@inproceedings{PrommesbergerDamsLangeretal., author = {Prommesberger, Christian and Dams, Florian and Langer, Christoph and Schreiner, Rupert and Rutkowski, S. and Bornmann, Benjamin and M{\"u}ller, G{\"u}ntner}, title = {Simulation of electron trajectories of a field emission electron source in triode configuration by using finite element methods}, series = {24th International Vacuum Nanoelectronics Conference (IVNC), 2011 : 18 - 22 July 2011, Historische Stadthalle Wuppertal, Germany}, booktitle = {24th International Vacuum Nanoelectronics Conference (IVNC), 2011 : 18 - 22 July 2011, Historische Stadthalle Wuppertal, Germany}, publisher = {IEEE}, address = {Piscataway, NJ}, isbn = {978-3-00-035081-8}, issn = {2380-6311}, pages = {144 -- 145}, abstract = {The finite element simulation program COMSOL Multiphysics® was used to simulate the emission efficiency of a silicon tip electron source in triode configuration for different geometries and electrode potentials. The simulation predicts a maximum emission efficiency of 84\% for an optimized structure. In a second simulation a gate electrode was concentrically arranged above a single CNT column. Here, the efficiency was simulated as a function of gate hole geometry, electrode potentials and distances between the electrodes. The simulation shows that a conical shape of the gate hole results in an efficiency up to nearly 100\%.}, language = {en} } @inproceedings{BornmannMingelsSerbunetal., author = {Bornmann, Benjamin and Mingels, Stephan and Serbun, Pavel and L{\"u}tzenkirchen-Hecht, Dirk and M{\"u}ller, G{\"u}ntner and Prommesberger, Christian and Langer, Christoph and Dams, Florian and Schreiner, Rupert}, title = {Photosensitivity of electron field emission from B-doped Si-tip arrays}, series = {25th International Vacuum Nanoelectronics Conference (IVNC) ; Jeju, Korea (South), 09.07.2012 - 13.07.2012}, booktitle = {25th International Vacuum Nanoelectronics Conference (IVNC) ; Jeju, Korea (South), 09.07.2012 - 13.07.2012}, publisher = {IEEE}, isbn = {978-1-4673-1984-3}, issn = {2380-6311}, doi = {10.1109/IVNC.2012.6316980}, pages = {1 -- 2}, abstract = {The electron current from field-emitting B-doped Si-tip arrays under illumination was studied. An improved cathode design with a patch of 271 tips yielded a reproducible cathode current between 0.2-2000 nA in the electric field range of 3.8-6.6 V/μm. The plateau in the Fowler-Nordheim plot shows the actual carrier depletion and leads to a very stable emission at ~1 μA with a current noise of less than 3.3 \%. Color-filtered halogen lamp illumination was used to investigate the photo-sensitivity of the saturation current. The intensity-normalized current switching ratio increases nonlinearly with the photon energy. This hints either for secondary generation in the conduction band or deeper valence band excitation. The first is supported by a rough estimation of the quantum efficiency. Further experiments with a tunable laser and electron spectroscopy are planned.}, language = {en} } @inproceedings{SerbunNavitskiMuelleretal., author = {Serbun, Pavel and Navitski, Aliaksandr and M{\"u}ller, G{\"u}ntner and Schreiner, Rupert and Prommesberger, Christian and Langer, Christoph and Dams, Florian}, title = {Scaling of the field emission current from B-doped Si-tip arrays}, series = {25th International Vacuum Nanoelectronics Conference (IVNC) ; Jeju, Korea (South), 09.07.2012 - 13.07.2012}, booktitle = {25th International Vacuum Nanoelectronics Conference (IVNC) ; Jeju, Korea (South), 09.07.2012 - 13.07.2012}, publisher = {IEEE}, address = {Piscataway, N.J.}, isbn = {978-1-4673-1984-3}, issn = {2380-6311}, doi = {10.1109/IVNC.2012.6316965}, pages = {1 -- 2}, abstract = {We have fabricated a test chip with various hexagonal arrays of B-doped Si tips (height ~ 3 μm, apex radius <; 30 nm, number 1-4447, resistivity 4 Ωcm, 100 orientation) in triangular arrangement (pitch 10 μm, density 1.16×10 6 cm -2 ) in order to systematically investigate the field emission current scaling with the number N of tips. Regulated voltage scans for 1 nA revealed rather efficient emission from nearly all tips of the arrays at an average field of 15 V/μm. The expected current plateau was always obtained at fields around 20 V/μm, but its width strongly increased with N. In this carrier depletion range, the single tip provided a much higher stability (<; 5\%) of the current (2-3 nA) than at lower (>; 50 \%) and higher currents (>; 30\%). Integral current measurements of the hexagonal arrays resulted in a statistically improved current stability (<; 1\%) but only a weak increase of the total current with N 0.28 yet. These results will be discussed with respect to the remaining inhomogeneity of the tips.}, 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{DamsNavitskiPrommesbergeretal., author = {Dams, Florian and Navitski, Aliaksandr and Prommesberger, Christian and Serbun, Pavel and Langer, Christoph and M{\"u}ller, G{\"u}nter and Schreiner, Rupert}, title = {Homogeneous Field Emission Cathodes With Precisely Adjustable Geometry Fabricated by Silicon Technology}, series = {IEEE Transactions on Electron Devices}, volume = {59}, journal = {IEEE Transactions on Electron Devices}, number = {10}, publisher = {IEEE}, issn = {0018-9383}, doi = {10.1109/TED.2012.2206598}, pages = {2832 -- 2837}, abstract = {Silicon-based cathodes with precisely aligned field emitter arrays of sharp tips applicable for miniaturized electron sources were successfully fabricated and characterized. This was made possible by an improved fabrication process using wet thermal oxidation, wet etching, and reactive-ion etching steps with adjustable anisotropy. As substrate materials, both p-doped silicon and n-doped silicon were used. The cathode chips contain about 3 × 10 5 Si tips/cm 2 in a triangular array with tip heights of 2.5 μm, tip radii of less than 30 nm, and spacing of 20 μm. Well-aligned field emission (FE) and excellent homogeneity from all tips (i.e., 100\% efficiency) and maximum stable currents of typically 0.1 μA (0.6 μA) for p (n)-type Si were reproducibly achieved. The current-voltage characteristics of the p-Si tips exhibit the expected saturation at around 10 nA with around ten times better current stability, whereas the n-Si tips show the usual Fowler-Nordheim behavior. Additional coating of the Si tips with 5-nm Cr and 10-nm Au layers resulted in improved stability and at least five times higher average FE current limits (about 3 μA) at about 30\% higher operation voltage.}, language = {en} } @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} } @article{LangerBerndtSchreiner, author = {Langer, Christoph and Berndt, Dominik and Schreiner, Rupert}, title = {Sensitivity of thermal conductivity vacuum gauges for constant current and constant temperature operation}, series = {Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics}, volume = {40}, journal = {Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics}, number = {5}, publisher = {AIP Publishing}, doi = {10.1116/6.0001964}, abstract = {To optimize the measurement range of thermal conductivity vacuum gauges, an expression for the sensitivity is required that takes into account all geometrical, material-specific, and operating parameters. Therefore, equations of the sensor output signal as a function of the pressure for the constant current and the constant temperature mode have been developed analytically. Based on these equations, the sensitivity of the vacuum gauge and its influencing parameters was investigated and discussed. For comparable conditions, the constant temperature operation shows a significantly higher sensitivity for high pressures, while the constant current operation shows higher sensitivity at low pressures. The sensitivity in both the constant current and the constant temperature mode depends on the ratio of the filament surface area and the parasitic thermal conductance. In addition, for the constant current operation, the sensitivity also depends on the current value and the temperature coefficient of the filament resistor. For the constant temperature operation, the sensitivity additionally depends on the distance of the filament and the reference plane. However, to extend the measurement range of a thermal conductivity vacuum gauge toward low pressures, a reduction of the parasitic thermal conductance is mandatory for both the constant current and the constant temperature mode.}, 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} } @inproceedings{MingelsPorshynSerbunetal., author = {Mingels, S. and Porshyn, V. and Serbun, Pavel and L{\"u}tzenkirchen-Hecht, Dirk and M{\"u}ller, G{\"u}nter and Prommesberger, Christian and Langer, Christoph and Schreiner, Rupert and Lutzenkirchen-Hecht, Dirk}, title = {Photo-enhanced field emission properties of p-doped black Si arrays}, series = {2016 29th International Vacuum Nanoelectronics Conference (IVNC), 11-15 July 2016, Vancouver, BC, Canada}, booktitle = {2016 29th International Vacuum Nanoelectronics Conference (IVNC), 11-15 July 2016, Vancouver, BC, Canada}, publisher = {IEEE}, doi = {10.1109/IVNC.2016.7551447}, pages = {1 -- 2}, abstract = {We have carried out systematic investigations of p-type black Si field emitter arrays under laser illumination. As expected the current-voltage characteristic revealed a strong saturation providing a high photosensitivity, which had a maximum on-off ratio of 43 at a maximum current of 13 μA. The saturation current was stable in the dark as well as under illumination with fluctuations <;0.7\%. Results from time-resolved measurements of the photo-sensitivity showed a rather fast response but a long decay time. Electron spectra in the dark and under laser illumination revealed the origin of the emission.}, 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} }