@inproceedings{KoenigGuertlerŻarnowskaetal., author = {Koenig, Eric and Guertler, Katherine and Żarnowska, Dorota and Horbačauskienė, Jolita}, title = {Developing English language competence for global engineers}, series = {2020 IEEE Global Engineering Education Conference (EDUCON): 27-30 April 2020, Porto, Portugal}, booktitle = {2020 IEEE Global Engineering Education Conference (EDUCON): 27-30 April 2020, Porto, Portugal}, doi = {10.1109/EDUCON45650.2020.9125208}, pages = {242 -- 249}, abstract = {English language skills are essential to professional communication in international engineering environments. Given the concomitant degree of specialization, university-level coursework in English for Specific Purposes is an essential component of engineering student preparation. This large-scale survey of university students of engineering in three European countries provides important insight into the most relevant language skills, with the goal of informing communicative, task-based curricula for Technical English courses.}, language = {en} } @inproceedings{KoenigGuertler, author = {Koenig, Eric and Guertler, Katherine}, title = {Are you experienced? Technical and interpersonal communication prioritization in engineering ESP}, series = {Proceedings of Languages for Specific Purposes in Higher Education - Current Trends, Approaches and Issues, Brno University of Technology/Tschechien}, booktitle = {Proceedings of Languages for Specific Purposes in Higher Education - Current Trends, Approaches and Issues, Brno University of Technology/Tschechien}, language = {en} } @article{HanischBlicharskiJanzenKrenzeretal., author = {Hanisch-Blicharski, Anja and Janzen, Andreas and Krenzer, Boris and Wall, S. and Klasing, Friedrich and Kalus, Annika and Frigge, Tim and Kammler, Martin and Horn-von Hoegen, Michael}, title = {Ultra-fast electron diffraction at surfaces: from nanoscale heat transport to driven phase transitions}, series = {Ultramicroscopy}, volume = {127}, journal = {Ultramicroscopy}, publisher = {Elsevier}, doi = {10.1016/j.ultramic.2012.07.017}, pages = {2 -- 8}, abstract = {Many fundamental processes of structural changes at surfaces occur on a pico- or femtosecond time scale. In order to study such ultra-fast processes, we have combined modern surface science techniques with fs-laser pulses in a pump-probe scheme. Reflection high energy electron diffraction (RHEED) with grazing incident electrons ensures surface sensitivity for the probing electron pulses. Utilizing the Debye-Waller effect, we studied the cooling of vibrational excitations in monolayer adsorbate systems or the nanoscale heat transport from an ultra-thin film through a hetero-interface on the lower ps-time scale. The relaxation dynamics of a driven phase transition far away from thermal equilibrium is demonstrated with the In-induced (8×2) reconstruction on Si(111). This surface exhibits a Peierls-like phase transition at 100K from a (8×2) ground state to (4×1) excited state. Upon excitation by a fs-laser pulse, this structural phase transition is driven into an excited (4×1) state at a sample temperature of 20K. Relaxation into the (8×2) ground state occurs after more than 150 ps.}, language = {en} } @incollection{KoenigGuertlerTlukova, author = {Koenig, Eric and Guertler, Katherine and Tlukov{\´a}, Jolana}, title = {Harnessing learners' domain expertise for LSP curriculum development: Experience-based best practices and strategies}, series = {New to the LSP Classroom? A Selection of Monographs on Successful Practices}, booktitle = {New to the LSP Classroom? A Selection of Monographs on Successful Practices}, editor = {Vranova, Martina}, publisher = {Vernon Press}, address = {Wilmington, DE}, isbn = {978-1-64889-150-2}, pages = {131 -- 146}, abstract = {In Chapter 7, a team of authors from European technical universities addresses the most common challenge novice LSP practitioners usually have—inadequate knowledge of the target domain. They propose strategies to develop the language instructor's technical terminology and concepts. Struggling with feelings of intimidation in an alienating environment of the technical English classroom led the authors to a realization that the best source of target-domain knowledge is their own students. Interacting with students and receiving and appreciating subject-matter input from them bridges the gap between LSP practitioners with humanistic training and their technology-oriented students. By creating the classroom culture of two sets of experts in cooperation to solve a problem, both the teachers and the students can symbiotically learn from each other. Such teacher-student cooperation will give novice LSP practitioners a considerable head start. Moreover, it ensures that course design and curriculum can be tailored to the students' needs. Such student-guided input will also make up for the intensely felt lack of contact between LSP instructors and experts teaching subject-matter courses. The reflections on the unenviable situation of LSP instructors in an environment where everybody else but them has the target-domain knowledge is then followed by a list of specific in-class and take-home activities that incorporate the student-domain expertise in the ESP classroom. All these activities can be adapted to any language, level of proficiency, or target domain.}, language = {en} } @incollection{KoenigGuertler, author = {Koenig, Eric and Guertler, Katherine}, title = {Supporting weaker students in the mixed-level ESL classroom}, series = {English Language Teaching Through the Lens of Experience}, booktitle = {English Language Teaching Through the Lens of Experience}, editor = {Haase, Christoph}, publisher = {Cambridge Scholars Publisher}, address = {Newcastle-upon-Tyne}, isbn = {978-1-5275-3718-7}, pages = {181 -- 194}, language = {en} } @inproceedings{LangerPrommesbergerDamsetal., author = {Langer, Christoph and Prommesberger, Christian and Dams, Florian and Schreiner, Rupert}, title = {Theoretical investigations into the field enhancement factor of silicon structures}, series = {25th International Vacuum Nanoelectronics Conference (IVNC) - Jeju, Korea (South), 09.- 13.07.2012}, booktitle = {25th International Vacuum Nanoelectronics Conference (IVNC) - Jeju, Korea (South), 09.- 13.07.2012}, publisher = {IEEE}, address = {Piscataway, N.J.}, isbn = {978-1-4673-1984-3}, issn = {2380-6311}, doi = {10.1109/IVNC.2012.6316886}, abstract = {In order to optimize our field-emitting silicon structures, the influence of geometric parameters like aspect ratio, aperture angle and curvature on the field enhancement factor was investigated by finite element simulations. A universal geometric model consisting of a rounded triangle and elliptic curvatures was taken for modeling a variety of different silicon tip as well as ridge structures. Whereas, a high dependency of the field enhancement on the aperture angle was found, the simulations show that the elliptic curvature affects the field enhancement only marginal.}, language = {en} } @article{PrommesbergerBachmannDuesbergetal., author = {Prommesberger, Christian and Bachmann, Michael and D{\"u}sberg, Felix and Langer, Christoph and Ławrowski, Robert Damian and Hofmann, Martin and Pahlke, Andreas and Schreiner, Rupert}, title = {Regulation of the Transmitted Electron Flux in a Field-Emission Electron Source Demonstrated on Si Nanowhisker Cathodes}, series = {IEEE Transactions on Electron Devices}, volume = {64}, journal = {IEEE Transactions on Electron Devices}, number = {12}, publisher = {IEEE}, issn = {5128-5133}, doi = {10.1109/TED.2017.2763239}, abstract = {We report on a method to stabilize the transmitted electron flux in a field-emission electron source using an external regulation circuit. The electron source was realized with an array of silicon (Si) nanowhiskers on the top of elongated pillar structures, a mica spacer, and an extraction grid made of Si. As for most applications, the emitted electron current from the cathode is not as crucial as the transmitted electron flux through the extraction grid toward the anode. We investigated a method which allows the regulation directly by the emitted electron flux and not merely on the cathode current. By using this method, we were able to stabilize the emitted electron flux of our electron source down to values below 1\%. Simultaneously, it was shown that there is the possibility to stabilize the influencing value in the real application as well. The effectiveness of this method was demonstrated successfully with an X-ray source setup. The measured X-ray photon count rate was stabilized to a standard deviation of 0.30\% at a pressure of 1 × 10 -7 mbar. Even in harsh environment of 2 × 10 -5 mbar, a stabilization of the X-ray photon count rate down to a value of 0.63\% was achieved.}, language = {en} } @article{LangerBomkeHausladenetal., author = {Langer, Christoph and Bomke, Vitali and Hausladen, Matthias and Ławrowski, Robert Damian and Prommesberger, Christian and Bachmann, Michael and Schreiner, Rupert}, title = {Silicon Chip Field Emission Electron Source Fabricated by Laser Micromachining}, series = {Journal of Vacuum Science \& Technology B}, volume = {38}, journal = {Journal of Vacuum Science \& Technology B}, number = {1}, publisher = {AIP Publishing}, doi = {10.1116/1.5134872}, abstract = {The components for a silicon chip electron source were fabricated by laser micromachining using pulsed laser ablation and wet chemical cleaning and etching dips. The field emission electron source consists of a silicon field emission cathode with 4 × 4 conical shaped emitters with a height of 250 μm and a tip radius of about 50 nm, a 50 μm thick laser-structured mica spacer, and a silicon grid electrode with a grid periodicity of 200 μm and a bar width of 50 μm. These three components are combined to a single chip with the size of 14 × 10 mm2 and the thickness of 1 mm to form the electron source. Several of these devices were characterized in ultrahigh vacuum. Onset voltages of about 165 V and cathode currents of about 15 μA for voltages lower than 350 V were observed. Operating the electron source with an anode voltage of 500 V and an extraction grid voltage of 300 V yielded a cathode current of 4.5 μA ± 8.9\%, an anode current of 4.0 μA ± 9.6\%, and a corresponding grid transmittance of 89\%. Regulating the anode current by the extraction grid voltage, an extremely stable anode current of 5.0 μA ± 0.017\% was observed. A long-term measurement over 120 h was performed, and no significant degradation or failure was observed.}, language = {en} } @article{BreuerBachmannDuesbergetal., author = {Breuer, Janis and Bachmann, Michael and D{\"u}sberg, Felix and Pahlke, Andreas and Edler, Simon and Langer, Christoph and Prommesberger, Christian and Ławrowski, Robert Damian and Schreiner, Rupert and Serbun, Pavel and L{\"u}tzenkirchen-Hecht, Dirk}, title = {Extraction of the current distribution out of saturated integral measurement data of p-type silicon field emitter arrays}, series = {Journal of Vacuum Science and Technology B}, volume = {36}, journal = {Journal of Vacuum Science and Technology B}, number = {5}, publisher = {AIP Publishing}, doi = {10.1116/1.5035189}, abstract = {At the moment, only complicated techniques are known for the determination of array properties of field emitter arrays such as the number of active tips, the current distribution, or the individual tip radii. In this work, a method for extracting these parameters from integral measurement data is presented. A model describing the characteristics of a single emitter, including the saturation as a function of the applied voltage and the emitter radius, is developed. It is shown that experimental data of field emitter arrays can be represented as the sum of these functions and the characteristic parameters can be fitted to field emission data of an array. Using this method, the values of the radii as well as the parameters of distribution models can be determined directly. Analysis of experimental data from p-type Si emitter arrays shows that only 1-2\% of the tips contribute significantly.}, language = {en} } @article{EdlerBachmannBreueretal., author = {Edler, Simon and Bachmann, Michael and Breuer, Janis and Dams, Florian and D{\"u}sberg, Felix and Hofmann, Martin and Jakšič, Jasna and Pahlke, Andreas and Langer, Christoph and Ławrowski, Robert Damian and Prommesberger, Christian and Schreiner, Rupert}, title = {Influence of adsorbates on the performance of a field emitter array in a high voltage triode setup}, series = {Journal of Applied Physics}, volume = {122}, journal = {Journal of Applied Physics}, doi = {10.1063/1.4987134}, abstract = {In the present work, black-silicon field emitter arrays (FEAs) are investigated regarding the influence of residual gas pressure on the characteristics and lifetime in the high voltage triode setup. Current-voltage-characteristics at different pressure levels are recorded and show a decreasing emission current with rising pressure. This decrease can be explained by an increase of the work function and charging of the emitter surface caused by adsorbates. The emission current can be restored to its initial value by heating of the FEA up to 110 °C during active emission. With this regeneration procedure, an extended lifetime from about 20 h to 440 h at a residual gas pressure of 10-5 mbar is achieved.}, 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{BachmannDamsDuesbergetal., author = {Bachmann, Michael and Dams, Florian and D{\"u}sberg, Felix and Hofmann, Martin and Pahlke, Andreas and Langer, Christoph and Ławrowski, Robert Damian and Prommesberger, Christian and Schreiner, Rupert and Serbun, Pavel and L{\"u}tzenkirchen-Hecht, Dirk and M{\"u}ller, G{\"u}nter}, title = {Extraction of the characteristics of current-limiting elements from field emission measurement data}, series = {Journal of Vacuum Science \& Technology B}, volume = {35}, journal = {Journal of Vacuum Science \& Technology B}, number = {2}, doi = {10.1116/1.4971768}, abstract = {In this contribution, the authors will present an algorithm to extract the characteristics of nonideal field emission circuit elements from saturation-limited field emission measurement data. The method for calculating the voltage drop on current-limiting circuit elements is based on circuit theory as well as Newton's method. Since the only assumption the authors make on the current-limiting circuit is a connection in series, this method is applicable to most field emission data showing saturation. To be able to determine the significance of any parameter output, the uncertainties of data and extracted parameters as well as the parameter correlations are fully taken into account throughout the algorithm. N-type silicon samples with varying external serial resistors are analyzed. All results show a good agreement to the nominal resistor values. Additionally, several p-type samples are analyzed, showing a diodelike behavior. The extracted current-limiting characteristics of the p-type samples are in good agreement with a pn-junction model. The stability of the emission current of the p-type samples is measured by constant voltage measurements and compared to the extracted current-limiting characteristics. The application of the algorithm to measurement data shows that the given algorithm is a valuable tool to analyze field emission measurement data influenced by nonemissive processes.}, language = {en} } @inproceedings{LangerHausladenPrommesbergeretal., author = {Langer, Christoph and Hausladen, Matthias and Prommesberger, Christian and Ławrowski, Robert Damian and Bachmann, Michael and D{\"u}sberg, Felix and Pahlke, Andreas and Shamonin (Chamonine), Mikhail and Schreiner, Rupert}, title = {Field emission current investigation of p-type and metallized silicon emitters in the frequency domain}, 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.2018.8520127}, pages = {1-2}, abstract = {We investigated two different field emitter arrays consisting of 10×10 p-type and 10×10 undoped Au-coated high aspect ratio silicon tips. The I-V characterization of the p-type sample showed a pronounced saturation for voltages higher than 500 V and a maximum emission current of 39 nA. The metallized sample revealed a FN-like emission up to several μA. The metallized and the p-type sample operating below the saturation region showed high current fluctuations of ±16\%. Whereas, the metallized sample with current regulation and the p-type sample in the saturation yielded a current stability of ±0.4\% and ±0.3\%, respectively. Investigations in the frequency domain revealed the for field emission typical 1/f-noise. By operating in the saturation region (p-type sample) or using an emission current regulation (metallized sample) the noise level was reduced by at least 20 dB. Finally, the p-type sample was illuminated by a light emitting diode to increase and modulate the emission current in the saturation region. The emission current was increased by a factor of 3.7 to 145 nA. With this configuration we emulated an unstable emission behavior and evaluated the performance of our emission current regulation circuit.}, language = {en} } @article{PrommesbergerLangerŁawrowskietal., author = {Prommesberger, Christian and Langer, Christoph and Ławrowski, Robert Damian and Schreiner, Rupert}, title = {Investigations on the long-term performance of gated p-type silicon tip arrays with reproducible and stable field emission behavior}, series = {Journal of Vacuum Science \& Technology B}, volume = {35}, journal = {Journal of Vacuum Science \& Technology B}, number = {1}, doi = {10.1116/1.4972519}, abstract = {The authors report on the fabrication and characterization of p-type Si tip arrays with an integrated gate electrode for applications as field emission electron sources. After the reactive ion etching of the emitters, the combined thermal dry and wet oxidation was used for both the sharpening of the emitters and for the realization of an enhanced insulation layer. Au was evaporated in a self-aligned process as gate electrode. Arrays of 16 Si tips were fabricated with tip heights of about 3 μm and tip radii of about 20 nm with integrated gate electrode concentrically positioned ≈2 μm below the tip apex. Integral measurements with an additional anode showed improved field emission properties with a reproducible and stable emission behavior. A fast activation of the tips, low onset voltages of about 30 V, and moderate field emission currents up to 0.55 μA were noticed. The field emission parameters were calculated using the Fowler-Nordheim characteristics. A pronounced saturation regime was observed, and current fluctuations of less than ±1\% were investigated for 30 min. Long-term measurements were carried out for a period of more than 8 h. In the first 6 h of operation, the authors observed a drift of the emission current from 0.35 to 0.55 μA caused by an increased emission surface.}, language = {en} } @inproceedings{ŁawrowskiHausladenSchreiner, author = {Ławrowski, Robert Damian and Hausladen, Matthias and Schreiner, Rupert}, title = {Individually Addressable Fully Integrated Field Emission Electron Source Fabricated by Laser Micromachining of Silicon}, series = {33rd International Vacuum Nanoelectronics Conference (IVNC): 6-10 July 2020, Lyon}, booktitle = {33rd International Vacuum Nanoelectronics Conference (IVNC): 6-10 July 2020, Lyon}, publisher = {IEEE}, isbn = {978-1-7281-9454-7}, doi = {10.1109/IVNC49440.2020.9203470}, pages = {1 -- 2}, abstract = {A cathode with individually addressable Si tips allows the observation of the activation procedure and emission behaviour of each field emission emitter at any time of the measurement. The cathode consists of an array of 2x2 conically shaped emitter structures, which were fabricated by laser micromachining and wet etching of a Si substrate bonded on a glass carrier. Using the same process, a Si extractions grid was fabricated and mounted onto the emitter. Integral field emission measurements were performed in a diode configuration in a vacuum chamber at pressures of about 10- 9 mbar. The emitters show an onset voltage between 200 V and 300 V. The emission current for each emitter on the cathode was regulated to a given value (1.0 μA, 2.5μA, 5.0μA) by an external regulating circuit and was recorded individually during the measurement. With such approach, the relation between the emission behaviour and the geometry of emitters can be studied in detail. In addition, the current stabilization of each emitters of an array can be investigated, which led to a current stability of better than 0.5\%.}, language = {en} } @inproceedings{PrommesbergerŁawrowskiLangeretal., author = {Prommesberger, Christian and Ławrowski, Robert Damian and Langer, Christoph and Mecani, Mirgen and Huang, Yifeng and She, Juncong and Schreiner, Rupert}, title = {Field emission properties of ring-shaped Si ridges with DLC coating}, series = {Proc. SPIE 10248, Nanotechnology VIII, 102480H (30 May 2017)}, volume = {102480H}, booktitle = {Proc. SPIE 10248, Nanotechnology VIII, 102480H (30 May 2017)}, editor = {Tiginyanu (Ed.), Ion M.}, publisher = {Society of Photo-Optical Instrumentation Engineers (SPIE)}, doi = {10.1117/12.2265627}, abstract = {We report on the fabrication and the emission characterization of single ring-shaped Si ridges with a coating of diamond-like carbon (DLC). The reactive ion etching and the subsequent inductively coupled plasma step were adjusted to realize ring-shaped Si ridges with a height of 7.5 μm respectively 15 μm and an apex radius of 20 - 25 nm. The samples were coated with a DLC layer (thickness ≈ 2 - 5 nm) by a filtered cathodic vacuum arc deposition system in order to lower the work function of the emitter and to improve the field emission characteristics. The field emission characterizations were done in diode configuration with cathode and anode separated by a 50 μm thick mica spacer. A higher emission current was carried out for the ring-shaped Si ridge in comparison to the point-shaped Si tips due to the increased emission area. The highest emission current of 0.22 μA at 1000 V was measured on a DLC-coated sample with the highest aspect ratio. No degradation of the emission current was observed in the plateau regime during a measurement period of 6 h. Finally, no decreasing performance of the field emission properties was found due to changes in the geometry or destructions.}, language = {en} } @inproceedings{ŁawrowskiLangerPrommesbergeretal., author = {Ławrowski, Robert Damian and Langer, Christoph and Prommesberger, Christian and Schreiner, Rupert}, title = {Field emission from three-dimensional epitaxial grown GaN-microrods}, 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.2016.7551477}, pages = {87 -- 88}, abstract = {A novel three-dimensional epitaxial technique allows on patterned substrates the realization of gallium nitride pillars, also known as nano- and microrods. The typical dimensions of the microrods are in the range of one micron for the radius of the hexagonal footprint and about 10 μm in height. The microrods consist of a semiconductor heterostructure with an n GaN core, a n-GaN shell, a p GaN shell and an intermediate quantum well layer. The field emission properties were investigated in diode configuration by integral field emission measurements in a vacuum chamber at pressures around 10 -9 mbar. The spacer was mica with a thickness of 50 μm. A metallized fine-meshed nitride grid (or a metallized Si-grid) was used as anode. A current of about 1 μA at a voltage of 1250 V (1750 V) was measured. An onset field of about 12.5 MV/m (20 MV/m) and field enhancement factors in the range of 200 to 500 (150 to 300) were found. The investigation with the fine-meshed grid showed an expected pronounced saturation region.}, language = {en} } @inproceedings{PrommesbergerLangerŁawrowskietal., author = {Prommesberger, Christian and Langer, Christoph and Ławrowski, Robert Damian and Schreiner, Rupert}, title = {Field emission from black silicon structures with integrated gate electrode}, 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.2016.7551532}, pages = {219 -- 220}, abstract = {Black silicon structures with integrated gate electrode were realized by using an improved fabrication process. An enhanced insulation layer was achieved by a combination of dry and wet oxidation, and a gold layer was evaporated as gate electrode. The black silicon structures were prepared with a RIE/ICP etching process at room temperature. Arrays of 16 and 100 apertures with buried p-doped black silicon whiskers have been fabricated. These structures have an emitter height of approximately 1.5 μm with tip radii between 5 nm and 30 nm. The whiskers are surrounded by the gate electrode in a distance of 1.5 μm. Integral field emission measurements yielded an onset voltage of 92 V for 16 apertures and 60 V for 100 apertures for an emission current of 1 nA. Maximum emission currents up to 0.2 μA were observed for the array with 100 apertures at a cathode voltage of 200 V. Stability measurements showed a current fluctuation of ± 21\% at a mean value of the emission current of 12 nA over a period of 30 minutes for 16 apertures with b-Si whiskers.}, language = {en} } @inproceedings{ŁawrowskiLangerPrommesbergeretal., author = {Ławrowski, Robert Damian and Langer, Christoph and Prommesberger, Christian and Schreiner, Rupert}, title = {Microrods and microlines by three-dimensional epitaxially grown GaN for field emission cathodes}, series = {International Vacuum Nanoelectronics Conference (IVNC), 30th, 2017, Regensburg}, booktitle = {International Vacuum Nanoelectronics Conference (IVNC), 30th, 2017, Regensburg}, publisher = {IEEE}, doi = {10.1109/IVNC.2017.8051576}, pages = {130 -- 131}, abstract = {The three-dimensional epitaxial technique allows the realization of gallium nitride lines in addition to the rods. To optimize the properties of GaN-based field emission cathodes further investigations and an improvement of the epitaxial process were performed. The microrods and microlines consist of a one-order higher n-doped gallium nitride in comparison to the gallium nitride layer on the sapphire substrate. The typical height of the microrods and -lines is about 5 μm. The field emission properties of these structures were investigated in diode configuration by integral field emission measurements at pressures below 10 -9 mbar. For the microrods (microlines) a voltage of 1100 V (2000 V) was measured for a field emission current of about 0.5 μA with an onset field of about 12 MV/m (24 MV/m). Furthermore, the field enhancement factors for microrods and -lines are in the range of 300 and 200, respectively.}, language = {en} } @inproceedings{BachmannDamsDuesbergetal., author = {Bachmann, Michael and Dams, Florian and D{\"u}sberg, Felix and Hofmann, Martin and Pahlke, Andreas and Langer, Christoph and Ławrowski, Robert Damian and Prommesberger, Christian and Schreiner, Rupert}, title = {Extraction of the characteristics of limiting elements from field emission measurement data}, 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.2016.7551474}, pages = {81 -- 82}, abstract = {In this contribution we will present an algorithm to extract the characteristics of non-Fowler-Nordheim (FN) circuit elements from saturation limited field emission (FE) measurement data. The method for calculating the voltage drop on limiting circuit elements is based on circuit theory as well as Newton's method. Since no assumption on the limiting circuit is made, this method is applicable to any FE data showing saturation. To be able to determine the significance of any parameter output, the uncertainties of data and extracted parameters are fully taken into account throughout the algorithm. External serial resistors and a limiting p-doped substrate are analyzed, where the latter shows a diode-like behavior.}, language = {en} } @inproceedings{LangerPrommesbergerŁawrowskietal., author = {Langer, Christoph and Prommesberger, Christian and Ławrowski, Robert Damian and Schreiner, Rupert and Huang, Yifeng and She, Juncong}, title = {Gated p-Si field emission cathode applied in an ionization vacuum gauge}, 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.2016.7551500}, pages = {145 -- 146}, abstract = {A commercial Bayard-Alpert ionization vacuum gauge was equipped with a field emission electron source based on a cathode consisting of an array of 16 gated, p-doped, and DLC-coated Si-tips and characterized. An anode current of about 1.3 μA led to an ion current of 7 fA at 3×10 -7 mbar and 0.8 pA at 4×10 -5 mbar. Whereas at pressures higher than 4×10 -5 mbar the emission current of the electron source decreased, the ratio of ion and anode current remained linear. A nearly constant sensitivity of ~ 17 mbar -1 of the ionization vacuum gauge within the investigated pressure range was depicted.}, language = {en} } @inproceedings{BachmannDamsDuesbergetal., author = {Bachmann, Michael and Dams, Florian and D{\"u}sberg, Felix and Hofmann, Martin and Pahlke, Andreas and Langer, Christoph and Ławrowski, Robert Damian and Prommesberger, Christian and Schreiner, Rupert}, title = {Control of the electron source current}, series = {International Vacuum Nanoelectronics Conference (IVNC), 30th, 2017, Regensburg}, booktitle = {International Vacuum Nanoelectronics Conference (IVNC), 30th, 2017, Regensburg}, publisher = {IEEE}, doi = {10.1109/IVNC.2017.8051550}, pages = {66 -- 67}, abstract = {A control circuit to stabilize the flux of electrons transmitted through an extractor electrode is presented. By controlling the emission current a fluctuation with a standard deviation of 0.015\% is observed. However, the achievable stability of the transmitted electron current is limited due to a variation of the extraction grid current ratio showing a standard deviation of 4.33\%. By regulating the difference of the emission current and the extraction grid current an improved stability of the transmitted electron current down to a standard deviation of 0.280\% is observed. Even with operation at 2 × 10 -5 mbar a standard deviation of 0.558\% is achieved.}, language = {en} } @inproceedings{ŁawrowskiSchreinerLinghuetal., author = {Ławrowski, Robert Damian and Schreiner, Rupert and Linghu, Shuangyi and Gu, Fuxing}, title = {Field Emission Behaviour of Single-Crystal Pd Nanowires}, series = {33rd International Vacuum Nanoelectronics Conference (IVNC): 6-10 July 2020, Lyon, France}, booktitle = {33rd International Vacuum Nanoelectronics Conference (IVNC): 6-10 July 2020, Lyon, France}, publisher = {IEEE}, isbn = {978-1-7281-9454-7}, doi = {10.1109/IVNC49440.2020.9203510}, pages = {1 -- 2}, abstract = {Single-crystal Pd nanowires with typically 100 nm diameters and lengths from several micrometers to tens of micrometers were grown on Al 2 O 3 substrates in a furnace with Ar atmosphere. Integral field emission measurements of such samples after Pd coating (~10 nm) were performed in a diode configuration with a 50 μm mica spacer in a vacuum chamber at pressures of about 10 -9 mbar. The IV measurement of the sample shows an integral emission current up to 2 μA at a voltage of 500 V (10 MV/m) and an onset voltage for a current of 1 nA of about 275 V. The corresponding Fowler-Nordheim plot show a linear behavior, like expected for a metal needle.}, language = {en} } @inproceedings{PrommesbergerLangerŁawrowskietal., author = {Prommesberger, Christian and Langer, Christoph and Ławrowski, Robert Damian and Schreiner, Rupert}, title = {Benzocyclobutene as a novel integrated spacer material in a field emission electron source}, series = {International Vacuum Nanoelectronics Conference (IVNC), 30th, 2017, Regensburg}, booktitle = {International Vacuum Nanoelectronics Conference (IVNC), 30th, 2017, Regensburg}, publisher = {IEEE}, doi = {10.1109/IVNC.2017.8051605}, pages = {192 -- 193}, abstract = {For the realization of a miniaturized field emission electron source we tested benzocyclobutene (BCB) as a new spacer material between cathode and anode. We fabricated black silicon emitters and characterized the emission behavior with an integrated 5 μm thin and large-area spacer of BCB. The integrated BCB layer allows the realization of a compact electron source with only two components consisting of a cathode with BCB and a grid. The comparison with other spacer materials like polyimide (25 μm thickness) or mica (50 μm thickness) revealed for the cathode with BCB a significantly reduced operational voltage of 240 V for a field emission current of 1 μA.}, language = {en} } @inproceedings{ŁawrowskiLangerPrommesbergeretal., author = {Ławrowski, Robert Damian and Langer, Christoph and Prommesberger, Christian and Schreiner, Rupert}, title = {Light emitting diodes based on three-dimensional epitaxial grown crystalline GaN rods}, series = {7. MikroSystemTechnik Kongress "MEMS, Mikroelektronik, Systeme", 23.-25. Oktober 2017, M{\"u}nchen}, booktitle = {7. MikroSystemTechnik Kongress "MEMS, Mikroelektronik, Systeme", 23.-25. Oktober 2017, M{\"u}nchen}, publisher = {VDE-Verlag}, address = {M{\"u}nchen}, isbn = {978-3-8007-4491-6}, pages = {131 -- 134}, language = {en} } @inproceedings{LindnerBerndtTschurtschenthaletal., author = {Lindner, Matthias and Berndt, Dominik and Tschurtschenthal, Karl and Ehrlich, Ingo and Jungbauer, Bastian and Schreiner, Rupert and Pipa, Andrei V. and Hink, R{\"u}diger and Foest, R{\"u}diger and Brandenburg, Ronny and Neuwirth, Daniel and Karpen, Norbert and Bonaccurso, Elmar and Weichwald, Robert and Max, Alexander and Caspari, Ralf}, title = {Aircraft Icing Mitigation by DBD-based Micro Plasma Actuators}, series = {AIAA AVIATION 2020 FORUM: June 15-19, 2020}, booktitle = {AIAA AVIATION 2020 FORUM: June 15-19, 2020}, doi = {10.2514/6.2020-3243}, abstract = {We present the application of plasma actuators as a technology for ice prevention at airfoils. The miniaturized dielectric barrier discharge (DBD) plasma actuators (PA) were fabricated by means of microelectromechanical systems (MEMS). We elucidate how to make the actuator samples scalable and applicable to any desired shape by the use of flexible inorganic zirconia substrates. For this purpose, we applied our developed embedding method to integrate the micro actuators in modern carbon/glass fiber reinforced polymer (CFRP/GFRP) materials. Next, the embedded actuator samples were mounted on a mechanical air profile-like fixture and placed in the icing wind tunnel iCORE. The samples were tested in rime ice conditions at temperatures of -15 to -20° C and air speeds up to 30 m/s. Unlike other groups we used a thin film zirconia substrate as dielectric for the plasma actuator. Due to the low substrate thickness of just 150 µm, an operating voltage of 2 kVRMS is already sufficient enough for a stable plasma formation. The experiments show that the operated actuator was able to prevent the ice formation and first indications of a De-icing function were also found. Hence, we show that it is feasible to realize an anti-icing system with zirconia-based plasma actuators operated at lower voltages compared to conventional ones.}, language = {en} } @article{ŁawrowskiHausladenBuchneretal., author = {Ławrowski, Robert Damian and Hausladen, Matthias and Buchner, Philipp and Schreiner, Rupert}, title = {Silicon Field Emission Electron Source With Individually Controllable Single Emitters}, series = {IEEE Transactions on Electron Devices}, volume = {68}, journal = {IEEE Transactions on Electron Devices}, number = {8}, publisher = {IEEE}, doi = {10.1109/TED.2021.3093374}, pages = {4116 -- 4122}, abstract = {An electron source with an array of individually controllable single tips allows the observation of each emitter current simultaneously as well as the measurement of the integral current. Furthermore, the initial activation process of the individual tips and current distribution of the source can be examined. The Si cathode consists of an array of 2 x 2 conically shaped emitter structures on a borosilicate glass substrate. The emitters were fabricated by laser micromachining and wet etching. Integral field emission (FE) measurements were performed in a diode configuration in a vacuum chamber at pressures of about 10(-9) mbar with a self-aligned Si extraction grid, due to adjustment pins. The total emission current was regulated to a predefined value (4.0, 10, 20, 40, and 50 mu A) by an external regulating circuit and recorded individually during the measurement. The onset voltage for a current of 1 nA varied between 320 and 430 V. The voltage conversion factor is in the range of 7.6 x 10(4) cm(-1) to 1.3 x 10(5) cm(-1). Constant currentmeasurementsover a longer periodof time (1800 values with a sample rate of 0.5 Hz) were performed and show a total current fluctuation less than 0.6\% due to the regulation circuit. Despite the stable total current in regulated operation, it was observed that the individual emitters fluctuate up to 75\% for low (similar to 10(-8) A) and 5\% for high (similar to 10(-5) A) currents.}, language = {en} } @article{BachmannDuesbergPahlkeetal., author = {Bachmann, Michael and D{\"u}sberg, Felix and Pahlke, Andreas and Edler, Simon and Schels, Andreas and Herdl, Florian and Ławrowski, Robert Damian and Schreiner, Rupert}, title = {High current silicon nanowire field emitter arrays}, series = {Journal of Vacuum Science \& Technology B}, volume = {40}, journal = {Journal of Vacuum Science \& Technology B}, number = {1}, publisher = {AIP Publishing}, doi = {10.1116/6.0001639}, abstract = {Arrays of n-doped silicon nanowire field emitters with a high aspect ratio are realized by a novel dry etching technique. Compared to the high current silicon emitters in the literature, the manufacturing process is much simpler and requires only a single photolithography step and two dry etching steps. The cathodes realized with this method exhibit a total current of 20 mA from an active area of 4×4 mm2, which is significantly higher than that for most known structures made from silicon and also represents good performance in comparison with other emitter types, e.g., carbon nanotubes. In addition to characterization in ultrahigh vacuum, measurements at 10-5 mbar are performed and compared with our recent silicon emitters. Compared to these cathodes, the structures with the nanowires exhibit at least two orders of magnitude higher current-carrying capability.}, language = {en} } @article{RemskarHuettelShubinaetal., author = {Remskar, Maja and H{\"u}ttel, Andreas K. and Shubina, Tatiana V. and Seabaugh, Alan and Fathipour, Sara and Ławrowski, Robert Damian and Schreiner, Rupert}, title = {Confinement Related Phenomena in MoS2 Tubular Structures Grown from Vapour Phase}, series = {Israel Journal of Chemistry}, volume = {62}, journal = {Israel Journal of Chemistry}, number = {3-4}, publisher = {Wiley}, issn = {1869-5868}, doi = {10.1002/ijch.202100100}, pages = {1 -- 11}, abstract = {We review recently discovered phenomena observed in the MoS2 tubular structures, which were synthesized by a lasting chemical transport reaction nearly at chemical equilibrium. Such MoS2 nanotubes are distinguished by low density of structural defects, thin walls and a high aspect ratio, which intrinsically provide a confined, edge-free geometry. Quantum confinement with single electron conductance was recorded and a bright exciton photoluminescence with appearance of whispering gallery modes was observed. In addition, the field-effect transistors and field emitters based on single MoS2 nanotubes were demonstrated. These discoveries revitalize research of MoS2 curved structures grown from vapour phase, which were reported several decades ago.}, language = {en} } @inproceedings{ŁawrowskiBachmannSchreiner, author = {Ławrowski, Robert Damian and Bachmann, Michael and Schreiner, Rupert}, title = {Field Emission Arrays from Graphite Fabricated by Laser Micromachining}, series = {34th International Vacuum Nanoelectronics Conference (IVNC): 7/5/2021 - 7/9/2021, Lyon, France}, booktitle = {34th International Vacuum Nanoelectronics Conference (IVNC): 7/5/2021 - 7/9/2021, Lyon, France}, publisher = {IEEE}, isbn = {978-1-6654-2589-6}, doi = {10.1109/IVNC52431.2021.9600736}, pages = {1 -- 2}, abstract = {Arrays of 4x4 conical shaped emitters were directly structured by laser micromaching. Assembled as an electron source with a spacer and Si-grid, they were investigated by means of IV-measurement in ultra-high vacuum. The IV-measurements of the sample show integral emission currents up to 10 µA at a voltage of 1000 V (11 MV/m). Initially, an ideal FN-behaviour is noticeable. The deviation for higher voltage values in the FN-plot is caused by the change of the work function, which was proven by numerical calculations.}, language = {en} } @inproceedings{LindnerBerndtJungbaueretal., author = {Lindner, Matthias and Berndt, Dominik and Jungbauer, Bastian and Ehrlich, Ingo and Schreiner, Rupert and Pipa, Andrei V. and Hink, R{\"u}diger and Foest, R{\"u}diger and Brandenburg, Ronny and Max, Alexander and Caspari, Ralf}, title = {Fabrication, surface integration and testing of miniaturized dielectric barrier discharge plasma actuators for active flow control applications}, series = {AIAA Aviation 2019 Forum, 17-21 June 2019, Dallas, Texas}, booktitle = {AIAA Aviation 2019 Forum, 17-21 June 2019, Dallas, Texas}, doi = {10.2514/6.2019-2998}, language = {en} } @inproceedings{LangerŁawrowskiPrommesbergeretal., author = {Langer, Christoph and Ławrowski, Robert Damian and Prommesberger, Christian and Dams, Florian and Serbun, Pavel and Bachmann, Michael and M{\"u}ller, G{\"u}nter and Schreiner, Rupert}, title = {High aspect ratio silicon tip cathodes for application in field emission electron sources}, 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.2014.6894824}, pages = {222 -- 223}, abstract = {Precisely aligned arrays of sharp tip structures on top of elongated pillars were realized by using an improved fabrication process including an additional inductively-coupled-plasma reactive-ion etching step. Arrays of n-type and p-type silicon with 271 tips have been fabricated and investigated. Those structures have a total height of 5-6 µm and apex radii less than 20nm. Integral field emission measurements of the arrays yielded low onset-fields in the range of 8-12V=µm and field enhancement factors between 300 and 700. The I-E curves of n-type structures showed the usual Fowler-Nordheim behaviour, whereas p-type structures revealed a significant saturation region due to the limited number of electrons in the conduction band and a further carrier depletion effect caused by the pillar. The maximum integral current in the saturation region was 150 nA at fields above 30V=µm. An excellent stability of the emission current of less than ± 2\% fluctuation was observed in the saturation region. For n-type Si a maximum integral current of 10 µA at 24V=µm and an average current stability with a fluctuation of ± 50\% were measured.}, language = {en} } @article{BachmannDuesbergLangeretal., author = {Bachmann, Michael and D{\"u}sberg, Felix and Langer, Christoph and Herdl, Florian and Bergbreiter, Lukas and Dams, Florian and Miyakawa, Natuski and Eggert, Tobias and Pahlke, Andreas and Edler, Simon and Prommesberger, Christian and Ławrowski, Robert Damian and Hausladen, Matthias and Schreiner, Rupert}, title = {Vacuum-sealed field emission electron gun}, series = {Journal of Vacuum Science \& Technology B}, volume = {38}, journal = {Journal of Vacuum Science \& Technology B}, number = {2}, publisher = {AIP Publishing}, doi = {10.1116/1.5139316}, abstract = {A compact vacuum-sealed field emission electron gun with an operation voltage below 5 kV is presented. With a 150 nm thick pyrolytic carbon membrane, a transmission of 40\% at 5 kV is obtained. For more than 2500 h of continuous operation at an emission current of 100 nA, no significant increase (<50V ) and almost no degradation were found. From this measurement, a lifetime of more than 10 000 h at continuous operation with approximately a linear increase of the extraction voltage from about 545 V to about 730 V is predicted. This electron source enables application of field emitter arrays in poor vacuum or even ambient pressure. ACKNOWLEDGMENT This work was supported by the German Federal Ministry for Economic Affairs and Energy under Project No. ZF4081502GM8. C.P., R.L., M.H., and R.S. were supported by Grant No. ZF4562901GM8.}, language = {en} } @article{LangerPrommesbergerŁawrowskietal., author = {Langer, Christoph and Prommesberger, Christian and Ławrowski, Robert Damian and Dams, Florian and Schreiner, Rupert}, title = {Simulation and Fabrication of Silicon Field Emission Cathodes for Cold Electron Sources}, series = {Advanced Materials Research}, volume = {1024}, journal = {Advanced Materials Research}, doi = {10.4028/www.scientific.net/amr.1024.48}, pages = {48 -- 51}, abstract = {We report on the simulation and fabrication of nanostructured silicon surfaces for field emission (FE) applications, e.g. ionization sensors and x-ray tubes. For the design and optimization of field-emitting silicon structures, the influence of the geometric parameters like tip height, apex radius, aperture angle and curvature shape on the field enhancement factor was investigated by simulation using finite element method. A universal geometric model which describes the real geometry of our silicon structures sufficiently accurate was taken for modeling a variety of different silicon tip structures as well as ridge structures. While a high dependency of the field enhancement on the aspect ratio and the aperture angle was found, the simulations show that the elliptic curvature affects the field enhancement only marginally. Finally, an improved process for fabrication of such silicon structures on n-type as well as p-type substrate is described, using reactive ion etching with adjustable anisotropy, wet thermal oxidation and wet etching.}, language = {en} } @article{ŁawrowskiBachmannSchreiner, author = {Ławrowski, Robert Damian and Bachmann, Michael and Schreiner, Rupert}, title = {Field emission arrays from graphite fabricated by laser micromachining}, series = {Journal of Vacuum Science \& Technology B}, volume = {40}, journal = {Journal of Vacuum Science \& Technology B}, number = {2}, publisher = {AIP Publishing}, doi = {10.1116/6.0001547}, abstract = {Laser micro structuring allows the manufacturing of conical shaped emitters on a graphitized carbon substrate without any additional treatment. Integral field emission measurements were performed in a diode configuration with a 50 µm mica spacer and a metalized Si-grid in a vacuum chamber at pressures of about 10-9 mbar. Emission currents up to 10 µA at a voltage of 1000 V (11 MV/m) with a positive current drift were observed for an array of 16 emitters. A strong modification of the emitter tip is noticeable after individual measurements. A comparable alteration of the surface is also achieved by an electrochemical treatment of the samples with a potassium hydroxide solution. However, the IV-measurements of such samples show higher onset voltages, but also higher integral emission currents. For all arrays an ideal FN behaviour is only noticeable at applied voltages below 625 V (7 MV/m). Numerical calculations indicate that the deviation in the FN-plot for higher voltage values is caused by the change of the effective work function.}, language = {en} } @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{ŁawrowskiDemlVargheseetal., author = {Ławrowski, Robert Damian and Deml, Sonja and Varghese, T. and Schimpke, T.}, title = {Leuchtdiodenchips mit dreidimensional epitaktisch gewachsenen kristallinen GaN S{\"a}ulen}, series = {7. MikroSystemTechnik Kongress "MEMS, Mikroelektronik, Systeme", 23.-25. Oktober 2017, M{\"u}nchen}, booktitle = {7. MikroSystemTechnik Kongress "MEMS, Mikroelektronik, Systeme", 23.-25. Oktober 2017, M{\"u}nchen}, publisher = {VDE-Verlag}, address = {M{\"u}nchen}, isbn = {978-3-8007-4491-6}, pages = {131 -- 134}, abstract = {Um die Eigenschaften von Leuchtdioden zu verbessern und den Herstellungsprozess zu vereinfachen, wurde ein erweitertes Verfahren der metallorganischen Gasphasenepitaxie verwendet, um dichtgepackte dreidimensionale GaN-S{\"a}ulen mit hohen Aspektverh{\"a}ltnis auf Chipoberfl{\"a}chen zu wachsen. Diese selbstorganisierenden dreidimensionalen Strukturen sollen einerseits die lichtabstrahlende Oberfl{\"a}che der Leuchtdiode bei gleichbleibender Chipgr{\"o}ße vergr{\"o}ßern und andererseits durch die nichtpolaren Kristallebenen an den Seiten- und Deckfl{\"a}chen der S{\"a}ulen die Effizienz dieser Bauteile erh{\"o}hen. Messungen an ersten Bauteilen, die mit dieser Methode realisiert wurden, zeigen eine homogene blaue Emission bei Wellenl{\"a}ngen 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.}, 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} } @incollection{ŁawrowskiPrommesbergerLangeretal., author = {Ławrowski, Robert Damian and Prommesberger, Christian and Langer, Christoph and Dams, Florian and Schreiner, Rupert}, title = {Feldemissionselektronenquellen basierend auf Siliziumemittern mit hohen Aspektverh{\"a}ltnis}, series = {Forschungsbericht der OTH Regensburg 2013}, booktitle = {Forschungsbericht der OTH Regensburg 2013}, address = {Regensburg}, pages = {47 -- 48}, language = {de} } @article{LindnerPipaBrandenburgetal., author = {Lindner, Matthias and Pipa, Andrei V. and Brandenburg, Ronny and Schreiner, Rupert}, title = {Expansion of surface barrier discharge scrutinized}, series = {Plasma Sources Science and Technology}, volume = {31}, journal = {Plasma Sources Science and Technology}, number = {10}, publisher = {IOP Publishing}, doi = {10.1088/1361-6595/ac95bf}, abstract = {Developing the fundamentals for the electrical diagnostics of surface dielectric barrier discharges (SDBDs) is of enormous importance for several applications, for example, flow control and gas cleaning. The main challenge is to account for the discharge expansion along the dielectric surface. Typically, a linear expansion with the amplitude of the applied voltage is observed. In this work, we report on a step-wise SDBD expansion along the Al 2 O 3 dielectric surface. More specific, the discharge occupied a certain area after ignition, which remained constant until the voltage exceeded the critical amplitude V L . This absence of expansion is seen as a linear dependence of the discharge power on the applied voltage and it was additionally confirmed by photographs with long exposure times. This novel phenomenon is more pronounced for thicker dielectrics. It is suggested that the derivative of the charge-voltage characteristics can be used for the determination of all essential parameters of the simplest equivalent circuit of SDBDs. Moreover, it was shown that the derivative of the charge-voltage characteristics for the positive half-cycle of the discharge agrees numerically with the voltage dependence of the reactor capacitance derived from photographs. This agreement between both measurement methods indicates a similar step-wise expansion of the SDBD even if a voltage amplitude above V L is applied. …}, language = {en} } @inproceedings{MingelsBornmannLuetzenkirchenHechtetal., author = {Mingels, Stephan and Bornmann, Benjamin and L{\"u}tzenkirchen-Hecht, Dirk and M{\"u}ller, G{\"u}nter and Langer, Christoph and Prommesberger, Christian and Schreiner, Rupert}, title = {Electric Field Dependence of Photoemission from n- and p-type Si Crystals}, series = {Proceedings, 35th International Free Electron Laser Conference (FEL 2013) : New York, NY, USA, August 26-19, 2013}, booktitle = {Proceedings, 35th International Free Electron Laser Conference (FEL 2013) : New York, NY, USA, August 26-19, 2013}, editor = {Scholl, Caitlin and Schaa, Volker R.W.}, publisher = {Curran}, address = {Red Hook, NY}, isbn = {9783954501267}, pages = {339 -- 343}, abstract = {The performance of free electron lasers depends on the brilliance of the electron source. Nowadays photo-cathodes (e.g. Cs2Te) are used despite of their high emittance. To develop robust and more brilliant cathodes we have built up an UHV system which enables systematic photoemission (PE) measurements with a tunable pulsed laser (hv) at high electric fields (E). First results on Au and Ag crystals revealed only low quantum efficiency (QE) due to fast electron relaxation. Hence, we have started QE(hv,E) investigations on n- and p-Si wafers. Resonant PE was observed above as well as below the work function O, which can be assigned to optical transitions in the electronic band structure or explained by thermally excited states at the bottom of the conduction band. As expected, only low QE values were achieved even for n-Si probably due to surface oxide. Moreover, a significant rise of the QE peaks above O were obtained for n-Si at E >8 MV/m but limited by the occurrence of parasitic field emission from dust particles.}, language = {en} } @inproceedings{SchreinerPrommesbergerLangeretal., author = {Schreiner, Rupert and Prommesberger, Christian and Langer, Christoph and Dams, Florian and Serbun, Pavel and Bornmann, Benjamin and Navitski, Aliaksandr and M{\"u}ller, G{\"u}nter}, title = {Highly uniform and stable electron field emission from B-doped Si-tip arrays for applications in integrated vacuum microelectronic devices}, series = {25th International Vacuum Nanoelectronics Conference (IVNC) - Jeju, Korea (South), 09.07. - 13.07.2012}, booktitle = {25th International Vacuum Nanoelectronics Conference (IVNC) - Jeju, Korea (South), 09.07. - 13.07.2012}, publisher = {IEEE}, address = {Piscataway, NJ.}, isbn = {978-1-4673-1984-3}, issn = {2380-6311}, doi = {10.1109/IVNC.2012.6316857}, pages = {1 -- 2}, abstract = {In order to improve the uniformity and field emission stability of p-type silicon tip arrays for pulsed sensor applications, we have systematically studied the influence of the fabrication parameters on the tip shape and the specific operating conditions. Based on detailed design calculations of the field enhancement, we have fabricated a series of hexagonal arrays of B-doped Si-tips in a triangular arrangement, each containing a different number of tips (91, 575 and 1300) of 1 μm height, 20 nm apex radius, and 20 μm pitch. The field emission properties of both individual tips and complete arrays were investigated with by field emission scanning microscopy. The current plateaus of these tips typically occur at about 10 nA and 60 V/μm field level. In this carrier depletion range, single tips provide the highest current stability (<; 4\%) and optical current switching ratios of ~2.5. Rather homogeneous emission of the tip arrays leads to an almost linear scaling of the saturation current (2 nA/tip) and to a much improved current stability (<; 1\%) measured over 1 hour.}, language = {en} }