TY - CONF A1 - Sachse, René T1 - Spectroscopic ellipsometry for the determination of thickness and porosity of mesoporous metal oxide films N2 - Thin mesoporous metal oxide films are versatile and attractive candidates for several energy applications like photovoltaics, electrolysis or batteries. Due to their high surface area and ordered pore structure, mesoporous metal oxides demonstrate higher activities. The performance of the porous films is affected by properties like size and shape of the mesopores as well as the crystallinity of the framework. The exact determination and metrological evaluation of the complex morphology of thin mesoporous films requires a new analytical approach employing to combined data of different analytical methods. In this contribution we present a novel evaluation procedure for spectroscopic ellipsometry (SE) to analyse thin mesoporous iridium oxide films. Mesoporous iridium oxide films were prepared via dip-coating of a solution containing a triblock-copolymer as structure directing agent and an iridium precursor in ethanol. Deposited films were calcined in air at temperatures between 300 and 600 °C. Their morphology was studied with SEM and an electron probe microanalysis (EPMA)and correlated via SE with a Bruggeman effective medium approximation (BEMA). The developed SE model described the film thickness as well as the porosity. Figure 1a shows a top-view SEM image of mesoporous IrO2 film calcined at 375 °C. The image reveals that the films exhibit a well-ordered mesopore structure with an average pore diameter of 16 nm and a periodic distance between pore centres of 24 nm (FFT inset). Figure 1b is a parity plot of film thicknesses determined by cross-section SEM versus SE of IrO2 film samples prepared at different calcination temperatures. The porosity from the SE model is in good agreement to the porosity values obtained by EPMA. The contribution will assess in detail the novel approach to analyse the morphology and porosity of thin metal oxide films with spectroscopic ellipsometry. Moreover, the advantages of the new developed approach will be discussed as well as combination of datasets from multiple measurements to development new methods for innovative energy technologies. T2 - 30. Deutsche Zeolith-Tagung und Jahrestreffen der ProcessNet-Fachgruppe Adsorption CY - Kiel, Germany DA - 28.02.2018 KW - Mesoporous materials KW - Iridium oxide films KW - Electro catalyst KW - Spectroscopic ellipsometry KW - Thin film metrology KW - Multi-sample analysis PY - 2018 AN - OPUS4-45101 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Arinchtein, A. A1 - Schnack, R. A1 - Kraffert, K. A1 - Radnik, Jörg A1 - Dietrich, P. A1 - Sachse, René A1 - Krähnert, R. T1 - Role of Water in Phase Transformations and Crystallization of Ferrihydrite and Hematite N2 - The oxides, hydroxides, and oxo-hydroxides of iron belong to the most abundant materials on earth. They also feature a wide range of practical applications. In many environments, they can undergo facile phase transformations and crystallization processes. Water appears to play a critical role in many of these processes. Despite numerous attempts, the role of water has not been fully revealed yet. We present a new approach to study the influence of water in the crystallization and phase transformations of iron oxides. The approach employs model-type iron oxide films that comprise a defined homogeneous nanostructure. The films are exposed to air containing different amounts of water reaching up to pressures of 10 bar. Ex situ analysis via scanning electron microscopy, Transmission electron microscopy, selected area electron diffraction, and X-ray diffraction is combined with operando near-ambient pressure X-ray photoelectron spectroscopy to follow water-induced changes in hematite nd ferrihydrite. Water proves to be critical for the nucleation of ematite domains in ferrihydrite, the resulting crystallite orientation, and the underlying crystallization mechanism. KW - Iron oxide KW - Ferrihydrite KW - Hematite KW - Water KW - NAP-XPS KW - High pressure PY - 2020 DO - https://doi.org/10.1021/acsami.0c05253 VL - 12 SP - 38714 EP - 38722 PB - ACS Publication AN - OPUS4-51201 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -