@inproceedings{SchreinerDamsPrommesbergeretal., author = {Schreiner, Rupert and Dams, Florian and Prommesberger, Christian and Bornmann, Benjamin and Serbun, Pavel and Navitski, Aliaksandr and M{\"u}ller, G{\"u}nter}, title = {Silicon-based integrated field emission electron sources for sensor application}, series = {24th International Vacuum Nanoelectronics Conference (IVNC), 2011 : 18 - 22 July 2011, Wuppertal, Germany}, booktitle = {24th International Vacuum Nanoelectronics Conference (IVNC), 2011 : 18 - 22 July 2011, Wuppertal, Germany}, publisher = {IEEE}, address = {Piscataway, NJ}, pages = {19 -- 20}, abstract = {We report on the design, fabrication and characterization of p-type silicon field emitter arrays for the application in compact fast switchable electron sources. Since standard silicon technology has been used to prepare the devices, they can be easily integrated with other silicon based sensors and electronic components, too. The emitter arrays consist of approx. 3×105 tips per cm2, with a tip radius less than 20 nm. By using self-aligned processes, an integrated gate electrode with a diameter of  3 μm was placed concentrically around the tips. A mesh of silicon-beams with a grating period of 100 μm and beam width of 20 μm forms the anode of the electron source. A glass wafer (thickness 300 μm) acts as spacer between anode and Si-tip cathode. Characterization of the field emission properties of the emitter arrays was performed by high resolution field emission scanning microscopy. The emitter arrays exhibit a highly stable and very homogeneous emission. A maximum stable current of 0.1 μA per tip was found. A saturation level in the voltage current characteristics, which was found at around 10 nA, supports current stabilisation and will enable optical modulation of the emission current.}, language = {en} } @inproceedings{BornmannMingelsSerbunetal., author = {Bornmann, Benjamin and Mingels, Stephan and Serbun, Pavel and L{\"u}tzenkirchen-Hecht, Dirk and M{\"u}ller, G{\"u}nter and Prommesberger, Christian and Langer, Christoph and Dams, Florian and Schreiner, Rupert}, title = {Photosensitivity of electron field emission from B-doped Si-tip arrays}, series = {25th International Vacuum Nanoelectronics Conference (IVNC) ; Jeju, Korea (South), 09.07.2012 - 13.07.2012}, booktitle = {25th International Vacuum Nanoelectronics Conference (IVNC) ; Jeju, Korea (South), 09.07.2012 - 13.07.2012}, publisher = {IEEE}, isbn = {978-1-4673-1984-3}, issn = {2380-6311}, doi = {10.1109/IVNC.2012.6316980}, pages = {1 -- 2}, abstract = {The electron current from field-emitting B-doped Si-tip arrays under illumination was studied. An improved cathode design with a patch of 271 tips yielded a reproducible cathode current between 0.2-2000 nA in the electric field range of 3.8-6.6 V/μm. The plateau in the Fowler-Nordheim plot shows the actual carrier depletion and leads to a very stable emission at ~1 μA with a current noise of less than 3.3 \%. Color-filtered halogen lamp illumination was used to investigate the photo-sensitivity of the saturation current. The intensity-normalized current switching ratio increases nonlinearly with the photon energy. This hints either for secondary generation in the conduction band or deeper valence band excitation. The first is supported by a rough estimation of the quantum efficiency. Further experiments with a tunable laser and electron spectroscopy are planned.}, language = {en} } @inproceedings{LangerPrommesbergerDamsetal., author = {Langer, Christoph and Prommesberger, Christian and Dams, Florian and Serbun, Pavel and Bornmann, Benjamin and Mingels, Stephan and M{\"u}ller, G{\"u}nter and Schreiner, Rupert}, title = {Si-Feldemissionskathoden f{\"u}r Anwendungen in miniaturisierten Ionisationsvakuumsensoren}, series = {Verhandlungen der Deutschen Physikalischen Gesellschaft e.V. (DPG), Regensburg, 10. - 15. M{\"a}rz 2013}, booktitle = {Verhandlungen der Deutschen Physikalischen Gesellschaft e.V. (DPG), Regensburg, 10. - 15. M{\"a}rz 2013}, publisher = {Deutsche Physikalische Gesellschaft e.V.}, abstract = {Feldemissionselektronenquellen sind aufgrund ihrer prinzipiellen Vorteile gegen{\"u}ber Gl{\"u}hkathoden bereits seit l{\"a}ngerer Zeit Gegenstand der Forschung und werden bisher nur in einigen Spezialanwendungen erfolgreich eingesetzt. Hierbei werden Einzelspitzen mit Spannungen im kV-Bereich und Str{\"o}men im nA-Bereich betrieben. Dagegen werden f{\"u}r miniaturisierte Sensorsysteme eher Spannungen von ca. 100 V und Str{\"o}me von ca. 1 mA ben{\"o}tigt. Dazu wurden bisher meist Feldemissionskathoden mit CNTs vorgeschlagen, welche f{\"u}r Anwendungen in der Halbleiterindustrie aufgrund des Kohlenstoffanteils nicht erw{\"u}nscht sind. Ziel unserer Arbeit ist es, Si-basierte Elektronenquellen zu realisieren, die mit anderen miniaturisierten Vakuumsensoren auf einem Chip integrierbar sind. Mithilfe eines optimierten Herstellungsprozesses konnten wir p-Si-Spitzenarrays mit Spitzenradien von wenigen nm realisieren [1]. Messungen an diesen Strukturen zeigen ein sehr homogenes Emissionsverhalten, das vor allem im S{\"a}ttigungsbereich bei Emissionsstr{\"o}men von ca. 10 nA pro Spitze zeitlich stabil (Schwankungen < 5 \%) und optisch schaltbar (Faktor > 2.5) ist [2].}, language = {de} } @article{BornmannMingelsDamsetal., author = {Bornmann, Benjamin and Mingels, Stephan and Dams, Florian and Prommesberger, Christian and Schreiner, Rupert and L{\"u}tzenkirchen-Hecht, Dirk and M{\"u}ller, G{\"u}nter}, title = {Electron spectrometer in adjustable triode configuration for photo-induced field emission measurements}, series = {The Review of scientific instruments}, volume = {83}, journal = {The Review of scientific instruments}, number = {1}, publisher = {American Institute of Physics}, address = {Melville, NY}, doi = {10.1063/1.3673475}, abstract = {We have constructed a new ultrahigh vacuum apparatus with a triode configuration for the systematic investigation of photo-induced field emission (PFE) from metallic or semiconducting cathodes. These are exposed to electric fields up to 400 MV∕m and laser irradiation by means of hole or mesh gates. Cathodes and gates are in situ exchangeable and adjustable with high precision to ensure a homogeneous extraction of electrons which are partially transmitted to the fixed electron spectrometer. Its hemispherical sector analyzer provides an energy resolution limit of 8 meV. The commissioning of the measurement system has been performed with a tungsten needle. Its temperature showed up in the high-energy tail of the electron spectrum, while its work function was derived from the spectral low-energy part combined with the integral current-voltage curve. First PFE measurements on B-doped Si-tip arrays yielded a small field emission current increase under green laser illumination. A shift and splitting of the energy spectra was observed which revealed different emission regimes as well as the photosensitivity of the cathode due to carrier excitation into the conduction band. For the full exploitation of the PFE system, a tunable laser over a wide eV-range is required.}, language = {en} } @inproceedings{BornmannMingelsLuetzenkirchenHechtetal., author = {Bornmann, Benjamin and Mingels, Stephan and L{\"u}tzenkirchen-Hecht, Dirk and M{\"u}ller, G{\"u}nter and Dams, Florian and Schreiner, Rupert}, title = {Field emission spectroscopy studies on photo-sensitive p-doped Si-tip arrays}, series = {24th International Vacuum Nanoelectronics Conference (IVNC), 2011 : 18 - 22 July 2011, Historische Stadthalle Wuppertal, Germany}, booktitle = {24th International Vacuum Nanoelectronics Conference (IVNC), 2011 : 18 - 22 July 2011, Historische Stadthalle Wuppertal, Germany}, publisher = {IEEE}, isbn = {978-3-00-035081-8}, issn = {2380-6311}, pages = {101 -- 102}, abstract = {The influence of laser illumination on the integral as well as on the energy-resolved electron currents from well-defined p-doped Si-tip arrays was investigated. First results have provided stable cathode currents between 100 nA and 500 μA in a field range of 2-20 V/μm. Green laser illumination resulted in an enhanced cathode current and an increased population of the conduction band which can be seen in the spectra. Charging of the cathode surface, however, leads to a shift and broadening of the spectra which complicate their analysis. Therefore, further experiments with a rotatable cathode and a varying number of tips as well as with a tunable laser are planned.}, language = {en} } @inproceedings{PrommesbergerDamsLangeretal., author = {Prommesberger, Christian and Dams, Florian and Langer, Christoph and Schreiner, Rupert and Rutkowski, S. and Bornmann, Benjamin and M{\"u}ller, G{\"u}nter}, title = {Simulation of electron trajectories of a field emission electron source in triode configuration by using finite element methods}, series = {24th International Vacuum Nanoelectronics Conference (IVNC), 2011 : 18 - 22 July 2011, Historische Stadthalle Wuppertal, Germany}, booktitle = {24th International Vacuum Nanoelectronics Conference (IVNC), 2011 : 18 - 22 July 2011, Historische Stadthalle Wuppertal, Germany}, publisher = {IEEE}, address = {Piscataway, NJ}, isbn = {978-3-00-035081-8}, issn = {2380-6311}, pages = {144 -- 145}, abstract = {The finite element simulation program COMSOL Multiphysics® was used to simulate the emission efficiency of a silicon tip electron source in triode configuration for different geometries and electrode potentials. The simulation predicts a maximum emission efficiency of 84\% for an optimized structure. In a second simulation a gate electrode was concentrically arranged above a single CNT column. Here, the efficiency was simulated as a function of gate hole geometry, electrode potentials and distances between the electrodes. The simulation shows that a conical shape of the gate hole results in an efficiency up to nearly 100\%.}, language = {en} } @inproceedings{BachmannDamsDuesbergetal., author = {Bachmann, Michael and Dams, Florian and D{\"u}sberg, F. and Hofmann, Martin and Pahlke, Andreas and Langer, Christoph and Ławrowski, Robert Damian and Prommesberger, Christian and Schreiner, Rupert}, title = {Stability investigation of high aspect ratio n-type silicon field emitter arrays}, series = {2015 28th International Vacuum Nanoelectronics Conference (IVNC), 13-17 July 2015, Guangzhou, China}, booktitle = {2015 28th International Vacuum Nanoelectronics Conference (IVNC), 13-17 July 2015, Guangzhou, China}, publisher = {IEEE}, doi = {10.1109/IVNC.2015.7225584}, pages = {204 -- 205}, abstract = {Electron sources based on silicon field emitter arrays, produced in processes based on semiconductor technology, are good candidates for a miniaturized X-ray source. A key parameter for this application is the stability of the X-ray photon flux and, thus, the emission current. In the present work we have investigated the influence of the residual gas pressure and a resistor in series on the emission stability of a high aspect ratio n-type silicon emitter array with hybrid extraction electrode. An increase of current fluctuations was found for pressures above 10-6 mbar. High resistances in series to the emitter array alter the emission characteristics, but greatly suppress spikes in the emission current and improve its stability. This, however, strongly depends on the bias point. The field enhancement factor is not affected by the resistance. In a long term measurement the emission current was found to be constant after an initial phase of degradation.}, language = {en} } @article{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 sub-ppbv-level Acetone and Ethanol Quantum Cascade Laser Based Photoacoustic Sensor- Characterization and Multi-Component Spectra Recording in Synthetic Breath}, series = {Photoacoustics}, volume = {30}, journal = {Photoacoustics}, publisher = {Elsevier}, issn = {2213-5979}, doi = {10.1016/j.pacs.2023.100473}, pages = {1 -- 12}, 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 8263 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} } @article{MenzelKammlerConradetal., author = {Menzel, Andreas and Kammler, Martin and Conrad, E. H. and Yeh, V. and Hupalo, Myron and Tringides, Michael C.}, title = {Kinetics measurements of Pb island growth on Si(111)}, series = {Physical Review B}, volume = {67}, journal = {Physical Review B}, number = {16}, publisher = {American Physical Society}, doi = {10.1103/PhysRevB.67.165314}, abstract = {We present the results of kinetics experiments on quantum-size-effects (QSE) Pb islands formed on Si(111). We have looked at the evolution of seven-layer Pb islands from five-layer Pb islands due to the transport of Pb atoms from the interisland region, overcoming a barrier at the island edges, and moving to the island tops. By analyzing low-energy electron-diffraction and scanning-tunneling microscopy data, we have estimated the barrier for layer formation in this system to be ∼0.32eV. This energy is much larger than that expected from QSE electronic contributions alone.}, language = {en} } @inproceedings{SerbunNavitskiMuelleretal., author = {Serbun, Pavel and Navitski, Aliaksandr and M{\"u}ller, G{\"u}nter and Schreiner, Rupert and Prommesberger, Christian and Langer, Christoph and Dams, Florian}, title = {Scaling of the field emission current from B-doped Si-tip arrays}, series = {25th International Vacuum Nanoelectronics Conference (IVNC) ; Jeju, Korea (South), 09.07.2012 - 13.07.2012}, booktitle = {25th International Vacuum Nanoelectronics Conference (IVNC) ; Jeju, Korea (South), 09.07.2012 - 13.07.2012}, publisher = {IEEE}, address = {Piscataway, N.J.}, isbn = {978-1-4673-1984-3}, issn = {2380-6311}, doi = {10.1109/IVNC.2012.6316965}, pages = {1 -- 2}, abstract = {We have fabricated a test chip with various hexagonal arrays of B-doped Si tips (height ~ 3 μm, apex radius <; 30 nm, number 1-4447, resistivity 4 Ωcm, 100 orientation) in triangular arrangement (pitch 10 μm, density 1.16×10 6 cm -2 ) in order to systematically investigate the field emission current scaling with the number N of tips. Regulated voltage scans for 1 nA revealed rather efficient emission from nearly all tips of the arrays at an average field of 15 V/μm. The expected current plateau was always obtained at fields around 20 V/μm, but its width strongly increased with N. In this carrier depletion range, the single tip provided a much higher stability (<; 5\%) of the current (2-3 nA) than at lower (>; 50 \%) and higher currents (>; 30\%). Integral current measurements of the hexagonal arrays resulted in a statistically improved current stability (<; 1\%) but only a weak increase of the total current with N 0.28 yet. These results will be discussed with respect to the remaining inhomogeneity of the tips.}, language = {en} } @masterthesis{Zhang, type = {Bachelor Thesis}, author = {Zhang, Yunjia}, title = {Microcontroller Programming of a Contactless Optical Position Measurement Device}, address = {Regensburg}, doi = {10.35096/othr/pub-8464}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-84647}, school = {Ostbayerische Technische Hochschule Regensburg}, pages = {37}, abstract = {This thesis focuses on programming a microcontroller to receive and process data from a waveguide optic distance sensor, and to visualize the measured distance on a display screen. During the measurement process, LED moves above the 3D-printed D-shaped waveguide. The light transmitted through the waveguide is converted into photocurrents by photodiodes located at both ends of the optical waveguide, which are then converted into voltage signals through specific electronic components. By computing the ratio of the optical power detected at each end, the relative position of the LED along the waveguide can be determined. In this project, a microcontroller is used to acquire the voltage data, correct measurement errors, calculate the LED position, and display the result on screen in real time. Compared to manual calculation of photocurrent values, using a microcontroller for automated data processing greatly improves speed and efficiency. At the same time, real-time visualization enhances the system's practicality and usability, making it more suitable for future applications.}, language = {en} } @inproceedings{KammlerHornvonHoegenVossetal., author = {Kammler, Martin and Horn- von Hoegen, Michael and Voss, N. and Tringides, Michael C. and Menzel, Andreas and Conrad, E. H.}, title = {Surface Dynamics of Stepped Si(001) Studied by Temporal Leed Spectroscopy}, series = {Collective Diffusion on Surfaces: Correlation Effects and Adatom Interactions (NATO Science Series II: Mathematics, Physics and Chemistry}, volume = {29}, booktitle = {Collective Diffusion on Surfaces: Correlation Effects and Adatom Interactions (NATO Science Series II: Mathematics, Physics and Chemistry}, publisher = {Springer}, doi = {10.1007/978-94-010-0816-7_3}, pages = {23 -- 32}, abstract = {We present the first demonstration of Temporal LEED Spectroscopy's ability to measure surface dynamics as shown by a study of step dynamics on vicinal Si(001). While we measure activation energies consistent with other work, the observed microscopic mechanism driving the fluctuations is inconsistent with previous claims. We exclude evaporation/condensation of atoms from the steps as the rate limiting kinetics in the temperature range of this experiment. Possible reasons for these differences are discussed.}, language = {en} } @article{StreubuehrKalusZhouetal., author = {Streub{\"u}hr, C. and Kalus, Annika and Zhou, Ping and Ligges, Manuel and Hanisch-Blicharski, Anja and Kammler, Martin and Bovensiepen, U. and Horn-von Hoegen, Michael and von der Linde, D.}, title = {Comparing ultrafast surface and bulk heating using time-resolved electron diffraction}, series = {Applied Physics Letters}, volume = {104}, journal = {Applied Physics Letters}, publisher = {American Institute of Physics}, doi = {10.1063/1.4872055}, pages = {1 -- 3}, abstract = {From measurements of the transient Debye-Waller effect in Bismuth, we determine the buildup time of the random atomic motion resulting from the electronic relaxation after short pulse laser excitation. The surface sensitive reflection high energy electron diffraction and transmission electron diffraction yield a time constant of about 12 ps and 3 ps, respectively. The different energy transfer rates indicate relatively weak coupling between bulk and surface vibrational modes. (C) 2014 AIP Publishing LLC.}, language = {en} } @incollection{WeiglMuellerPangerletal., author = {Weigl, Stefan and M{\"u}ller, Max and Pangerl, Jonas and R{\"u}ck, Thomas}, title = {Scopes and Limits of Photoacoustic Spectroscopy in Modern Breath Analysis}, series = {Breath Analysis}, booktitle = {Breath Analysis}, publisher = {Springer nature}, isbn = {978-3-031-18526-7}, doi = {10.1007/11663_2022_22}, pages = {101 -- 159}, abstract = {Photoacoustic spectroscopy is a viable tool for trace gas detection in various application fields. In recent years, this technique has been exploited more and more for modern breath analysis as well. Within this chapter, a holistic overview of photoacoustic spectroscopy is presented, while maintaining the relationship to breath analysis. Therefore, a concise description of the fundamentals of photoacoustic spectroscopy is provided. This is essential for understanding the scopes and limits of this outstanding measurement technique being described within this chapter. In the past several different types of photoacoustic measurement setups for trace gas detection have emerged, including different light sources, modulation techniques, and detection schemes. These are described shortly and advantages as well as disadvantages, especially in relation to breath analysis, are highlighted. Though being a promising sensor principle, measurement devices based on photoacoustic spectroscopy are still rare on the sensor market, especially when it comes to trace gas detection in complex gas matrices, e.g., human breath exhale. One main reason is due to possible molecular interactions influencing the relaxational behavior of the analyte altering the sensor signal. Recent results shedding light on the intricate relaxational processes within complex gas matrices are discussed in detail, providing approaches to overcome this issue. Finally, various applications of photoacoustic spectroscopy in breath analysis are described demonstrating the great potential of this technology.}, 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}, series = {Europ{\"a}isches Patentblatt (09.12.2020) zur Anmeldung: OTH Regensburg, Anmeldenummer: 19179054.2, Patentnummer 1001/3748327, Ver{\"o}ffentlichungsnummer: 3 748 327}, journal = {Europ{\"a}isches Patentblatt (09.12.2020) zur Anmeldung: OTH Regensburg, Anmeldenummer: 19179054.2, Patentnummer 1001/3748327, Ver{\"o}ffentlichungsnummer: 3 748 327}, pages = {395 -- 396}, language = {en} } @article{ŁawrowskiPirkerKanekoetal., author = {Ławrowski, Robert Damian and Pirker, Luka and Kaneko, Keita and Kokubo, Hiroki and Bachmann, Michael and Ikuno, Takashi and Remskar, Maja and Schreiner, Rupert}, title = {Field emission from nanotubes and flakes of transition metal dichalcogenides}, series = {Journal of Vacuum Science and Technology B}, volume = {38}, journal = {Journal of Vacuum Science and Technology B}, number = {3}, publisher = {AIP Publishing}, doi = {10.1116/1.5140474}, pages = {032801}, abstract = {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.}, language = {en} } @article{KleshchSerbunLuetzenkirchenHechtetal., author = {Kleshch, Victor I. and Serbun, Pavel and L{\"u}tzenkirchen-Hecht, Dirk and Orekhov, Anton and Ivanov, Victor E. and Prommesberger, Christian and Langer, Christoph and Schreiner, Rupert and Obraztsov, Alexander N.}, title = {A Comparative Study of Field Emission from Pristine, Ion-treated and Tungsten Nanoparticle-decorated p-type Silicon Tips}, series = {Physica Status Solidi B}, volume = {256}, journal = {Physica Status Solidi B}, number = {9}, publisher = {Wiley}, doi = {10.1002/pssb.201800646}, abstract = {The field electron emission characteristics of individual tips of a silicon field emitter array are analyzed. The array of conical-shaped tips is fabricated on a p-type silicon wafer by using reactive ion etching and sharpening oxidation. The tips are decorated with single tungsten nanoparticles at their apexes. Furthermore, the focused ion beam is also used to increase surface conductivity of some of the tips. Comparative measurements of field emission are performed by using the scanning anode probe field emission microscopy technique. All types of tips demonstrated emission activation consisting of a sudden current increase at a certain value of the applied voltage. Compared to the pristine tips, a noticeable reduction of the saturation effect in the current-voltage characteristics and a smaller light sensitivity for the decorated tips is found. For ion-treated tips, saturation effects and light sensitivity are completely suppressed. Scanning electron microscopy observations reveal the formation of single nanoscale protrusions extending from the metal particles and from the apexes of bare ion-treated tips after exposure under strong electric fields during the field emission measurements. The influence of protrusions growth on characteristics of silicon field emitter arrays is discussed.}, language = {en} } @inproceedings{SerbunPorshynMuelleretal., author = {Serbun, Pavel and Porshyn, Vitali and M{\"u}ller, G{\"u}nter and L{\"u}tzenkirchen-Hecht, Dirk and Prommesberger, Christian and Langer, Christoph and Ławrowski, Robert Damian and Schreiner, Rupert}, title = {Field emission behavior of single n- and p-type black Si pillar structures}, series = {International Vacuum Nanoelectronics Conference (IVNC), 31st, 2018, Kyoto, Japan}, booktitle = {International Vacuum Nanoelectronics Conference (IVNC), 31st, 2018, Kyoto, Japan}, publisher = {IEEE}, doi = {10.1109/IVNC.2018.8520292}, pages = {1-2}, abstract = {We have investigated the properties of single n- and p-type black silicon (b-Si) pillars with a height of 20 μ m under strong electric field and halogen lamp or laser illumination. For both type of b-Si pillar structures, I-V measurements revealed strong activation effects, which consisted in sudden current increases during the first up/down voltage sweeps. The maximum reproducible emission current from a single n-type b-Si pillar structure was about 15 μ A. A pronounced saturation region at 240 nA was observed for a single p-type b-Si pillar. The current fluctuation over time showed a standard deviation of 28\% and 2.5\% for n- and p-type single b-Si pillar structures, respectively. Optical switching under halogen lamp illumination resulted in at least 3 times higher saturation currents and showed a linear dependence of the FE current on the laser power.}, language = {en} } @article{MingelsPorshynPrommesbergeretal., author = {Mingels, Stephan and Porshyn, Vitali and Prommesberger, Christian and Langer, Christoph and Schreiner, Rupert and L{\"u}tzenkirchen-Hecht, Dirk and M{\"u}ller, G{\"u}nter}, title = {Photosensitivity of p-type black Si field emitter arrays}, series = {Journal of Applied Physics}, volume = {119}, journal = {Journal of Applied Physics}, number = {16}, doi = {10.1063/1.4948328}, abstract = {We have investigated the properties of black Si field emitter arrays under strong electric fields and laser illumination. A low onset field of 1.8 MV/m for an emission current of 1 nA was obtained. A pronounced saturation region of the dark and photo-enhanced current was observed, which provided a short-term stability of 0.1\% at 0.4 μA and 0.7\% at 1.0 μA, respectively. As maximum value for the photosensitivity, an on-off current switching ratio of 43 reaching about 13 μA was achieved at a laser power of 15 mW. Electron spectra in the dark and under laser illumination are presented, showing a current and light-sensitive voltage drop across the emitters as well as hints for hot electron emission.}, language = {en} } @inproceedings{SerbunPorshynMuelleretal., author = {Serbun, Pavel and Porshyn, Vitali and M{\"u}ller, G{\"u}nter and Mingels, Stephan and L{\"u}tzenkirchen-Hecht, Dirk and Bachmann, Michael and D{\"u}sberg, Felix and Dams, Florian and Hofmann, Martin and Pahlke, Andreas and Prommesberger, Christian and Langer, Christoph and Ławrowski, Robert Damian and Schreiner, Rupert}, title = {Field emission behavior of Au-tip-coated p-type Si pillar structures}, series = {29th International Vacuum Nanoelectronics Conference (IVNC), 2016, 11-15 July, Vancouver, BC, Canada}, booktitle = {29th International Vacuum Nanoelectronics Conference (IVNC), 2016, 11-15 July, Vancouver, BC, Canada}, publisher = {IEEE}, issn = {2380-6311}, doi = {10.1109/IVNC.2016.7551516}, pages = {181 -- 182}, abstract = {Precisely aligned high-aspect-ratio (HAR) silicon tip arrays were fabricated using enhanced reactive ion etching with an inductively-coupled-plasma followed by a sharpening oxidation. A gold thin film was then sputtered only on the tips of the HAR structures. Field-emission (FE) properties from Au-coated HAR p-Si tip array cathodes have been systematically investigated by means of field emission scanning microscopy (FESM). A rather high efficiency of the HAR Si structures (71\% at 550 V), but limited homogeneous FE with currents of 1-600 nA might be correlated with the varying geometry of the tips and the presence of oxides. I-V measurements of single Au-coated HAR emitters revealed activation effects and the saturation current region at 3 nA. An increase of the saturation current by 4 orders of magnitude was observed during 20 hours of conditioning at constant voltage, which finally resulted in nearly reproducible FN curves with a ß-factor of 473. An excellent stability of the emission current of less than 1 \% was obtained during the additional long-time conditioning at constant voltage. Optical switching under halogen lamp illumination resulted in at least 2 times higher saturation currents and showed a linear dependence of the FE current on the light color temperature.}, language = {en} } @inproceedings{SerbunPorshynLuetzenkirchenHechtetal., author = {Serbun, Pavel and Porshyn, Vitali and L{\"u}tzenkirchen-Hecht, Dirk and Prommesberger, Christian and Langer, Christoph and Ławrowski, Robert Damian and Schreiner, Rupert}, title = {Photosensitivity of single silicon high-aspect-ratio tips with different doping levels}, series = {International Vacuum Nanoelectronics Conference (IVNC), 31st, 2018, Kyoto, Japan}, booktitle = {International Vacuum Nanoelectronics Conference (IVNC), 31st, 2018, Kyoto, Japan}, publisher = {IEEE}, doi = {10.1109/IVNC.2018.8520288}, pages = {1-2}, abstract = {Photosensitivity of single lightly p-doped, highly p-doped, with an integrated p/n junction and intrinsic high-aspect-ratio (HAR) silicon tips was investigated in an ultra-high vacuum environment. The current-voltage characteristics (I-V) of the lightly doped p-type HAR tips showed a characteristic current saturation at around 10-12 nA, whereas the HAR Si tips with p/n junction showed similar saturation phenomena, however, at much smaller current values starting at ~20-30 pA. Optical switching under a halogen lamp illumination resulted in at least 2-4 times higher saturation currents and showed a linear dependence between the illumination power and the FE current, for both types of structures. In case of the highly p-doped HAR tips optical current switching effects, i. e. current saturation, were observed at rather low current levels 1-2 pA. Intrinsic HAR Si-tips showed relative unstable field emission behavior without a clear evidence of the photosensitivity.}, language = {en} } @inproceedings{SchreinerLangerPrommesbergeretal., author = {Schreiner, Rupert and Langer, Christoph and Prommesberger, Christian and Ławrowski, Robert Damian and Dams, Florian and Bachmann, Michael and D{\"u}sberg, F. and Hofmann, Martin and Pahlke, Andreas and Serbun, Pavel and Mingels, Stephan and M{\"u}ller, G{\"u}nter}, title = {Semiconductor field emission electron sources using a modular system concept for application in sensors and x-ray-sources}, series = {2015 28th International Vacuum Nanoelectronics Conference (IVNC), 13-17 July 2015, Guangzhou, China}, booktitle = {2015 28th International Vacuum Nanoelectronics Conference (IVNC), 13-17 July 2015, Guangzhou, China}, publisher = {IEEE}, doi = {10.1109/IVNC.2015.7225572}, pages = {178 -- 179}, abstract = {Semiconductor field emitters are suitable candidates for applications, which require a very stable field emission (FE) current and a high emission uniformity over the entire emission area. By using different materials and geometries, we are able to vary the FE characteristics within a wide range. Each specific application requires its own optimized design for the cathode as well as for the other parts of the FE electron source. To meet as many of these requirements as possible while using only a limited number of different prefabricated components, we established a modular system concept for our FE electron source. This allows the implementation of almost every cathode material. For first characterizations, we used gated p-type Si cathodes with 16 tips. We obtained stable FE currents of 0.4 μA for a grid-potential of 400 V and a gate potential of 100 V. Almost 100\% of the electrons are emitted towards the grid-electrode. Parasitic leakage paths, as well as the electron emission towards the gate-electrode can be neglected. Approximately 10\% of the electrons are transmitted through the grid and reach the external anode. This is in good agreement with the optical transmission through the grid-mesh.}, language = {en} } @inproceedings{ŁawrowskiLangerPrommesbergeretal., author = {Ławrowski, Robert Damian and Langer, Christoph and Prommesberger, Christian and Schreiner, Rupert and Mingels, Stephan and Porshyn, Vitali and Serbun, Pavel and M{\"u}ller, G{\"u}nter}, title = {Field emission from surface textured GaN with buried double-heterostructures}, series = {2015 28th International Vacuum Nanoelectronics Conference (IVNC), 13-17 July 2015, Guangzhou, China}, booktitle = {2015 28th International Vacuum Nanoelectronics Conference (IVNC), 13-17 July 2015, Guangzhou, China}, publisher = {IEEE}, doi = {10.1109/IVNC.2015.7225548}, pages = {106 -- 107}, abstract = {In this contribution we report on field emission (FE) cathodes based on thin-film LED-technology and surface texturing. The FE cathode can be used both as an n-GaN cathode with an electrical contact at the top side metallization as well as a pn-GaN diode contacting only the p-GaN layer at the bottom side of the structure. The local and integral FE properties of the textured surface of the LED structure were investigated. For n-GaN an integral emission current up to 1.0 μA at an electric field of 19 V/μm was achieved. The pn-GaN diode measurements showed an integral current saturation behavior with two orders of magnitude lower FE currents. Regulated voltage scans obtained by FE scanning microscopy revealed a well-distributed emission over the whole cathode area. Measurements under pulsed tunable laser illumination and moderate electric fields indicated charge carrier generation in the buried double-heterostructures at photon energies below 3.5 eV besides normal photoemission above 4.1 eV.}, language = {en} } @inproceedings{BresinskyReusner, author = {Bresinsky, Markus and Reusner, Florian}, title = {GLOBE - Learn and Innovate Digitization by a Virtual Collaboration Exercise and Living Lab}, series = {Interactivity, Game Creation, Design, Learning, and Innovation. 6th International Conference, ArtsIT 2017, and Second International Conference, DLI 2017, Heraklion, Crete, Greece, October 30-31, 2017, Proceedings}, booktitle = {Interactivity, Game Creation, Design, Learning, and Innovation. 6th International Conference, ArtsIT 2017, and Second International Conference, DLI 2017, Heraklion, Crete, Greece, October 30-31, 2017, Proceedings}, publisher = {Springer Nature}, doi = {10.1007/978-3-319-76908-0_26}, pages = {273 -- 281}, abstract = {This paper presents an advanced interactive learning platform .dot that implements the GLOBE exercise, using innovative information and communication technologies to enhance learning and development of management and leadership skills in a complex organizational setting. GLOBE on the one hand focuses on competences around ICT and virtual collaboration, and on the other hand on digital transformation, technologies and tools at higher education institutions. By this applied science, learning and developing on the real-world platform, analysis and drive of digital innovation and transformation can be fostered. The main goal is to co-create knowledge and solutions in the following focused subjects: Management and leadership of multidisciplinary, multinational and multicultural virtual and real collaboration in a complex organizational environment. GLOBE uses real world scenarios (e.g. United Nations mission) and involves real world actors. This comprehensive educational approach should enhance learning techniques and leverage learning progress with hands-on experiences and applied science in the context of ICT and virtual collaboration, and the embodied dynamics of behavior to support innovation and development.}, language = {en} } @inproceedings{MingelsPorshynSerbunetal., author = {Mingels, Stephan and Porshyn, Vitali and Serbun, Pavel and L{\"u}tzenkirchen-Hecht, Dirk and M{\"u}ller, G{\"u}nter and Prommesberger, Christian and Langer, Christoph and Schreiner, Rupert and Lutzenkirchen-Hecht, Dirk}, title = {Photo-enhanced field emission properties of p-doped black Si arrays}, series = {2016 29th International Vacuum Nanoelectronics Conference (IVNC), 11-15 July 2016, Vancouver, BC, Canada}, booktitle = {2016 29th International Vacuum Nanoelectronics Conference (IVNC), 11-15 July 2016, Vancouver, BC, Canada}, publisher = {IEEE}, doi = {10.1109/IVNC.2016.7551447}, pages = {1 -- 2}, abstract = {We have carried out systematic investigations of p-type black Si field emitter arrays under laser illumination. As expected the current-voltage characteristic revealed a strong saturation providing a high photosensitivity, which had a maximum on-off ratio of 43 at a maximum current of 13 μA. The saturation current was stable in the dark as well as under illumination with fluctuations <;0.7\%. Results from time-resolved measurements of the photo-sensitivity showed a rather fast response but a long decay time. Electron spectra in the dark and under laser illumination revealed the origin of the emission.}, language = {en} } @inproceedings{HauslerFischerWunderlichetal., author = {Hausler, Peter and Fischer, Johannes and Wunderlich, Lukas and Recum, Patrick and Peller, Sebastian and Hirsch, Thomas and Bierl, Rudolf}, title = {Miniaturisierte Sensoren basierend auf Oberfl{\"a}chenplasmonenresonanz, Chancen und Herausforderungen}, series = {DGaO-Proceedings 2021}, booktitle = {DGaO-Proceedings 2021}, publisher = {Dt. Gesellschaft f{\"u}r angewandte Optik}, address = {Erlangen-N{\"u}rnberg}, abstract = {Derzeit gibt es zahlreiche Bereiche, wie Umwelt Monitoring und zivile Infrastruktur in denen geeignete Sensoren f{\"u}r die {\"U}berwachung der Systeme fehlen. SPR-basierte Sensoren haben das Potential diese L{\"u}cke zu schließen. Um f{\"u}r den Einsatz in der Umwelt tauglich zu werden, m{\"u}ssen die Sensoren noch robuster werden. Hier wird eine m{\"o}gliche L{\"o}sung gezeigt.}, language = {de} } @techreport{HoellerQuirtMahnetal., author = {H{\"o}ller, Christoph and Quirt, David and Mahn, Jeffrey and M{\"u}ller-Trapet, Markus}, title = {Guide to calculating airborne sound transmission in buildings}, edition = {5th edition}, publisher = {National Research Council of Canada. Construction}, doi = {10.4224/40001814}, abstract = {In recent years, the science and engineering for controlling sound transmission in buildings have shifted from a focus on individual assemblies such as walls or floors, to a focus on performance of the complete system. Standardized procedures for calculating the overall transmission, combined with standardized measurements to characterize sub-assemblies, provide much better prediction of sound transmission between adjacent indoor spaces. The International Standards Organization (ISO) has published a calculation method, ISO 15712-1 that uses laboratory test data for sub-assemblies such as walls and floors as inputs for a detailed procedure to calculate the expected sound transmission between adjacent rooms in a building. This standard works very well for some types of construction, but to use it in a North American context one must overcome two obstacles - incompatibility with the ASTM standards used by our construction industry, and low accuracy of its predictions for lightweight wood or steel frame construction. To bypass limitations of ISO 15712-1, this Guide explains how to merge ASTM and ISO test data in the ISO calculation procedure, and provides recommendations for applying extended measurement and calculation procedures for specific common types of construction. This Guide was developed in a project established by the National Research Council of Canada to support the transition of construction industry practice to using apparent sound transmission class (ASTC) for sound control objectives in the National Building Code of Canada (NBCC). However, the potential range of application goes beyond the minimum requirements of the NBCC - the Guide also facilitates design to provide enhanced sound insulation, and should be generally applicable to construction in both Canada and the USA. This publication contains a limited set of examples for several types of construction, to provide an introduction and overview of the ASTC calculation procedure. Additional examples and measurement data can be found in the companion documents to this Guide, namely NRC Research Reports RR-333 to RR-337. Furthermore, the calculation procedure outlined and illustrated in this Guide is also used by the software web application soundPATHS, which is available for free on the website of the National Research Council of Canada (see the references in Section 7 of this Guide for access details). Au cours des derni{\`e}res ann{\´e}es, les scientifiques et les ing{\´e}nieurs ont fait porter leurs efforts en mati{\`e}re d'att{\´e}nuation de la transmission du son dans les b{\^a}timents davantage sur le rendement du syst{\`e}me dans sa totalit{\´e} que sur les ensembles de construction individuels. Les m{\´e}thodes normalis{\´e}es de calcul de la transmission globale, combin{\´e}es {\`a} des mesures normalis{\´e}es de caract{\´e}risation des sous-ensembles, permettent de mieux pr{\´e}dire la transmission du son entre des espaces int{\´e}rieurs adjacents. L'Organisation internationale de normalisation (ISO) a publi{\´e} une m{\´e}thode de calcul, la norme ISO 15712-1, qui utilise des donn{\´e}es d'essai en laboratoire pour les sous-ensembles, comme les murs et les planchers, comme donn{\´e}es d'entr{\´e}e en vue d'une m{\´e}thode d{\´e}taill{\´e}e de calcul de la transmission du son pr{\´e}vue entre des pi{\`e}ces adjacentes dans un b{\^a}timent. Cette norme fonctionne tr{\`e}s bien pour certains types de construction, mais pour l'utiliser dans un contexte nord-am{\´e}ricain, il faut surmonter deux obstacles - l'incompatibilit{\´e} avec les normes ASTM utilis{\´e}es par notre industrie de la construction et la faible exactitude de ses pr{\´e}visions pour la construction {\`a} ossature de bois ou d'acier l{\´e}g{\`e}re. Pour contourner les limites de la norme ISO 15712-1, le pr{\´e}sent guide explique comment fusionner les donn{\´e}es d'essai de l'ISO et de l'ASTM dans la m{\´e}thode de calcul de l'ISO, et formule des recommandations relativement {\`a} l'application de m{\´e}thodes {\´e}largies de mesure et de calcul pour des types de construction courants. Le pr{\´e}sent guide a {\´e}t{\´e} {\´e}labor{\´e} dans le cadre d'un projet mis sur pied par le Conseil national de recherches du Canada afin d'appuyer la transition de la pratique de l'industrie de la construction vers l'utilisation d'un indice de transmission du son apparent (ITSA) satisfaisant aux objectifs de r{\´e}duction rigoureux du Code national du b{\^a}timent du Canada (CNBC). Toutefois, l'{\´e}ventail potentiel d'applications va au-del{\`a} des exigences minimales du CNBC - le Guide facilite aussi une conception visant {\`a} am{\´e}liorer l'insonorisation et devrait s'appliquer de fa{\c{c}}on g{\´e}n{\´e}rale {\`a} la construction tant au Canada qu'aux {\´E}tats-Unis. La pr{\´e}sente publication contient un ensemble limit{\´e} d'exemples pour plusieurs types de construction, afin de fournir une introduction et un aper{\c{c}}u de la m{\´e}thode de calcul de l'ITSA. On trouvera d'autres exemples et donn{\´e}es de mesure dans les documents d'accompagnement du pr{\´e}sent guide, {\`a} savoir, les rapports de recherche RR-333 {\`a} RR-337 du CNRC. De plus, la m{\´e}thode de calcul d{\´e}crite et illustr{\´e}e dans le pr{\´e}sent guide est {\´e}galement utilis{\´e}e par l'application Web soundPATHS, disponible gratuitement sur le site Web du Conseil national de recherches du Canada (voir les r{\´e}f{\´e}rences {\`a} la section 7 du pr{\´e}sent guide pour les d{\´e}tails d'acc{\`e}s).}, language = {en} } @inproceedings{ShymanovichNicoulLuetal., author = {Shymanovich, Uladzimir and Nicoul, Matthieu and Lu, Wei and Tarasevitch, A. and Kammler, Martin and Horn-von Hoegen, Michael and von der Linde, D. and Sokolowski-Tinten, Klaus and Phipps, Claude}, title = {Coherent acoustic and optical phonons in laser-excited solids studied by ultrafast time-resolved X-ray diffraction}, series = {AIP Conference Proceedings}, booktitle = {AIP Conference Proceedings}, number = {1}, publisher = {AIP}, doi = {10.1063/1.3507146}, pages = {558 -- 566}, abstract = {We apply ultrafast time-resolved X-ray diffraction to directly study coherent acoustic and optical phonons in laser-excited materials. In Au the ps acoustic response has been investigated with the particular goal to clarify the interplay of electronic and thermal pressure contributions. In Bi the extreme softening of the coherently excited A 1 g optical phonon presents strong indication that upon intense laser-excitation the Peierls-transition which determines the equilibrium structure of Bi can be reversed. In FeRh we studied the lattice response after a fast laser-induced anti-ferromagnetic to ferromagnetic phase transition.}, language = {en} } @article{PayerKleinAcetetal., author = {Payer, Thomas and Klein, C. and Acet, M. and Ney, V. and Kammler, Martin and Meyer zu Heringdorf, Frank-Joachim and Horn-von Hoegen, Michael}, title = {High-quality epitaxial Bi(111) films on Si(111) by isochronal annealing}, series = {Thin Solid Films}, volume = {520}, journal = {Thin Solid Films}, number = {23}, publisher = {Elsevier}, doi = {10.1016/j.tsf.2012.06.004}, pages = {6905 -- 6908}, abstract = {Bi(111) films grown on Si(111) at room temperature show a significantly higher roughness compared to Bi films grown on Si(100) utilizing a kinetic pathway based on a low-temperature process. Isochronal annealing steps of 3 min duration each with temperatures up to 200 °C cause a relaxation of the Bi films' lattice parameter toward the Bi bulk value and yield an atomically flat Bi surface. Driving force for the relaxation and surface reordering is the magic mismatch of 11 Bi atoms to 13 Si atoms that emerges at annealing temperatures above 150 °C and reduces the remaining strain to less than 0.2\%.}, language = {en} } @techreport{HoellerQuirtMuellerTrapet, author = {H{\"o}ller, Christoph and Quirt, David and Mueller-Trapet, Markus}, title = {Apparent sound insulation in wood-framed buildings}, publisher = {National Research Council of Canada. Construction}, doi = {10.4224/23002820}, abstract = {This Report presents the results from substantial experimental studies of sound transmission, together with an explanation of calculation procedures to predict the sound transmission between adjacent spaces in a building with wood-framed walls and floors. This Report presents two types of experimental data for wood-framed constructions: - Test data for direct sound transmission through typical wood-framed wall assemblies and wood-framed floor assemblies, plus a summary of trends for such constructions and references to compilations of additional data - Test data for flanking sound transmission measured following the procedures of ISO 10848 for coupled wall/floor junctions and wall/wall junctions Worked examples for calculating the apparent sound transmission class (ASTC) rating between adjacent dwelling units are presented to illustrate how the experimental data can be applied.}, language = {en} } @inproceedings{ZhouStreubuehrKalusetal., author = {Zhou, Ping and Streub{\"u}hr, C. and Kalus, Annika and Frigge, Tim and Wall, S. and Hanisch-Blicharski, Anja and Kammler, Martin and Ligges, Manuel and Bovensiepen, U. and von der Linde, D. and Horn-von Hoegen, Michael}, title = {Ultrafast time resolved reflection high energy electron diffraction with tilted pump pulse fronts}, series = {EPJ Web of Conferences - XVIIIth International Conference on Ultrafast Phenomena}, volume = {41}, booktitle = {EPJ Web of Conferences - XVIIIth International Conference on Ultrafast Phenomena}, publisher = {EPJ}, doi = {10.1051/epjconf/20134110016}, abstract = {We present time-resolved RHEED from a laser excited Pb(111) surface using a pulse front tilter for the compensation of the velocity mismatch of electrons and light. The laser pulses with tilted fronts were characterized by a spatially resolving cross correlator. The response of the surface upon excitation was observed to be less than 2 ps.}, language = {en} } @inproceedings{LuNicoulShymanovichetal., author = {Lu, Wei and Nicoul, Matthieu and Shymanovich, Uladzimir and Tarasevitch, A. and Kammler, Martin and Horn-von Hoegen, Michael and von der Linde, D. and Sokolowski-Tinten, Klaus}, title = {Transient reversal of a Peierls-transition: Extreme phonon softening in laser-excited Bismuth}, series = {International Conference on Ultrafast Phenomena, Snowmass}, booktitle = {International Conference on Ultrafast Phenomena, Snowmass}, number = {ME41}, publisher = {Optica Publishing Group}, doi = {10.1364/UP.2010.ME41}, abstract = {Laser-excited coherent optical phonons in Bismuth were investigated using time-resolved X-ray diffraction. The observed extreme softening of the excited A1g-mode presents strong indication that the Peierls-distortion defining the equilibrium structure of Bismuth is transiently reversed.}, language = {en} } @article{PortavoceKammlerHulletal., author = {Portavoce, A. and Kammler, Martin and Hull, Robert and Reuter, Mark C. and Copel, M. and Ross, Frances M.}, title = {Growth of nanostructures by locally modified surface reactivity}, series = {Materials Science in Semiconductor Processing}, volume = {12}, journal = {Materials Science in Semiconductor Processing}, number = {1-2}, publisher = {Elsevier}, doi = {10.1016/j.mssp.2009.07.001}, pages = {25 -- 30}, abstract = {The chemical vapor deposition (CVD) of Si and Ge on Si(0 0 1) substrates covered by 1 monolayer of Ga has been studied. Ga modifies surface reactivity and surface atom mobility. We show that islanding occurs during Ga-mediated CVD even in the absence of strain, allowing for the formation of islands without a wetting layer or with a thinner wetting layer. The morphology of the grown layer is highly dependent on kinetic parameters, i.e. growth temperature and growth pressure, that control Si and Ge deposition and Ga desorption. Si Ga-mediated CVD promotes the formation of self-assembled epitaxial Si islands exhibiting {1 1 3} facets. Ge islands grown by Ga-mediated CVD present reduced lateral sizes and an increased surface density compared to non Ga-mediated CVD. The growth morphology (particularly island size and density) can be understood by considering a qualitative model in which atoms are deposited only on sites whose dangling bonds are not passivated by Ga. We suggest that modification of surface reactivity during surfactant-mediated CVD can thus provide a new degree of freedom for quantum dot fabrication.}, language = {en} } @article{PortavoceKammlerHulletal., author = {Portavoce, A. and Kammler, Martin and Hull, Robert and Reuter, Mark C. and Ross, Frances M.}, title = {Mechanism of the nanoscale localization of Ge quantum dot nucleation on focused ion beam templated Si(001) surfaces}, series = {Nanotechnology}, volume = {17}, journal = {Nanotechnology}, number = {17}, publisher = {IOP}, doi = {10.1088/0957-4484/17/17/028}, pages = {4451 -- 4455}, abstract = {We investigate the fundamental mechanism by which self-assembled Ge islands can be nucleated at specific sites on Si(001) using ultra-low-dose focused ion beam (FIB) pre-patterning. Island nucleation is controlled by a nanotopography that forms after the implantation of Ga ions during subsequent thermal annealing of the substrate. This nanotopography evolves during the annealing stage, changing from a nanoscale annular depression associated with each focused ion beam spot to a nanoscale pit, and eventually disappearing (planarizing). The correspondence of Ge quantum dot nucleation sites to the focused ion beam features requires a growth surface upon which the nanotopography is preserved. A further key observation is that the Ge wetting layer thickness is reduced in patterned regions, allowing the formation of islands on the templated regions without nucleation elsewhere. These results provide routes to the greatly enhanced design and control of quantum dot distributions and dimensions.}, language = {en} } @article{RossKammlerReuteretal., author = {Ross, Frances M. and Kammler, Martin and Reuter, Mark C. and Hull, Robert}, title = {In-situ observations of self-assembled island nucleation on patterned substrates}, series = {Philosophical Magazine}, volume = {84}, journal = {Philosophical Magazine}, number = {25-26}, publisher = {Taylor \& Francis}, doi = {10.1080/14786430410001671430}, pages = {2687 -- 2702}, abstract = {We compare in-situ electron microscopy observations of Ge island growth on Si surfaces modulated by different techniques. Si(001) substrates were patterned either using a focused Ga ion beam or lithographically to produce similar feature sizes. In the case of the focused-ion-beam patterned substrates, chemical or strain effects caused by low Ga doses control the positions at which islands nucleate. Nucleation on topographically modulated substrates, with the pattern produced either by high-dose sputtering or lithographically, is controlled by the nature of the side walls of topographic features. The two patterning approaches have different benefits in creating arrays of islands for device applications.}, language = {en} } @article{MenzelConradTringidesetal., author = {Menzel, Andreas and Conrad, E. H. and Tringides, Michael C. and Kammler, Martin and Horn- von Hoegen, Michael}, title = {Finite collection time effects in autocovariance function measurements}, series = {Journal of Applied Physics}, volume = {93}, journal = {Journal of Applied Physics}, number = {4}, publisher = {AIP Publishing}, doi = {10.1063/1.1537466}, pages = {2229 -- 2235}, abstract = {In this paper we discuss how finite data sets influence experimental measurements of the autocovariance function. Autocovariance estimators are biased, meaning that the expectation value for any measured autocovariance function is not identical to the actual autocovariance function. In this work we show that the measured autocovariance function for a finite length time series must become negative for some lag times. We derive analytic corrections to these finite time errors for different types of correlated random sequences. Our results explain the apparent anticorrelated noise observed in experimental observations.}, language = {en} } @article{KammlerHullReuteretal., author = {Kammler, Martin and Hull, Robert and Reuter, Mark C. and Ross, Frances M.}, title = {Lateral control of self-assembled island nucleation by focused-ion-beam micropatterning}, series = {Applied Physics Letters}, volume = {82}, journal = {Applied Physics Letters}, number = {7}, doi = {10.1063/1.1542680}, pages = {1093 -- 1095}, abstract = {We demonstrate that the nucleation sites of nanoscale, self-assembled Ge islands on Si(001) can be controlled by patterning the Si surface in situ with a focused ion beam. At low doses of 6000 Ga+ ions per <100 nm spot, the selective growth is achieved without modifying the initial surface topography. At larger doses, topographic effects produced by sputtering and redeposition control the selective nucleation sites. Islands grown on irradiated spots are smaller with higher aspect ratio than islands grown on clean Si(001), suggesting a strong surfactant effect of Ga.}, language = {en} } @article{SokolowskiTintenBlomeBlumsetal., author = {Sokolowski-Tinten, Klaus and Blome, Christian and Blums, Juris and Shymanovich, Uladzimir and Nicoul, Matthieu and Cavalleri, Andrea and Tarasevitch, A. and Horn-von Hoegen, Michael and Kammler, Martin and von der Linde, D.}, title = {Ultrafast X-ray diffraction}, series = {Ultrafast Phenomena XIV}, volume = {79}, journal = {Ultrafast Phenomena XIV}, publisher = {Springer}, doi = {10.1007/3-540-27213-5_53}, pages = {170 -- 174}, abstract = {In the last few years the generation of femtosecond pulses in the X-ray regime has become possible. These ultrashort X-ray pulses have enabled femtosecond time- resolution to be extended to X-rays.}, language = {en} } @inproceedings{HoellerZeitlerReinholdetal., author = {H{\"o}ller, Christoph and Zeitler, Berndt and Reinhold, Steffi and Jakob, A. and Hopkins, C.}, title = {Charakterisierung von K{\"o}rperschallquellen auf der Empfangsplatte mit Hilfe von orthogonalen Funktionen}, series = {Tagungsband - DAGA 2019 : 45. Jahrestagung f{\"u}r Akustik : 18.-21. M{\"a}rz 2019, Rostock}, booktitle = {Tagungsband - DAGA 2019 : 45. Jahrestagung f{\"u}r Akustik : 18.-21. M{\"a}rz 2019, Rostock}, publisher = {Deutsche Gesellschaft f{\"u}r Akustik e.V.}, address = {Berlin}, isbn = {978-3-939296-14-0}, pages = {93 -- 96}, language = {de} } @article{KammlerHullPortavoceetal., author = {Kammler, Martin and Hull, Robert and Portavoce, A. and Reuter, Mark C. and Ross, Frances M.}, title = {In-Situ Focused Ion Beam Micropatterning of Ge Islands}, series = {Microscopy and Microanalysis}, volume = {9}, journal = {Microscopy and Microanalysis}, number = {S02}, publisher = {Microscopy Society of America}, doi = {10.1017/S1431927603441214}, pages = {132 -- 134}, language = {en} } @article{MoserJobstBierletal., author = {Moser, Elisabeth and Jobst, Simon and Bierl, Rudolf and Jenko, Frank}, title = {A Deep Learning System to Transform Cross-Section Spectra to Varying Environmental Conditions}, series = {Vibrational Spectroscopy}, volume = {122}, journal = {Vibrational Spectroscopy}, number = {September}, publisher = {Elsevier}, issn = {0924-2031}, doi = {10.1016/j.vibspec.2022.103410}, abstract = {Absorption cross-sections provide a basis for many gas sensing applications. Therefore, any error in molecular cross-sections caused by varying environmental conditions propagates to spectroscopic applications. Original molecular cross-sections in varying environmental conditions can only be simulated for some molecules, whereas for most multi-atom molecules, one must rely on high-precision measurements at certain environmental configurations. In this study, a deep learning system trained with simulated absorption cross-sections for predicting cross-sections at a different pressure configuration is presented. The system's capability to transfer to measured, multi-atom cross-sections is demonstrated. Thus, it provides an alternative to (pseudo-) line lists whenever the required information for simulation is unavailable. The predictive performance of the system was evaluated on validation data via simulation, and its transfer learning capabilities were demonstrated on actual measurement chlorine nitrate data. From the comparison between the system and line lists, the system shows slightly worse performance than pseudo-line lists but its predictive quality is still deemed acceptable with less than 5\% relative integral change with a highly localized error around the peak center. This opens a promising way for further research to use deep learning to simulate the effect of varying environmental conditions on absorption cross-sections.}, language = {en} } @inproceedings{SchreinerLangerPrommesbergeretal., author = {Schreiner, Rupert and Langer, Christoph and Prommesberger, Christian and Mingels, Stephan and Serbun, Pavel and M{\"u}ller, G{\"u}nter}, title = {Field emission from surface textured extraction facets of GaN light emitting diodes}, series = {26th International Vacuum Nanoelectronics Conference (IVNC), 8-12 July 2013, Roanoke, VA, USA}, booktitle = {26th International Vacuum Nanoelectronics Conference (IVNC), 8-12 July 2013, Roanoke, VA, USA}, publisher = {IEEE}, doi = {10.1109/ivnc.2013.6624721}, abstract = {We report on the field emission properties of GaN LED surfaces. The textured extraction facet acts both as light scattering layer in order to increase the light extraction efficiency of the LED as well as nanostructured cathode surface for the field emission (FE) of electrons. The LED emits blue light with a peak wavelength of around 450 nm. The FE properties were investigated by a scanning microscope. Integral measurements as well as regulated voltage scans for 1 nA FE current over an area of 400 * 400 µm2were used to investigate both overall and local FE properties. A high number of well-distributed emitters with an average field enhancement factor ß of 85 and stable integral emission currents up to 100 µA at an electric field of   80 V/µm ({\O}anode= 880 µm) were found. Photo-field-emission spectroscopy (PFES) using a tunable pulsed laser revealed an enhanced photo absorption of the InGaN/GaN quantum well structures near the emission wavelength of the LED (<3.5 eV), whereas at high photon energies (>4.1 eV) photoemission from the GaN surface was observed.}, language = {en} } @inproceedings{MoserPangerlJobstetal., author = {Moser, Elisabeth and Pangerl, Jonas and Jobst, Simon and Weigl, Stefan and Bierl, Rudolf}, title = {Modeling the Photoacoustic Spectrum of a Quantum Cascade Laser for Human Breath}, series = {Optical Sensors and Sensing Congress 2022 (AIS, LACSEA, Sensors, ES): July 11 - 15, 2022, Vancouver, British Columbia Canada}, booktitle = {Optical Sensors and Sensing Congress 2022 (AIS, LACSEA, Sensors, ES): July 11 - 15, 2022, Vancouver, British Columbia Canada}, publisher = {Optica Publishing Group}, isbn = {978-1-957171-10-4}, doi = {10.1364/AIS.2022.ATu3G.2}, abstract = {A modeling approach to create a photoacoustic spectrum from synthetic data is presented and evaluated. The resulting model reaches a MAPE score of 2.7\% and can be used to enable data-driven development in future work.}, subject = {Quantenkaskadenlaser}, language = {en} } @article{GoldschmidtMoserNitzscheetal., author = {Goldschmidt, Jens and Moser, Elisabeth and Nitzsche, Leonard and Bierl, Rudolf and W{\"o}llenstein, J{\"u}rgen}, title = {Improving the performance of artificial neural networks trained on synthetic data in gas spectroscopy - a study on two sensing approaches}, series = {tm - Technisches Messen}, journal = {tm - Technisches Messen}, edition = {Online ver{\"o}ffentlicht}, publisher = {Oldenbourg Wissenschaftsverlag}, doi = {10.1515/teme-2023-0051}, abstract = {Artificial neural networks (ANNs) are used in quantitative infrared gas spectroscopy to predict concentrations on multi-component absorption spectra. Training of ANNs requires vast amounts of labelled training data which may be elaborate and time consuming to obtain. Additional data can be gained by the utilization of synthetically generated spectra, but at the cost of systematic deviations to measured data. Here, we present two approaches to train ANNs with a combination of comparatively small, measured data sets and synthetically generated data. For the first approach a neural network is trained hybridly with synthetically generated infrared absorption spectra of mixtures of N2O and CO and measured zero-gas spectra, taken with a mid-infrared dual comb spectrometer. This improves the mean absolute error (MAE) of the network predictions from 0.46 to 0.01 ppmV and 0.24 to 0.01 ppmV for the concentration predictions of N2O and CO respectively for zero-gas measurements which was previously observed for training with purely synthetic data. At the same time a similar performance on spectra from gas mixtures of 0-100 ppmV N2O and 0 to 60 ppmV CO was achieved. For the second approach an ANN pre-trained on synthetic infrared spectra of mixtures of acetone and ethanol is retrained on a small dataset consisting of 26 spectra taken with a mid-infrared photoacoustic spectrometer. In this case the MAE for the concentration predictions of ethanol and acetone are improved by 45 \% and 20 \% in comparison to purely synthetic training. This shows the capability of using synthetically generated data to train ANNs in combination with small amounts of measured data to further improve neural networks for gas sensing and the transferability between different sensing approaches.}, language = {en} } @inproceedings{UlreichMoserOlbrichetal., author = {Ulreich, Fabian and Moser, Elisabeth and Olbrich, Florian and Ebert, Martin and Bierl, Rudolf and Kaup, Andr{\´e}}, title = {Luminance Simulation in CARLA under Cloud Coverage - Model Validation and Implications}, series = {2023 IEEE International Workshop on Metrology for Automotive (MetroAutomotive), -30 June 2023, Modena, Italy}, booktitle = {2023 IEEE International Workshop on Metrology for Automotive (MetroAutomotive), -30 June 2023, Modena, Italy}, editor = {Keil, Rudolf and Tschorn, Jan Alexander and T{\"u}mler, Johannes and Altinsoy, Mehmet Ercan}, publisher = {IEEE}, isbn = {979-8-3503-2187-6}, doi = {10.1109/MetroAutomotive57488.2023.10219098}, pages = {228 -- 233}, abstract = {To decrease the number of kilometers driven during the development of autonomous cars or driving assistance systems, performant simulation tools are necessary. Currently, domain distance effects between simulation and reality are limiting the successful application of rendering engines in data-driven perception tasks. In order to mitigate those domain distance effects, simulation tools have to be as close to reality as possible for the given task. For optical sensors like cameras, the luminance of the scene is essential. We provide within this paper a method to measure the luminance of rendered scenes within CARLA, an often used open-source simulation environment. Thereby, it is possible to validate the environment and weather models by taking real-world measurements with photometric sensors or with the help of open-source weather data, published e.g. by the German federal service for weather data (DWD - "Deutscher Wetterdienst"). Employing our proposed luminance measurement, the domain gap resulting from the simulation can be specified, which makes it possible to evaluate the statements about the safety of the automated driving system determined within the simulation. We show that the ratio between global and diffuse radiation modeled by the default atmosphere models within CARLA are under limited conditions similar to real-world measurements taken by the DWD. Nevertheless, we show, that the ratio's temporal variability in real-world situations is not modeled by CARLA.}, language = {en} } @article{MuellerWeiglMuellerWilliamsetal., author = {M{\"u}ller, Max and Weigl, Stefan and M{\"u}ller-Williams, Jennifer and Lindauer, Matthias and R{\"u}ck, Thomas and Jobst, Simon and Bierl, Rudolf and Matysik, Frank-Michael}, title = {Comparison of photoacoustic spectroscopy and cavity ring-down spectroscopy for ambient methane monitoring at Hohenpeißenberg}, series = {Atmospheric Measurement Techniques}, volume = {16}, journal = {Atmospheric Measurement Techniques}, number = {18}, publisher = {Copernicus Publications}, issn = {1867-8548}, doi = {10.5194/amt-16-4263-2023}, pages = {4263 -- 4270}, abstract = {With an atmospheric concentration of approximately 2000 parts per billion (ppbV, 10-9), methane (CH4) is the second most abundant greenhouse gas (GHG) in the atmosphere after carbon dioxide (CO2). The task of long-term and spatially resolved GHG monitoring to verify whether climate policy actions are effective is becoming more crucial as climate change progresses. In this paper we report the CH4 concentration readings of our photoacoustic (PA) sensor over a 5 d period at Hohenpeißenberg, Germany. As a reference device, a calibrated cavity ring-down spectrometer, Picarro G2301, from the meteorological observatory of the German Weather Service (DWD) was employed. Trace gas measurements with photoacoustic instruments promise to provide low detection limits at comparably low costs. However, PA devices are often susceptible to cross-sensitivities related to fluctuating environmental conditions, e.g. ambient humidity. The obtained results show that for PA sensor systems non-radiative relaxation effects induced by varying humidity are a non-negligible factor. Applying algorithm compensation techniques, which are capable of calculating the influence of non-radiative relaxation effects on the photoacoustic signal, increase the accuracy of the photoacoustic sensor significantly. With an average relative deviation of 1.11 \% from the G2301, the photoacoustic sensor shows good agreement with the reference instrument.}, language = {en} } @article{FritzReisAdamsetal., author = {Fritz, D. M. and Reis, D. A. and Adams, B. and Akre, R. A. and Arthur, J. and Blome, Christian and Bucksbaum, P. H. and Cavalieri, A. L. and Engemann, S. and Fahy, S. and Falcone, R. W. and Fuoss, P. H. and Gaffney, K. J. and George, M. J. and Hajdu, J. and Hertlein, M. P. and Hillyard, P. B. and Horn-von Hoegen, Michael and Kammler, Martin and Kaspar, J. and Kienberger, R. and Krejcik, P. and Lee, S. H. and Lindenberg, A. M. and McFarland, B. and Meyer, D. and Montagne, T. and Murray, E. D. and Nelson, A. J. and Nicoul, Matthieu and Pahl, R. and Rudati, J. and Schlarb, H. and Siddons, D. P. and Sokolowski-Tinten, Klaus and Tschentscher, Th and von der Linde, D. and Hastings, J. B.}, title = {Ultrafast bond softening in bismuth: mapping a solid's interatomic potential with X-rays}, series = {Science}, volume = {315}, journal = {Science}, number = {5812}, publisher = {AAAS}, doi = {10.1126/science.1135009}, pages = {633 -- 636}, abstract = {Intense femtosecond laser excitation can produce transient states of matter that would otherwise be inaccessible to laboratory investigation. At high excitation densities, the interatomic forces that bind solids and determine many of their properties can be substantially altered. Here, we present the detailed mapping of the carrier density-dependent interatomic potential of bismuth approaching a solid-solid phase transition. Our experiments combine stroboscopic techniques that use a high-brightness linear electron accelerator-based x-ray source with pulse-by-pulse timing reconstruction for femtosecond resolution, allowing quantitative characterization of the interatomic potential energy surface of the highly excited solid.}, language = {en} } @inproceedings{SokolowskiTintenBlomeBlumsetal., author = {Sokolowski-Tinten, Klaus and Blome, Christian and Blums, Juris and Shymanovich, Uladzimir and Nicoul, Matthieu and Cavalleri, Andrea and Tarasevitch, A. and Horn-von Hoegen, Michael and Kammler, Martin and von der Linde, Dietrich}, title = {Ultrafast X-ray diffraction}, series = {Ultrafast Phenomena XIV}, volume = {79}, booktitle = {Ultrafast Phenomena XIV}, editor = {Kobayashi, Tetsuro}, publisher = {Springer}, address = {Berlin, Heidelberg}, isbn = {978-3-540-27213-7}, doi = {10.1007/3-540-27213-5_53}, pages = {170 -- 174}, abstract = {In the last few years the generation of femtosecond pulses in the X-ray regime has become possible. These ultrashort X-ray pulses have enabled femtosecond time- resolution to be extended to X-rays.}, language = {en} } @article{KammlerHornvonHoegenVossetal., author = {Kammler, Martin and Horn- von Hoegen, Michael and Voss, N. and Tringides, Michael C. and Menzel, Andreas and Conrad, E. H.}, title = {Si(001) step dynamics: A temporal low-energy electron diffraction study}, series = {Physical Review B}, volume = {65}, journal = {Physical Review B}, number = {7}, publisher = {APS}, doi = {10.1103/PhysRevB.65.075312}, abstract = {We present equilibrium measurements of the dynamics of steps on Si(001) using temporal electron-diffraction spectroscopy. Activation energies and the rate limiting kinetics are identified for 950K<~T<~1130K. Unlike previous studies at higher temperatures, we can exclude evaporation and condensation of atoms or dimers from the step edges as the rate limiting process in this temperature regime. The possible reason for this difference is discussed in terms of a crossover from different rate-limiting kinetics.}, language = {en} } @inproceedings{NavitskiSerbunMuelleretal., author = {Navitski, Aliaksandr and Serbun, Pavel and M{\"u}ller, G{\"u}nter and Schreiner, Rupert and Dams, Florian}, title = {Efficient and reliable field emission from silicon tip arrays for miniaturized electron sources}, series = {2011 24th International Vacuum Nanoelectronics Conference ; 18-22 July 2011 Wuppertal}, booktitle = {2011 24th International Vacuum Nanoelectronics Conference ; 18-22 July 2011 Wuppertal}, publisher = {IEEE}, address = {Piscataway, NJ}, isbn = {978-3-00-035081-8}, issn = {2380-6311}, pages = {71 -- 72}, abstract = {Silicon-based cathodes with precisely aligned field emitter arrays (FEA) applicable for miniaturized electron sources were successfully developed and fabricated. The cathode chips contain about 3×105 Si tips/cm2 in a triangular array with a tip height of 2.5 μm, tip radius of 20 nm, and lateral distance between tips of 20 μm. Amazingly homogeneous and well-aligned field emission (FE) from all tips (i.e. 100\% efficiency) and maximum stable currents of typically 0.1 μA for p- and 0.6 μA for n-type Si were reproducibly achieved. Current-voltage characteristics of p-type Si tips exhibit the expected saturation at around 10 nA due to limited supply of electrons from a depletion layer, while the n-type Si tips show the usual FN behaviour. Additional coating of the Si tips with a 10 nm Au layer resulted in at least 5 times higher average FE current levels i.e. typically 3 μA but lead, however, to a 30\% increase of the onset voltage.}, language = {en} }