@misc{Vokkethur, type = {Master Thesis}, author = {Vokkethur, Rachana}, title = {Design, simulation, fabrication, measurement, and analysis of 3D-printed radio frequency conductive structures}, address = {Regensburg}, doi = {10.35096/othr/pub-8780}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-87809}, school = {Ostbayerische Technische Hochschule Regensburg}, pages = {iv, 65}, abstract = {Additive manufacturing has emerged as a disruptive technology in the field of electronics, offering new possibilities for the fabrication of complex, lightweight, and customizable components. Conventional PCB manufacturing relies on multi-step processes and is limited to planar geometries, making it less suitable for rapid prototyping or integration into non-standard surfaces. In contrast, Fused Deposition Modelling (FDM) provides a cost-effective and accessible approach to directly fabricate functional electronic structures by combining conductive and dielectric materials within a single printing process. This thesis examines the design, simulation, fabrication, measurement and analysis of 3D-printed conductive transmission lines utilising FDM technology. A conductive filament and a dielectric filament are employed to realise fully integrated microstrip and coaxial structures. Electromagnetic simulations are performed to optimise the geometry for RF performance, and the printed prototypes are experimentally characterised using vector network analyser measurements. The analysis focuses on the transmission coefficients and the reflection coefficients, providing insights into impedance matching, insertion loss, and frequency-dependent behaviour. These findings confirm that FDM-based additive manufacturing can produce functional RF structures with reliable performance, despite material and fabrication limitations. The work demonstrates the potential of 3D printing as a flexible and low-cost method for prototyping radio frequency components, highlighting future directions that include improved material characterisation, connector integration, and the design of more advanced components, such as filters and antennas.}, language = {en} } @misc{KrysztofBaranowskiZychlaetal., author = {Krysztof, Michal and Baranowski, Kamil and Zychla, Michal and Hausladen, Matthias and Schreiner, Rupert and Kn{\´a}pek, Aleksandr}, title = {MP61 - Detection of Electron Beam in Atmospheric Pressure Using CMOS Image Sensor}, series = {EUROSENSORS XXXVII ; 07.09.2025 - 10.09.2025 ; Wroclaw ; Poster I}, journal = {EUROSENSORS XXXVII ; 07.09.2025 - 10.09.2025 ; Wroclaw ; Poster I}, publisher = {AMA}, doi = {10.5162/EUROSENSORS2025/MP61}, pages = {325 -- 326}, abstract = {In the article, a new detection system that enables observation of the electron beam signal passing through a gas layer at atmospheric pressure is presented. An experimental setup consisting of an elec-tron gun (electron emitter, extraction, and focus electrodes), silicon nitride membrane, and a CMOS image sensor is described, as well as first image of the electron beam spot after passing through 400 µm of air at atmospheric pressure is presented.}, language = {en} } @inproceedings{SadequeAhmmedHossainetal., author = {Sadeque, Md. Golam and Ahmmed, Tanvir and Hossain, Md. Aowal and Rahman, Md. Naimur and Sarker, Md Tanjil and Ramasamy, Gobbi}, title = {A Novel CWT-CNN Framework for Driver Fatigue Detection from EEG Signals}, series = {2025 Multimedia University Engineering Conference (MECON), 21-23 July 2025, Cyberjaya, Malaysia}, booktitle = {2025 Multimedia University Engineering Conference (MECON), 21-23 July 2025, Cyberjaya, Malaysia}, publisher = {IEEE}, isbn = {979-8-3315-5549-8}, doi = {10.1109/MECON67253.2025.11277149}, pages = {6}, abstract = {Fatigued driving has been a significant contributor to traffic accidents globally, posing serious threats to both human life and economic stability. Machine learning techniques based on electroencephalography (EEG) are showing promise for detecting driver fatigue, excelling other physiological modalities in this regard. However, it requires a lot of exertion, demands domain knowledge, and may not generalize effectively across different datasets to manually extract features from EEG signals. Therefore, investigating innovative deep-learning architectures that can effectively extract discriminative characteristics from unprocessed EEG data is necessary. This paper proposes a novel framework for driver fatigue detection from EEG signals using Continuous Wavelet Transform (CWT) and Convolutional Neural Networks (CNN). Rather than depending on hand-crafted feature extraction, we use CWT to convert EEG data into time-frequency spectrum pictures. After concatenating these spectral images from every channel, a CNN is fed to learn discriminative features for driver normal and fatigued states automatically. An average classification accuracy of 98.3\% is obtained by evaluating the proposed CWT-CNN system on a publicly available EEG dataset comprising recordings from twelve subjects. The results obtained indicate that the CWT-CNN framework has enormous potential to create strong driver fatigue detection systems, thereby enhancing road safety.}, language = {en} } @unpublished{FischerHirschReitmeieretal., author = {Fischer, Johannes and Hirsch, Thomas and Reitmeier, Torsten and Bierl, Rudolf}, title = {Real-time hardware-based processing of high-precision detector signals for surface plasmon resonance spectroscopy}, doi = {10.2139/ssrn.5971170}, pages = {16}, abstract = {Surface plasmon resonance (SPR) is limited by small-signal detectability and drift when subtraction occurs in software after digitization. We introduce an SPR detector that performs on-detector amplification and analog differential readout, eliminating moving parts and software-heavy correction. The hardware-native subtraction boosts the usable ADC range and suppresses illumination and environmental noise. In fixed-angle refractive-index steps (NaCl), the platform resolves Δn_min ≈ 1.8 × 10⁻⁷ RIU compared to 4.6-7.2 × 10⁻⁶ RIU on a commercial comparator and improves small-signal SNR by up to ∼5,000-fold, while remaining competitive at high signal levels. In a model IgG-BSA assay, the detector's low noise floor clarifies early binding and equilibrium transitions. By generating inherently clean raw signals, this hardware-native approach dramatically enhances sensitivity and long-term stability for label-free biosensing and inline process analytics while rendering AI-based or complex post-processing entirely unnecessary. The concept generalizes across platforms and opens a compact route to robust, high-fidelity SPR in complex environments, with a clear path toward multi-wavelength and arrayed detectors for high-throughput chemical monitoring.}, language = {en} } @inproceedings{BartlHausladenAsgharzadeetal., author = {Bartl, Mathias and Hausladen, Matthias and Asgharzade, Ali and Buchner, Philipp and Krysztof, Michal and Kn{\´a}pek, Alexandr and Bachmann, Michael and Schreiner, Rupert}, title = {Experimental method for investigation of the emission pattern characteristics of individual field emission tips using a CMOS image sensor}, series = {38th International Vacuum Nanoelectronics Conference (IVNC)}, booktitle = {38th International Vacuum Nanoelectronics Conference (IVNC)}, publisher = {IEEE}, doi = {10.1109/IVNC65669.2025.11121040}, pages = {2}, abstract = {The emission pattern characteristics of individual silicon field emission tips were investigated using a CMOS image sensor. The quality of the image was improved by spatial and temporal averaging, so that individual emission centers could be identified and their temporal changes investigated. By mapping the emission current onto the image, the distribution of the current density on the image sensor could be calculated.}, language = {en} } @inproceedings{JannsenEhrnsperger, author = {Jannsen, Kai and Ehrnsperger, Matthias}, title = {Edge-efficient convolutional neural network for real-time doppler radar gesture recognition}, series = {2025 IEEE Radar Conference (RadarConf25), 4.-9. Oktober 2025, Krakow}, booktitle = {2025 IEEE Radar Conference (RadarConf25), 4.-9. Oktober 2025, Krakow}, publisher = {IEEE}, isbn = {979-8-3315-4433-1}, doi = {10.1109/RadarConf2559087.2025.11205096}, pages = {877 -- 881}, abstract = {Embedded gesture recognition using radar sensors enables intuitive and robust human-machine interfaces, which is appealing for automotive applications such as trunk opening via foot gesture. Designing a radar-based classifier that runs ondevice (edge) under strict resource constraints poses several challenges. The system must achieve real-time inference (e.g. under 200 ms) on a microcontroller unit (MCU), while maintaining high accuracy, and minimize false detections. This paper focuses on a binary classification task, while distinguishing a valid trunkopening "kick" gesture from other motions. Firstly, we evaluate classical machine learning (cML) models (Random Forests or support vector machines (SVMs)) for baseline performance, however they face difficulties with higher false positive rates and do not meet real time criteria. We then employ Convolutional Neural Networks (CNNs) and apply neural architecture search (NAS) to discover a compact CNN tailored for a 60 GHz Doppler radar dataset of 50 subjects, each with 10 leg gestures. By constraining network depth, filter sizes, and hyperparameters, NAS yields a small but accurate "edge" CNN that fits within the limited memory of a STM32 Nucleo F446RE microcontroller. The final model achieves 95.1 \% accuracy on the binary classification task with 96.6 \% precision and 2.17 \% false positive rate (FPR), and requires only 167.5 ms to run inference on the MCU.}, language = {en} } @inproceedings{BaranowskiZychlaKrysztofetal., author = {Baranowski, Kamil and Zychla, Michał and Krysztof, Michał and Ż{\´o}łtowski, Michał and Hausladen, Matthias and Schreiner, Rupert and Kn{\´a}pek, Aleksandr}, title = {Experimenal method for studying electron beams in gaseous environments using a CMOS image sensor}, series = {38th International Vacuum Nanoelectronics Conference (IVNC)}, booktitle = {38th International Vacuum Nanoelectronics Conference (IVNC)}, publisher = {IEEE}, isbn = {979-8-3315-3705-0}, doi = {10.1109/IVNC65669.2025.11120851}, pages = {2}, abstract = {Detecting and analyzing electron beams in atmospheric conditions remains a significant challenge due to scattering and absorption of electrons by gas molecules. In this work, a novel approach using a CMOS image sensor for real-time electron beam detection after its transmission through air is presented. The setup enables visualization of beam divergence, emission profiles, and dynamic behavior under atmospheric pressure. Presented results demonstrate the potential of CMOS image sensor for electron beam analysis in gaseous environment.}, language = {en} } @inproceedings{AllahamBurdaKnapeketal., author = {Allaham, Mohammad M. and Burda, Daniel and Kn{\´a}pek, Alexandr and Krysztof, Michał and Baranowski, Kamil and Hausladen, Matthias and Schreiner, Rupert}, title = {Testing the performance of tungsten-graphite cathodes as MEMS Electron microscope electron source}, series = {38th International Vacuum Nanoelectronics Conference (IVNC)}, booktitle = {38th International Vacuum Nanoelectronics Conference (IVNC)}, publisher = {IEEE}, doi = {10.1109/IVNC65669.2025.11121041}, pages = {2}, abstract = {This work presents preliminary results of the performance testing of exfoliated graphene layers deposited on the nanotip of a tungsten field emission cathode. The obtained tungsten-graphite cathodes were then operated in a 3D-printed MEMS electron microscope testing model for later applications. The results were promising, where a maximum emission current of 50.2 μA was obtained with an extraction voltage of 1 kV and anode voltage of 3 kV.}, language = {en} } @article{WolfgrammAbbSampetal., author = {Wolfgramm, Alex and Abb, Valerius and Samp, Artur and Samp, Rafal and Hoffmann, Jens Christoph and M{\"u}ller, Rainer and Kammler, Martin}, title = {Structural and functional evolution of HKUST-1 nanoparticles induced by ball milling}, series = {Next Materials}, volume = {10}, journal = {Next Materials}, publisher = {Elsevier}, doi = {10.1016/j.nxmate.2025.101544}, pages = {7}, abstract = {In this study, the effect of post-synthetic ball milling on the structural and functional properties of as-synthesized nanoparticles of the copper-based metal-organic framework (MOF) HKUST-1 was investigated for the first time. Nanoparticles were synthesized using sodium formate as a capping agent. The crystalline particles were subjected to a controlled ball milling process, which induced significant structural changes. Powder X-ray diffraction (PXRD) revealed a reduction in crystallite size from 91 nm to 21 nm and the introduction of microstrain, partially disrupting the MOF's long-range crystalline order, as evidenced by peak broadening and the diminished intensity of high-angle reflections. Particle morphology pre- and post-milling was further studied with scanning electron microscopy (SEM) imaging, verifying a narrow particle size distribution of ± 22 nm after milling. Fourier-transform infrared spectroscopy (FTIR) indicated protonation of carboxylate groups in the larger pores of the framework, likely due to moisture incorporation during milling. Brunauer-Emmett-Teller (BET) surface area analysis showed a substantial decrease in specific surface area from 521 m²/g to 226 m²/g, suggesting a partial collapse of the porous framework. We discuss the applicability of ball milling as a versatile means of post-synthetic approach to reduce MOF particle sizes, a key element in the preparation of MOF-based thin films using inks or polymers.}, language = {en} } @inproceedings{AsgharzadeBartlHausladenetal., author = {Asgharzade, Ali and Bartl, Mathias and Hausladen, Matthias and Chen, Yang and Buchner, Philipp and Edler, Simon and Bachmann, Michael and She, Juncong and Schreiner, Rupert}, title = {Investigation on the influence of internal voltage drops on the emission behavior of silicon field emission arrays using CMOS image sensor}, series = {38th International Vacuum Nanoelectronics Conference (IVNC)}, booktitle = {38th International Vacuum Nanoelectronics Conference (IVNC)}, publisher = {IEEE}, doi = {10.1109/IVNC65669.2025.11120937}, pages = {2}, abstract = {In this paper we report on an improved measurement and analysis method for determining the emission current distribution of field emitter arrays with CMOS sensors. It can also be used for field emission arrays where not all surfaces of the emitters are at the same electrical potential (e.g. for p-doped Si tips, where a strong current saturation occurs). To demonstrate the functionality of this method, a n-doped field emission array was measured using a variable external series resistance. Brightness variations in emission spots were analyzed to re-calculate the known series resistances for comparison. The re-calculated value is in good agreement with the actual value of the resistance. This method offers a quantitative approach to assess internal voltage drop effects on field emission using optical readout}, language = {en} } @phdthesis{Lindner, author = {Lindner, Matthias}, title = {Miniaturisierte dielektrische Barrierenentladungen und ihre Anwendung f{\"u}r das Anti- bzw. De-Icing von aerodynamischen Oberfl{\"a}chen}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:384-opus4-1118933}, pages = {XI, 155}, abstract = {Das grundlegende physikalische Verst{\"a}ndnis und die kontinuierliche Weiterentwicklung von dielektrischen Oberfl{\"a}chenbarrierenentladungen (SDBDs) sowie der damit erbundenen elektrischen Diagnostik, sind f{\"u}r eine Vielzahl von Niedertemperaturplasmaanwendungen von entscheidender Bedeutung. In Bezug auf die Anwendung dieser Plasmatechnologie in der Luftfahrt liegt neben der bereits umfassend erforschten aktiven Str{\"o}mungskontrolle zunehmend der Schwerpunkt auf der Vermeidung von Eisablagerungen auf aerodynamischen Komponenten. Die Bildung von Eis auf Oberfl{\"a}chen wie zum Beispiel den Tragfl{\"a}chen kann unter extremen Wetterbedingungen erhebliche Leistungsdefizite hervorrufen und zu ernsthaften Sicherheitsrisiken f{\"u}hren. In Anbetracht der signifikanten Vorteile gegen{\"u}ber traditionellen Enteisungsmethoden steht die Erforschung von SDBDs im Mittelpunkt des anwendungsorientierten Abschnitts dieser Arbeit. Vorliegende Arbeit untergliedert sich in einen grundlegenden und einen anwendungsbezogenen Teil. Darin werden sowohl die physikalischen Eigenschaften und Prozesse von SDBDs analysiert als auch ihre potenziellen Anwendungen in Bezug auf Flugsicherheit und Effizienz untersucht. Die wissenschaftliche Forschung hat in der Vergangenheit erhebliche Anstrengungen unternommen, um ein umfassendes Verst{\"a}ndnis der physikalischen Vorg{\"a}nge, die im Zusammenhang mit SDBDs stehen, zu erarbeiten. Insbesondere die pr{\"a}zise Bestimmung der r{\"a}umlichen Ausdehnung der Entladung entlang der dielektrischen Oberfl{\"a}che - die {\"u}blicherweise in direkter Proportionalit{\"a}t zur Amplitude der angelegten Spannung steht - ist hierbei eine herausfordernde Aufgabe. Diese umfangreichen Studien sind essenziell, um die Entladungseigenschaften und die grundlegenden physikalischen Prozesse zu verstehen, was erhebliche Anwendungspotenziale er{\"o}ffnet. Parallel zu diesen grundlegenden Studien hat sich auch der praktische Einsatz von SDBDs zur Verhinderung der Eisbildung auf aerodynamischen Bauteilen bedeutend weiterentwickelt. Untersuchungen legen nahe, dass L{\"o}sungen auf Basis von SDBDs im Vergleich zu konventionellen Enteisungsmethoden, wie beispielsweise chemischen Enteisungsmitteln oder thermischen Systemen, ein h{\"o}heres Effizienz- und Wirkungspotential besitzen k{\"o}nnten. Allerdings wurden bisherige Entwicklungen von SDBDs haupts{\"a}chlich auf Basis der Leiterplattentechnologie realisiert, was bestimmte Begrenzungen in Bezug auf ihre Anwendbarkeit f{\"u}r Anti-Icing- Technologie mit sich bringt. Im ersten Teil dieser Arbeit wurde die sequentielle Ausbreitung der SDBD-Entladung entlang der dielektrischen Al2O3-Oberfl{\"a}che systematisch analysiert. Die durchgef{\"u}hrten experimentellen Untersuchungen zeigten, dass die Entladungen unmittelbar nach dem Erreichen der Z{\"u}ndspannung einen fest definierten Bereich belegen, der bis zum Erreichen einer kritischen Spannungsamplitude VL stabil bleibt. Anzumerken ist auch, dass das Ausbleiben der Plasmaausbreitung innerhalb dieses Spannungsbereichs zu einer linearen Korrelation zwischen der Entladungsleistung und der angelegten Spannungsamplitude f{\"u}hrt. Diese tiefergehenden Einblicke in die Dynamik der Entladung k{\"o}nnen dazu beitragen, den Einsatz von SDBDs in diversen Anwendungsbereichen effizienter zu gestalten. Im zweiten Teil der Arbeit steht die Entwicklung und Implementierung eines innovativen Ansatzes zur Realisierung von SDBDs im Vordergrund, der auf der Nutzung von D{\"u}nnschichtsubstra-Vten und mikroelektromechanischen Systemen (MEMS) basiert. Die Verwendung dieser Technologie erlaubt einen pr{\"a}ziseren Design- und Fertigungsprozess von Elektrodenstrukturen, was sich positiv auf die Effizienz der Enteisung auswirken kann. Zur Beurteilung des Anti-Icing-Potenzials der entwickelten MEMS-SDBDs wurde ein direkter Vergleich mit konventionellen PCB-SDBDs durchgef{\"u}hrt. Die Ergebnisse legen nahe, dass die 35 μm dicken Elektroden der PCB-SDBDs eine Oberfl{\"a}chenvereisung f{\"o}rdern, die vorrangig durch die Elektrodenkanten induziert wird. Im Gegensatz dazu wurde dieser Effekt bei den deutlich d{\"u}nneren, lediglich 0.3 μm dicken, mittels MEMS gefertigten Elektroden nicht festgestellt. Diese Beobachtungen deuten darauf hin, dass SDBDs, die mit MEMS-Technologien gefertigt wurden, einen signifikanten Vorteil in Anti-Icing-Anwendungen aufweisen k{\"o}nnten und stellen somit einen wesentlichen Fortschritt in der Forschung und Anwendung von SDBDs dar. Die in dieser Arbeit vorgelegten Forschungsergebnisse und innovativen Methoden liefern zahlreiche neue Erkenntnisse, die das Potential besitzen, sowohl das Verst{\"a}ndnis als auch die Anwendung von SDBDs wesentlich zu erweitern. So best{\"a}tigen die Langzeitbelichtungsaufnahmen das neu entdeckte Ph{\"a}nomen einer sequenziellen Ausbreitung des Entladungsplasmas, das bei SDBDs mit dickeren Dielektrika st{\"a}rker ausgepr{\"a}gt ist. Eine neu entwickelte Methodik erm{\"o}glicht die Anwendung der Ladungs-Spannungs-Charakteristik von SDBDs, um essenzielle Parameter f{\"u}r ein vereinfachtes Ersatzschaltbild abzuleiten. Dar{\"u}ber hinaus wurde eine bemerkenswerte numerische {\"U}bereinstimmung zwischen der Ladungs-Spannungs-Charakteristik f{\"u}r den positiven Halbzyklus der Entladung und der aus den optischen Aufnahmen abgeleiteten spannungsabh{\"a}ngigen Reaktorkapazit{\"a}t festgestellt. Diese Erkenntnisse {\"o}ffnen neueWege f{\"u}r die Optimierung und Anwendung von SDBDs in verschiedenen technischen Bereichen. Weiterhin identifizierte die durchgef{\"u}hrte Erosionsstudie Titan als optimal geeignetes Material f{\"u}r MEMS-Elektroden aufgrund seiner hohen Korrosionsbest{\"a}ndigkeit und ausgezeichneten elektrischen Leitf{\"a}higkeit. Es wurden auch Potentiale zur Optimierung von MEMS-SDBDs durch die Auswahl geeigneter dielektrischer Materialien und geeigneter SDBD-Geometrien aufgezeigt. Eine solche Optimierung k{\"o}nnte die Enteisungseffizienz weiter verbessern, indem beispielsweise die dielektrischen Eigenschaften an die spezifischen Anwendungsanforderungen angepasst werden. Innovative Designkonzepte, wie eine gezielte Anordnung der Elektroden oder die Integration von Sensoren zur {\"U}berwachung des Enteisungsprozesses, k{\"o}nnten ebenfalls zur Leistungsf{\"a}higkeit und Zuverl{\"a}ssigkeit von MEMS-SDBDs beitragen. Ein weiterer bedeutender Aspekt ist die Anwendung von Piezotransformatoren zur Generierung der ben{\"o}tigten Hochspannung f{\"u}r SDBD-Systeme. Dieser innovative Ansatz k{\"o}nnte die Effizienz des auf SDBD-Technologie basierenden Enteisungsverfahrens optimieren und somit zur Verbesserung der Leistungsf{\"a}higkeit und Sicherheit von Flugzeugen unter extremen Wetterbedingungen beitragen. Das Forschungsfeld bietet viel Raum f{\"u}r zuk{\"u}nftige Studien, was die Bedeutung und Zukunftsrelevanz der in dieser Arbeit gewonnenen Ergebnisse hervorhebt.}, subject = {Kaltes Plasma}, language = {de} } @phdthesis{Jonker2023, author = {Jonker, Dirk}, title = {Advanced nanofabrication techniques for electron emission devices}, isbn = {978-90-365-5632-3}, doi = {10.3990/1.9789036556323}, pages = {362}, year = {2023}, abstract = {The goal of this thesis is to develop an electron injection source based on a cold field emission cathode that ultimately functions as an alternative electron source used during the Birch reduction process. The experimental configuration to conduct an alternative Birch reduction involves the combination of various physical domains, including solid-state physics, physics of interfaces, electrochemistry, and fluid dynamics. The body of this thesis discusses the fabrication and characterization of a silicon nanocone array. It also presents a self-aligned method to incorporate an electronic gate structure that may function as an extractor grid. The emission behavior and transport properties of the silicon nanocones are assessed by scanning tunneling microscopy by performing measurements on flat silicon and silicon nanocone surfaces containing different dopant types and doping concentrations. Furthermore, additional experimental work is conducted to replace a thermally grown silicon dioxide layer with platinum silicide and characterize the electrical properties by means of scanning tunneling microscopy. Lastly, the thesis discusses the fabrication of two plasmonic structures and evaluates the plasmonic modes, surface enhancement, and Raman activity.}, language = {en} } @phdthesis{Weigl, author = {Weigl, Stefan}, title = {Development of a sensor system for human breath acetone analysis based on photoacoustic spectroscopy}, doi = {10.5283/epub.44776}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:355-epub-447768}, pages = {xlii, 282}, abstract = {The breath analysis section of this thesis outlines the potentials but also emphasises the concomitant challenges of human breath analysis. The section further describes the usefulness of a point-of-care (POC) device for breath acetone detection. In addition, it covers various breath analysis related subjects, which can be useful considering further developments of breath analysers. This includes an extensive summary involving the high abundant endogenous as well as the exogenous breath species present in a clinical environment. Subsequently, a detailed discussion about the theoretical aspects of absorption spectra is provided, forming the basis for the spectral interference chapter. Classical absorption spectroscopy (AS) is compared with photoacoustic spectroscopy (PAS) in view of trace gas analysis. Different modulation schemes for signal generation, i.e. amplitude modulation (AM) and wavelength modulation (WM) are part of the comparison, while the advantages and disadvantages of each technique are highlighted. As a result, PAS is considered superior to AS and hence is selected as the method of choice regarding the development of a sensor for breath acetone detection. A detailed mathematical derivation of the photoacoustic signal generation as well as the signal enhancement by means of acoustic resonance amplification is provided. Moreover, several phenomena causing signal attenuation are outlined, including vibrational-translational (VT) relaxation, vibrational-vibrational (VV) energy transfer mechanism, acoustic detuning and photodissociation. Various simulations regarding spectral interferences in the infra-red (IR) and ultraviolet (UV) region are presented, demonstrating the susceptibility towards spectral cross-sensitivities in the IR region, hence, rather suggesting the UV region for acetone detection. However, this simulation can be easily adopted to other target analytes and serves as a basis for multicomponent analysis approaches in the IR region using tuneable light sources. Ultra sensitive acetone detection employing a high power UV LED is presented and a detailed analysis considering the effects of environmental parameters onto the photoacoustic signal, including temperature, pressure, LED duty cycle and flow rate, is provided. In addition, general cross-sensitivities of the photoacoustic signal towards the high abundant species O2, CO2 and H2O have been investigated and discussed. Moreover, several LED and photoacoustic cell (PAC) combinations have been compared in order to evaluate improvement approaches regarding an enhancement of the system's sensitivity. Finally, photoacoustic sensor setups employing an interband cascade laser (ICL) or a quantum cascade laser (QCL) have been studied and compared to various UV setups in view of different key performance parameters, including the limits of detection (LOD) and the normalised noise equivalent absorption (NNEA) coefficients. The juxtaposition of the different approaches once more emphasises the extraordinary sensitivity of photoacoustic spectroscopy. To the best of the author's knowledge, the LODs (3σ) of the UV LED based photoacoustic measurement in typical breath conditions (12.5 ppbV) and the LOD of the QCL measurement (0.79 ppbV) provide two world records. First, regarding photoacoustic acetone detection using an UV LED and second, in view of other published results for photoacoustic acetone detection in general.}, language = {en} } @article{BuchnerHausladenBartletal., author = {Buchner, Philipp and Hausladen, Matthias and Bartl, Mathias and Bachmann, Michael and Schreiner, Rupert}, title = {High current field emission from Si nanowires on pillar structures}, series = {Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics}, volume = {42}, journal = {Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics}, number = {2}, publisher = {AIP}, issn = {2166-2754}, doi = {10.1116/6.0003384}, abstract = {We investigate the influence of the geometry and doping level on the performance of n-type silicon nanowire field emitters on silicon pillar structures. Therefore, multiple cathodes with 50 by 50 pillar arrays (diameter: 5 μm, height: 30 μm, spacing: 50 μm) were fabricated and measured in diode configuration. In the first experiment, we compared two geometry types using the same material. Geometry 1 is black silicon, which is a highly dense surface covering a forest of tightly spaced silicon needles resulting from self-masking during a plasma etching process of single crystal silicon. Geometry 2 are silicon nanowires, which are individual spaced-out nanowires in a crownlike shape resulting from a plasma etching process of single crystal silicon. In the second experiment, we compared two different silicon doping levels [n-type (P), 1-10 and <0.005 Ω cm] for the same geometry. The best performance was achieved with lower doped silicon nanowire samples, emitting 2 mA at an extraction voltage of 1 kV. The geometry/material combination with the best performance was used to assemble an integrated electron source. These electron sources were measured in a triode configuration and reached onset voltages of about 125 V and emission currents of 2.5 mA at extraction voltages of 400 V, while achieving electron transmission rates as high as 85.0\%.}, language = {en} } @inproceedings{SchreinerMulotGauggeletal., author = {Schreiner, Rupert and Mulot, M. and Gauggel, H. P. and Schweizer, H. and Laue, C. K. and Wallenstein, R.}, title = {Dynamic and spectral properties of red DFB lasers}, series = {Technical Digest. Summaries of papers presented at the Conference on Lasers and Electro-Optics. Postconference Technical Digest (IEEE Cat. No.01CH37170) ; Baltimore, May 6 - 11, 2001 (Trends in optics and photonics series ; 56)}, booktitle = {Technical Digest. Summaries of papers presented at the Conference on Lasers and Electro-Optics. Postconference Technical Digest (IEEE Cat. No.01CH37170) ; Baltimore, May 6 - 11, 2001 (Trends in optics and photonics series ; 56)}, publisher = {IEEE}, isbn = {1-55752-662-1}, doi = {10.1109/CLEO.2001.947498}, pages = {81 -- 82}, abstract = {Summary form only given. Narrow linewidth GaInP/AlGaInP DFB lasers are promising light sources for spectroscopy, for optical data storage systems and for plastic optical fiber WDM applications. However, little is known about the dynamic behavior of red DFB lasers. In this paper, we report on the dynamic and spectral properties of those devices. The lasers were first characterized under cw operation at 25/spl deg/C. Threshold currents are /spl sim/14 mA (475 /spl mu/m length) and /spl sim/18 mA (900 /spl mu/m length). The lasers show stable single mode emission at 680 nm with a SMSR better than -25 dB. The spectral linewidth of the 900 /spl mu/m long devices was measured by using a scanning-Fabry-Perot interferometer.}, language = {en} } @misc{HummelLechner, author = {Hummel, Helmut and Lechner, Alfred}, title = {Miniaturized on-line trace analysis [Patentschrift]}, organization = {Ostbayerische Technische Hochschule Regensburg}, abstract = {The invention relates to a measuring apparatus comprising an apparatus for forming a liquid optical waveguide having a substrate (1) having an at least partially curved closed microchannel (2) having a low-refractive coating (13), whereby there is formed in the substrate (1) at least one feed line (6) for supplying liquid, and whereby there is provided at least at one end of the closed microchannel (2) an apparatus for coupling light axially into the closed microchannel and/or for coupling light axially out of the closed microchannel (2), further comprising a light source (4), a light detector (5), and a first liquid pump (9) which supplies a sample liquid (7) to the closed microchannel (2) via the at least one feed line (6, 6a).}, language = {de} } @inproceedings{BarikRawatMannaetal., author = {Barik, Ranjan Kumar and Rawat, Vikram Singh and Manna, Subhrajit and Bandyopadhyay, Ayan Kumar and Hausladen, Matthias and Asgharzade, Ali and Schreiner, Rupert}, title = {On Chip Electron Gun Design Using Silicon Tip Field Emitter Array}, series = {2025 IEEE Microwaves, Antennas, and Propagation Conference (MAPCON), 14-18. Dezember 2025, Kochi, India}, booktitle = {2025 IEEE Microwaves, Antennas, and Propagation Conference (MAPCON), 14-18. Dezember 2025, Kochi, India}, publisher = {IEEE}, isbn = {979-8-3315-3722-7}, doi = {10.1109/MAPCON65020.2025.11426578}, pages = {4}, abstract = {Silicon based silicon tip array emitter has developed at OTH Regensburg, Germany. This array emitter is the basis for development of a novel electron gun. This field emitter electron sources were fabricated using laser-micromachining technique followed by MEMS technology. In this work, the design and development of electron gun using complete silicon structure is reported. The goal of this work is to develop electron gun using less effort, easy and hassle free technique.}, language = {en} } @article{TanSchreinerHausladenetal., author = {Tan, Jing Jie and Schreiner, Rupert and Hausladen, Matthias and Asgharzade, Ali and Edler, Simon and Bartsch, Julian and Bachmann, Michael and Schels, Andreas and Kwan, Ban-Hoe and Ng, Danny Wee-Kiat and Hum, Yan-Chai}, title = {SiMiC: Context-aware silicon microstructure characterization using attention-based convolutional neural networks for field-emission tip analysis}, series = {Journal of Vacuum Science \& Technology B}, volume = {43}, journal = {Journal of Vacuum Science \& Technology B}, number = {6}, publisher = {AVS}, doi = {10.1116/6.0005068}, abstract = {Accurate characterization of silicon microstructures is essential for advancing microscale fabrication, quality control, and device performance. Traditional analysis using scanning electron microscopy (SEM) often requires labor-intensive, manual evaluation of feature geometry, limiting throughput and reproducibility. In this study, we propose SiMiC: Context-aware Silicon Microstructure Characterization Using Attention-based Convolutional Neural Networks for Field-Emission Tip Analysis. By leveraging deep learning, our approach efficiently extracts morphological features—such as size, shape, and apex curvature—from SEM images, significantly reducing human intervention while improving measurement consistency. A specialized dataset of silicon-based field-emitter tips was developed, and a customized convolutional neural network architecture incorporating attention mechanisms was trained for multiclass microstructure classification and dimensional prediction. Comparative analysis with classical image processing techniques demonstrates that SiMiC achieves high accuracy while maintaining interpretability. The proposed framework establishes a foundation for data-driven microstructure analysis directly linked to field-emission performance, opening avenues for correlating emitter geometry with emission behavior and guiding the design of optimized cold-cathode and SEM electron sources. The related dataset and algorithm repository that could serve as a baseline in this area can be found at https://research.jingjietan.com/?q=SIMIC.}, language = {en} }