WE-123 : a 256-channel dry electrode cap for rapid high-density EEG. - In: Clinical neurophysiology, ISSN 1872-8952, Bd. 141 (2022), S. S63-S64
https://doi.org/10.1016/j.clinph.2022.07.167
Frequenzkamm-gekoppelte Metrologielaser für die interferometrische Längenmessung in Nanopositionier- und Nanomessmaschinen :
Comb-referenced metrology laser for interferometric length measurements in nanopositioning and nanomeasuring machines. - In: Technisches Messen, ISSN 2196-7113, Bd. 89 (2022), 10, S. 687-703
In this article a new approach for the direct traceability of interferometric length measurements in nanopositioning- and measuring machines is presented. The concept is based on an optical frequency comb tied to a GPS disciplined oscillator. The frequency comb serves as a highly stable reference laser with traceable optical frequencies. By directly stabilizing the metrology lasers of a nanopositioning and -measuring machine to a single comb line a permanent link of the laser frequency to an atomic clock is created allowing direct traceability to the SI meter definition. The experimental conditions to provide traceability will be discussed. Furthermore, it is demonstrated how the long-term frequency stability of an individual comb line can be transferred onto the metrology lasers enhancing their stability by three orders of magnitude.
https://doi.org/10.1515/teme-2022-0013
Extensions for the design of a two photon based direct laser writer for large-area, high precision nanostructuring :
Erweiterungen zum Aufbau eines zwei Photonen basierten direkten Laserschreibers zur großflächigen, hochpäzisen Nanostrukturierung. - In: Technisches Messen, ISSN 2196-7113, Bd. 89 (2022), S. S55-S60
Zur Realisierung extrem feiner Strukturen spielen direkte Laserschreibprozesse, basierend auf Zwei-Photonen-Absorptionsverfahren (2PA), eine zentrale Rolle in der Mikro- und Nanofabrikation. Dafür ist neben einem Lasersystem ein hochpräzises Positioniersystem notwendig. Meist basieren diese Positioniersysteme auf Prinzipien, die ohne zusätzliche Stiching-Verfahren nur kleine Positionierbereiche ermöglichen. Für piezoelektrische Tische sind zum Beispiel nur einige hundert Mikrometer möglich. Auf Galvanometer-Scannern basierten Systemen können sogar nur Positionierbereiche von wenigen zehn Mikrometern realisiert werden. Um ohne zusätzliche Stiching Verfahren größere Fertigungsbereiche mit hoher Präzision für Mikro- und Nanostrukturierung zu ermöglichen, wurde ein Aufbau aus einem Femtosekundenlaser für 2PA und einer Nanopositionier- und Nanomessmaschine (NMM-1) entwickelt [3]. Die NMM-1 wurde an der TU Ilmenau zusammen mit der SIOS Meßtechnik GmbH entwickelt, mit einem Positioniervolumen von 25 mm × 25 mm × 5 mm und einer Positionierauflösung im Sub-Nanometerbereich. Dieser Aufbau wurde in den letzten Jahren weiter entwickelt und Strukturbreiten konnten reduziert werden [2]. Der Schwerpunkt liegt dabei auf der Entwicklung einer funktionalen Einheit aus Femtosekundenlaser und NMM-1. Dies soll die Komplexität erhöhen und die Homogenität der geschriebenen Strukturen stark verbessern.
https://doi.org/10.1515/teme-2022-0058
A bottom-up approach for the radius and roundness measurement of micro spheres :
Ein Bottom-up Ansatz für die Radius- und Rundheitsmessung von Mikrokugeln. - In: Technisches Messen, ISSN 2196-7113, Bd. 89 (2022), S. S101-S106
Die mangelnde Verfügbarkeit von präzise charakterisierten Kugeln im Submillimeterbereich schränkt derzeit die Leistungsfähigkeit von Mikro- und Nano-Koordinatenmessgeräten ein. Aus diesem Grund werden am Institut für Prozessmess- und Sensortechnik der TU Ilmenau neue Ansätze zur Messung solcher Kugeln untersucht und daraus entsprechende Messverfahren entwickelt. Ein vielversprechender Ansatz basiert dabei auf einer Reihe von Oberflächenscans im Zusammenhang mit einem Stitching-Algorithmus. Als Oberflächensensor kommt zur Zeit ein Atomkraftmikroskop (AFM) im Kontaktmodus zum Einsatz. Eine rückführbare Messung erfordert eine präzise Charakterisierung der AFM-Spitzenform und deren Unsicherheit, um diesen Einfluss zu korrigieren und die Unsicherheit fortzupflanzen sowie möglichen Verschleiß der AFM-Spitze während des Messvorgangs festzustellen. Diese Aspekte fanden bisher keine Beachtung. Ausgehend von dem publizierten Stand wurde deshalb die Messstrategie und der Auswertealgorithmus durch eine geeignete Strategie zur Korrektur des Spitzenformeinflusses sowie der Ermittlung der Spitzenform erweitert. Diese wurde experimentell durch den Einsatz unterschiedlicher AFM-Spitzen mit nominellen Radien von 100 nm bis 2 μm an einer 300 μm-Rubin-Kugel untersucht. Im Rahmen des Beitrags werden dazu erste Ergebnisse vorgestellt und diskutiert.
https://doi.org/10.1515/teme-2022-0073
Entwicklung eines neuartigen Magnetsystems für eine 1 kg-Planck-Waage :
Development of a novel magnet system for a 1 kg Planck balance. - In: Technisches Messen, ISSN 2196-7113, Bd. 89 (2022), S. S31-S36
The following paper presents the development of a novel magnet system for use in a 1 kg Planck balance. For this purpose, several preliminary theoretical and experimental investigations were carried out and an optimized prototype magnetic system was modeled, designed and built based on the results. Initial measurements showed that the magnet system with an outer diameter of 104 mm and a height of 50 mm achieved a constant average value of 85.25 N A^-1 at a range of motion of ±0.6 mm.
https://doi.org/10.1515/teme-2022-0043
Development of low-gain avalanche detectors in the frame of the acceptor removal phenomenon. - In: Physica status solidi, ISSN 1862-6319, Bd. 219 (2022), 17, 2200177, S. 1-7
Low-gain avalanche detectors (LGAD) suffer from an acceptor removal phenomenon due to irradiation. This acceptor removal phenomenon is investigated in boron, gallium, and indium implanted samples by 4-point-probe (4pp) measurements, low-temperature photoluminescence spectroscopy (LTPL), and secondary ion mass spectrometry (SIMS) before and after irradiation with electrons and protons. Different co-implantation species are evaluated with respect to their ability to reduce the acceptor removal phenomenon. In case of boron, the beneficial effect is found to be most pronounced for the low-dose fluorine and high-dose nitrogen co-implantation. In case of gallium, the low-dose implantations of carbon and oxygen are found to be beneficial. For indium, the different co-implantation species have no beneficial effect. SIMS boron concentration depth profiles measured before and after irradiation show no indication of a fast movement of boron at room temperature. Hence, the discussed BSi-Sii-defect explanation approach of the acceptor removal phenomenon seems to be more likely than the other discussed Bi-Oi-defect explanation approach.
https://doi.org/10.1002/pssa.202200177
Low-temperature photoluminescence investigation of light-induced degradation in boron-doped CZ silicon. - In: Physica status solidi, ISSN 1862-6319, Bd. 219 (2022), 17, 2200180, S. 1-9
Light-induced degradation (LID) in boron-doped Czochralski grown (CZ) silicon is a severe problem for silicon devices such as solar cells or radiation detectors. Herein, boron-doped CZ silicon is investigated by low-temperature photoluminescence (LTPL) spectroscopy. An LID-related photoluminescence peak is already found while analyzing indium-doped p-type silicon samples and is associated with the ASi-Sii defect model. Herein, it is investigated whether a similar peak is present in the spectra of boron-doped p-type CZ silicon samples. The presence of change in the photoluminescence signal intensity due to activation of the boron defect is investigated as well. Numerous measurements on boron-doped samples are made. For this purpose, samples with four different boron doping concentrations are analyzed. The treatments for activation of the boron defect are based on the LID cycle. During an LID cycle, an additional peak or shoulder neither in the areas of the boron-bound exciton transverse acoustic and nonphonon-assisted peaks (BTA, BNP) nor in the area of the boron-bound exciton transverse optical phonon-assisted peak (BTO) is found. The defect formation also does not lead to a lower photoluminescence (PL) intensity ratio BTO(BE)/ITO(FE).
https://doi.org/10.1002/pssa.202200180
Reliable deep learning based localization with CSI fingerprints and multiple base stations. - In: 2022 IEEE International Conference on Communications, (2022), S. 3214-3219
Deep learning (DL) methods have been recently proposed for user equipment (UE) localization in wireless communication networks, based on the channel state information (CSI) between a UE and multiple base stations (BSs) in the uplink. With the CSI from the available BSs, UE localization can be performed in different ways. On the one hand, a single neural network (NN) can be trained for the UE localization by considering the CSI from all the available BSs as one overall fingerprint of the user’s location. On the other hand, the CSI at each BS can be used to obtain an estimate of the UE’s position with a separate NN at each BS, and then the position estimates of all BSs are combined to obtain an overall estimate of the UE position. In this work, we show that UE localization with the latter approach can achieve a higher positioning accuracy. We propose to consider the uncertainty in the UE localization at each BS, such that overall UE’s position is determined by combining the position estimates of the different BSs based on the uncertainty at each BS. With this approach, a more reliable position estimate can be obtained in case of variations in the channel.
https://doi.org/10.1109/ICC45855.2022.9838535
Prestine C60 fullerene as a novel agent in sonodynamic treatment of cancer cells. - In: FEBS Open Bio, ISSN 2211-5463, Bd. 12 (2022), S. 74
https://doi.org/10.1002/2211-5463.13440
Investigation of the directional characteristics of the emitted airborne sound by friction stir welding for online process monitoring. - In: 2nd International Conference on Advanced Joining Processes (AJP 2021), (2022), S. 41-56
Currently, destructive or non-destructive testing methods are used to verify the weld seam quality subsequent to the manufacturing process. Therefore, pre-processes such as visible or mechanical testing require additional efforts, which can lead to expensive reworking or rejection of the components. The acoustic process characterization for Friction Stir Welding (FSW) applications permits a comparatively new approach of process monitoring to detect weld seam irregularities by the characterization of the emitted noise in the audible frequency range (airborne sound signal). In previous publications, the acoustic detection of weld seam irregularities was mostly based on structure-borne sound sensors. Although a correlation between weld defects and audio signals has been demonstrated, there are process-related deficits in the use of structure-borne sound sensors. These include a fixed installation position and limited applicability for large-scale components such as battery cases. In contrast airborne sound sensors (microphones) can be mounted directly in the area of the joining process and thus influences of component size, joining materials, and weld seam geometry can be reduced. However, the use of airborne sound sensors for FSW applications requires preparatory considerations on the sensor position towards the joining process (sidely, in front of or behind the processing tool). Therefore, in this study an approach will be presented to evaluate the directional characteristic of the airborne sound emitted by the FSW process. First, the positioning of the microphone for the various welding directions were investigated. This was done to determine a suitable microphone orientation during the process. Then, the general determination of audio signals from the FSW process will be considered and compared to the process force feedback. Further, it was demonstrated that acoustic analysis can be used for detection of weld seam irregularities such as flash formation on 5 mm AA 5754 H111 sheets. All experiments were performed with a robotized FSW setup that was modified by a self-developed acoustic measuring device.