@article{SchelsEdlerHerdletal., author = {Schels, Andreas and Edler, Simon and Herdl, Florian and Hansch, Walter and Bachmann, Michael and Ritter, Daniela and Dudeck, Markus and Duesberg, Felix and Meyer, Manuel and Pahlke, Andreas and Hausladen, Matthias and Buchner, Philipp and Schreiner, Rupert}, title = {In situ quantitative field emission imaging using a low-cost CMOS imaging sensor}, series = {Journal of Vacuum Science \& Technology B}, volume = {40}, journal = {Journal of Vacuum Science \& Technology B}, number = {1}, publisher = {AIP Publishing}, doi = {10.1116/6.0001551}, abstract = {Spatially resolved field emission measurements represent an important factor in further development of existing field emitter concepts. In this work, we present a novel approach that allows quantitative analysis of individual emission spots from integral current-voltage measurements using a low-cost and commercially available CMOS camera. By combining different exposure times to extrapolate oversaturated and underexposed pixels, a near congruence of integral current and image brightness is shown. The extrapolation also allows parallel investigation of all individual tips participating in the total current with currents ranging from a few nanoampere to one microampere per tip. The sensitivity, which is determined by the integral brightness-to-current ratio, remains unchanged within the measurement accuracy even after ten full measurement cycles. Using a point detection algorithm, the proportional current load of each individual tip of the field emitter array is analyzed and compared at different times during the initial measurement cycle. Together with the extracted I-V curves of single emission spots from the integral measurement, the results indicate the effect of premature burnout of particularly sharp tips during conditioning of the emitter.}, language = {en} } @article{EdlerSchelsHerdletal., author = {Edler, Simon and Schels, Andreas and Herdl, Florian and Hansch, Walter and Bachmann, Michael and Dudeck, Markus and Duesberg, Felix and Pahlke, Andreas and Hausladen, Matthias and Buchner Philipp, and Schreiner, Rupert}, title = {Origin of the current saturation level of p-doped silicon field emitters}, series = {Journal of Vacuum Science \& Technology B}, volume = {40}, journal = {Journal of Vacuum Science \& Technology B}, number = {1}, publisher = {AIP Publishing}, doi = {10.1116/6.0001554}, abstract = {Using p-type semiconductors for field emitters is one simple way to realize an integrated current limiter to improve the lifetime of the cathode. In this work, the origin of the current saturation of p-type silicon emitters is investigated in detail. Single emitters are electrically characterized and compared to simulation results. With a simulation model considering a high surface generation rate and elevated tip temperature, a good agreement to the measured data is found. This observation is supported further by alteration of the surface experimentally. Electrical measurements after different treatments in hydrofluoric acid as well as heated and subsequent operation at room temperature are well explained by the influence of surface generation. Furthermore, it is shown that the field penetration leads to a small voltage drop and a strong geometry-dependent reduction of the field enhancement factor.}, language = {en} } @inproceedings{BuchnerBomkeHausladenetal., author = {Buchner, Philipp and Bomke, Vitali and Hausladen, Matthias and Edler, Simon and Bachmann, Michael and Schreiner, Rupert}, title = {Investigation on the Emission Behaviour of p-doped Silicon Field Emission Arrays with Individually Controllable Single Tips}, series = {2021 34th International Vacuum Nanoelectronics Conference (IVNC): 7/5/2021 - 7/9/2021, Lyon, France}, booktitle = {2021 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/IVNC52431.2021.9600756}, pages = {1 -- 2}, abstract = {Four individually controllable emission tips consisting of <111> p-Type silicon, were structured on a glass substrate by laser ablation. A matching extraction grid was manufactured in the same manner and aligned with the emitters. The resulting samples were characterized in ultra-high vacuum. As expected, the individual currents show a strong saturation and in the saturation region a considerably lower current fluctuation than n-type silicon due to charge carrier depletion. The individual tips behave completely independent behaviour from each other and the overall emission can be deduced from the sum of the currents through the individual tips.}, language = {en} } @inproceedings{SchelsHerdlHausladenetal., author = {Schels, Andreas and Herdl, Florian and Hausladen, Matthias and Wohlfartsst{\"a}tter, Dominik and Bachmann, Michael and Edler, Simon and D{\"u}sberg, Felix and Pahlke, Andreas and Buchner, Philipp and Schreiner, Rupert and Hansch, Walter}, title = {Beta Factor Mapping of Individual Emitting Tips During Integral Operation of Field Emission Arrays}, series = {2023 IEEE 36th International Vacuum Nanoelectronics Conference (IVNC), 10-13 July 2023, Cambridge, MA, USA}, booktitle = {2023 IEEE 36th International Vacuum Nanoelectronics Conference (IVNC), 10-13 July 2023, Cambridge, MA, USA}, publisher = {IEEE}, isbn = {979-8-3503-0143-4}, doi = {10.1109/IVNC57695.2023.10188957}, pages = {224 -- 226}, abstract = {Emission uniformity mappings of field emitter arrays provide important insight into degradation mechanisms, but are often laborious, non-integral, costly, or not quantifiable. Here, a low-cost Raspberry Pi HQ camera is used as an extraction anode to quantify the emission distribution in field emitter arrays. A verification measurement using controlled SEM electron beams proves, that current-voltage characteristics of individual emission sites can be determined by combining the integral electrical data with the image data. The characteristics are used to quantify the field enhancement factors of an 30x30 silicon field emitter array during integral operation. Comparison of the field enhancement factor distributions before and after a one-hour constant current operation at 1 µA shows an increase from 50 actively emitting tips before to 156 after the measurement. It is shown, that the distribution of field enhancement factors shifts towards lower values, due to the increasing degradation for high field enhancement tips, especially above 1500.}, language = {en} } @inproceedings{HausladenBuchnerSchelsetal., author = {Hausladen, Matthias and Buchner, Philipp and Schels, Andreas and Edler, Simon and Bachmann, Michael and Schreiner, Rupert}, title = {An Integrated Field Emission Electron Source on a Chip Fabricated by Laser-Micromachining and Mems Technology}, series = {2023 IEEE 36th International Vacuum Nanoelectronics Conference (IVNC), 10-13 July 2023, Cambridge, MA, USA}, booktitle = {2023 IEEE 36th International Vacuum Nanoelectronics Conference (IVNC), 10-13 July 2023, Cambridge, MA, USA}, publisher = {IEEE}, isbn = {979-8-3503-0143-4}, doi = {10.1109/IVNC57695.2023.10189001}, pages = {115 -- 116}, abstract = {A silicon field emission electron source consisting of a cathode and a grid electrode has been fabricated by laser micromachining. The cathode features 21×21 tips on an area of 4×4 mm 2 , With a self-aligning MEMS technology for the aperture grid, a high electron transmission (99 \%) was achieved. Onset voltages of 50…70 V were observed for an emission current of 1 nA. A stable emission current of 1 mA ± 1.3 \% at an extraction voltage of 250 V was observed during a 30-min operation.}, language = {en} } @inproceedings{BuchnerHausladenSchelsetal., author = {Buchner, Philipp and Hausladen, Matthias and Schels, Andreas and Herdl, Florian and Edler, Simon and Bachmann, Michael and Schreiner, Rupert}, title = {An Integrated Silicon Nanowire Field Emission Electron Source on a Chip with High Electron Transmission}, series = {2023 IEEE 36th International Vacuum Nanoelectronics Conference (IVNC), 10-13 July 2023, Cambridge, MA, USA}, booktitle = {2023 IEEE 36th International Vacuum Nanoelectronics Conference (IVNC), 10-13 July 2023, Cambridge, MA, USA}, publisher = {IEEE}, isbn = {979-8-3503-0143-4}, doi = {10.1109/IVNC57695.2023.10188878}, pages = {6 -- 8}, abstract = {Silicon nanowire field emission arrays (50 × 50 pillars) were fabricated on a silicon glass hybrid wafer. The glass acts both as the support for the whole structure and insulator between cathode and extraction grid. The extraction grid matches the emitter structures and is optically aligned and adhered to the emitter chip by a vacuum compatible epoxide adhesive. These chips exhibit an emission current of about 600 μA at an extraction voltage of 300 V. The electron transmission through the grid is above 80 \%. 58-hour longtime measurements were conducted showing low degradation of the emission current and high stability of electron transmission.}, language = {en} } @inproceedings{HausladenSchelsBuchneretal., author = {Hausladen, Matthias and Schels, Andreas and Buchner, Philipp and Bartl, Mathias and Asgharzade, Ali and Edler, Simon and Wohlfartsst{\"a}tter, Dominik and Bachmann, Michael and Schreiner, Rupert}, title = {Improved Method for Determining the Distribution of FEA Currents by Optical CMOS Sensors}, series = {37th International Vacuum Nanoelectronics Conference (IVNC), 15-19 July 2024, Brno, Czech Republic}, booktitle = {37th International Vacuum Nanoelectronics Conference (IVNC), 15-19 July 2024, Brno, Czech Republic}, publisher = {IEEE}, doi = {10.1109/IVNC63480.2024.10652543}, pages = {1 -- 2}, abstract = {CMOS image sensors are utilized to determine the time- and spatially-resolved distribution of the electron emission of silicon field emission arrays. During initial experiments, rather low field emission currents already visibly damaged the sensor surface, altering the system accuracy over the measurement time. Therefore, we coated the sensor surface with copper for protection. In contrast to the original insulating surface, the Cu coating provides a conductive surface for incident electrons and improves heat dissipation in addition. This prevents localized surface charges and surface damages which stabilize the system accuracy.}, 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 Hausladen, Matthias and Buchner, Philipp and Schreiner, Rupert}, title = {The "LED-version" of the electron gun: An electron source for operation in ambient pressure environments based on silicon field emitter arrays}, series = {Vakuum in Forschung und Praxis}, volume = {35}, journal = {Vakuum in Forschung und Praxis}, number = {3}, publisher = {Wiley}, doi = {10.1002/vipr.202300801}, pages = {32 -- 37}, abstract = {We report on our progress to develop and optimize electron sources for practical applications. A simple fabrication process is introduced based on a wafer dicing saw and a wet chemical etch step without the need for a clean room. Due to the formation of crystal facets the samples show a homogeneous geometry throughout the array. Characterization techniques are developed to systematically compare various arrays. A very defined measurement procedure based on current controlled IV-sweeps as well as lifetime measurements at various currents is proposed. To investigate the current distribution in the array a commercial CMOS detector is used and shows the potential for in depth analysis of the arrays. Finally, a compact hermetically sealed housing is presented enabling electron generation in atmospheric pressure environments.}, language = {en} } @article{HausladenSchelsBuchneretal., author = {Hausladen, Matthias and Schels, Andreas and Buchner, Philipp and Bartl, Mathias and Asgharzade, Ali and Edler, Simon and Wohlfartsst{\"a}tter, Dominik and Bachmann, Michael and Schreiner, Rupert}, title = {Measurement of field emission array current distributions by metal-coated CMOS image sensors}, series = {Journal of Vacuum Science \& Technology B}, volume = {42}, journal = {Journal of Vacuum Science \& Technology B}, number = {6}, publisher = {AIP Publishing}, doi = {10.1116/6.0004074}, abstract = {A CMOS image sensor is utilized to determine the time- and spatially resolved distribution of the total electron emission current of a silicon field emission array. The sensor measures electron emission without the need for phosphorus screens or scintillators as converters. However, in initial experiments, rather low field emission currents of several hundreds of nanoamperes per emitter already damaged the sensor surface, which altered the systems' signal response over the measurement time. In consequence, we coated the CMOS sensor surface with a Cu layer for surface protection. In contrast to the original insulating surface, Cu is an excellent current- and heat-conductor, which avoids lens charging by providing a conductive path for incident electrons and has an improved heat dissipation capability. Measurements using a segmented field emission cathode with four individually addressable tips demonstrate a consistent correlation between the emission current and the sensor signal of the metal-coated image sensor. Furthermore, the characterization of a field emission array showed that single tip emission currents of up to 12 μA per tip are measurable without discernible damage effects of the sensor's surface.}, language = {en} } @article{HausladenSchelsAsgharzadeetal., author = {Hausladen, Matthias and Schels, Andreas and Asgharzade, Ali and Buchner, Philipp and Bartl, Mathias and Wohlfartsst{\"a}tter, Dominik and Edler, Simon and Bachmann, Michael and Schreiner, Rupert}, title = {Investigation of Influencing Factors on the Measurement Signal of a CMOS Image Sensor for Measuring Field Emission Currents}, series = {Sensors}, volume = {25}, journal = {Sensors}, number = {5}, publisher = {MDPI}, doi = {10.3390/s25051529}, pages = {17}, language = {en} } @inproceedings{AsgharzadeBartlHausladenetal., author = {Asgharzade, Ali and Bartl, Mathias and Hausladen, Matthias and Chen, Yang and Buchner, Philipp and Edler, Simon and Bachmann, Michael and She, Juncong and Schreiner, Rupert}, title = {Investigation on the influence of internal voltage drops on the emission behavior of silicon field emission arrays using CMOS image sensor}, series = {38th International Vacuum Nanoelectronics Conference (IVNC)}, booktitle = {38th International Vacuum Nanoelectronics Conference (IVNC)}, publisher = {IEEE}, doi = {10.1109/IVNC65669.2025.11120937}, pages = {2}, abstract = {In this paper we report on an improved measurement and analysis method for determining the emission current distribution of field emitter arrays with CMOS sensors. It can also be used for field emission arrays where not all surfaces of the emitters are at the same electrical potential (e.g. for p-doped Si tips, where a strong current saturation occurs). To demonstrate the functionality of this method, a n-doped field emission array was measured using a variable external series resistance. Brightness variations in emission spots were analyzed to re-calculate the known series resistances for comparison. The re-calculated value is in good agreement with the actual value of the resistance. This method offers a quantitative approach to assess internal voltage drop effects on field emission using optical readout}, language = {en} }