@article{ŁawrowskiPrommesbergerLangeretal., author = {Ławrowski, Robert Damian and Prommesberger, Christian and Langer, Christoph and Dams, Florian and Schreiner, Rupert}, title = {Improvement of Homogenity and Aspect Ratio of Silicon Tips for Field Emission by Reactive-Ion Etching}, series = {Advances in materials science and engineering}, volume = {2014}, journal = {Advances in materials science and engineering}, publisher = {Hindawi}, doi = {10.1155/2014/948708}, abstract = {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.}, language = {en} } @misc{BiekerSchlaakWilfertetal., author = {Bieker, Johannes and Schlaak, Helmut F. and Wilfert, Stefan and Ławrowski, Robert Damian and Hausladen, Matthias and Schreiner, Rupert}, title = {Development of FE-based electron sources for XHVion gauges in cryogenic vacuum environments}, series = {32nd International Vacuum Nanoelectronics Conference (IVNC 2019), 22.-26.07.2019, Cincinnati, USA}, journal = {32nd International Vacuum Nanoelectronics Conference (IVNC 2019), 22.-26.07.2019, Cincinnati, USA}, language = {en} } @misc{ŁawrowskiHausladenSchreiner, author = {Ławrowski, Robert Damian and Hausladen, Matthias and Schreiner, Rupert}, title = {Individually Addressable Silicon Field Emission Cathodes Fabricated by Laser Micromachining}, series = {7th ITG International Vacuum Electronics Workshop (IVEW) 2020 and 13th International Vacuum Electron Sources Conference (IVeSC) 2020, 26. - 29.5.2020, Bad Honnef}, journal = {7th ITG International Vacuum Electronics Workshop (IVEW) 2020 and 13th International Vacuum Electron Sources Conference (IVeSC) 2020, 26. - 29.5.2020, Bad Honnef}, language = {en} } @misc{HausladenŁawrowskiSchreiner, author = {Hausladen, Matthias and Ławrowski, Robert Damian and Schreiner, Rupert}, title = {Fast Pulse Source for Field Emission Applications}, series = {7th ITG International Vacuum Electronics Workshop (IVEW) 2020 and 13th International Vacuum Electron Sources Conference (IVeSC) 2020, 26. - 29.5.2020, Bad Honnef}, journal = {7th ITG International Vacuum Electronics Workshop (IVEW) 2020 and 13th International Vacuum Electron Sources Conference (IVeSC) 2020, 26. - 29.5.2020, Bad Honnef}, language = {en} } @inproceedings{PrommesbergerLangerŁawrowskietal., author = {Prommesberger, Christian and Langer, Christoph and Ławrowski, Robert Damian and Muller, F. and Dams, Florian and Schreiner, Rupert and Serbun, Pavel and M{\"u}ller, G{\"u}nter}, title = {Comparison of integral and local field-emission properties of Mo-coated p-Si tip 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.2015.7225579}, pages = {192 -- 193}, abstract = {Silicon tip arrays were fabricated by means of reactive ion etching followed by oxidation for final sharpening and molybdenum thin film coating. The field-emission (FE) properties of these Mo-coated p-Si tip arrays were systemically investigated by different measurement techniques. Integral measurements in diode configuration yielded a turn-on field (for 1 nA) of 22 V/μm and nearly stable FE currents up to 6.6 μA at 38 V/μm. The effective field enhancements factor extracted from the FN plots is about 180. Detailed investigations of these FE arrays were also performed by means of field emission scanning microscopy combined with electron microscopy. A rather limited efficiency of the tips (50\% at 1500 V) and FE homogeneity (180 nA at 700 V) might be correlated with the varying morphology of the tips and the presence of oxides. Local I-V measurements of selected single tips revealed both activation and deactivation effects, which finally resulted in nearly reproducible I-V curves. Current stability measurements at a constant voltage showed rather large fluctuations (0.1-1 μA) of the FE current, which could be reduced up to 1.7\% by using of a PID-regulated voltage source. SEM images showed unchanged tip shape after the current processing.}, language = {en} } @inproceedings{ŁawrowskiLangerPrommesbergeretal., author = {Ławrowski, Robert Damian and Langer, Christoph and Prommesberger, Christian and Dams, Florian and Bachmann, Michael and Schreiner, Rupert}, title = {Fabrication and simulation of silicon structures with high aspect ratio for field emission devices}, series = {2014 27th International Vacuum Nanoelectronics Conference (IVNC), 6-10 July 2014, Engelberg, Switzerland}, booktitle = {2014 27th International Vacuum Nanoelectronics Conference (IVNC), 6-10 July 2014, Engelberg, Switzerland}, publisher = {IEEE}, doi = {10.1109/IVNC.2014.6894805}, pages = {193 -- 194}, abstract = {To obtain higher field enhancement factors of Si-tip structures, we present an improved fabrication process utilizing reactive-ion etching (RIE) with an inductively coupled plasma (ICP). In our design, a pillar under the tips is realized by a combination of RIE with ICP. With adjusted power settings (≈ 240 W) and step times (<; 5 s), vertical slopes with a low roughness of approximately 10 nm to 20 nm are possible. The remaining silicon is oxidized thermally to sharpen the emitters. A final tip radius of R <; 20 nm is obtained for the tips of the emitters. The pillar height HP can be mainly adjusted by the duration of the ICP-etching step. A total emitter height of H ≈ 6 μm with a pillar height of HP ≈ 5 μm is achieved. Simulations with COMSOL Multiphysics® are applied to calculate the field enhancement factor β. A two-dimensional model is used in rotational symmetry. In addition to the previous model, a pillar with a varying diameter {\O}P and height HP is added. A conventional emitter (H = 1 μm and R = 20 nm) placed on a pillar of the height HP ≈ 5 μm approximately results in a three times higher β-factor (β≈ 105). By decreasing the diameter {\O}P a slight increase of the β-factor is observed. However, the aspect ratio of the emitter mainly influences on the β-factor.}, language = {en} } @inproceedings{PrommesbergerLangerŁawrowskietal., author = {Prommesberger, Christian and Langer, Christoph and Ławrowski, Robert Damian and Dams, Florian and Schreiner, Rupert and Ławrowski, Robert Damian}, title = {Gated p-Si field emitter arrays for sensor applications}, series = {2015 28th International Vacuum Nanoelectronics Conference (IVNC)}, booktitle = {2015 28th International Vacuum Nanoelectronics Conference (IVNC)}, publisher = {IEEE}, doi = {10.1109/IVNC.2015.7225567}, pages = {164 -- 165}, abstract = {We report on gated p-type Si-tip array cathodes for implementation into field emission electron sources for sensor applications. Arrays of 16 and 100 tips with tip heights of 3 μm and tip radii below 30 nm with integrated gate electrodes concentrically positioned 2 μm below the tip apexes were fabricated using an improved process, which leads to an enhanced isolation layer quality with sufficient breakdown field strengths and low leakage currents. Integral measurements with a fixed grid potential of 400 V showed emission currents up to 35 μA for 100 tips at a cathode voltage of 150 V and an almost negligible parasitic gate current. The array with 16 p-type Si-tips showed a significant stabilization of the emission current in the range of 0.3 - 0.4 μA, for cathode voltages between 90 V and 150 V. The current fluctuation in this saturation regime was measured for 10 minutes and a value of less than ± 1\% was observed. No degradation of the cathode was found after 6 hours of operation at a constant cathode voltage of 100 V and a constant grid voltage of 400 V.}, language = {en} } @inproceedings{LangerPrommesbergerŁawrowskietal., author = {Langer, Christoph and Prommesberger, Christian and Ławrowski, Robert Damian and M{\"u}ller, F. and Schreiner, Rupert and Serbun, Pavel and M{\"u}ller, G{\"u}nter}, title = {Enhanced field emission from p-doped black silicon on pillar structures}, 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.2015.7225547}, pages = {104 -- 105}, abstract = {Aligned square arrays of black silicon (b-Si) on top of pillars were fabricated on p-type silicon substrate by a deep-etching step combined with a b-Si process. Two 10×10 arrays with pillar heights of 8 μm and 20 μm and one b-Si reference sample without pillars were investigated. Integral field emission (FE) measurements of the arrays yielded rather low onset-fields between 6.4 V/μm and 13.5 V/μm and field enhancement factors between 430 and 800. The I-V curves showed typical Fowler-Nordheim behavior for low fields, whereas a saturation region was observed at higher fields. The maximum integral current in the saturation region was 8 μA at a field of 20 V/μm. The stability of the emission current was investigated over 3 hours and revealed moderate fluctuations of ± 8\% in the saturation region. Voltage scans showed well-aligned FE from nearly all pillars.}, language = {en} } @inproceedings{PrommesbergerŁawrowskiLangeretal., author = {Prommesberger, Christian and Ławrowski, Robert Damian and Langer, Christoph and Dams, Florian and Schreiner, Rupert}, title = {Realisierung von Siliziumspitzenarrays mit integrierter Gate-Elektrode f{\"u}r Anwendungen in der Vakuumsensorik}, series = {4. Landshuter Symposium Mikrosystemtechnik, Mikrosystemtechnik als Schl{\"u}sseltechnologie der Systemintegration, Tagungsband zum Symposium 12./13. M{\"a}rz 2014, Hochschule Landshut}, booktitle = {4. Landshuter Symposium Mikrosystemtechnik, Mikrosystemtechnik als Schl{\"u}sseltechnologie der Systemintegration, Tagungsband zum Symposium 12./13. M{\"a}rz 2014, Hochschule Landshut}, address = {Landshut}, isbn = {978-3-9812696-5-9}, pages = {36 -- 41}, abstract = {Bei der Feldemission (kalte Emission) k{\"o}nnen Elektronen durch ein starkes elektrisches Feld eine glatte und leitende Oberfl{\"a}che verlassen. Die Elektronen tunneln dabei durch eine Potentialbarriere, deren Breite durch ein {\"a}ußeres elektrisches Feld verkleinert wird. Durch das Hinzuf{\"u}gen einer integrierten Gate-Elektrode um eine Siliziumspitze kann die notwendige Einsatzspannung f{\"u}r Feldemission deutlich gesenkt werden. Zwischen Si-Kathode und Gate-Elektrode befindet sich dabei eine Isolationsschicht, die h{\"o}chste Anforderungen bez{\"u}glich der elektrischen Durchbruchsfestigkeit erf{\"u}llen muss. Mit einer Kombination aus Trocken- (Schichtdicke 50 nm) und Feuchtoxid (Schichtdicke 950 nm) konnte eine Isolationsschicht entwickelt werden, die im integrierten Aufbau eine minimale Durchbruchsfeldst{\"a}rke von 3,2 MV/cm aufweist. F{\"u}r die Realisierung von Siliziumkathoden mit integrierter Gate-Elektrode wurde ein bereits bestehender Herstellungsprozess um zus{\"a}tzliche Prozessschritte erweitert. Die {\"U}bertragung der lateralen Position der Spitze erfolgt durch Strukturierung des Umkehrlacks AZ5214 und einer RIE-{\"A}tzung der zuvor hergestellten SiO2-Schicht. Nach dem Entfernen der Lackschicht wird die vertikale Struktur der Siliziumspitzen durch einen RIE-{\"A}tzprozess mit den Prozessgasen SF6 und O)2 realisiert. Aus einer thermischen Oxidation bei 940 °C resultiert anschließend die Isolationsschicht zwischen Si-Kathode und Gate-Elektrode . Gleichzeitig wird diese Ansch{\"a}rfeoxidation auch zur Realisierung der endg{\"u}ltigen Spitzengeometrie verwendet. Durch die lithographische Strukturierung des Photolacks AZ5214 kann dabei die Fl{\"a}che der aufgedampften Gate-Elektrode festgelegt werden. Die Gate-Elektrode wird in einem selbstjustierenden Prozessschritt exakt konzentrisch um die Si-Spitze aufgedampft. Der gerichtete Aufdampfprozess bewirkt eine Abschattung, so dass das Oxidpl{\"a}ttchen nicht komplett von Metall ummantelt wird. Die Opferschicht aus Photolack wird mit den nicht ben{\"o}tigten Metallfl{\"a}chen in einem Lift-off-Prozess entfernt.}, language = {de} } @inproceedings{ŁawrowskiLangerPrommesbergeretal., author = {Ławrowski, Robert Damian and Langer, Christoph and Prommesberger, Christian and Dams, Florian and Serbun, Pavel and M{\"u}ller, G{\"u}nter and Schreiner, Rupert}, title = {Spitzen- und Kantenemitter aus Silizium mit einem hohen Aspektverh{\"a}ltnis f{\"u}r Ionisationsgassensoren}, series = {Mikrosystemtechnik als Schl{\"u}sseltechnologie der Systemintegration : 4. Landshuter Symposium Mikrosystemtechnik ; Tagungsband zum Symposium ; 12./13. M{\"a}rz 2014, Hochschule Landshut}, booktitle = {Mikrosystemtechnik als Schl{\"u}sseltechnologie der Systemintegration : 4. Landshuter Symposium Mikrosystemtechnik ; Tagungsband zum Symposium ; 12./13. M{\"a}rz 2014, Hochschule Landshut}, publisher = {Cluster Mikrosystemtechnik}, address = {Landshut}, isbn = {978-3-9812696-5-9}, pages = {28 -- 35}, abstract = {Durch die Optimierung von reaktivem Ionen{\"a}tzen mit induktiv gekoppeltem Plasma ist die Herstellung von verschiedenen Siliziumkathoden mit hoher Anisotropie und hohem Aspektverh{\"a}ltnis f{\"u}r Feldemissionsanwendungen m{\"o}glich. Simulationen mit COMSOL Multiphysics untermauern das Potential von solchen Spitzen- und Kantenfeldemittern. Die Ergebnisse der Simulation zeigen einen zwei- bis sechsfach h{\"o}heren Feld{\"u}berh{\"o}hungsfaktor der tiefge{\"a}tzten Strukturen im Vergleich zu identischen Emittern ohne zus{\"a}tzliche Tiefen{\"a}tzung. Feldemissionsmessungen best{\"a}tigen die Simulationsergebnisse. Der modifizierte Herstellungsprozess der Feldemitter erm{\"o}glicht somit einen zuverl{\"a}ssigen Betrieb von Feldemissionselektronenquellen bei kleineren makroskopischen Feldst{\"a}rken. Außerdem weisen die Messungen des Emissionsstroms im S{\"a}ttigungsbereich eine weitgehende Unabh{\"a}ngigkeit vom elektrischen Feld auf. Lokale Feldemissionsmessungen ergeben dadurch eine deutliche Stromstabilisierung, welche {\"u}ber große Feldst{\"a}rkenbereiche konstant bleibt. Die Nutzung der HAR-Emitter (high aspect ratio) ist damit eine gute Voraussetzung f{\"u}r einen zuverl{\"a}ssigen Betrieb der Emissionskathoden bei kleinen Feldst{\"a}rken f{\"u}r die Anwendung in Ionisationsgassensoren.}, language = {de} } @article{ŁawrowskiPrommesbergerLangeretal., author = {Ławrowski, Robert Damian and Prommesberger, Christian and Langer, Christoph and Dams, Florian and Schreiner, Rupert}, title = {Improvement of Homogeneity and Aspect Ratio of Silicon Tips for Field Emission by Reactive-Ion Etching}, series = {Advances in Materials Science and Engineering. Special issue: Advances in Smart Materials and Applications}, volume = {2014}, journal = {Advances in Materials Science and Engineering. Special issue: Advances in Smart Materials and Applications}, publisher = {Hindawi}, issn = {1687-8442}, doi = {10.1155/2014/948708}, pages = {1 -- 6}, abstract = {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.}, language = {en} } @inproceedings{ŁawrowskiPrommesbergerLangeretal., author = {Ławrowski, Robert Damian and Prommesberger, Christian and Langer, Christoph and Dams, Florian and Schreiner, Rupert}, title = {Influence of reactive ion etching parameters on the geometry of silicon tip cathodes for field emission}, series = {Applied Research Conference 2013, ARC 2013 : 17th and 18th October 2013, Deggendorf}, booktitle = {Applied Research Conference 2013, ARC 2013 : 17th and 18th October 2013, Deggendorf}, publisher = {Shaker}, address = {Aachen}, isbn = {978-3-8440-2274-2}, pages = {67 -- 69}, language = {en} }