Lau effect using LED array for lithography. - In: Nanomanufacturing and metrology, ISSN 2520-8128, Bd. 4 (2021), 3, S. 165-174
Illumination with LEDs is of increasing interest in imaging and lithography. In particular, compared to lasers, LEDs are temporally and spatially incoherent, so that speckle effects can be avoided by the application of LEDs. Besides, LED arrays are qualified due to their high optical output power. However, LED arrays have not been widely used for investigating optical effects, e.g., the Lau effect. In this paper, we propose the application of an LED array for realizing the Lau effect by taking into account the influence of the coherence properties of illumination on the Lau effect. Using spatially incoherent illumination with the LED array or a single LED, triangular distributed Lau fringes can be obtained. We apply the obtained Lau fringes in the optical lithography to produce analog structures. Compared to a single LED, the Lau fringes using the LED array have significantly higher intensities. Hence, the exposure time in the lithography process is largely reduced.
https://doi.org/10.1007/s41871-021-00108-4
Heterodyne standing-wave interferometer with improved phase stability. - In: Nanomanufacturing and metrology, ISSN 2520-8128, Bd. 4 (2021), 3, S. 190-199
This paper describes a standing-wave interferometer with two laser sources of different wavelengths, diametrically opposed and emitting towards each other. The resulting standing wave has an intensity profile which is moving with a constant velocity, and is directly detected inside the laser beam by two thin and transparent photo sensors. The first sensor is at a fixed position, serving as a phase reference for the second one which is moved along the optical axis, resulting in a frequency shift, proportional to the velocity. The phase difference between both sensors is evaluated for the purpose of interferometric length measurements.
https://doi.org/10.1007/s41871-021-00098-3
Highly anisotropic fluorine-based plasma etching of ultralow expansion glass. - In: Advanced engineering materials, ISSN 1527-2648, Bd. 23 (2021), 6, 2001336, insges. 10 S.
Deep etching of glass and glass ceramics is far more challenging than silicon etching. For thermally insensitive microelectromechanical and microoptical systems, zero-expansion materials such as Zerodur or ultralow expansion (ULE) glass are intriguing. In contrast to Zerodur that exhibits a complex glass network composition, ULE glass consists of only two components, namely, TiO2 and SiO2. This fact is highly beneficial for plasma etching. Herein, a deep fluorine-based etching process for ULE 7972 glass is shown for the first time that yields an etch rate of up to 425 nm min^-1 while still achieving vertical sidewall angles of 87˚. The process offers a selectivity of almost 20 with respect to a nickel hard mask and is overall comparable with fused silica. The chemical surface composition is additionally investigated to elucidate the etching process and the impact of the tool configuration in comparison with previously published etching results achieved in Zerodur. Therefore, deep and narrow trenches can be etched in ULE glass with high anisotropy, which supports a prospective implementation of ULE glass microstructures, for instance, in metrology and miniaturized precision applications.
https://doi.org/10.1002/adem.202001336
Three-dimensional platinum nanoparticle-based bridges for ammonia gas sensing. - In: Scientific reports, ISSN 2045-2322, Bd. 11 (2021), 12551, S. 1-9
This study demonstrates the fabrication of self-aligning three-dimensional (3D) platinum bridges for ammonia gas sensing using gas-phase electrodeposition. This deposition scheme can guide charged nanoparticles to predetermined locations on a surface with sub-micrometer resolution. A shutter-free deposition is possible, preventing the use of additional steps for lift-off and improving material yield. This method uses a spark discharge-based platinum nanoparticle source in combination with sequentially biased surface electrodes and charged photoresist patterns on a glass substrate. In this way, the parallel growth of multiple sensing nodes, in this case 3D self-aligning nanoparticle-based bridges, is accomplished. An array containing 360 locally grown bridges made out of 5 nm platinum nanoparticles is fabricated. The high surface-to-volume ratio of the 3D bridge morphology enables fast response and room temperature operated sensing capabilities. The bridges are preconditioned for ˜ 24 h in nitrogen gas before being used for performance testing, ensuring drift-free sensor performance. In this study, platinum bridges are demonstrated to detect ammonia (NH3) with concentrations between 1400 and 100 ppm. The sensing mechanism, response times, cross-sensitivity, selectivity, and sensor stability are discussed. The device showed a sensor response of ˜ 4% at 100 ppm NH3 with a 70% response time of 8 min at room temperature.
https://doi.org/10.1038/s41598-021-91975-w
Electrical conductivity adjustment for interface capacitive-like storage in sodium-ion battery. - In: Advanced functional materials, ISSN 1616-3028, Bd. 31 (2021), 24, 2101081, insges. 11 S.
Sodium-ion battery (SIB) is significant for grid-scale energy storage. However, a large radius of Na ions raises the difficulties of ion intercalation, hindering the electrochemical performance during fast charge/discharge. Conventional strategies to promote rate performance focus on the optimization of ion diffusion. Improving interface capacitive-like storage by tuning the electrical conductivity of electrodes is also expected to combine the features of the high energy density of batteries and the high power density of capacitors. Inspired by this concept, an oxide-metal sandwich 3D-ordered macroporous architecture (3DOM) stands out as a superior anode candidate for high-rate SIBs. Taking Ni-TiO2 sandwich 3DOM as a proof-of-concept, anatase TiO2 delivers a reversible capacity of 233.3 mAh g^-1 in half-cells and 210.1 mAh g^-1 in full-cells after 100 cycles at 50 mA g^-1. At the high charge/discharge rate of 5000 mA g^-1, 104.4 mAh g^-1 in half-cells and 68 mAh g^-1 in full-cells can also be obtained with satisfying stability. In-depth analysis of electrochemical kinetics evidence that the dominated interface capacitive-like storage enables ultrafast uptaking and releasing of Na-ions. This understanding between electrical conductivity and rate performance of SIBs is expected to guild future design to realize effective energy storage.
https://doi.org/10.1002/adfm.202101081
Improving the performance of a radio-frequency localization system in adverse outdoor applications. - In: EURASIP journal on wireless communications and networking, ISSN 1687-1499, (2021), 123, S. 1-26
In outdoor RF localization systems, particularly where line of sight can not be guaranteed or where multipath effects are severe, information about the terrain may improve the position estimate's performance. Given the difficulties in obtaining real data, a ray-tracing fingerprint is a viable option. Nevertheless, although presenting good simulation results, the performance of systems trained with simulated features only suffer degradation when employed to process real-life data. This work intends to improve the localization accuracy when using ray-tracing fingerprints and a few field data obtained from an adverse environment where a large number of measurements is not an option. We employ a machine learning (ML) algorithm to explore the multipath information. We selected algorithms random forest and gradient boosting; both considered efficient tools in the literature. In a strict simulation scenario (simulated data for training, validating, and testing), we obtained the same good results found in the literature (error around 2 m). In a real-world system (simulated data for training, real data for validating and testing), both ML algorithms resulted in a mean positioning error around 100 ,m. We have also obtained experimental results for noisy (artificially added Gaussian noise) and mismatched (with a null subset of) features. From the simulations carried out in this work, our study revealed that enhancing the ML model with a few real-world data improves localization’s overall performance. From the machine ML algorithms employed herein, we also observed that, under noisy conditions, the random forest algorithm achieved a slightly better result than the gradient boosting algorithm. However, they achieved similar results in a mismatch experiment. This work’s practical implication is that multipath information, once rejected in old localization techniques, now represents a significant source of information whenever we have prior knowledge to train the ML algorithm.
https://doi.org/10.1186/s13638-021-02001-6
The business model data facilitator in consulting :
Das Geschäftsmodell Data Facilitator im Consulting. - In: HMD, ISSN 2198-2775, Bd. 58 (2021), 3, S. 552-564
Mit der Vervielfachung des Datenvolumens und der raschen Weiterentwicklung entsprechender Analysemethoden und Werkzeuge gibt es immer mehr Unternehmen, insbesondere aus dem kleineren Mittelstand, die aufgrund mangelnder Ressourcen und Fähigkeiten nicht in der Lage sind, ihre Datenschätze zu heben und daraus gute Entscheidungen im Hinblick auf ihre Produkte, Prozesse und Geschäftsmodelle abzuleiten. Vor diesem Hintergrund wird im vorliegenden Beitrag ein Data Facilitator Geschäftsmodell für Consultingunternehmen vorgeschlagen. Um nicht im Wettbewerb zurückzufallen, lagern hierin Unternehmen Aufgaben der Datenaufbereitung, Analyse und Interpretation an ein Beratungsunternehmen aus, das sich auf solche Themen spezialisiert hat. Berater erhalten dabei Zugriff auf kritische Datenströme des Kunden, die dann auf regelmäßiger Basis fachkundig, unter Einsatz moderner Analyseinstrumente untersucht werden. Es geht darum, frühzeitig "schwache Signale" für zukünftige kritische Entwicklungen beim Kunden zu erkennen oder Ideen für geschäftliche Verbesserungen zu entwickeln. Dabei werden die Ergebnisse dem Kunden nicht kommentarlos übermittelt, sondern Auffälligkeiten von den Beratern unter Einbringung ihres Fachwissens mit den Kunden diskutiert und interpretiert. Der Kunde trifft dann gegebenenfalls Entscheidungen auf Basis der vorliegenden Datenlage. Da diese Dienstleistung fortlaufend erbracht wird, sind hierfür neue Bezahlmodelle im Consulting sinnvoll, wie z.B. eine monatliche Pauschale. Für eine erfolgreiche Umsetzung des Geschäftsmodells sind in der Praxis eine Reihe von Problemen zu bewältigen, worauf im Beitrag ebenfalls eingegangen wird.
https://doi.org/10.1365/s40702-021-00723-1
Alcohol in social media: where is the space for prevention? :
Alkohol in sozialen Medien: wo ist der Platz für Prävention?. - In: Bundesgesundheitsblatt, Gesundheitsforschung, Gesundheitsschutz, ISSN 1437-1588, Bd. 64 (2021), 6, S. 697-706
https://doi.org/10.1007/s00103-021-03335-8
Study on friction in automotive shock absorbers, part 2: Validation of friction simulations via novel single friction point test rigs. - In: Vehicles, ISSN 2624-8921, Bd. 3 (2021), 2, S. 197-211
https://doi.org/10.3390/vehicles3020013
Study on friction in automotive shock absorbers, part 1: Friction simulation using a dynamic friction model in the contact zone of an FEM model. - In: Vehicles, ISSN 2624-8921, Bd. 3 (2021), 2, S. 212-232
https://doi.org/10.3390/vehicles3020014