TY - CONF A1 - Hertwig, Andreas T1 - Determining thermal transitions in thin polymer layers by means of spectroscopic ellipsometry N2 - Thin polymer layers have enormous technical significance as polymer coatings on materials are very cost-effective for tailoring properties of surfaces. Apart from technical aspects in their use, thin polymer layers can be used to determine dimensional aspects in properties of material, such as confinement effects. In this work, we investigated several different polymer layer materials and determined their glass transition region by means of temperature-dependent spectroscopic ellipsometry. We have optimised our fitting procedure of the ellipsometric data produced in temperature ramp experiments. By this, we could measure the dependence of Tg on the layer thickness in a wide variety of thickness values, proving the existence of confinement effects in the investigated systems. We compare numerical methods for determining the location of the glass transition and discuss the possibilities of different analysis methods when determining thermal transitions. We also discuss the simultaneous existence of these transitions and annealing effects and the implications on the accuracy of the determined data. T2 - 12th Workshop Ellipsometry 2023 CY - Prague, Czech Republic DA - 18.09.2023 KW - Thin Films KW - Polymers KW - Ellipsometry KW - Themal Transitions PY - 2023 AN - OPUS4-58413 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Calibration samples and the GUM-compliant determination of uncertainties in ellipsometry N2 - Ellipsometry is well known as a highly sensitive and reproducible surface analysis technique. However, in a context of metrological applications, the most important property of a measurement process is accuracy, relying on statistical precision, (reproducibility) and trueness (in an absolute sense versus a given standard). The latter is much more difficult to achieve. In this presentation, we discuss the possibility of establishing ellipsometry in a diverse metrological landscape by means of defining standard procedures and best practice methodologies for the measurement and for calibration purposes. The most important task of this approach is to determine the model-inherent uncertainty, originating from parameter coupling. We achieve this by means of sensitivity analysis of the parameters resulting from the fit process. We discuss the definition of reference materials by which accuracy can be made available for ellipsometry, passed along between ellipsometry laboratories and for other measurement techniques. The determination of uncertainty is presented in this work for a number of examples involving difficult analysis models employed for samples from different production environments. We present a standardization initiative with the goal to disseminate this work into an international standard alongside an inter-laboratory study comparing the results for complex samples gained by laboratories with different instrumentation. We also present the results gained within EURAMET projects focused on the metrology of materials with strong non-idealities used in photovoltaics and other energy technology. T2 - Workshop Ellipsometry 2018 CY - Chemnitz, Germany DA - 19.03.2018 KW - Ellipsometric metrology KW - Reference samples KW - Reference procedures KW - Standardization PY - 2018 AN - OPUS4-44674 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Characterisation of Non-ideal Samples with Spectroscopic Mapping and Imaging Ellipsometry T2 - Workshop Quantitative 3D-Mikroskopie von Oberflächen CY - Braunschweig, Germany DA - 2015-04-28 PY - 2015 AN - OPUS4-33400 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Reference coatings for thin film technology - beyond the state of the art T2 - 6th Workshop Ellipsometry CY - Berlin, Germany DA - 2011-02-02 PY - 2011 AN - OPUS4-23064 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Blistering and layer modification of hydrogenated amorphous carbon layers induced by femtosecond laser pulse irration T2 - Bunsentagung 2011 CY - Berlin, Germany DA - 2011-06-02 PY - 2011 AN - OPUS4-23361 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Hydrogen-containing amorphous carbon layers as optical materials for the NIR and MIR spectral range T2 - Plasma Surface Engineering (PSE 2006) CY - Garmisch-Partenkirchen, Germany DA - 2006-09-11 PY - 2006 AN - OPUS4-12468 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - MgF2 moderate temperature sol-gel deposition for optical UV-applications T2 - BESSY Usertreffen CY - Berlin, Germany DA - 2006-12-07 PY - 2006 AN - OPUS4-14221 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Moderate temperrature sol-gel deposition of fluoride films for optical UV-applications: an ellipsometrc study on homogeneity T2 - International Conference on Spectroscopic Ellipsoemtry CY - Stockholm, Sweden DA - 2007-06-11 PY - 2007 AN - OPUS4-14955 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Certification of reference materials and validation of reference procedures: challenges on ellipsometry T2 - International Conference on Spectroscopic Ellipsoemtry CY - Stockholm, Sweden DA - 2007-06-11 PY - 2007 AN - OPUS4-14957 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Standardisation in the analysis of complex thin film systems with ellipsometry T2 - Workshop Ellipsometry 2012 CY - Leipzig, Germany DA - 2012-03-05 PY - 2012 AN - OPUS4-25685 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Enhanced SPR-ellipsometric gas sensors with doped dielectric layers T2 - ICSE 6 Konferenz CY - Kyoto, Japan DA - 2013-05-26 PY - 2013 AN - OPUS4-28802 LA - deu 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 - Otremba, Frank A1 - An, Q. A1 - Bäßler, Ralph A1 - Hertwig, Andreas A1 - Rehfeldt, Rainer A1 - Hidde, Gundula T1 - Investigation of mechanical stress and B10 exposure on FKM polymer N2 - Biofuels, particularly biodiesel, have gained significant attention as an alternative to traditional fossil fuels in recent years. Unlike diesel, which contains hundreds of compounds, biodiesel only contains a few compounds in the C16-C18 carbon chain. However, the use of biodiesel in automobile and transportation applications can result in problems of degradation or even damage in materials. Among the commonly used polymer materials, fluorocarbon (FKM) shows excellent performance and high stability and compatibility towards oil, diesel, ethanol, and other chemicals. FKM is a family of fluorocarbon-based fluoroelastomer materials, which provide excellent high-temperature and chemical stability compared to other elastomers. As a result, FKM is widely used in chemical processes such as petroleum refining, where it is used for sealings, pumps, and other components. T2 - TMS 2024 153rd Annual Meeting & Exhibition Supplemental Proceedings CY - Orlando, Florida, USA DA - 03.03.2024 KW - B10 exposure KW - FKM polymer PY - 2024 AN - OPUS4-59636 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 - International conference on spectroscopic ellipsometry (ICSE-7) CY - Berlin, Germany DA - 06.06.2016 KW - Spectroscopic Ellipsometry KW - Electron Microscopy KW - Multi-method Metrology KW - Porous Materials KW - Thin Films KW - Titanium Dioxide PY - 2016 AN - OPUS4-37202 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hülagü, Deniz A1 - Hertwig, Andreas T1 - Correlative analysis of graphene: Advancing ellipsometry as a fast routine method N2 - Graphene (G) and graphene oxide (GO) are key materials for various applications, yet their structural and thickness inhomogeneities calls for rapid, reliable characterization. In this work, we performed a correlative analysis, combining spectroscopic (SE) and imaging ellipsometry (IE) with complementary microscopy techniques to investigate monolayer graphene and GO flakes on SiO₂/Si substrates. SEM, owing to its high resolution and excellent contrast, delivered a comprehensive overview of the monolayer graphene (Figure 1a) and enabled the clear identification of individual GO flakes (c). However, SEM does not provide layer-thickness information. In this case, SE served as a fast and non-destructive method capable of quantitative thickness determination through optical modeling, revealing a graphene layer thickness of 0.7 nm (b), corresponding to a monolayer. The GO flake identified by SEM was subsequently analyzed by AFM, a well-established technique providing nanoscale height profiles with high accuracy (d–f). AFM results further revealed flake thicknesses of a few monolayers. However, AFM is time-consuming, restricted to small scan areas, and does not offer a full overview of the sample. WLIM complemented these results by providing large-area imaging, enabling the visualization of multiple flakes simultaneously. Nevertheless, it is not able to quantify the exact thickness (e). In contrast, IE enabled non-destructive, substrate-independent thickness of GO flakes with single-atomic-layer precision and improved sensitivity, once the ellipsometer settings were optimized for material and thickness contrast and fixed during imaging, bridging the gap between overview imaging and quantitative nanoscale analysis (g–h). While SE provides non-destructive, quantitative thickness information for homogeneous monolayer graphene, GO flakes require imaging-based methods. Therefore, IE represents an attractive alternative, offering large-area maps of GO flakes together with local layer-thickness information. This correlative approach establishes a foundation for standardized, large-area quality assessment of such 2D materials. T2 - 13th Workshop on Spectroscopic Ellipsometry WSE 2026 CY - Genova, Italy DA - 09.02.2026 KW - Monolayer graphene KW - Graphene oxide KW - Correlative Analysis KW - SEM KW - Spectroscopic ellipsometry KW - Imaging ellipsometry KW - AFM PY - 2026 AN - OPUS4-65708 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -