TY - JOUR A1 - Hülagü, Deniz A1 - Ermilova, Elena A1 - Weise, Matthias A1 - de Préville, Sophie A1 - Hoffmann, Johannes A1 - Morán‐Meza, José A1 - Piquemal, François A1 - Hertwig, Andreas T1 - Multimethod Electrical Characterization of Thin Indium Tin Oxide Films: Structuring and Calibration Sample Development for Scanning Probe Microscopy N2 - Indium tin oxide (ITO), a transparent conductive oxide, is widely used in optoelectronic applications due to its electrical conductivity, optical transparency, and chemical stability. This study employs spectroscopic ellipsometry (SE) to analyze ITO layers, enabling nondestructive determination of film thickness, dielectric functions, and bulk conductivity. Electrical properties derived from SE are compared with those obtained using the four‐point probe method (4PM) to improve metrological tools for nanotechnology applications and optimize deposition process monitoring for better control of film properties. This work also investigates the chemical stability of ITO layers under etching conditions and explores the development of new sheet resistance standards for scanning microwave microscopy (SMM). The results show that ITO resistivity, calculated from fitted SE data, increases with oxygen flow rate up to 5 cm3(STP) min−1. Good agreement is observed between sheet resistance values obtained by SE and 4PM up to 3 cm3(STP) min−1. Additionally, the sheet resistance values of a distinct set of microstructured ITO samples with different ITO layer thicknesses are determined by SMM, which are highly consistent with those obtained by the 4PM. KW - Ellipsometry KW - Indium tin oxide (ITO) KW - Scanning microwave microscopy (SMM) KW - Sheet resistance calibration standards KW - ITO wet etching PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-626242 DO - https://doi.org/10.1002/pssa.202400871 SN - 1862-6300 VL - 222 IS - 14 SP - 1 EP - 18 PB - Wiley CY - Hoboken, New Jersey, USA AN - OPUS4-62624 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lucassen, F. A1 - Franz, G. A1 - Wirth, R. A1 - Weise, Matthias A1 - Hertwig, Andreas T1 - The morphology of the reaction front of the dissolution-precipitation reaction rutile + wollastonite = titanite in time series experiments at 600 °C/400 MPa N2 - Fluid-assisted mass transport reactions by dissolution-precipitation, where a precursor mineral reacts with a fluid, play an important role in metamorphism and metasomatism. We investigated titanite growth on rutile in time series experiments between one and 107 days at constant P-T conditions of 600 °C and 400 MPa in the system TiO2-CaO-SiO2-Na2O-HCl-H2O. A two-capsule assemblage allows for transport of Ca and Si from dissolving wollastonite to dissolving rutile, the Ti-source, in a NaCl-bearing aqueous fluid, according to the general reaction CaSiO3 + TiO2 = CaTiSiO5. Complete overgrowth of rutile by titanite occurred after just one day of experiment. Fine-grained lozenge-shaped titanite crystals of short-time runs (up to 14 days) reorganize to larger predominantly prismatic crystals after >14 days. After investigation by scanning electron microscopy, the titanite overgrowth was removed from the rutile by hydrofluoric acid, to provide a three-dimensional view of the dissolution-reaction front on the rutile surface. The morphology of the rutile surface is dominated by humps or ridges beneath the central region of a titanite crystal and valleys at the grain boundaries between adjacent titanite crystals. The dissolution pattern on the rutile surface mimics the titanite overgrowth and changes with changing grain size and shape of the titanite with longer run times. The preferred dissolution of rutile in the valleys is clearly linked to the position of the titanite grain boundaries, which served as pathways for fluid-assisted element transport. Rutile-titanite and titanite-titanite boundaries show a significant porosity in transmission electron microscopy images of foils prepared by focused ion beam milling. The large-scale dissolution pattern on the rutile surface is independent of the crystallographic orientation of the rutile and entirely dominated by the arrangement of titanite crystals in the overgrowth. Dissolution features on a scale smaller than ~1 µm are dominated by stepwise dissolution and etch-pits following the crystallographic orientation of the rutile. Similar observations were made in experiments with an additional Al-source, although these experiments result in a different overgrowth pattern; i.e., an exposed rutile surface is always present and solitary titanite crystals are accompanied by partial overgrowths. Quantitative characterization of the surface morphology by white-light interference microscopy demonstrates that, with increasing grain size of titanite, dissolution of rutile is strongly enhanced at the titanite grain boundaries. Natural examples of titanite overgrowths on rutile show the same relations between element pathways, arrangement of titanite crystals and 3D dissolution pattern on rutile as in the experimental systems. We conclude that the transport of Ti away from the rutile and of Ca + Si into the reaction rim occurred in a grain boundary fluid, the composition of which must have been strongly different from the composition of the bulk fluid in the experiment, as well as in the natural system. The reaction progress depends on the availability of a fluid, and relicts of rutile in titanite indicate restricted availability of fluid in the natural system (e.g., a fluid pulse that was consumed by the reactions). The reaction examined here can serve as a proxy for other reactions of the conversion of oxide minerals (e.g., spinel or corundum) into silicates. KW - Experimental mineralogy KW - Rutile KW - Titanite KW - Dissolution-precipitation KW - Reaction morphology KW - Geochemistry & Geophysics PY - 2012 DO - https://doi.org/10.2138/am.2012.3742 SN - 0003-004X SN - 1945-3027 VL - 97 IS - 5-6 SP - 828 EP - 839 PB - Mineralogical Society of America CY - Washington, DC AN - OPUS4-27680 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Khropost, Diana A1 - Riethmüller, Franziska A1 - Döhring, Thorsten A1 - Flachs, Dennis A1 - Hülagü, Deniz A1 - Hertwig, Andreas A1 - Cotroneo, Vincenzo A1 - gibertini, eugenio T1 - Polydopamine – a bio-inspired polymer for X-ray mirror coatings and other technical applications N2 - Although the organic molecule dopamine (3,4-dihydroxyphenethylamine) is commonly known as one of the “hormones of happiness”, thin polymer films of polydopamine (PDA) also have interesting technical properties. PDA is a very strong glue that sticks on almost everything, even under water. In nature, PDA is found in the byssal thread cuticles of mussels. When produced by dip-coating, the self-organizing PDA layers grow in a reproducible thickness of single or multiple molecule monolayers of a few nanometres thickness only. Here we present an optimized preparation regime as derived from polymerization analysis through absorption spectroscopy. One application is the use of thin PDA overcoatings to increase the soft X-ray reflectivity of astronomical X-ray mirrors. Furthermore, we give an outlook to other technical applications for this interesting material, presenting this bio-inspired organic polymer as an innovative technical solution for the future, with applications such as PDA-based super-capacitors and its promising role in enhancing separator materials for batteries. T2 - SPIE Optics + Optoelectronics 2025 CY - Prague, Czech Republic DA - 07.04.2025 KW - X-ray mirrors KW - Reflectivity KW - Polydopamine KW - Ellipsometry PY - 2025 DO - https://doi.org/10.1117/12.3056298 VL - 13531 SP - 1 EP - 11 PB - SPIE AN - OPUS4-63630 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Khropost, Diana A1 - Riethmüller, Franziska A1 - Stanik, Eva A1 - Döhring, Thorsten A1 - Hertwig, Andreas A1 - Hülagü, Deniz T1 - Polydopamine -a bionic material and its potential applications for batteries N2 - Polydopamine (PDA) recently came into focus as an innovative material for applications in various technical fields. It is a very strong glue that sticks on almost everything, even under water: In nature, PDA is found in the byssal thread cuticles of mussels. In 2007, Lee et al. first showed that dipping substrates into a solution of dopamine results in the formation of thin PDA films on numerous materials. The simple preparation and the high durability of these coatings have stimulated growing research interest and a wide variety of applications in energy, biomedical and environmental science, and other fields. We have investigated thin layers of PDA with different methods including ellipsometry, tactile measurements of the layer thickness and in situ absorption measurements during the polymerization process. During polymerization the dopamine solution shows a progressive colour change from transparent to brown that has been monitored by spectrometric measurements. The increasing absorption of the cuvette with dopamine solution can be seen in figure 1. The absorption levels off after approximately 2,5 h of polymerization time, thus indicating termination of the primary formation of the PDA film. This data shows that for homogeneous layer growth it is advantageous to interrupt the process after two hours. To generate a higher layer thickness, the samples need to be cleaned and immersed in a fresh dopamine solution subsequently. In addition, ellipsometry measurements on polydopamine layers could determine the corresponding coating thickness as well as its complex refractive index over a broad wavelength range. T2 - Materials Week 2025 CY - Frankfurt am Main, Germany DA - 02.04.2025 KW - Polydopamine KW - Ellipsometry KW - Leyer thickness PY - 2025 AN - OPUS4-63636 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scholtz, Lena A1 - Tavernaro, Isabella A1 - Eckert, J. G. A1 - Lutowski, Marc A1 - Geißler, Daniel A1 - Hertwig, Andreas A1 - Hidde, Gundula A1 - Bigall, N. C. A1 - Resch-Genger, Ute T1 - Influence of nanoparticle encapsulation and encoding on the surface chemistry of polymer carrier beads N2 - Surface-functionalized polymer beads encoded with molecular luminophores and nanocrystalline emitters such as semiconductor nanocrystals, often referred to as quantum dots (QDs), or magnetic nanoparticles are broadly used in the life sciences as reporters and carrier beads. Many of these applications require a profound knowledge of the chemical nature and total number of their surface functional groups (FGs), that control bead charge, colloidal stability, hydrophobicity, and the interaction with the environment and biological systems. For bioanalytical applications, also the number of groups accessible for the subsequent functionalization with, e.g., biomolecules or targeting ligands is relevant. In this study, we explore the influence of QD encoding on the amount of carboxylic acid (COOH) surface FGs of 2 μm polystyrene microparticles (PSMPs). This is done for frequently employed oleic acid and oleylamine stabilized, luminescent core/shell CdSe QDs and two commonly used encoding procedures. This included QD addition during bead formation by a thermally induced polymerization reaction and a post synthetic swelling procedure. The accessible number of COOH groups on the surface of QD-encoded and pristine beads was quantified by two colorimetric assays, utilizing differently sized reporters and electrostatic and covalent interactions. The results were compared to the total number of FGs obtained by a conductometric titration and Fourier transform infrared spectroscopy (FTIR). In addition, a comparison of the impact of QD and dye encoding on the bead surface chemistry was performed. Our results demonstrate the influence of QD encoding and the QD-encoding strategy on the number of surface FG that is ascribed to an interaction of the QDs with the carboxylic acid groups on the bead surface. These findings are of considerable relevance for applications of nanoparticle-encoded beads and safe-by-design concepts for nanomaterials. KW - Optical spectroscopy KW - Particle KW - Optical assay KW - IR spectroscopy KW - Fluorescence KW - Quantum yield KW - Quality assurance KW - Nano KW - Synthesis KW - Surface chemistry KW - Quantification KW - Method KW - Conductometry PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-581502 DO - https://doi.org/10.1038/s41598-023-38518-7 SN - 2045-2322 VL - 13 IS - 1 SP - 1 EP - 15 PB - Springer Nature CY - London AN - OPUS4-58150 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Measurement of porous TiO2 layers with spectroscopic ellipsometry - a multi-method study N2 - By means of an effective medium (EMA) based approach, it is possible to use spectroscopic ellipsometry to determine the mixing ratios between air and material in porous dielectrics and calculate a quantitative value of the porosity for these materials. As this method is model-based, it is very difficult to provide a quantitative measure for the accuracy of porosity values determined by this method. Valuable additional information can often be obtained by combining ellipsometry with other complementary methods. In the present study, the ellipsometry results were validated by Electron Probe Microanalysis (EPMA) with the option of layer analysis (by the socalled “STRATAGem” approach), gravimetry, and electron microscopy. We analysed porous TiO2 thin layers synthesised by means of a template synthesis Approach (evaporation induced self assembly). Ellipsometry measurements on porous samples are difficult to analyse due to the complexity of the models necessary. Often it is difficult to decide if the measured data contains enough information to successfully determine the target quantities (mixing ratio, dielectric function of the matrix material). One method to decrease the complexity of the fit and therefore use the measurement data most efficiently is a multi-sample analysis. In the present case, multi-sample analysis was used for determining the porosity factors of the individual layers while using one common set of dielectric function values for the matrix in all cases. While the results of the fit analysis in this case can be used to show the feasibility and also the limitations of the multi-method approach, the porosity values themselves show a promising agreement between the Independent methods. It can therefore be concluded that determining porosity values with ellipsometry is in accordance to other methods to the level of accuracy provided by the complementary methodologies. T2 - ICSE-7, 7th International Conference on Spectroscopic Ellipsometry CY - Berlin, Germany DA - 5.6.2016 KW - Spectroscopic ellipsometry KW - Electrolysis KW - Catalysis KW - Thin film metrology KW - Porous materials PY - 2016 AN - OPUS4-39940 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Normung in der Oberflächen-und Schichttechnik N2 - Report über Normungsaktivitäten im Bereich der Messtechnk an Oberflächen und dünnen Schichten. Übersicht über Methoden und Vorstellung von laufenden Projekten mit Bezug zur Normung T2 - PlasmaGermany Herbstmeeting 2022 CY - Bielefeld, Germany DA - 07.11.2022 KW - Oberflächenmesstechnik KW - Spektroskopie KW - Ellipsometrie KW - XPS KW - Dünne Schichten PY - 2022 AN - OPUS4-56483 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - An, Q. A1 - Bäßler, Ralph A1 - Hertwig, Andreas A1 - Rehfeldt, Rainer A1 - Hidde, Gundula A1 - Otremba, Frank T1 - Investigation of Mechanical Stress and B10 Exposure on FKM Polymer N2 - Mechanical stress often accelerates the failure of polymer materials. The aim of this research is to study the interaction between the sealing material FKM and biofuels B10 (heating oil with 10% biodiesel). The mechanical stress test was carried out in a special apparatus. Both mechanical and non-mechanical stress tests were conducted on specimens at 20, 40, and 70 °C for 28 days to document changes in mass, volume, and tensile properties. Both increasing temperature and mechanical stress have a significant effect on the tensile strength of the FKM polymer when exposed to B10. The combination of increasing temperature and mechanical stress induced rupture within 2 h. It was also established that FKM polymer with pre-exposure in B10 survived longer during mechanical stress compared to specimens exposed only to air. With the support of infrared (IR) spectroscopy, we were able to confirm the penetration of B10 into the FKM polymer. T2 - TMS 2024 Annual Meeting & Exhibition Teilnahme mit Präsentation CY - Orlando-Florida / USA DA - 03.03.2024 KW - Biofuels KW - Sealing materials KW - Mechanical stress KW - Change in tensile properties PY - 2024 SN - 978-3-031-50349-8 DO - https://doi.org/10.1007/978-3-031-50349-8_108 SP - 1253 EP - 1261 PB - Springer CY - Orlando-Florida / USA AN - OPUS4-59638 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 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-514627 DO - https://doi.org/10.1002/app.49826 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 - Rastgou, Masoud A1 - Hülagü, Deniz A1 - Danilenko, Aleksandr A1 - Manoocheri, Farshid A1 - Hertwig, Andreas A1 - Ikonen, Erkki T1 - Comparison of thin-film thickness measurements using ellipsometry and reflectometry with uniform samples N2 - This study evaluates spectroscopic ellipsometry and reflectometry using high-quality SiO2 and Al2O3 thin-films on Si substrates, thereby facilitating a detailed assessment of consistency of measurement results and uncertainty analyses. The results with detailed uncertainty budgets indicate good agreement between the two methods across a broad layer thickness range from 10 nm to 2000 nm, with deviations remaining well within the measurement uncertainties. Ellipsometry results have lower uncertainty than reflectometry results especially with the thinner layers, whereas reflectometry uncertainties are lower with the thickest layers studied. This work underscores the importance of rigorous thickness characterization and reliable uncertainty evaluation as critical factors in advancing both modeling and measurement practices in thin-film metrology. KW - Ellipsometry KW - Reflectometry KW - Thin Film Metrology KW - Measurement Accuracy PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-655209 DO - https://doi.org/10.1088/1681-7575/ae3964 SN - 0026-1394 VL - 63 IS - 1 SP - 1 EP - 14 PB - IOP Publishing CY - Bristol, UK AN - OPUS4-65520 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kirner, Sabrina V. A1 - Slachciak, Nadine A1 - Elert, Anna Maria A1 - Griepentrog, Michael A1 - Fischer, Daniel A1 - Hertwig, Andreas A1 - Sahre, Mario A1 - Dörfel, Ilona A1 - Sturm, Heinz A1 - Pentzien, Simone A1 - Koter, Robert A1 - Spaltmann, Dirk A1 - Krüger, Jörg A1 - Bonse, Jörn T1 - Tribological performance of titanium samples oxidized by fs-laser radiation, thermal heating, or electrochemical anodization N2 - Commercial grade-1 titanium samples (Ti, 99.6%) were treated using three alternative methods, (i) femtosecond laser processing, (ii) thermal heat treatment, and (iii) electrochemical anodization, respectively, resulting in the formation of differently conditioned superficial titanium oxide layers. The laser processing (i) was carried out by a Ti:sapphire laser (pulse duration 30 fs, central wavelength 790 nm, pulse repetition rate 1 kHz) in a regime of generating laser-induced periodic surface structures (LIPSS). The experimental conditions (laser fluence, spatial spot overlap) were optimized in a sample-scanning setup for the processing of several square-millimeters large surface areas covered homogeneously by these nanostructures. The differently oxidized titanium surfaces were characterized by optical microscopy, micro Raman spectroscopy, variable angle spectroscopic ellipsometry, and instrumented indentation testing. The tribological performance was characterized in the regime of mixed friction by reciprocating sliding tests against a sphere of hardened steel in fully formulated engine oil as lubricant. The specific tribological performance of the differently treated surfaces is discussed with respect to possible physical and chemical mechanisms. KW - Femtosecond laser KW - Titanium KW - Oxidation KW - Friction PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-445609 DO - https://doi.org/10.1007/s00339-018-1745-8 SN - 0947-8396 SN - 1432-0630 VL - 124 IS - 4 SP - 326, 1 EP - 10 PB - Springer-Verlag AN - OPUS4-44560 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - How can ellipsometry help us to understand ultrashort pulse laser material processing? N2 - Laser processing of materials is a key technology in many fields of modern production. Still, more work is needed to understand the mechanisms behind laser material interaction. Recently, ellipsometry has become a valuable tool for investigating materials pre and post laser irradiation. Imaging ellipsometry and time-resolved methods boost this work and open up the path to a much better understanding of light interaction with solid state surfaces. We use spectroscopic single-spot and imaging ellipsometry to investigate treated and untreated surfaces. The goal is to determine changes in the material dielectric function, as well as geometric changes in surface layers (oxidation, modification, ablation, blistering). A good knowledge of bulk dielectric functions is often needed to model processes caused by laser irradiation. Imaging ellipsometry can play an important role in the post-analysis of laser treated sites on surfaces if combined with other methods such as IR-spectroscopy, SEM, topometric methods, Raman-spectroscopy, and XPS. In this work, we present the results of several studies to investigate laser-treated materials by means of ellipsometry. We cover the following topics: • Ablation of amorphous carbon layers, role of intra-layer interference effects on the result • Amorphisation behaviour of c-Si, depending on the crystal orientation, • Understanding the role of bulk and surface properties on ablation behaviour of classical and multicomponent high-entropy metals, T2 - 13th Workshop on Spectroscopic Ellipsometry CY - Genova, Italy DA - 09.02.2026 KW - Ellipsometry KW - Laser Ablation KW - Femtosecond Technology KW - Surface and Thin Layer Technology KW - Laser Surface processing PY - 2026 AN - OPUS4-65521 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -