@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{KleshchSerbunOrekhovetal., author = {Kleshch, Victor I. and Serbun, Pavel and Orekhov, Anton and L{\"u}tzenkirchen-Hecht, Dirk and Obraztsov, Alexander N. and Prommesberger, Christian and Langer, Christoph and Schreiner, Rupert and Lutzenkirchen-Hecht, Dirk}, title = {Field emission properties of p-type silicon tips decorated with tungsten nanoparticles}, series = {2017 30th International Vacuum Nanoelectronics Conference (IVNC), 10-14 July 2017, Regensburg, Germany}, booktitle = {2017 30th International Vacuum Nanoelectronics Conference (IVNC), 10-14 July 2017, Regensburg, Germany}, publisher = {IEEE}, doi = {10.1109/IVNC.2017.8051580}, pages = {138 -- 139}, abstract = {An array of conical-shaped p-type silicon tips was fabricated by using reactive ion etching and sharpening oxidation. The apex of each tip was decorated by a tungsten hemispherical nanoparticle. Field emission properties of the tips were measured by a tungsten-needle anode positioned above the tip apex. Tips decorated with tungsten nanoparticles demonstrated a smaller saturation region in current-voltage characteristics compared to the pristine tips. An emission activation process, which consisted in sudden current increase at certain value of applied voltage, was observed for the decorated silicon tips. This behavior was explained by the formation of vertical protrusions extending from the metal particles revealed by scanning electron microscopy after field emission experiments.}, language = {en} } @article{KleshchSerbunLuetzenkirchenHechtetal., author = {Kleshch, Victor I. and Serbun, Pavel and L{\"u}tzenkirchen-Hecht, Dirk and Orekhov, Anton S. and Ivanov, Victor E. and Prommesberger, Christian and Langer, Christoph and Schreiner, Rupert and Obraztsov, Alexander N.}, title = {A Comparative Study of Field Emission from Pristine, Ion-treated and Tungsten Nanoparticle-decorated p-type Silicon Tips}, series = {Physica Status Solidi B}, volume = {256}, journal = {Physica Status Solidi B}, number = {9}, publisher = {Wiley}, doi = {10.1002/pssb.201800646}, abstract = {The field electron emission characteristics of individual tips of a silicon field emitter array are analyzed. The array of conical-shaped tips is fabricated on a p-type silicon wafer by using reactive ion etching and sharpening oxidation. The tips are decorated with single tungsten nanoparticles at their apexes. Furthermore, the focused ion beam is also used to increase surface conductivity of some of the tips. Comparative measurements of field emission are performed by using the scanning anode probe field emission microscopy technique. All types of tips demonstrated emission activation consisting of a sudden current increase at a certain value of the applied voltage. Compared to the pristine tips, a noticeable reduction of the saturation effect in the current-voltage characteristics and a smaller light sensitivity for the decorated tips is found. For ion-treated tips, saturation effects and light sensitivity are completely suppressed. Scanning electron microscopy observations reveal the formation of single nanoscale protrusions extending from the metal particles and from the apexes of bare ion-treated tips after exposure under strong electric fields during the field emission measurements. The influence of protrusions growth on characteristics of silicon field emitter arrays is discussed.}, 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{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} } @article{MingelsPorshynPrommesbergeretal., author = {Mingels, S. and Porshyn, V. and Prommesberger, Christian and Langer, Christoph and Schreiner, Rupert and L{\"u}tzenkirchen-Hecht, Dirk and M{\"u}ller, G{\"u}nter}, title = {Photosensitivity of p-type black Si field emitter arrays}, series = {Journal of Applied Physics}, volume = {119}, journal = {Journal of Applied Physics}, number = {16}, doi = {10.1063/1.4948328}, abstract = {We have investigated the properties of black Si field emitter arrays under strong electric fields and laser illumination. A low onset field of 1.8 MV/m for an emission current of 1 nA was obtained. A pronounced saturation region of the dark and photo-enhanced current was observed, which provided a short-term stability of 0.1\% at 0.4 μA and 0.7\% at 1.0 μA, respectively. As maximum value for the photosensitivity, an on-off current switching ratio of 43 reaching about 13 μA was achieved at a laser power of 15 mW. Electron spectra in the dark and under laser illumination are presented, showing a current and light-sensitive voltage drop across the emitters as well as hints for hot electron emission.}, language = {en} } @inproceedings{MingelsBornmannLuetzenkirchenHechtetal., author = {Mingels, Stephan and Bornmann, Benjamin and L{\"u}tzenkirchen-Hecht, Dirk and M{\"u}ller, G{\"u}ntner 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{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} } @article{BornmannMingelsDamsetal., author = {Bornmann, Benjamin and Mingels, Stephan and Dams, Florian and Prommesberger, Christian and Schreiner, Rupert and L{\"u}tzenkirchen-Hecht, Dirk and M{\"u}ller, G{\"u}ntner}, title = {Electron spectrometer in adjustable triode configuration for photo-induced field emission measurements}, series = {The Review of scientific instruments}, volume = {83}, journal = {The Review of scientific instruments}, number = {1}, publisher = {American Institute of Physics}, address = {Melville, NY}, doi = {10.1063/1.3673475}, abstract = {We have constructed a new ultrahigh vacuum apparatus with a triode configuration for the systematic investigation of photo-induced field emission (PFE) from metallic or semiconducting cathodes. These are exposed to electric fields up to 400 MV∕m and laser irradiation by means of hole or mesh gates. Cathodes and gates are in situ exchangeable and adjustable with high precision to ensure a homogeneous extraction of electrons which are partially transmitted to the fixed electron spectrometer. Its hemispherical sector analyzer provides an energy resolution limit of 8 meV. The commissioning of the measurement system has been performed with a tungsten needle. Its temperature showed up in the high-energy tail of the electron spectrum, while its work function was derived from the spectral low-energy part combined with the integral current-voltage curve. First PFE measurements on B-doped Si-tip arrays yielded a small field emission current increase under green laser illumination. A shift and splitting of the energy spectra was observed which revealed different emission regimes as well as the photosensitivity of the cathode due to carrier excitation into the conduction band. For the full exploitation of the PFE system, a tunable laser over a wide eV-range is required.}, language = {en} } @inproceedings{BornmannMingelsLuetzenkirchenHechtetal., author = {Bornmann, Benjamin and Mingels, Stephan and L{\"u}tzenkirchen-Hecht, Dirk and M{\"u}ller, G{\"u}ntner and Dams, Florian and Schreiner, Rupert}, title = {Field emission spectroscopy studies on photo-sensitive p-doped Si-tip arrays}, 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}, isbn = {978-3-00-035081-8}, issn = {2380-6311}, pages = {101 -- 102}, abstract = {The influence of laser illumination on the integral as well as on the energy-resolved electron currents from well-defined p-doped Si-tip arrays was investigated. First results have provided stable cathode currents between 100 nA and 500 μA in a field range of 2-20 V/μm. Green laser illumination resulted in an enhanced cathode current and an increased population of the conduction band which can be seen in the spectra. Charging of the cathode surface, however, leads to a shift and broadening of the spectra which complicate their analysis. Therefore, further experiments with a rotatable cathode and a varying number of tips as well as with a tunable laser are planned.}, language = {en} }