@misc{LautenschlaegerLeisDendorferetal., author = {Lautenschl{\"a}ger, Toni and Leis, Alexander and Dendorfer, Sebastian and Palm, Christoph and Schreiner, Rupert and Langer, Christoph and Prommesberger, Christian and Ławrowski, Robert Damian and Dams, Florian and Bornmann, Benjamin and Navitski, Aliaksandr and Serbun, Pavel and M{\"u}ller, G{\"u}nter and Liebetruth, Thomas and Kohlert, Dieter and Pernsteiner, Jochen and Schreier, Franz and Heerklotz, Sabrina and Heerklotz, Allwin and Boos, Alexander and Herwald, Dominik and Monkman, Gareth J. and Treiber, Daniel and Mayer, Matthias and H{\"o}rner, Eva and Bentz, Alexander and Shamonin (Chamonine), Mikhail and Johansen, S{\o}ren Peter and Reichel, Marco and Stoll, Andrea and Briem, Ulrich and Dullien, Silvia and Renkawitz, Tobias and Weber, Tim and Dendorfer, Sebastian and Grifka, Joachim and Penzkofer, Rainer and Barnsteiner, K. and Jovanovik, M. and Wernecke, P. and V{\"o}gele, A. and Bachmann, T. and Pl{\"o}tz, Martin and Schliekmann, Claus and Wels, Harald and Helmberger, Paul and Kaspar, Marcel and H{\"o}nicka, M. and Schrammel, Siegfried and Enser, Markus and Schmidmeier, Monika and Schroll-Decker, Irmgard and Haug, Sonja and Gelfert, Verena and Vernim, Matthias}, title = {Forschungsbericht 2012}, editor = {Baier, Wolfgang}, address = {Regensburg}, organization = {Ostbayerische Technische Hochschule Regensburg}, doi = {10.35096/othr/pub-783}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-7834}, pages = {64}, language = {de} } @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{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} }