@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}ntner}, 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} } @article{LangerPrommesbergerŁawrowskietal., author = {Langer, Christoph and Prommesberger, Christian and Ławrowski, Robert Damian and Schreiner, Rupert and Serbun, Pavel and M{\"u}ller, G{\"u}nter and D{\"u}sberg, Felix and Hofmann, Martin and Bachmann, Michael and Pahlke, Andreas}, title = {Field emission properties of p-type black silicon on pillar structures}, series = {Journal of Vacuum Science \& Technology B}, volume = {34}, journal = {Journal of Vacuum Science \& Technology B}, number = {2}, doi = {10.1116/1.4943919}, abstract = {Arrays of black silicon field emission pillar structures were fabricated on p-type silicon substrates. Two types of samples with the same number of pillars (arrays of 10 × 10) but different pillar heights (8 and 20 μm) were prepared as well as a black silicon reference sample without pillars. The field emission properties of these cathodes were investigated both by means of integral current-voltage measurements and by field emission scanning microscopy. Samples with a pillar height of 20 μm revealed onset fields as low as 6.4 V/μm, field enhancement factors up to 800, and emission currents up to 8 μA at an applied field of 20 V/μm. Due to the p-type material, a saturation of the emission current for fields above 11 V/μm was observed. This saturation leads to a stable operation with a current fluctuation of less than ±8\%. It was found that samples with a pillar height of 20 μm showed improved emission characteristics compared to samples with a pillar height of 8 μm or without pillars. The voltage maps revealed an increased emission homogeneity after a "burn-in" sequence of the sample. The current map showed that a few of the pillars dominate the emission. Integral current stability measurements were performed under different vacuum pressures, in order to investigate altered emission behavior and a potential degradation of the emitters. At pressures above 10-6 mbar, the sample starts to degrade irreversibly. Nevertheless, even after a harsh treatment over 30 min at 5 × 10-5 mbar and at an applied field of 23 V/μm, the cathode was still operating, and did not fail during further operation over 20 h at 5 × 10-8 mbar and at an applied field of 28 V/μm.}, language = {en} } @article{SchreinerLangerPrommesbergeretal., author = {Schreiner, Rupert and Langer, Christoph and Prommesberger, Christian and Dams, Florian}, title = {Compact and Energy-Efficient Field Emission Cathodes for Sensor Applications}, series = {Advanced Materials Research}, volume = {1024}, journal = {Advanced Materials Research}, publisher = {Scientific.net}, doi = {10.4028/www.scientific.net/amr.1024.372}, pages = {372 -- 375}, abstract = {We report on miniaturized silicon field emitter arrays for the application in compact and energy-saving vacuum-microelectronic devices, e.g. sensors or x-ray tubes. Since standard silicon semiconductor technology has been used for the fabrication, they may be easily integrated with other silicon based circuits and devices on the same chip. The silicon tip geometry and the operating conditions were optimized in order to obtain highly uniform and stable electron field emission from large area cathode arrays. A series of uniform hexagonal tip arrays containing each 547 tips were fabricated and characterized. The electron emission properties of both individual tips as well as of complete emitter arrays were investigated. A saturation level in the voltage-current characteristics was found, which can be explained by the limitation of the supply of electrons due to the p-type silicon wafer material. When operating the arrays in the current saturation regime at an emission current of ~ 1 nA per tip, a highly stable and low noise emission can be observed.}, language = {en} } @article{BerndtMuggliWittweretal., author = {Berndt, Dominik and Muggli, Josef and Wittwer, Franz and Langer, Christoph and Heinrich, Stephan and Knittel, Thorsten and Schreiner, Rupert}, title = {MEMS-based thermal conductivity sensor for hydrogen gas detection in automotive applications}, series = {Sensors and Actuators A: Physical}, volume = {305}, journal = {Sensors and Actuators A: Physical}, number = {April}, publisher = {Elsevier}, doi = {10.1016/j.sna.2019.111670}, abstract = {Accurate detection of hydrogen gas in vehicle interiors is very important for the future of a fuel cell car. Since this type of gas is highly volatile and flammable, the measurement methods have to be very reliable and precise due to safety reasons. In this paper a thermal conductivity sensor for hydrogen gas detection is presented, exhibiting a lower detection limit of 2000 ppm hydrogen in laboratory air. The sensor element is realized by micro-fabrication techniques on silicon wafers. The heated filament is exposed by a selective wet etching process creating a micro-hotplate on a thin membrane. In order to minimize power consumption, the sensor is operated in pulsed mode. Hydrogen gas detection was carried out using a synthetic gas testbench. Measurements of hydrogen contents ranging from 0\% to 4\% with an increment of 0.5\% were successfully performed for ambient gas temperatures between -15°C and 84°C. Including humidity, high moisture contents have the greatest influence on thermal conductivity. This was predicted in theoretical investigations and confirmed in experiments. For evaluation, both the change in resistance ΔR as well as the time constant τ were taken as sensor output. For both quantities, the previously established theoretical relationship with thermal conductivity could be confirmed.}, language = {en} } @inproceedings{LindnerBerndtPrommesbergeretal., author = {Lindner, Matthias and Berndt, Dominik and Prommesberger, Christian and Langer, Christoph and Schreiner, Rupert}, title = {Field emission assisted micro plasma discharges at vacuum and atmospheric pressures}, series = {31st International Vacuum Nanoelectronics Conference (IVNC), 2018, Kyoto, Japan}, booktitle = {31st International Vacuum Nanoelectronics Conference (IVNC), 2018, Kyoto, Japan}, doi = {10.1109/IVNC.2018.8520181}, pages = {2}, abstract = {Spatially confined non-equilibrium plasmas at vacuum and atmospheric pressure in the dimensions from a few microns to one millimeter are a promising approach to the generation and maintenance of stable glow discharges. The realization of these micro-discharges or micro-plasmas enable more accurate investigations in the field of micro plasma research. We report on field emission assisted micro plasmas excited by an alternating current with frequencies up to 1 kHz. Due to the field enhancement caused by an array of Si nano-tip structures the ignition voltage of stable plasma discharges can be reduced by 30\%.}, language = {en} } @inproceedings{BerndtLindnerTschurtschenthaleretal., author = {Berndt, Dominik and Lindner, Matthias and Tschurtschenthaler, Karl and Langer, Christoph and Schreiner, Rupert}, title = {Miniaturized Plasma Actuator Flow Measurements by MEMS-Based Thermal Conductivity Sensors}, series = {MDPI Proceedings of Eurosensors 2018, 9-12 September, Graz}, volume = {Vol.13}, booktitle = {MDPI Proceedings of Eurosensors 2018, 9-12 September, Graz}, number = {2}, doi = {10.3390/proceedings2130939}, abstract = {The gasflow created by a minaturized dielectric barrier discharge (DBD) plasma actuator is measured by a MEMS-based thermal conductivity gas sensor giving an indication of flow velocity and flow direction. The possiblity of several sensors in a small area gives a far better accuracy of local flow phenomena compared to conventional sensors. This is important for a better understanding of plasma- induced flow characteristics.}, language = {en} } @article{LangerBerndtSchreiner, author = {Langer, Christoph and Berndt, Dominik and Schreiner, Rupert}, title = {Sensitivity of thermal conductivity vacuum gauges for constant current and constant temperature operation}, series = {Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics}, volume = {40}, journal = {Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics}, number = {5}, publisher = {AIP Publishing}, doi = {10.1116/6.0001964}, abstract = {To optimize the measurement range of thermal conductivity vacuum gauges, an expression for the sensitivity is required that takes into account all geometrical, material-specific, and operating parameters. Therefore, equations of the sensor output signal as a function of the pressure for the constant current and the constant temperature mode have been developed analytically. Based on these equations, the sensitivity of the vacuum gauge and its influencing parameters was investigated and discussed. For comparable conditions, the constant temperature operation shows a significantly higher sensitivity for high pressures, while the constant current operation shows higher sensitivity at low pressures. The sensitivity in both the constant current and the constant temperature mode depends on the ratio of the filament surface area and the parasitic thermal conductance. In addition, for the constant current operation, the sensitivity also depends on the current value and the temperature coefficient of the filament resistor. For the constant temperature operation, the sensitivity additionally depends on the distance of the filament and the reference plane. However, to extend the measurement range of a thermal conductivity vacuum gauge toward low pressures, a reduction of the parasitic thermal conductance is mandatory for both the constant current and the constant temperature mode.}, language = {en} } @inproceedings{SerbunPorshynMuelleretal., author = {Serbun, Pavel and Porshyn, V. and M{\"u}ller, G{\"u}nter and Mingels, S. 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} } @misc{BroserFalterŁawrowskietal., author = {Broser, Christian and Falter, Thomas and Ławrowski, Robert Damian and Altenbuchner, Amelie and V{\"o}gele, Daniel and Koss, Claus and Schlampp, Matthias and Dunnweber, Jan and Steffens, Oliver and Heckner, Markus and Jaritz, Sabine and Schiegl, Thomas and Corsten, Sabine and Lauer, Norina and Guertler, Katherine and Koenig, Eric and Haug, Sonja and Huber, Dominik and Birkenmaier, Clemens and Krenkel, Lars and Wagner, Thomas and Justus, Xenia and Saßmannshausen, Sean Patrick and Kleine, Nadine and Weber, Karsten and Braun, Carina N. and Giacoppo, Giuliano and Heinrich, Michael and Just, Tobias and Schreck, Thomas and Schnabl, Andreas and Gilmore, Amador T{\´e}ran and Roeslin, Samuel and Schmid, Sandra and Wellnitz, Felix and Malz, Sebastian and Maurial, Andreas and Hauser, Florian and Mottok, J{\"u}rgen and Klettke, Meike and Scherzinger, Stefanie and St{\"o}rl, Uta and Heckner, Markus and Bazo, Alexander and Wolff, Christian and Kopper, Andreas and Westner, Markus and Pongratz, Christian and Ehrlich, Ingo and Briem, Ulrich and Hederer, Sebastian and Wagner, Marcus and Schillinger, Moritz and G{\"o}rlach, Julien and Hierl, Stefan and Siegl, Marco and Langer, Christoph and Hausladen, Matthias and Schreiner, Rupert and Haslbeck, Matthias and Kreuzer, Reinhard and Br{\"u}ckl, Oliver and Dawoud, Belal and Rabl, Hans-Peter and Gamisch, Bernd and Schmidt, Ottfried and Heberl, Michael and G{\"a}nsbauer, Bianca and Bick, Werner and Ellermeier, Andreas and Monkman, Gareth J. and Prem, Nina and Sindersberger, Dirk and Tschurtschenthaler, Karl and Aurbach, Maximilian and Dendorfer, Sebastian and Betz, Michael A. and Szecsey, Tamara and Mauerer, Wolfgang and Murr, Florian}, title = {Forschung 2018}, editor = {Baier, Wolfgang}, address = {Regensburg}, organization = {Ostbayerische Technische Hochschule Regensburg}, isbn = {978-3-9818209-5-9}, doi = {10.35096/othr/pub-1382}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-13826}, pages = {98}, subject = {Forschung}, language = {de} }