) ist eine hochempfindliche Messmethode, die es erlaubt, Gase und Fl{\"u}ssigkeiten zerst{\"o}rungs- und markierungsfrei in Echtzeit zu analysieren. Bisher vornehmlich im Labormaßstab in der Bioanalytik und dem Wirkstoffscreening eingesetzt, soll diese Technologie nun miniaturisiert und f{\"u}r weitere Anwendungsgebiete zug{\"a}nglich gemacht werden. Dazu wird ein kompakter Micro-Opto-Electro-Mechanical Systems Sensor (MOEMS) entwickelt, der mit Hilfe des SPR Imaging {\"A}nderungen der chemischen Zusammensetzung verschiedener Fl{\"u}ssigkeiten inline messen kann.}, language = {de} } @article{SchelsHerdlHausladenetal., author = {Schels, Andreas and Herdl, Florian and Hausladen, Matthias and Wohlfartsst{\"a}tter, Dominik and Edler, Simon and Bachmann, Michael and Pahlke, Andreas and Schreiner, Rupert and Hansch, Walter}, title = {Quantitative Field Emission Imaging for Studying the Doping-Dependent Emission Behavior of Silicon Field Emitter Arrays}, series = {Micromachines}, volume = {14}, journal = {Micromachines}, number = {11}, publisher = {MDPI}, doi = {10.3390/mi14112008}, abstract = {Field emitter arrays (FEAs) are a promising component for novel vacuum micro- and nanoelectronic devices, such as microwave power amplifiers or fast-switching X-ray sources. However, the interrelated mechanisms responsible for FEA degradation and failure are not fully understood. Therefore, we present a measurement method for quantitative observation of individual emission sites during integral operation using a low-cost, commercially available CMOS imaging sensor. The emission and degradation behavior of three differently doped FEAs is investigated in current-regulated operation. The measurements reveal that the limited current of the p-doped emitters leads to an activation of up to 55\% of the individual tips in the array, while the activation of the n-type FEA stopped at around 30\%. This enhanced activation results in a more continuous and uniform current distribution for the p-type FEA. An analysis of the individual emitter characteristics before and after a constant current measurement provides novel perspectives on degradation behavior. A burn-in process that trims the emitting tips to an integral current-specific ideal field enhancement factor is observed. In this process, blunt tips are sharpened while sharp tips are dulled, resulting in homogenization within the FEA. The methodology is described in detail, making it easily adaptable for other groups to apply in the further development of promising FEAs.}, language = {en} } @inproceedings{SchelsHerdlHausladenetal., author = {Schels, Andreas and Herdl, Florian and Hausladen, Matthias and Wohlfartsst{\"a}tter, Dominik and Bachmann, Michael and Edler, Simon and D{\"u}sberg, Felix and Pahlke, Andreas and Buchner, Philipp and Schreiner, Rupert and Hansch, Walter}, title = {Beta Factor Mapping of Individual Emitting Tips During Integral Operation of Field Emission Arrays}, series = {2023 IEEE 36th International Vacuum Nanoelectronics Conference (IVNC), 10-13 July 2023, Cambridge, MA, USA}, booktitle = {2023 IEEE 36th International Vacuum Nanoelectronics Conference (IVNC), 10-13 July 2023, Cambridge, MA, USA}, publisher = {IEEE}, isbn = {979-8-3503-0143-4}, doi = {10.1109/IVNC57695.2023.10188957}, pages = {224 -- 226}, abstract = {Emission uniformity mappings of field emitter arrays provide important insight into degradation mechanisms, but are often laborious, non-integral, costly, or not quantifiable. Here, a low-cost Raspberry Pi HQ camera is used as an extraction anode to quantify the emission distribution in field emitter arrays. A verification measurement using controlled SEM electron beams proves, that current-voltage characteristics of individual emission sites can be determined by combining the integral electrical data with the image data. The characteristics are used to quantify the field enhancement factors of an 30x30 silicon field emitter array during integral operation. Comparison of the field enhancement factor distributions before and after a one-hour constant current operation at 1 µA shows an increase from 50 actively emitting tips before to 156 after the measurement. It is shown, that the distribution of field enhancement factors shifts towards lower values, due to the increasing degradation for high field enhancement tips, especially above 1500.}, language = {en} } @inproceedings{HerdlKueddelsmannSchelsetal., author = {Herdl, Florian and Kueddelsmann, Maximillian J. and Schels, Andreas and Bachmann, Michael and Edler, Simon and Wohlfartsst{\"a}tter, Dominik and D{\"u}sberg, Felix and Prugger, Alexander and Dillig, Michael and Dams, Florian and Schreiner, Rupert and Coile{\´a}in, Cormac {\´O}. and Zimmermann, Stefan and Pahlke, Andreas and Duesberg, Georg S.}, title = {Characterization and Operation of Graphene-Oxide-Semiconductor Emitters at Atmospheric Pressure Levels}, series = {2023 IEEE 36th International Vacuum Nanoelectronics Conference (IVNC), 10-13 July 2023, Cambridge, MA, USA}, booktitle = {2023 IEEE 36th International Vacuum Nanoelectronics Conference (IVNC), 10-13 July 2023, Cambridge, MA, USA}, publisher = {IEEE}, isbn = {979-8-3503-0143-4}, doi = {10.1109/IVNC57695.2023.10188974}, pages = {14 -- 16}, abstract = {In recent years Graphene-Oxide-Semiconductor (GOS) electron emitters have attracted a lot of interest due to their outstanding durability in modest vacuum conditions. However, the performance at ambient pressure remains largely unexplored. In this study GOS-emitters are characterized in nitrogen and air at atmospheric pressure, and compared with their vacuum characteristics. For this purpose, lifetime and IV-characteristics measurements are shown. Furthermore, the GOS-emitter was operated as an ionization source for ion mobility spectrometry (IMS) at ambient conditions.}, language = {en} } @inproceedings{HausladenBuchnerSchelsetal., author = {Hausladen, Matthias and Buchner, Philipp and Schels, Andreas and Edler, Simon and Bachmann, Michael and Schreiner, Rupert}, title = {An Integrated Field Emission Electron Source on a Chip Fabricated by Laser-Micromachining and Mems Technology}, series = {2023 IEEE 36th International Vacuum Nanoelectronics Conference (IVNC), 10-13 July 2023, Cambridge, MA, USA}, booktitle = {2023 IEEE 36th International Vacuum Nanoelectronics Conference (IVNC), 10-13 July 2023, Cambridge, MA, USA}, publisher = {IEEE}, isbn = {979-8-3503-0143-4}, doi = {10.1109/IVNC57695.2023.10189001}, pages = {115 -- 116}, abstract = {A silicon field emission electron source consisting of a cathode and a grid electrode has been fabricated by laser micromachining. The cathode features 21×21 tips on an area of 4×4 mm 2 , With a self-aligning MEMS technology for the aperture grid, a high electron transmission (99 \%) was achieved. Onset voltages of 50…70 V were observed for an emission current of 1 nA. A stable emission current of 1 mA ± 1.3 \% at an extraction voltage of 250 V was observed during a 30-min operation.}, language = {en} } @inproceedings{BuchnerHausladenSchelsetal., author = {Buchner, Philipp and Hausladen, Matthias and Schels, Andreas and Herdl, Florian and Edler, Simon and Bachmann, Michael and Schreiner, Rupert}, title = {An Integrated Silicon Nanowire Field Emission Electron Source on a Chip with High Electron Transmission}, series = {2023 IEEE 36th International Vacuum Nanoelectronics Conference (IVNC), 10-13 July 2023, Cambridge, MA, USA}, booktitle = {2023 IEEE 36th International Vacuum Nanoelectronics Conference (IVNC), 10-13 July 2023, Cambridge, MA, USA}, publisher = {IEEE}, isbn = {979-8-3503-0143-4}, doi = {10.1109/IVNC57695.2023.10188878}, pages = {6 -- 8}, abstract = {Silicon nanowire field emission arrays (50 × 50 pillars) were fabricated on a silicon glass hybrid wafer. The glass acts both as the support for the whole structure and insulator between cathode and extraction grid. The extraction grid matches the emitter structures and is optically aligned and adhered to the emitter chip by a vacuum compatible epoxide adhesive. These chips exhibit an emission current of about 600 μA at an extraction voltage of 300 V. The electron transmission through the grid is above 80 \%. 58-hour longtime measurements were conducted showing low degradation of the emission current and high stability of electron transmission.}, language = {en} } @inproceedings{HausladenSchelsBuchneretal., author = {Hausladen, Matthias and Schels, Andreas and Buchner, Philipp and Bartl, Mathias and Asgharzade, Ali and Edler, Simon and Wohlfartsst{\"a}tter, Dominik and Bachmann, Michael and Schreiner, Rupert}, title = {Improved Method for Determining the Distribution of FEA Currents by Optical CMOS Sensors}, series = {37th International Vacuum Nanoelectronics Conference (IVNC), 15-19 July 2024, Brno, Czech Republic}, booktitle = {37th International Vacuum Nanoelectronics Conference (IVNC), 15-19 July 2024, Brno, Czech Republic}, publisher = {IEEE}, doi = {10.1109/IVNC63480.2024.10652543}, pages = {1 -- 2}, abstract = {CMOS image sensors are utilized to determine the time- and spatially-resolved distribution of the electron emission of silicon field emission arrays. During initial experiments, rather low field emission currents already visibly damaged the sensor surface, altering the system accuracy over the measurement time. Therefore, we coated the sensor surface with copper for protection. In contrast to the original insulating surface, the Cu coating provides a conductive surface for incident electrons and improves heat dissipation in addition. This prevents localized surface charges and surface damages which stabilize the system accuracy.}, language = {en} } @article{BachmannDuesbergPahlkeetal., author = {Bachmann, Michael and D{\"u}sberg, Felix and Pahlke, Andreas and Edler, Simon and Schels, Andreas and Herdl, Florian and Hausladen, Matthias and Buchner, Philipp and Schreiner, Rupert}, title = {The "LED-version" of the electron gun: An electron source for operation in ambient pressure environments based on silicon field emitter arrays}, series = {Vakuum in Forschung und Praxis}, volume = {35}, journal = {Vakuum in Forschung und Praxis}, number = {3}, publisher = {Wiley}, doi = {10.1002/vipr.202300801}, pages = {32 -- 37}, abstract = {We report on our progress to develop and optimize electron sources for practical applications. A simple fabrication process is introduced based on a wafer dicing saw and a wet chemical etch step without the need for a clean room. Due to the formation of crystal facets the samples show a homogeneous geometry throughout the array. Characterization techniques are developed to systematically compare various arrays. A very defined measurement procedure based on current controlled IV-sweeps as well as lifetime measurements at various currents is proposed. To investigate the current distribution in the array a commercial CMOS detector is used and shows the potential for in depth analysis of the arrays. Finally, a compact hermetically sealed housing is presented enabling electron generation in atmospheric pressure environments.}, language = {en} } @masterthesis{Zhong, type = {Bachelor Thesis}, author = {Zhong, Gantong}, title = {Calibration and Performance Evaluation of Contactless Optical Position Sensors Based on 3D Printed Optical Waveguides}, address = {Regensburg}, doi = {10.35096/othr/pub-8466}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-84668}, school = {Ostbayerische Technische Hochschule Regensburg}, pages = {35}, abstract = {This work presents the design, implementation, and performance evaluation of a positionsensing system based on a 3D printed optical waveguide. Building upon the conceptual foundation of D-shaped polymer optical fiber (POF) sensors [1], this study introduces a novel waveguide structure fabricated via multi-material fused filament fabrication (FFF) 3D printing. The waveguide incorporates a square-core geometry with integrated mechanical brackets and selective black cladding layer to enhance optical confinement and minimize boundary-induced nonlinearity. Three successive design iterations were developed and evaluated, with each version refined based on calibration results and structural observations. The final version demonstrated high fabrication stability and improved optical behavior, enabling consistent calibration across multiple samples. Using a center-corrected linear attenuation model, the position of a side-coupled LED was estimated from dual photodiode signals and compared with true light source position. The measurement results for five independently printed waveguides show mean absolute errors below 0.2 mm and standard deviations as low as 0.268 mm. The sensor response was found to be highly linear over the 5-55 mm sensing range, with worst-case errors bounded within ±1.7 mm. Compared with traditional D-shaped POF sensors, where performance is limited by manual polishing variability and nonuniform attenuation, the 3D-printed approach offers superior linearity, submillimeter accuracy, and batch-to-batch reproducibility. These findings prove the feasibility of 3D-printed optical waveguides in scalable and precise position sensing applications, marking a further step toward the batch fabrication and and potential industrialization of contactless optical position sensors. A conclusion of the research findings and suggestions for future improvements were provided at the end of this thesis, offering insights for the further development in this area.}, language = {en} }