TY - CHAP A1 - Ławrowski, Robert Damian A1 - Deml, Sonja A1 - Varghese, T. A1 - Schimpke, T. T1 - Leuchtdiodenchips mit dreidimensional epitaktisch gewachsenen kristallinen GaN Säulen T2 - 7. MikroSystemTechnik Kongress "MEMS, Mikroelektronik, Systeme", 23.-25. Oktober 2017, München N2 - Um die Eigenschaften von Leuchtdioden zu verbessern und den Herstellungsprozess zu vereinfachen, wurde ein erweitertes Verfahren der metallorganischen Gasphasenepitaxie verwendet, um dichtgepackte dreidimensionale GaN-Säulen mit hohen Aspektverhältnis auf Chipoberflächen zu wachsen. Diese selbstorganisierenden dreidimensionalen Strukturen sollen einerseits die lichtabstrahlende Oberfläche der Leuchtdiode bei gleichbleibender Chipgröße vergrößern und andererseits durch die nichtpolaren Kristallebenen an den Seiten- und Deckflächen der Säulen die Effizienz dieser Bauteile erhöhen. Messungen an ersten Bauteilen, die mit dieser Methode realisiert wurden, zeigen eine homogene blaue Emission bei Wellenlängen von 450 nm und abgestrahlte Lichtleistungen von bereits mehr als 50 mW bei Stromdichten von 120 A/cm². Diese Ergebnisse sind bereits sehr vielversprechend und lassen eine deutliche Performancesteigerung bei Optimierung der Herstellungstechnologie erwarten. N2 - In order to increase the performance and to simplify the production of light emitting diode chips, an advanced metal organic vapor-phase-epitaxy process was used for the growth of densely packed high-aspect-ratio GaN microrods on the chip surface. The purpose of these self-organizing structures is, to increase the effective light emitting surface of the chip as well as to improve the efficiency. Measurements on first structures have shown blue emission at wavelengths of 450 nm and emitted output power of more than 50 mW at current densities of 120 A/cm². These promising results let us expect a significant improvement when optimizing the fabrication process further. T2 - Light emitting diodes based on three-dimensional epitaxial grown crystalline GaN rods KW - Aufbauorganisation KW - Ausgangsleistung KW - dreidimensionale Struktur KW - Fertigungstechnologie KW - Herstellungsablauf KW - Kristallebene KW - Leuchtdiode KW - Metalldampf KW - metallorganische Gasphasenepitaxie KW - organischer Dampf KW - Produktionsprozess KW - Stromdichte KW - Wellenlänge Y1 - 2017 SN - 978-3-8007-4491-6 SP - 131 EP - 134 PB - VDE-Verlag CY - München ER - TY - CHAP A1 - Ławrowski, Robert Damian A1 - Langer, Christoph A1 - Prommesberger, Christian A1 - Dams, Florian A1 - Serbun, Pavel A1 - Müller, Günter A1 - Schreiner, Rupert T1 - Spitzen- und Kantenemitter aus Silizium mit einem hohen Aspektverhältnis für Ionisationsgassensoren T2 - Mikrosystemtechnik als Schlüsseltechnologie der Systemintegration : 4. Landshuter Symposium Mikrosystemtechnik ; Tagungsband zum Symposium ; 12./13. März 2014, Hochschule Landshut N2 - Durch die Optimierung von reaktivem Ionenätzen mit induktiv gekoppeltem Plasma ist die Herstellung von verschiedenen Siliziumkathoden mit hoher Anisotropie und hohem Aspektverhältnis für Feldemissionsanwendungen möglich. Simulationen mit COMSOL Multiphysics untermauern das Potential von solchen Spitzen- und Kantenfeldemittern. Die Ergebnisse der Simulation zeigen einen zwei- bis sechsfach höheren Feldüberhöhungsfaktor der tiefgeätzten Strukturen im Vergleich zu identischen Emittern ohne zusätzliche Tiefenätzung. Feldemissionsmessungen bestätigen die Simulationsergebnisse. Der modifizierte Herstellungsprozess der Feldemitter ermöglicht somit einen zuverlässigen Betrieb von Feldemissionselektronenquellen bei kleineren makroskopischen Feldstärken. Außerdem weisen die Messungen des Emissionsstroms im Sättigungsbereich eine weitgehende Unabhängigkeit vom elektrischen Feld auf. Lokale Feldemissionsmessungen ergeben dadurch eine deutliche Stromstabilisierung, welche über große Feldstärkenbereiche konstant bleibt. Die Nutzung der HAR-Emitter (high aspect ratio) ist damit eine gute Voraussetzung für einen zuverlässigen Betrieb der Emissionskathoden bei kleinen Feldstärken für die Anwendung in Ionisationsgassensoren. KW - Emitter KW - Feldelektronenemission KW - Gassensor KW - Herstellung KW - Ionenemission KW - Silicium Y1 - 2014 SN - 978-3-9812696-5-9 SP - 28 EP - 35 PB - Cluster Mikrosystemtechnik CY - Landshut ER - TY - JOUR A1 - Ławrowski, Robert Damian A1 - Prommesberger, Christian A1 - Langer, Christoph A1 - Dams, Florian A1 - Schreiner, Rupert T1 - Improvement of Homogeneity and Aspect Ratio of Silicon Tips for Field Emission by Reactive-Ion Etching JF - Advances in Materials Science and Engineering. Special issue: Advances in Smart Materials and Applications N2 - The homogeneity of emitters is very important for the performance of field emission (FE) devices. Reactive-ion etching (RIE) and oxidation have significant influences on the geometry of silicon tips. The RIE influences mainly the anisotropy of the emitters. Pressure has a strong impact on the anisotropic factor. Reducing the pressure results in a higher anisotropy, but the etch rate is also lower. A longer time of etching compensates this effect. Furthermore an improvement of homogeneity was observed. The impact of uprating is quite low for the anisotropic factor, but significant for the homogeneity. At low power the height and undercut of the emitters are more constant over the whole wafer. The oxidation itself is very homogeneous and has no observable effect on further variation of the homogeneity. This modified fabrication process allows solving the problem of inhomogeneity of previous field emission arrays. Y1 - 2014 U6 - https://doi.org/10.1155/2014/948708 SN - 1687-8442 SN - 1687-8434 VL - 2014 SP - 1 EP - 6 PB - Hindawi ER - TY - CHAP A1 - Ławrowski, Robert Damian A1 - Prommesberger, Christian A1 - Langer, Christoph A1 - Dams, Florian A1 - Schreiner, Rupert T1 - Influence of reactive ion etching parameters on the geometry of silicon tip cathodes for field emission T2 - Applied Research Conference 2013, ARC 2013 : 17th and 18th October 2013, Deggendorf Y1 - 2013 SN - 978-3-8440-2274-2 SP - 67 EP - 69 PB - Shaker CY - Aachen ER - TY - CHAP A1 - Ławrowski, Robert Damian A1 - Prommesberger, Christian A1 - Langer, Christoph A1 - Dams, Florian A1 - Schreiner, Rupert T1 - Feldemissionselektronenquellen basierend auf Siliziumemittern mit hohen Aspektverhältnis T2 - Forschungsbericht der OTH Regensburg 2013 Y1 - 2013 UR - https://doi.org/10.35096/othr/pub-799 SP - 47 EP - 48 CY - Regensburg ER - TY - JOUR A1 - Weber, Karsten A1 - Dendorfer, Sebastian A1 - Süß, Franz A1 - Kubowitsch, Simone A1 - Schratzenstaller, Thomas A1 - Haug, Sonja A1 - Mohr, Christa A1 - Kiesl, Hans A1 - Drechsler, Jörg A1 - Westner, Markus A1 - Kobus, Jörn A1 - Schubert, Martin J. W. A1 - Zenger, Stefan A1 - Pietsch, Alexander A1 - Weiß, Josef A1 - Hinterseer, Sebastian A1 - Schieck, Roland A1 - Scherzinger, Stefanie A1 - Klettke, Meike A1 - Ringlstetter, Andreas A1 - Störl, Uta A1 - Bissyandé, Tegawendé F. A1 - Seeburger, Achim A1 - Schindler, Timo A1 - Ramsauer, Ralf A1 - Kiszka, Jan A1 - Kölbl, Andreas A1 - Lohmann, Daniel A1 - Mauerer, Wolfgang A1 - Maier, Johannes A1 - Scorna, Ulrike A1 - Palm, Christoph A1 - Soska, Alexander A1 - Mottok, Jürgen A1 - Ellermeier, Andreas A1 - Vögele, Daniel A1 - Hierl, Stefan A1 - Briem, Ulrich A1 - Buschmann, Knut A1 - Ehrlich, Ingo A1 - Pongratz, Christian A1 - Pielmeier, Benjamin A1 - Tyroller, Quirin A1 - Monkman, Gareth J. A1 - Gut, Franz A1 - Roth, Carina A1 - Hausler, Peter A1 - Bierl, Rudolf A1 - Prommesberger, Christian A1 - Ławrowski, Robert Damian A1 - Langer, Christoph A1 - Schreiner, Rupert A1 - Huang, Yifeng A1 - She, Juncong A1 - Ottl, Andreas A1 - Rieger, Walter A1 - Kraml, Agnes A1 - Poxleitner, Thomas A1 - Hofer, Simon A1 - Heisterkamp, Benjamin A1 - Lerch, Maximilian A1 - Sammer, Nike A1 - Golde, Olivia A1 - Wellnitz, Felix A1 - Schmid, Sandra A1 - Muntschick, Claudia A1 - Kusterle, Wolfgang A1 - Paric, Ivan A1 - Brückl, Oliver A1 - Haslbeck, Matthias A1 - Schmidt, Ottfried A1 - Schwanzer, Peter A1 - Rabl, Hans-Peter A1 - Sterner, Michael A1 - Bauer, Franz A1 - Steinmann, Sven A1 - Eckert, Fabian A1 - Hofrichter, Andreas ED - Baier, Wolfgang T1 - Forschungsbericht 2017 T3 - Forschungsberichte der OTH Regensburg - 2017 KW - Forschung KW - Forschungsbericht Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-13835 SN - 978-3-9818209-3-5 CY - Regensburg ER - TY - CHAP A1 - Bachmann, Michael A1 - Dams, Florian A1 - Düsberg, F. A1 - Hofmann, Martin A1 - Pahlke, Andreas A1 - Langer, Christoph A1 - Ławrowski, Robert Damian A1 - Prommesberger, Christian A1 - Schreiner, Rupert T1 - Stability investigation of high aspect ratio n-type silicon field emitter arrays T2 - 2015 28th International Vacuum Nanoelectronics Conference (IVNC), 13-17 July 2015, Guangzhou, China N2 - 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. KW - Current measurement KW - emission current stability KW - field emitter array KW - Field emitter arrays KW - RESISTANCE KW - Resistors KW - semiconductor field emission KW - silicon KW - silicon tips KW - Stability analysis KW - Thermal stability KW - XRF spectroscopy Y1 - 2015 U6 - https://doi.org/10.1109/IVNC.2015.7225584 SP - 204 EP - 205 PB - IEEE ER - TY - JOUR A1 - Ławrowski, Robert Damian A1 - Pirker, Luka A1 - Kaneko, Keita A1 - Kokubo, Hiroki A1 - Bachmann, Michael A1 - Ikuno, Takashi A1 - Remskar, Maja A1 - Schreiner, Rupert T1 - Field emission from nanotubes and flakes of transition metal dichalcogenides JF - Journal of Vacuum Science and Technology B N2 - Transition metal dichalcogenides such as MoS2 and WS2 are low-dimensional semiconductor materials. MoS2 and WS2 nanotubes and flakes were grown by a chemical transport reaction under a temperature gradient. I2 was used as a transport agent for previously synthesized MoS2 and WS2, respectively. These multilayered nanotubes are indirect bandgap semiconductors with a bandgap depending on their diameter. WS2 flakes were prepared by the sulfurization of thin WOx flakes. To increase the field enhancement of such low-dimensional structures by a higher aspect ratio, two approaches were examined: (a) the MoS2 and WS2 nanotubes were attached individually by a focused ion beam with Pt on dry etched n-type Si pillars and (b) the WS2 flakes were grown directly on the surface of the (n-type and p-type) Si pillars. Integral field emission measurements were performed in a diode configuration with a 50 μm mica spacer in a vacuum chamber at pressures of about 10−9 mbar. At a voltage of 900 V (18 MV/m), the integral emission current from the nanotubes is up to 11 μA for the lateral mounted MoS2 and about 1.3 μA (1.0 μA) for the upright mounted WS2 (MoS2). The onset voltage for a current of 1 nA is about 550 V for MoS2 and 500 V for WS2, respectively. The voltage conversion factor is in the range of 6 × 104–8 × 104 cm−1 for the nanotubes. The mounted MoS2 flakes show a field emission current of about 6 μA at 18 MV/m in contrast to the directly grown WS2 flakes, which show a pronounced saturation regime and, therefore, a lower emission current of about 0.5 μA is reached at 1500 V (25 MV/m). The WS2 flakes show a two times higher (1 × 105 cm−1) voltage conversion factor in comparison to the MoS2 flakes (5 × 104 cm−1). The extracted characteristics of the current-limiting part show a difference in the behavior of the extracted current-limiting characteristics between the lateral (linear) and upright mounted (exponential) nanotubes and the MoS2 flakes. In contrast, the WS2 flakes show charge carrier depletion effects. Y1 - 2020 U6 - https://doi.org/10.1116/1.5140474 VL - 38 IS - 3 SP - 032801 PB - AIP Publishing ER - TY - CHAP A1 - Serbun, Pavel A1 - Porshyn, Vitali A1 - Müller, Günter A1 - Lützenkirchen-Hecht, Dirk A1 - Prommesberger, Christian A1 - Langer, Christoph A1 - Ławrowski, Robert Damian A1 - Schreiner, Rupert T1 - Field emission behavior of single n- and p-type black Si pillar structures T2 - International Vacuum Nanoelectronics Conference (IVNC), 31st, 2018, Kyoto, Japan N2 - 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. KW - field emission KW - black silicon KW - photoemission Y1 - 2018 U6 - https://doi.org/10.1109/IVNC.2018.8520292 PB - IEEE ER - TY - CHAP A1 - Serbun, Pavel A1 - Porshyn, Vitali A1 - Müller, Günter A1 - Mingels, Stephan A1 - Lützenkirchen-Hecht, Dirk A1 - Bachmann, Michael A1 - Düsberg, Felix A1 - Dams, Florian A1 - Hofmann, Martin A1 - Pahlke, Andreas A1 - Prommesberger, Christian A1 - Langer, Christoph A1 - Ławrowski, Robert Damian A1 - Schreiner, Rupert T1 - Field emission behavior of Au-tip-coated p-type Si pillar structures T2 - 29th International Vacuum Nanoelectronics Conference (IVNC), 2016, 11-15 July, Vancouver, BC, Canada N2 - 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. KW - field emission KW - p-type Si-pillar array KW - surface oxide effects KW - photoemission Y1 - 2016 U6 - https://doi.org/10.1109/IVNC.2016.7551516 SN - 2380-6311 SP - 181 EP - 182 PB - IEEE ER -