Evaluation von MEMS-Führungskonzepten mit hohem Steifigkeitsverhältnis von Querrichtung und Hauptfunktionsrichtung. - In: Mikrosystemtechnik, (2022), S. 49-52
Neuartige Methode zur Bestimmung der Schwerpunkhöhe von Massenormalen :
Novel method for determining the center of gravity height of mass standards. - In: Sensors and Measuring Systems, (2022), S. 204-207
The most precise vacuum mass comparators have a resolution of 0.1 μg, operating at one kilogram [1]. The resolution represents a relative difference in weight of the artifacts of 1×10^(-10). Small deviations in the height of the center of gravity of the mass artifacts lead to a systematic error of the measurement results. For example a difference in the height of the center of gravity of 1 cm in Earth's gravitational field causes a relative systematic uncertainty contribution of 3.2×10^(-9). Therefore, it is important to know the artifacts' heights of the center of gravity. This paper introduces a novel approach to measure the height of the center of gravity of high-sensitive mass artifacts. The method allows to compare the mass of artifacts of unusual shape, inhomogeneous composition or hollow mass standards with uncertain internal geometry. For the determination, the mass artifacts are placed on three load cells, arranged at an angle of 120˚. The load cells are attached to the base, which stands on a high-precision tilt table [2]. The difference in force with variation of the inclination angles allows to calculate the height of the center of gravity of the artifacts. To verify the method, various mass standards of known geometry and composition are measured as described. In the end, the comparison between theoretically determined values and the measurement results shows a good agreement of the method.
https://ieeexplore.ieee.org/document/9861899
Hysteresis associated with intrinsic-oxide traps in gate-tunable tetrahedral CVD-MoS2 memristor. - In: IEEE 22nd International Conference on Nanotechnology (NANO), (2022), S. 527-530
We introduce back gated memristor based on CVD-grown 30-40 nm thick MoS2 channel. The device demonstrates bipolar behaviour and the measurements are consistent with the simulations performed within the intrinsic-oxide traps model. This confirms the theory that the source of hysteresis in thin-film MoS2 memristors is charge trapping on MoS2/SiO2 interface and the grain boundaries. The impact of back gate voltage bias, voltage sweep range and channel area on memristive effect was studied and quantified using hysteresis area. Hysteresis in bipolar memristors can be tuned by back gate voltage, which makes these devices promising for neuromorphic computing.
https://doi.org/10.1109/NANO54668.2022.9928717
Einsatz von gepulsten Lasern mit hoher Leistung in der Präzisionskraftmesstechnik - ein Schritt in die Richtung einer künftigen, SI-rückführbaren und praktischen Kraftquantisierung durch Photonenimpulse :
Deploying the high-power pulsed lasers in precision force metrology - towards SI traceable and practical force quantization by photon momentum. - In: Technisches Messen, ISSN 2196-7113, Bd. 89 (2022), 11, S. 757-777
Design and operational performance of table-top measurement apparatus is presented towards direct Planck constant traceable high accuracy and high precision small forces and optical power measurements within the SI unit system. Electromagnetic force compensation weighing balances, highly reflective mirrors and high-energy pulsed laser unit (static average power 20 W) are tailored together with a specially developed opto-electro-mechanical measurement infrastructure for cross-mapping the scale-systems of two different precision small force measurement methods. One of these methods obtains the force measurements by a state-of-the-art classical kinematic system employing the partial use of Kibble balance principle in the range of 10 nN to 4000 nN to be compared with forces generated due to quantum-mechanical effect namely the transfer of the momentum of photons from a macroscopic object. Detailed overview of the adapted measurement methodology, the static and the limits of dynamic measurement, the metrological traceability routes of the measurement parameters, quantities and their measurement uncertainties, parametric estimation of up (down)-scaling perspectives of the measurements are presented with respect to the state-of-the-art measurement principles and standard procedures within the newly redefined International System of Units (SI).
https://doi.org/10.1515/teme-2022-0080
Redundante Temperatursensorik für das Batterien-Monitoring. - In: EASS, (2022), S. 42-46
Der Einsatz redundanter Temperaturmesssysteme erlaubt es, die Betriebssicherheit von Sensorsystemen deutlich zu erhöhen. Solche Systeme bestehen aus mindestens zwei Sensoren gleicher oder unterschiedlicher Technologie bzw. Kennlinie. Der erste Fall wird als homogene, der letzte als diversitäre Redundanz bezeichnet. Insbesondere der Ausfall eines einzelnen Sensors kann auf diese Weise zuverlässig detektiert werden. Darüber hinaus kann bei Berücksichtigung einer eingeschränkten Zuverlässigkeit auch weiterhin ein Messwert ermittelt werden. Vor diesem Hintergrund besteht u. a. im Bereich der Automobilindustrie zunehmend Bedarf an selbstvalidierender Sensorik dieser Art.
Absolute distance measurements for in-situ interferometer characterisation using range-resolved interferometry. - In: Measurement science and technology, ISSN 1361-6501, Bd. 33 (2022), 12, 125024, S. 1-12
Range-resolved interferometry (RRI) allows the simultaneous demodulation of multiple interferometric signal sources and provides a tomographic view of all constituent interferometers that may be present in a setup. Through comparison with a reference distance of known length, absolute distance measurements can be performed. RRI is tailored to the use of laser frequency modulation through injection-current modulation of regular, monolithic laser diodes that are both cost-effective and highly coherent and therefore this approach promises broad applicability. In this paper, two methods for absolute distance measurement, one based on the direct evaluation of the signal peak positions and one based on the phase demodulation of an additional lock-in modulation signal, are experimentally demonstrated. Using an external verification displacement interferometer, both techniques are shown to achieve in-situ absolute distance measurements with systematic errors below over a 50 mm travel range. The aim of this paper is to establish the general suitability of RRI for absolute distance measurements and in-situ tomographic interferometer characterisation for precision engineering. In future, this approach could be used to diagnose interferometric setups for parasitic signal contributions, multiple reflections or to determine the dead path length for accurate environmental compensation, either for use during initial setup of, or for continuous operation alongside, a regular displacement measuring interferometer.
https://doi.org/10.1088/1361-6501/ac970a
Formation and characterization of three-dimensional tetrahedral MoS2 thin films by chemical vapor deposition. - In: Crystal growth & design, ISSN 1528-7505, Bd. 22 (2022), 9, S. 5229-5238
A method to synthesize the three-dimensional arrangement of bulk tetrahedral MoS2 thin films by solid source chemical vapor deposition of MoO3 and S is presented. The developed synthesizing recipe uses a temperature ramping with a constant N2 gas flow in the deposition process to grow tetrahedral MoS2 thin film layers. The study analyses the time-dependent growth morphologies, and the results are combined and presented in a growth model. A combination of optical, electron, atomic force microscopy, Raman spectroscopy, and X-ray diffraction are used to study the morphological and structural features of the tetrahedral MoS2 thin layers. The grown MoS2 is c-axis oriented 2H-MoS2. Additionally, the synthesized material is further used to fabricate back-gated field-effect transistors (FETs). The fabricated FET devices on the tetrahedral MoS2 show on/off current ratios of 10^6 and mobility up to ∼56 cm^2 V^-1 s^-1 with an estimated carrier concentration of 4 × 10^16 cm-3 for VGS = 0 V.
https://doi.org/10.1021/acs.cgd.2c00333
Conference measurement uncertainty Erfurt 2021 :
Tagung Messunsicherheit Erfurt 2021. - In: Technisches Messen, ISSN 2196-7113, Bd. 89 (2022), 10, S. 645-646
https://doi.org/10.1515/teme-2022-0088
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