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 - TY - CHAP A1 - Serbun, Pavel A1 - Porshyn, Vitali A1 - Lützenkirchen-Hecht, Dirk A1 - Prommesberger, Christian A1 - Langer, Christoph A1 - Ławrowski, Robert Damian A1 - Schreiner, Rupert T1 - Photosensitivity of single silicon high-aspect-ratio tips with different doping levels T2 - International Vacuum Nanoelectronics Conference (IVNC), 31st, 2018, Kyoto, Japan N2 - 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. KW - field emission KW - Si p/n junction KW - p-type Si KW - photosensitivity Y1 - 2018 U6 - https://doi.org/10.1109/IVNC.2018.8520288 PB - IEEE ER - TY - CHAP A1 - Schreiner, Rupert A1 - Langer, Christoph A1 - Prommesberger, Christian A1 - Ławrowski, Robert Damian A1 - Dams, Florian A1 - Bachmann, Michael A1 - Düsberg, F. A1 - Hofmann, Martin A1 - Pahlke, Andreas A1 - Serbun, Pavel A1 - Mingels, Stephan A1 - Müller, Günter T1 - Semiconductor field emission electron sources using a modular system concept for application in sensors and x-ray-sources T2 - 2015 28th International Vacuum Nanoelectronics Conference (IVNC), 13-17 July 2015, Guangzhou, China N2 - 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. KW - Anodes KW - CATHODES KW - electron sources KW - GEOMETRY KW - Iron KW - Logic gates KW - semiconductor field emission KW - silicon Y1 - 2015 U6 - https://doi.org/10.1109/IVNC.2015.7225572 SP - 178 EP - 179 PB - IEEE ER - TY - CHAP A1 - Ławrowski, Robert Damian A1 - Langer, Christoph A1 - Prommesberger, Christian A1 - Schreiner, Rupert A1 - Mingels, Stephan A1 - Porshyn, Vitali A1 - Serbun, Pavel A1 - Müller, Günter T1 - Field emission from surface textured GaN with buried double-heterostructures T2 - 2015 28th International Vacuum Nanoelectronics Conference (IVNC), 13-17 July 2015, Guangzhou, China N2 - 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. KW - CATHODES KW - Current measurement KW - Electric fields KW - field emission KW - Gallium nitride KW - GaN KW - Iron KW - Light emitting diodes KW - photoemission KW - Surface texture Y1 - 2015 U6 - https://doi.org/10.1109/IVNC.2015.7225548 SP - 106 EP - 107 PB - IEEE ER - TY - JOUR A1 - Pirker, Luka A1 - Ławrowski, Robert Damian A1 - Schreiner, Rupert A1 - Remškar, Maja A1 - Višić, Bojana T1 - MoₓWₓ₋₁S₂ Nanotubes for Advanced Field Emission Application JF - Advanced Functional Materials N2 - Transition metal dichalcogenide (TMDC) nanotubes complement the field of low-dimensional materials with their quasi-1D morphology and a wide set of intriguing properties. By introducing different transition metals into the crystal structure, their properties can be tailored for specific purpose and applications. Herein, the characterization and a subsequent preparation of single-nanotube field emission devices of MoxWx-1S2 nanotubes prepared via the chemical vapor transport reaction is presented. Energy-dispersive X-ray spectroscopy, Raman spectroscopy, and X-ray diffraction indicate that the molybdenum and tungsten atoms are randomly distributed within the crystal structure and that the material is highly crystalline. High resolution transmission electron microscopy and electron diffraction (ED) patterns further corroborate these findings. A detailed analysis of the ED patterns from an eight-layer nanotube reveal that the nanotubes grow in the 2H structure, with each shell consists of one bilayer. The work function of the nanotubes is comparable to that of pure MoS2 and lower of pure WS2 NTs, making them ideal candidates for field emission applications. Two devices with different geometrical setup are prepared and tested as field emitters, showing promising results for single nanotube field emission applications. Y1 - 2023 U6 - https://doi.org/10.1002/adfm.202213869 SN - 1616-3028 N1 - Early View. Online Version of Record before inclusion in an issue SP - 1 EP - 8 PB - Wiley ER - TY - JOUR A1 - Broser, Christian A1 - Falter, Thomas A1 - Ławrowski, Robert Damian A1 - Altenbuchner, Amelie A1 - Vögele, Daniel A1 - Koss, Claus A1 - Schlamp, Matthias A1 - Dunnweber, Jan A1 - Steffens, Oliver A1 - Heckner, Markus A1 - Jaritz, Sabine A1 - Schiegl, Thomas A1 - Corsten, Sabine A1 - Lauer, Norina A1 - Guertler, Katherine A1 - Koenig, Eric A1 - Haug, Sonja A1 - Huber, Dominik A1 - Birkenmaier, Clemens A1 - Krenkel, Lars A1 - Wagner, Thomas A1 - Justus, Xenia A1 - Saßmannshausen, Sean Patrick A1 - Kleine, Nadine A1 - Weber, Karsten A1 - Braun, Carina N. A1 - Giacoppo, Giuliano A1 - Heinrich, Michael A1 - Just, Tobias A1 - Schreck, Thomas A1 - Schnabl, Andreas A1 - Gilmore, Amador Téran A1 - Roeslin, Samuel A1 - Schmid, Sandra A1 - Wellnitz, Felix A1 - Malz, Sebastian A1 - Maurial, Andreas A1 - Hauser, Florian A1 - Mottok, Jürgen A1 - Klettke, Meike A1 - Scherzinger, Stefanie A1 - Störl, Uta A1 - Heckner, Markus A1 - Bazo, Alexander A1 - Wolff, Christian A1 - Kopper, Andreas A1 - Westner, Markus A1 - Pongratz, Christian A1 - Ehrlich, Ingo A1 - Briem, Ulrich A1 - Hederer, Sebastian A1 - Wagner, Marcus A1 - Schillinger, Moritz A1 - Görlach, Julien A1 - Hierl, Stefan A1 - Siegl, Marco A1 - Langer, Christoph A1 - Hausladen, Matthias A1 - Schreiner, Rupert A1 - Haslbeck, Matthias A1 - Kreuzer, Reinhard A1 - Brückl, Oliver A1 - Dawoud, Belal A1 - Rabl, Hans-Peter A1 - Gamisch, Bernd A1 - Schmidt, Ottfried A1 - Heberl, Michael A1 - Gänsbauer, Bianca A1 - Bick, Werner A1 - Ellermeier, Andreas A1 - Monkman, Gareth J. A1 - Prem, Nina A1 - Sindersberger, Dirk A1 - Tschurtschenthaler, Karl A1 - Aurbach, Maximilian A1 - Dendorfer, Sebastian A1 - Betz, Michael A. A1 - Szecsey, Tamara A1 - Mauerer, Wolfgang A1 - Murr, Florian ED - Baier, Wolfgang T1 - Forschung 2018 T3 - Forschungsberichte der OTH Regensburg - 2018 KW - Forschung KW - Forschungsbericht Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-13826 SN - 978-3-9818209-5-9 CY - Regensburg ER - TY - CHAP A1 - Ławrowski, Robert Damian A1 - Langer, Christoph A1 - Schreiner, Rupert A1 - Sellmair, Josef T1 - Nano Emitters on Silicon Pillar Structures generated by a Focused Electron Beam Induced Deposition T2 - International Vacuum Nanoelectronics Conference (IVNC), 31st, 2018, Kyoto, Japan N2 - Nano emitters were deposited by focused electron beam induced deposition of Trimethyl-(methylcyclopentadienyl)platinum(IV) on top of silicon pillars. The nano emitters were exactly positioned in the center on the top of up to four pillars of a quadratic arranged array of sixteen pillars with a pitch of 50 μm. 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. The Fowler-Nordheim plots show a linear behavior, like expected for an n-type silicon material and a metal needle. The I-V measurement of the most promising sample shows an integral emission current up to 2 μm at a voltage of 600 V (12 MV/m) and an onset voltage for a current of 1 nA of about 300 V. KW - field emission KW - nano emitter KW - focused electron beam induced deposition KW - MeCpPtMe3 Y1 - 2018 U6 - https://doi.org/10.1109/IVNC.2018.8520059 PB - IEEE ER -