TY - JOUR A1 - Sachse, René A1 - Hodoroaba, Vasile-Dan A1 - Kraehnert, R. A1 - Hertwig, Andreas T1 - Multilevel effective material approximation for modeling ellipsometric measurements on complex porous thin films JF - Advanced optical technologies N2 - Catalysts are important components in chemical processes because they lower the activation energy and thus determine the rate, efficiency and selectivity of a chemical reaction. This property plays an important role in many of today’s processes, including the electrochemical splitting of water. Due to the continuous development of catalyst materials, they are becoming more complex, which makes a reliable evaluation of physicochemical properties challenging even for modern analytical measurement techniques and industrial manufacturing. We present a fast, vacuum-free and non-destructive analytical approach using multi-sample spectroscopic ellipsometry to determine relevant material parameters such as film thickness, porosity and composition of mesoporous IrOx–TiOy films. Mesoporous IrOx–TiOy films were deposited on Si wafers by sol–gel synthesis, varying the composition of the mixed oxide films between 0 and 100 wt%Ir. The ellipsometric modeling is based on an anisotropic Bruggeman effective medium approximation (a-BEMA) to determine the film thickness and volume fraction of the material and pores. The volume fraction of the material was again modeled using a Bruggeman EMA to determine the chemical composition of the materials. The ellipsometric fitting results were compared with complementary methods, such as scanning electron microscopy (SEM), electron probe microanalysis (EPMA) as well as environmental ellipsometric porosimetry (EEP). KW - Electrochemical catalysts KW - Mixed metal oxide KW - Multi-sample analysis KW - Spectroscopic ellipsometry KW - Thin mesoporous films PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-551026 DO - https://doi.org/10.1515/aot-2022-0007 SN - 2192-8584 SN - 2192-8576 VL - 11 IS - 3-4 (Topical issue: Ellipsometry) SP - 137 EP - 147 PB - De Gruyter CY - Berlin AN - OPUS4-55102 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ortel, Erik A1 - Hertwig, Andreas A1 - Berger, D. A1 - Esposito, P. A1 - Rossi, A. M. A1 - Kraehnert, R. A1 - Hodoroaba, Vasile-Dan T1 - New approach on quantification of porosity of thin films via electron-excited X‑ray spectra JF - Analytical Chemistry N2 - One of the crucial characteristics of functionalized thin films is their porosity (i.e., the ratio between the pore volume and the volume of the whole film). Due to the very low amount of material per coated area corresponding to thin films, it is a challenge for analytics to measure the film porosity. In this work, we present an Approach to determine the porosity of thin films by means of electron probe microanalysis (EPMA) either by wavelength-dispersive X-ray spectrometry (WDX) or by energy-dispersive X-ray spectrometry (EDX) with a scanning electron microscope (SEM). The procedure is based on the calculation of the film mass deposition from electron-excited X-ray spectra. The mass deposition is converted into film density by division of measured film thickness. Finally, the film porosity is calculated from the measured film density and the density of bulk, nonporous film material. The general applicability of the procedure to determine the porosity is demonstrated on thin templated mesoporous TiO₂ films, dip-coated on silicon wafer, with controlled porosity in the range of 15 to 50%. The high accuracy of the mass deposition as determined from X-ray spectra was validated with independent methods (ICP-OES and weighing). Furthermore, for the validation of the porosity results, ellipsometry, interference fringes method (IFM), and focused ion beam (FIB) cross sectioning were employed as independent techniques. Hence, the approach proposed in the present study is proven to be suited as a new analytical tool for accurate and relatively fast determination of the porosity of thin films. KW - Porosity KW - X-rays KW - EDX KW - Thin film KW - TiO2 KW - Density KW - Mass deposition KW - STRATAGem PY - 2016 UR - http://pubs.acs.org/doi/abs/10.1021/acs.analchem.6b00847 DO - https://doi.org/10.1021/acs.analchem.6b00847 VL - 88 IS - 14 SP - 7083 EP - 7090 PB - ACS Publications CY - 1155 Sixteenth Street N.W., Washington, DC 20036 AN - OPUS4-36911 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ortel, Erik A1 - Kraehnert, R. A1 - Galbert, F. A1 - Hodoroaba, Vasile-Dan T1 - Thin film porosity determined by X-rays at SEM JF - Microscopy and microanalysis N2 - Various applications such as automotive catalysts, photocatalysis and sensors rely on thin coatings with high active surface area. The development of new and improved coatings requires in-depth understanding of the film morphology and texture. Especially the film porosity is a key parameter to identify structure-property relationships in applications. However, an accurate porosity determination of thin porous coatings is a challenging. In this contribution we present and discuss a new approach for determining the porosity of films by x-rays at SEM. KW - Thin film KW - Porosity KW - EDX KW - SEM KW - Stratagem KW - WDX PY - 2015 DO - https://doi.org/10.1017/S1431927615009319 SN - 1431-9276 SN - 1435-8115 VL - 21 IS - Suppl. 3 SP - Paper 0852, 1707 EP - 1708 PB - Cambridge University Press CY - New York, NY AN - OPUS4-34162 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sachse, René A1 - Hodoroaba, Vasile-Dan A1 - Hertwig, Andreas A1 - Kotil, L. A1 - Kraehnert, R. T1 - Analysis of elemental composition and porosity of mesoporous iridium titanium mixed oxide thin films for energy application by SEM/EDS JF - Microscopy and Microanalysis N2 - Porous materials play an important role in several fields of technology, especially for energy applications like photovoltaics, electrolysis or batteries. The activity of porous films is affected by properties like porosity, film thickness, chemical composition of the material as well as the crystallinity of the framework. The complex morphology of such porous films constitutes a challenge even for modern analytical techniques and requires new approaches employing the combination/complementation of data of different analytical methods. In this contribution we characterize thin mesoporous iridium-titanium mixed oxide film properties by Electron Probe Microanalysis (EPMA) with energy dispersive X-ray spectroscopy (EDS) at an SEM. KW - Electron probe microanalysis (EPMA) KW - Iridium-titanium mixed oxides KW - Spectroscopic ellipsometry KW - Mesoporous thin films KW - NanoSIMS PY - 2019 DO - https://doi.org/10.1017/S1431927619009589 SN - 1431-9276 (Print) SN - 1435-8115 (Online) VL - 25 IS - S2 (August) SP - 1770 EP - 1771 PB - Cambridge University Press CY - New York, NY, U.S.A. AN - OPUS4-48768 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rosu, Dana-Maria A1 - Ortel, Erik A1 - Hodoroaba, Vasile-Dan A1 - Kraehnert, R. A1 - Hertwig, Andreas ED - Hertwig, Andreas ED - Hinrichs, K. ED - Beck, Uwe ED - Esser, N. T1 - Ellipsometric porosimetry on pore-controlled TiO2 layers JF - Applied Surface Science N2 - The practical performance of surface coatings in applications like catalysis, water splitting or batteries depends critically on the coating materials’ porosity. Determining the porosity in a fast and nondestructive way is still an unsolved problem for industrial thin-films technology. As a contribution to calibrated, non-destructive, optical layer characterisation, we present a multi-method comparison study on porous TiO2 films deposited by sol-gel synthesis on Si wafers. The ellipsometric data were collected on a range of samples with different TiO2 layer thickness and different porosity values. These samples were produced by templated sol-gel synthesis resulting in layers with a well-defined pore size and pore density. The ellipsometry measurement data were analysed by means of a Bruggeman effective medium approximation (BEMA), with the aim to determine the mixture ratio of void and matrix material by a multi-sample analysis strategy. This analysis yielded porosities and layer thicknesses for all samples as well as the dielectric function for the matrix material. Following the idea of multi-method techniques in metrology, the data was referenced to imaging by electron microscopy (SEM) and to a new EPMA (electron probe microanalysis) porosity approach for thin film analysis. This work might lead to a better metrological understanding of optical porosimetry and also to better-qualified characterisation methods for nano-porous layer systems. 1. IntroductionPorous materials, especially porous thin films play an importantrole in chemical and physical technology in every case where thecontact area between two media has to be maximised. From cataly-sis to photochemistry and photovoltaics, the applications of porouslayer materials are diverse and numerous [1–6].The accurate and non-destructive characterisation of porousfilms for layered systems poses a challenge. This applies especiallyfor the key parameter of porous films, their porosity, i.e. the mix-ing ratio between the Matrix of the film (host material) and thepore volume which is empty or filled with a fluid medium (inclu-sions). This parameter influences most of the physical and chemicalproperties of a porous thin film and is therefore essential for theunderstanding as well as the optimisation of this class of materials. T2 - International Conference on Spectroscopic Ellipsometry (ICSE-7) CY - Berlin, Germany DA - 06.06.2016 KW - Spectroscopic ellipsometry KW - Porous materials KW - Porosimetry KW - Multi-sample analysis KW - Thin film metrology PY - 2017 DO - https://doi.org/10.1016/j.apsusc.2016.11.055 SN - 0169-4332 SN - 1873-5584 VL - 421 IS - Part B SP - 487 EP - 493 PB - Elsevier B.V. AN - OPUS4-42517 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sachse, René A1 - Hertwig, Andreas A1 - Kraehnert, R. A1 - Hodoroaba, Vasile-Dan T1 - Analysis of mesoporous iridium oxide thin films by the combined methodical approach SEM/EDS/STRATAGem JF - Microscopy and Microanalysis N2 - For the determination of porosity of Ir oxide thin films, electron probe microanalysis (EPMA) can be used as part of a combined SEM/EDS/STRATAGem analysis. The mass deposition (in μg cm-2) of films was calculated with the analysis software STRATAGem via k-values measured with EDS. The average density of coated films was obtained from the mass deposition and the film thickness as measured by the cross-section SEM. The porosity was calculated by dividing the average film density by the bulk (theoretical) density of the film material. Film porosities were counterchecked by spectroscopic ellipsometry (SE) using the Bruggeman effective medium approximation (BEMA). The results obtained by both analytical approaches/methods used, SEM/EDS/STRATAGem and SE were in good agreement. KW - Porous thin films KW - Iridium oxide KW - Electron probe microanalysis (EPMA) KW - Spectroscopic ellipsometry PY - 2018 UR - https://www.cambridge.org/core/journals/microscopy-and-microanalysis/article/analysis-of-mesoporous-iridium-oxide-thin-films-by-the-combined-methodical-approach-semedsstratagem/7607018338B542D8B8C4D944392781EF DO - https://doi.org/10.1017/S1431927618004300 SN - 1431-9276 SN - 1435-8115 VL - 24 IS - S1 (August) SP - 762 EP - 763 PB - Cambridge University Press CY - New York, NY, U.S.A. AN - OPUS4-45951 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -