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Weigel, Christoph; Brokmann, Ulrike; Hofmann, Meike; Behrens, Arne; Rädlein, Edda; Hoffmann, Martin; Strehle, Steffen; Sinzinger, Stefan
Perspectives of reactive ion etching of silicate glasses for optical microsystems. - In: Journal of optical microsystems, ISSN 2708-5260, Bd. 1 (2021), 4, S. 040901-1-040901-22

We provide a review of the latest research findings as well as the future potential of plasma-based etching technology for the fabrication of micro-optical components and systems. Reactive ion etching (RIE) in combination with lithographic patterning is a well-established technology in the field of micro- and nanofabrication. Nevertheless, practical implementation, especially for plasma-based patterning of complex optical materials such as alumino-silicate glasses or glass-ceramics, is still largely based on technological experience rather than established models. Such models require an in-depth understanding of the underlying chemical and physical processes within the plasma and at the glass-plasma/mask-plasma interfaces. We therefore present results that should pave the way for a better understanding of processes and thus for the extension of RIE processes toward innovative three-dimensional (3D) patterning as well as for the processing of chemically and structurally inhomogeneous silicate-based substrates. To this end, we present and discuss the results of a variety of microstructuring strategies for different application areas with a focus on micro-optics. We consider the requirements for refractive and diffractive micro-optical systems and highlight potentials for 3D dry chemical etching by selective tailoring of the material structure. The results thus provide first steps toward a knowledge-based approach to RIE processing of universal dielectric glass materials for optical microsystems, which also has a significant impact on other microscale applications.
Weigel, Christoph; Brokmann, Ulrike; Rädlein, Edda; Strehle, Steffen
Maskless pattern transfer into photostructurable glasses by deep plasma etching. - In: MikroSystemTechnik, (2021), S. 419-421

Westphalen, Jasper;
Implementierung eines Moduls zur großflächigen In-Line Blitzlampentemperung von gesputterten ITO-Schichten. - Ilmenau : Universitätsverlag Ilmenau, 2021. - 1 Online-Ressource (x, 109 Seiten). - (Werkstofftechnik aktuell ; Band 22)
Technische Universität Ilmenau, Dissertation 2020

Die Blitzlampentemperung (Flash Lamp Annealing - FLA) zählt zu den Kurzzeittemperverfahren (Rapid Thermal Annealing - RTA), da die Erwärmung und Abkühlung der Schicht im Bereich von Millisekunden liegen. Die mit Hilfe von Blitzlampen durchgeführte Temperung dient zur oberflächennahen Erwärmung von Festkörpern. Hierbei handelt es sich um einen thermischen Prozess, der Materialeigenschaften verändern kann. Durch die Blitzlampentemperung kann der Schichtwiderstand von transparenten leitfähigen Oxidschichten (Transparent Conductive Oxides - TCO) reduziert und die Transmission im sichtbaren Wellenlängenbereich erhöht werden. In der vorliegenden Forschungsarbeit wird das Prozessverhalten von dynamischen FLA-Prozessen bei Indium-Zinn-Oxid (ITO) Schichten experimentell dargelegt. Dazu wurde der Einfluss von verschiedenen Prozessparametern wie Energiedichte und Pulszeit des Xenonlichtblitzes erforscht. Erste Versuche zur Untersuchung des Einflusses der Blitzwiederholrate und der Geschwindigkeit des Substrates ließen sich erfolgreich durchführen. Die Herstellung aller Schichten erfolgte am Fraunhofer-Institut für Organische Elektronik, Elektronenstrahl- und Plasmatechnik (FEP) in der In-Line Sputteranlage ILA 750. Für die Blitzlampentemperung wurde das Lampensystem Xenon Flash Lamp Modul FLA 2x360w der Firma ROVAK GmbH genutzt. Das Modul ist Bestandteil der Beschichtungsanlage ILA 900 am Fraunhofer FEP und erlaubt sowohl die statische als auch die dynamische FLA-Behandlung von Substraten bis zu einer Größe von 600 mm x 1200 mm. Die unterschiedlichen Einstellungen der Blitze ließen sich optisch vermessen. Für ITO-Schichten mit einer Schichtdicke von 150 nm konnte nach der FLA-Behandlung ein Widerstand von 14 [Ohm] erreicht werden. Für die Transmission im sichtbaren Wellenlängenbereich wurden 87 % erzielt. Diese Werte sind vergleichbar mit einer konventionellen Temperung von ITO-Schichten im Ofen. Erfolgreich ließ sich zeigen, dass der FLAProzess an eine bestehende In-Line Prozessanlage implementiert werden kann.
Strugaj, Gentiana; Herrmann, Andreas; Rädlein, Edda
AES and EDX surface analysis of weathered float glass exposed in different environmental conditions. - In: Journal of non-crystalline solids, ISSN 0022-3093, Bd. 572 (2021), 121083

To characterize the influence of environmental conditions on glass weathering, two different float glasses were subjected to a six-month outdoor experiment that took place in Durres (seacoast, Albania), Ilmenau (rural, Germany) and Pristina (urban, Kosovo), three sites with largely different environmental conditions. Atmospheric deposits and meteorological conditions led this study to receive information about different weathering behaviour of two types of float glasses. Typical glass degradation effects and reaction products at the glass surface are shown and the impact of weathering and air quality parameters on the formation of reaction products and degradation is discussed. Surface changes have been localized using optical microscopy. Further investigations for receiving chemical information on the contaminations include Auger electron spectroscopy (AES) and scanning electron microscopy (SEM/EDX). Surface analyses indicate a high amount of weathering products such as chlorides, sulphates and carbonates followed by severe delamination effects for both types of glass exposed in Durres and Pristina. In contrast to this, low levels of soiling and degradation for the samples exposed in Ilmenau were detected.
Zekri, Mohamed; Herrmann, Andreas; Erlebach, Andreas; Damak, Kamel; Rüssel, Christian; Sierka, Marek; Maâlej, Ramzi
The structure of Gd3+-doped Li2O and K2O containing aluminosilicate glasses from molecular dynamics simulations. - In: Materials, ISSN 1996-1944, Bd. 14 (2021), 12, 3265, insges. 18 S.
Im Titel sind "3+" hochgestellt und "2" tiefgestellt

Understanding the atomic structure of glasses is critical for developing new generations of materials with important technical applications. In particular, the local environment of rare-earth ions and their distribution and clustering is of great relevance for applications of rare earth-containing glasses in photonic devices. In this work, the structure of Gd2O3 doped lithium and potassium aluminosilicate glasses is investigated as a function of their network modifier oxide (NMO-Li2O, K2O) to aluminum oxide ratio using molecular dynamics simulations. The applied simulation procedure yields a set of configurations, the so-called inherent structures, of the liquid state slightly above the glass transition temperature. The generation of a large set of inherent structures allows a statistical sampling of the medium-range order of the Gd3+ ions with less computational effort compared to other simulation methods. The resulting medium-range atomic structures of network former and modifier ions are in good agreement with experimental results and simulations of similar glasses. It was found that increasing NMO/Al ratio increases the network modifier coordination number with non-bridging oxygen sites and reduces the overall stability of the network structure. The fraction of non-bridging oxygen sites in the vicinity of Gd3+ ions increases considerably with decreasing field strength and increasing concentration of the network modifier ions. These correlations could be confirmed even if the simulation results of alkaline earth aluminosilicate glasses are added to the analysis. In addition, the structure predictions generally indicate a low driving force for the clustering of Gd3+. Here, network modifier ions of large ionic radii reduce the probability of Gd-O-Gd contacts.
Thieme, Christian; Herrmann, Andreas; Kracker, Michael; Patzig, Christian; Höche, Thomas; Rüssel, Christian
Microstructure investigation and fluorescence properties of europium-doped scheelite crystals in glass-ceramics made under different synthesis conditions. - In: Journal of luminescence, ISSN 0022-2313, Bd. 238 (2021), 118244
Reiß, Stephanie; Hopfeld, Marcus; Romanus, Henry; Pfeifer, Kerstin; Krischok, Stefan; Rädlein, Edda
Chemical changes of float glass surfaces induced by different sand particles and mineralogical phases. - In: Journal of non-crystalline solids, ISSN 0022-3093, Bd. 566 (2021), 120868

Particles play an important role in the storage, transportation and natural weathering of glasses, but their influence on glass degradation is little studied. In this work, the influence of main sand components is investigated. Feldspar exhibits the strongest leaching rate for the network former Na, while quartz has the lowest. The leaching rate of natural sands is in between. Based on these findings, a model describing the leaching mechanism was developed: Hereby, hydroxyl groups adhering on sand grains adsorb network modifiers by substituting their hydrogen by network formers from the glass surface. The amount of available hydroxyl groups determines the leaching rate. This model is supported by loss on ignition performed for the sands, which might be a suitable method to roughly estimate their leaching rates. The adsorption of network modifiers suppresses carbonate formation, dendritic growth and Mg diffusion in the glass surface region. Pimple-like crystal growth is observed.
Schneckenburger, Max; Hofele, Markus; Raab, Jonas; Ruck, Simon; Harrison, David; Riegel, Harald; Börret, Rainer
Additive manufactured injection moulds with optical quality surfaces. - In: Proceedings of the 20th International Conference of the European Society for Precision Engineering and Nanotechnology, (2020), S. 147-150

Pablos Martín, Araceli de; Herrmann, Andreas; Selle, Susanne; Oberleiter, Bastian; Rainer, Thomas; Höche, Thomas
Sintered porous glasses hosting luminescent species of different nature: Eu3+ ions and Tb3+-doped Ba2TiSi2O8 glass-ceramic powder. - In: Journal of non-crystalline solids, ISSN 0022-3093, Bd. 531 (2020), 119846
Im Titel sind "3+" hochgestellt, "2" und "8" tiefgestellt

We report on the employment of a nano-porous Vycor-type glass as host for two luminescent substances of very different physical and chemical nature, which share the same porous space. Firstly, BTS:Tb^3+ glass-ceramic nano-powders were infiltrated in the porous structure and secondly Eu^3+ ions from a nitrate aqueous solution were included afterwards. Upon sintering, the porous silica matrix collapses, embedding both luminescent species. We focused on the micro and nano-structure of the sintered glasses. Upon sintering a europium silicate phase crystallizes as monocrystalline hexagonal nano-rods, which coexist with amorphous round particles below 100 nm enriched in Eu and Si. Both kinds of particles are embedded in a cristobalite matrix. The interesting microstructure is reported for the first time. The sintering heating rate influences the microstructure after the sintering. The microstructure was investigated by a last generation TEM microscope with aberration correction, EDXS and an exhaustive electron diffraction analysis. The inclusion of BTS:Tb^3+ is only limited, and thus, the its role in the optical properties of the final material is negligible. Luminescence upon UV excitation shows the characteristic emission peaks of Eu^3+. This work highlights the possibility of combining several luminescent materials inside a silica matrix.
Hoell, Armin; Raghuwanshi, Vikram Singh; Bocker, Christian; Herrmann, Andreas; Rüssel, Christian; Höche, Thomas
Crystallization of BaF2 from droplets of phase separated glass - evidence of a core-shell structure by ASAXS. - In: CrystEngComm, ISSN 1466-8033, Bd. 22 (2020), 30, S. 5031-5039
Im Titel ist "2" tiefgestellt