TY - JOUR A1 - Ernst, O. C. A1 - Böttcher, K. A1 - Fischer, Daniel A1 - Uebel, D. A1 - Teubner, T. A1 - Boeck, T. T1 - Morphogenesis of liquid indium microdroplets on solid molybdenum surfaces during solidification at normal pressure and under vacuum conditions N2 - Electrical and optical applications based on micro- and nanoparticles have specific demands on their interfacial properties. These properties are strongly related to atmospheric conditions to which the particles were exposed during their formation. In this study, metallic In microparticles are synthesized by solidification of In droplets on an amorphous Mo substrate at normal pressure and under vacuum conditions. The influence of ambient pressure on the interface and surface shape is investigated. While solidification at atmospheric pressure leads to collapsed particles with undisturbed contact to the substrate, low pressures result in smooth spherical particles but with cavities inside. Numerical simulations with COMSOL Multiphysics reveal different temperature profiles and heat flux in particles during solidification for both cases. This indicates different starting conditions of the solidification, which leads to the described phenomenon eventually. The investigation of the varying process conditions on the particle shape in combination with the calculated and measured temperature curves over time gives valuable insights into new approaches to synthesize micro- and nanoparticles with defined interfacial properties. Both ambient pressure and cooling rate provide well-controllable and reliable parameters for the realization of different interfacial shapes. KW - Morphogenesis KW - Indium KW - Microdroplet KW - Molybdenum PY - 2022 U6 - https://doi.org/10.1021/acs.langmuir.1c02744 SN - 0743-7463 SN - 1520-5827 VL - 38 IS - 2 SP - 762 EP - 768 PB - ACS Publ. CY - Washington, DC AN - OPUS4-54242 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Fischer, Daniel A1 - Hertwig, Andreas A1 - Beck, Uwe A1 - Kormunda, M. A1 - Esser, N. T1 - Ellipsometric characterization of metal doped SnOx thin films for SPREE-based gas sensors N2 - Gas sensors are an important tool in various areas for example in industrial process control as well as Gas sensors are an important tool in various areas for example in industrial process control as well as safety applications or in research. A useful gas detector should be selective, precise, stable and cost-effective. In the present research a surface based gas detection technique is investigated using the SPR effect with ellipsometric readout. This technique is called surface plasmon resonance enhanced ellipsometry (SPREE). The sensor consists of a gold layer (40 nm) top-coated with a doped metal-oxide (M:SnOₓ, 5 nm). The coating is added by magnetron sputtering with doped targets with different doping concentrations. It could be shown that, without the top-coating, these type of sensors can detect various gases, e.g. CO, H2, O2, O3, He, N2, with sensitivities down to the ppm range (in air). The goal of the present study is to characterize the additional coating materials in dependence of the coating conditions. With the help of the doped-metal oxide, the sensitivity increases dramatically by a factor of 100. Additionally, a selectivity for specific gases is observed which depends on the doping conditions of the coating. Changing the properties of the plasma coating process and the doping metal gives access to a variety of different layers and enables us to find the best conditions. T2 - Leibniz Institut für Analytische Wissenschaften ISAS e.V. - Kolloqium CY - Berlin, Germany DA - 05.05.2016 KW - Ellipsometry KW - SPR effect KW - SnOx KW - Gas sensors PY - 2016 AN - OPUS4-37034 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kormunda, M. A1 - Fischer, Daniel A1 - Hertwig, Andreas A1 - Beck, Uwe A1 - Sebik, M. A1 - Esser, N. T1 - Preparation of pulsed DC magnetron deposited Fe-doped SnO2 coatings N2 - Iron-doped SnO2 coatings were deposited in a 50 kHz DC-pulsed magnetron sputtering discharge. The pulses had a duration of 4 µs in selected gas mixtures from pure argon up to 60% of oxygen at a constant total pressure of 0.2 Pa. A single target of SnO2 with Fe inset was used. The mass spectrometry study detected the gas-related ions Ar+, O2+ and O+, where the last one becomes the dominant positive ion at higher oxygen contents. Atomic oxygen ions had a higher energy as it resulted from the collision-caused dissociation on the target surface. The tin-related species were detected as Sn+ and SnO+. SnO2+ species were not detected. The deposition rate decreased by using gas mixtures with oxygen as well as the corresponding amount of Sn-related species in the plasma. The increase of oxygen also increased significantly the sheet resistance of the films. The XPS study showed that the iron concentration decreased by using additional oxygen. But the O/Sn ratio in the coatings was constant, contrary to the increased FeO/Fe ratio in the films. An additional analysis of the coatings by spectroscopic ellipsometry has shown a dependence of the polarizability and the permittivity on the amount of oxygen used during the deposition. In contrast, the study has found no such dependence for the absorption of the layers. KW - Coatings KW - Magnetron sputtering KW - Optical properties KW - Sheet resistivity KW - SnO2 PY - 2016 UR - http://onlinelibrary.wiley.com/doi/10.1002/pssa.201532882/full U6 - https://doi.org/10.1002/pssa.201532882 SN - 0031-8965 SN - 1862-6300 VL - 213 IS - 9 SP - 2303 EP - 2309 PB - WILEY-VCH Verlag GmbH & Co. KGaA CY - Weinheim AN - OPUS4-38106 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kage, Daniel A1 - Fischer, Linn A1 - Hoffmann, Katrin A1 - Thiele, T. A1 - Schedler, U. A1 - Resch-Genger, Ute T1 - Close spectroscopic look at dye-stained polymer microbeads N2 - Dye-stained micrometer-sized polymer beads are important tools in the life sciences with applications in biomedical, biochemical, and clinical research. Here, bead-based assays are increasingly used, for example, in DNA sequencing and the detection of autoimmune diseases or pathogenic microorganisms. Moreover, stained beads are employed as calibration tools for fluorescence microscopy and flow cytometry methods with increasing complexity. To address the requirements concerning the relevant fluorescence features, the spectroscopic properties of representative polymer beads with diameters ranging from about 1 to 10 μm stained with varying concentrations of rhodamine 6G were systematically assessed. The observed dependence of the spectral properties, fluorescence decay kinetics, and fluorescence quantum yields on bead size and dye loading concentration is attributed to different fluorescence characteristics of fluorophores located in the particle core and near-surface dye molecules. Supported by the fluorescence anisotropy measurements, the origin of the observed alteration of fluorescence features is ascribed to a combination of excitation energy transfer and polarity-related effects that are especially pronounced at the interface of the bead and the surrounding medium. The results of our studies underline the need to carefully control and optimize all Parameters that can affect the fluorescence properties of the dye-stained beads. KW - Fluorophore KW - Polymer particles KW - Photophysics KW - Life sciences KW - Standards PY - 2018 U6 - https://doi.org/10.1021/acs.jpcc.8b02546 SN - 1932-7447 VL - 122 IS - 24 SP - 12782 EP - 12791 PB - ACS Publications CY - Washington, DC AN - OPUS4-45453 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wu, Cheng-Chieh A1 - Weisbrich, S. A1 - Neitzel, F. A1 - Kadoke, Daniel A1 - Fischer, Michael A1 - Kohlhoff, Harald ED - Pastramă, Ştefan Dan ED - Constantinescu, Dan Mihai T1 - A Small-Scale Test Bridge for Measurement and Model-based Structural Analysis N2 - The Measurement- and Model-based Structural Analysis (MeMoS) integrates a finite element model into least squares adjustment and thus allows to evaluate a mechanical model and measurements in a combined analysis. To examine the capability to detect and localise damage using this integrated analysis MeMoS, a small-scale truss bridge made of aluminium profiles is built as a test specimen for this purpose. T2 - 35th Danubia Adria Symposium on Advances in Experimental Mechanics CY - Sinaia, Romania DA - 25.09.2018 KW - Structural analysis KW - Damage detection and localisation KW - Finite element method KW - Photogrammetry KW - Adjustment calculation PY - 2019 UR - http://www.sciencedirect.com/science/article/pii/S2214785319304894 U6 - https://doi.org/10.1016/j.matpr.2019.03.130 SN - 2214-7853 VL - 12 IS - 2 SP - 319 EP - 328 PB - Elsevier Ltd. AN - OPUS4-48053 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kormunda, M. A1 - Fischer, Daniel A1 - Hertwig, Andreas A1 - Beck, Uwe A1 - Sebik, M. A1 - Pavlik, J. A1 - Esser, N. T1 - Deposition and characterization of single magnetron deposited Fe:SnOx coatings N2 - Coatings deposited by magnetron co-sputtering from a single RF magnetron with a ceramic SnO2 target with iron inset in argon plasma were studied. The mass spectra of the process identified Sn+ and SnO+ species as the dominant species sputtered from the target, but no SnO2+ species were detected. The dominant positive ions in argon plasma are Ar+ species. The only detected negative ions were O-. Sputtered neutral tin related species were not detected. Iron related species were also not detected because their concentration is below the detection limit. The concentration of iron dopant in the tin oxide coatings was controlled by the RF bias applied on the substrate holder while the discharge pressure also has some influence. The iron concentration was in the range from 0.9 at.% up to 19 at.% increasing with the substrate bias while the sheet resistivity decreases. The stoichiometry ratio of O/(Sn + Fe) in the coatings increased from 1.7 up to 2 in dependence on the substrate bias from floating bias (- 5 V) up to - 120 V of RF self-bias, respectively. The tin in the coatings was mainly bonded in Sn4 + state and iron was mainly in Fe2 + state when other tin bonding states were detected only in a small amounts. Iron bonding states in contrary to elemental compositions of the coatings were not influenced by the RF bias applied on the substrate. The coatings showed high transparency in the visible spectral range. However, an increased metallic behavior could be detected by using a higher RF bias for the deposition. The X-ray diffraction patterns and electron microscopy pictures made on the coatings confirmed the presence of an amorphous phase. KW - Metal oxides KW - Transparent conductive oxides (TCO) KW - Magnetron KW - Optical properties KW - Ellipsometry KW - XPS characterzation PY - 2015 U6 - https://doi.org/10.1016/j.tsf.2015.11.009 SN - 0040-6090 VL - 595 IS - Part A SP - 200 EP - 208 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-35281 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Duwe, M. A1 - Quast, J.-H. A1 - Schneider, S. A1 - Fischer, Daniel A1 - Beck, Uwe T1 - Thin-film metrology of tilted and curved surfaces by imaging Mueller-matrix ellipsometry N2 - For the vast majority of ellipsometric measurements, the application of planar substrates is mandatory and requires a proper sample alignment prior to the measurement. Here, the authors present a generalized approach of how to extract the isotropic ellipsometric sample parameters from an imaging Mueller-matrix measurement even if the sample is significantly misaligned. They validate the method by layer-thickness calculations based on imaging Mueller-matrix measurements of flat crystalline silicon samples that were misaligned on purpose. Furthermore, they also exploit this method’s capabilities to perform spatially resolved layer-thickness measurements of a single-layer indium-tin-oxide coating on a fused-silica microlens without the need of realignment or repositioning of the sample during the measurement. T2 - 8th International conference on spectroscopic ellipsometry (ICSE-8) CY - Barcelona, Spain DA - 26.05.2019 KW - Metrology KW - Thin films KW - Polarization spectroscopy KW - Spectroskopic Imaging KW - Mueller-Matrix imaging ellipsometry PY - 2019 U6 - https://doi.org/10.1116/1.5122757 SN - 2166-2746 SN - 2327-9877 VL - 37 IS - 6 SP - 062908 PB - AIP CY - New York, NY AN - OPUS4-50209 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Fischer, Daniel A1 - Beck, Uwe A1 - Duwe, M. A1 - Schneider, S. T1 - Mueller-matrix imaging ellipsometry of structural anomalies and inhomogenities N2 - In the last years, the implementation of imaging ellipsometry in the variety of optical characterization techniques has shown tremendous potential to analyze the topology of surfaces in the lateral dimension. In the later studies, this contrast-rich surface images were affiliated with changes of the refraction indices, Absorption bands or layer thicknesses. However, it was realized that additional factors like curvature or scattering can have a great Impact on the ellipsometric readout of the analyzed system. In this study, we focus on the systematic evaluation of structural anomalies and inhomogenities of several Basic systems. This includes spherical particles as a model for microscopic curved surfaces in a range of 0.25 to 25 μm in diameter. In the macroscopic regime several conventional convex lenses were analyzed. Additional affords were made to generate microscopic concave model systems by applying nanoindentation with a spherical indentation unit. With this method calottes with a depth of 0.04 to 2 μm and radius of 2.5 μm were made. The macroscopic counterpart is delivered by conventional concave lens systems. For all systems, a variety of different bulk materials was investigated. This includes metal oxides, metals and polymers as well as combinations of each by applying coatings on the bulk materials with different layer thicknesses. To analyze these structural anomalies and inhomogenities properly, Mueller-Matrix imaging ellipsometry is the method of choice to address cross- and depolarization effects that occur due to the curved surfaces. Supplementary methods were used for an independent characterization of the topological properties of all structural anomalies and inhomogenities. This includes AFM and SEM for the microscopic samples (microparticles and nanoindented holes) and white light interferometry for the macroscopic lenses. This study results in a systematic screening of different coated and uncoated material systems with a topology that does not fit into conventional ellipsometry and thus is analyzed by Muller-Matrix imaging ellipsometry. This will help in quality control and is a contribution to the understanding of the polarizing effects of non-ideal Systems analyzed by ellipsometry. T2 - 8th International conference on spectroscopic ellipsometry (ICSE-8) CY - Barcelona, Spain DA - 26.05.2019 KW - Spectroskopic Imaging KW - Mueller-Matrix imaging ellipsometry KW - Structural anomalies KW - Structural inhomogenities PY - 2019 AN - OPUS4-48347 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Almalla, A. A1 - Hertwig, Andreas A1 - Fischer, Daniel A1 - Özcan Sandikcioglu, Özlem A1 - Witt, Julia T1 - Development of layer-by-layer assembled thin coatings on aluminium alloy AA2024-T3 for high resolution studies of local corrosion processes N2 - The aim of this study is to develop nanometer-thin epoxy-based films on aluminium alloy AA2024-T3 as a model coating system for high resolution corrosion studies. Spin coating was used for the layer-by-layer (LbL) deposition of poly-(ethylenimine) (PEI) and poly([o-cresyl glycidyl ether]-co-formaldehyde) (CNER) bilayers. The film chemistry and the cross-linking process were characterized by means of Fourier-transform infrared spectroscopy (FTIR). Ellipsometric data confirmed the linear increase of film thickness. The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) results indicate the improvement of the film barrier properties with increasing film thickness. Mapping of the topography and the volta potential was performed by means of scanning Kelvin probe force microscopy (SKPFM). The results indicate the presence of a homogeneous film structure, while the intermetallic phases can still be identified below the coating. The SKPFM Analysis confirmed that the model films are suitable for investigation of corrosion processes at the coating/metal interface. KW - Spectroscopy KW - Coatings KW - Electrochemistry KW - Microscopy KW - Resins PY - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-514627 SN - 0021-8995 VL - 137 IS - 48 SP - e49826-1 EP - e49826-9 PB - Wiley CY - New York, NY AN - OPUS4-51462 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fischer, Daniel A1 - Griepentrog, Michael A1 - Beck, Uwe A1 - Duwe, M. A1 - Quast, J.-H. A1 - Schneider, S. T1 - Effect of curvature of spherical microscopic indentations on the ellipsometric readout N2 - The authors describe and interpret curvature-related changes to the ellipsometric readout. As model system for a concave curvature, a set of three spherical microscopic indents in silicon (100) of different sizes was prepared by instrumented indentation testing using a spherical indenter. For reference, these samples were characterized by AFM to reveal the topography of each structure. The concavelike indents were analyzed by Mueller-Matrix imaging ellipsometry to extract lateral intensity images of 12 elements of the Mueller-Matrix. As a result of the detailed analysis of the image elements m22, m23, and m14, it was possible to correlate intensity changes and symmetry properties to depolarization and cross polarization induced by the edge threshold and the curved surface of the indent. KW - Spectroskopic Imaging KW - Mueller-Matrix imaging ellipsometry KW - Structural anomalies KW - Structural inhomogenities PY - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-498105 VL - 37 IS - 6 SP - 062906-1 EP - 062906-5 PB - American Vacuum Society AN - OPUS4-49810 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -