TY - JOUR A1 - Omar, Hassan A1 - Ahamadi, Shayan A1 - Hülagü, Deniz A1 - Hidde, Gundula A1 - Hertwig, Andreas A1 - Szymoniak, Paulina A1 - Schönhals, Andreas T1 - Investigations of the adsorbed layer of polysulfone: Influence of the thickness of the adsorbed layer on the glass transition of thin films N2 - This work studies the influence of the adsorbed layer on the glass transition of thin films of polysulfone. Therefore, the growth kinetics of the irreversibly adsorbed layer of polysulfone on silicon substrates was first investigated using the solvent leaching approach, and the thickness of the remaining layer was measured with atomic force microscopy. Annealing conditions before leaching were varied in temperature and time (0–336 h). The growth kinetics showed three distinct regions: a pre-growth step where it was assumed that phenyl rings align parallel to the substrate at the shortest annealing times, a linear growth region, and a crossover from linear to logarithmic growth observed at higher temperatures for the longest annealing times. No signs of desorption were observed, pointing to the formation of a strongly adsorbed layer. Second, the glass transition of thin polysulfone films was studied in dependence on the film thickness using spectroscopic ellipsometry. Three annealing conditions were compared: two with only a tightly bound layer formed in the linear growth regime and one with both tightly bound and loosely adsorbed layers formed in the logarithmic growth regime. The onset thickness and increase in the glass transition temperature increases with annealing time and temperature. These differences were attributed to the distinct conformations of the formed adsorbed layers. KW - Glass transition KW - Adsorbed Layer PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-607701 DO - https://doi.org/10.1063/5.0223415 SN - 0021-9606 VL - 161 IS - 5 SP - 1 EP - 12 PB - AIP Publishing AN - OPUS4-60770 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hülagü, Deniz A1 - Ermilova, Elena A1 - Weise, Matthias A1 - de Préville, Sophie A1 - Hoffmann, Johannes A1 - Morán-Meza, José A1 - Piquemal, Francois A1 - Hertwig, Andreas T1 - Characterization of electrical properties in microstructured ITO layers using spectroscopic ellipsometry N2 - Thin indium tin oxide (ITO) layers are essential in optoelectronics due to their good electrical conductivity, optical transparency in the visible and near infrared regions, substrate adherence and chemical stability. They are widely used in photovoltaic cells, displays, and organic LEDs, and as low emissivity coatings in smart windows and energy-efficient buildings. For nanophotonic devices, understanding the interplay of ITO’s optical and electrical properties is crucial. Electrical resistivity can be tuned by modifying deposition conditions and layer thickness. However, measuring these properties, especially on microstructured surfaces, remains challenging due to the issues like homogeneity and instability during etching. Spectroscopic ellipsometry (SE), a non-destructive and phase-sensitive optical technique, offers precise measurement of thin film thickness and dielectric properties. In this study, we investigated the layer thickness, optical constants, and sheet resistance of unstructured and microstructured ITO thin layers using SE. Unstructured layers were deposited via DC-magnetron sputtering on silicon (Si) substrates in argon (Ar) atmospheres with varying oxygen (O2) flows. This multi-technique approach enhances the understanding of ITO layer structuring and provides robust methodologies for correlating optical and electrical properties, advancing metrology for nanotechnology applications and material science. It also opens the pathway to new reference samples and calibration methods for electrical properties involving device-like structured samples. T2 - ICSE10 - 10th International Conference on Spectroscopic Ellipsometry CY - Boulder, CO, USA DA - 08.06.2025 KW - Ellipsometry KW - Indium tin oxide (ITO) KW - Scanning microwave microscopy (SMM) KW - Sheet resistance calibration standards KW - ITO wet etching PY - 2025 AN - OPUS4-63631 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - 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 - 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 - 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 - Hülagü, Deniz A1 - Tobias, Charlie A1 - Dao, Radek A1 - Komarov, Pavel A1 - Rurack, Knut A1 - Hodoroaba, Vasile-Dan T1 - Towards 3D determination of the surface roughness of core–shell microparticles as a routine quality control procedure by scanning electron microscopy N2 - AbstractRecently, we have developed an algorithm to quantitatively evaluate the roughness of spherical microparticles using scanning electron microscopy (SEM) images. The algorithm calculates the root-mean-squared profile roughness (RMS-RQ) of a single particle by analyzing the particle’s boundary. The information extracted from a single SEM image yields however only two-dimensional (2D) profile roughness data from the horizontal plane of a particle. The present study offers a practical procedure and the necessary software tools to gain quasi three-dimensional (3D) information from 2D particle contours recorded at different particle inclinations by tilting the sample (stage). This new approach was tested on a set of polystyrene core-iron oxide shell-silica shell particles as few micrometer-sized beads with different (tailored) surface roughness, providing the proof of principle that validates the applicability of the proposed method. SEM images of these particles were analyzed by the latest version of the developed algorithm, which allows to determine the analysis of particles in terms of roughness both within a batch and across the batches as a routine quality control procedure. A separate set of particles has been analyzed by atomic force microscopy (AFM) as a powerful complementary surface analysis technique integrated into SEM, and the roughness results have been compared. KW - Core–shell particles KW - Image analysis KW - Roughness KW - Scanning electron microscopy KW - Atomic force microscopy KW - Tilting KW - Batch analysis PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-607590 DO - https://doi.org/10.1038/s41598-024-68797-7 SN - 2045-2322 VL - 14 IS - 1 SP - 1 EP - 13 PB - Springer Science and Business Media LLC AN - OPUS4-60759 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Riedel, Soraya A1 - Hülagü, Deniz A1 - Bennet, Francesca A1 - Carl, Peter A1 - Flemig, Sabine A1 - Schmid, Thomas A1 - Schenk, J. A. A1 - Hodoroaba, Vasile-Dan A1 - Schneider, Rudolf T1 - Electrochemical Immunomagnetic Ochratoxin A Sensing: Steps Forward in the Application of 3,3’,5,5’- Tetramethylbenzidine in Amperometric Assays N2 - Electrochemical methods offer great promise in meeting the demand for user-friendly on-site devices for Monitoring important parameters. The food industry often runs own lab procedures, for example, for mycotoxin analysis, but it is a major goal to simplify analysis, linking analytical methods with smart technologies. Enzyme-linked immunosorbent assays, with photometric detection of 3,3’,5,5’-tetramethylbenzidine (TMB),form a good basis for sensitive detection. To provide a straightforward approach for the miniaturization of the detectionstep, we have studied the pitfalls of the electrochemical TMB detection. By cyclic voltammetry it was found that the TMB electrochemistry is strongly dependent on the pH and the electrode material. A stable electrode response to TMB could be achieved at pH 1 on gold electrodes. We created a smartphonebased, electrochemical, immunomagnetic assay for the detection of ochratoxin A in real samples, providing a solid basis forsensing of further analytes. KW - Ochratoxin A KW - Amperometry KW - Cyclic voltammetry KW - Electrochemistry KW - Immunoassay PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-530421 DO - https://doi.org/10.1002/celc.202100446 N1 - Geburtsname von Riedel, Soraya: Höfs, S. - Birth name of Riedel, Soraya: Höfs, S. VL - 8 IS - 13 SP - 2597 EP - 2606 AN - OPUS4-53042 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Hülagü, Deniz A1 - Tobias, Charlie A1 - Dao, R. A1 - Komarow, P. A1 - Rurack, Knut A1 - Hodoroaba, Vasile-Dan T1 - Dataset accompanying the publication "Towards 3D determination of the surface roughness of core-shell microparticles as a routine quality control procedure by scanning electron microscopy" N2 - This dataset accompanies the following publication: Hülagü, D., Tobias, C., Dao, R., Komarov, P., Rurack, K., Hodoroaba, V.-D., Towards 3D determination of the surface roughness of core-shell microparticles as a routine quality control procedure by scanning electron microscopy. Sci.Rep, 14, 17936 (2024), https://doi.org/10.1038/s41598-024-68797-7. It contains SEM and AFM-in-SEM images of polystyrene (PS) core particles, polystyrene-iron oxide (PS/Fe3O4) core-shell particles, and polystyrene-iron oxide-silica (PS/Fe3O4/SiO2) core-shell-shell particles. Please refer to the publication and its supporting information for more details on the acquisition and contents of the dataset, as well as the GitHub repository at https://github.Com/denizhulagu/roughness-analysis-by-electron-microscopy. The investigated particles were produced at BAM laboratories as previously described in: Hülagü, D. et al. Generalized analysis approach of the profile roughness by electron microscopy with the example of hierarchically grown polystyrene–iron oxide–silica core–shell–shell particles. Adv. Eng. Mater. 24, 2101344, https://doi.org/10.1002/adem.202101344 (2022). Tobias, C., Climent, E., Gawlitza, K. & Rurack, K. Polystyrene microparticles with convergently grown mesoporous silica shells as a promising tool for multiplexed bioanalytical assays. ACS Appl. Mater. Interfaces 13, 207, https://dx.doi.org/10.1021/acsami.0c17940 (2020). KW - Core–shell particles KW - Image analysis KW - Roughness KW - Scanning electron microscopy KW - Atomic force microscopy KW - Tilting KW - Batch analysis PY - 2024 UR - https://zenodo.org/records/11108726 DO - https://doi.org/10.5281/zenodo.11108725 PB - Zenodo CY - Geneva AN - OPUS4-60760 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hülagü, Deniz A1 - Tobias, Charlie A1 - Climent Terol, Estela A1 - Gojani, Ardian A1 - Rurack, Knut A1 - Hodoroaba, Vasile-Dan T1 - Generalized Analysis Approach of the Profile Roughness by Electron Microscopy with the Example of Hierarchically Grown Polystyrene–Iron Oxide–Silica Core–Shell–Shell Particles N2 - The roughness as a property of core–shell (CS) microparticles plays a key role in their functionality. Quantitative evaluation of the roughness of CS microparticles is, however, a challenging task with approaches using electron microscopy images being scarce and showing pronounced differences in terms of methodology and results. This work presents a generalized method for the reliable roughness determination of nonplanar specimens such as CS particles from electron microscopic images, the method being robust and reproducible with a high accuracy. It involves a self-written software package (Python) that analyzes the recorded images, extracts corresponding data, and calculates the roughness based on the deviation of the identified contour. Images of single particles are taken by a dual mode scanning electron microscopy (SEM) setup which permits imaging of the same field-of-view of the sample with high resolution and surface sensitive in SE InLens mode as well as in transmission mode (TSEM). Herein, a new type of polystyrene core–iron oxide shell–silica shell particles is developed to serve as a set of lower micrometer-sized study objects with different surface roughness; the analysis of their images by the semiautomatic workflow is demonstrating that the particles’ profile roughness can be quantitatively obtained. KW - Core–shell particles KW - Image analysis KW - Nanoparticles KW - Roughness KW - SEM KW - transmission mode PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-542576 DO - https://doi.org/10.1002/adem.202101344 SP - 1 EP - 9 PB - Wiley-VCH AN - OPUS4-54257 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hülagü, Deniz A1 - Hirahara, Kenta A1 - Fischer, Daniel A1 - Florian, Camilo A1 - Schusterbauer, Robert A1 - Ermilova, Elena A1 - Krüger, Jörg A1 - Unterreiner, Andreas-Neil A1 - Bonse, Jörn A1 - Hertwig, Andreas T1 - Using imaging ellipsometry to understand femtosecond laser materials processing of group IV materials N2 - Laser materials processing is an important tool for creating and shaping new materials. Laser machining, especially with ultrashort pulses offers the modification of surfaces, thin coatings, and bulk materials with an unprecedented precision and control. The most desired feature of pulsed laser processing in the femtosecond range is that the heat-affected zone in the irradiated material will be extremely small. To better understand the mechanisms involved during laser irradiation, it is important to analyse the outcome of light-matter interaction with spectroscopic methods. Ellipsometry, especially spectroscopic imaging ellipsometry (SIE), has become an important tool for this in recent times, as it gives access to local layer thicknesses, materials dielectric functions, and features like changes in surface roughness. This work includes an overview over our recent studies examining near-infrared fs-laser surface processing of different group IV materials. The superficial phase change of silicon from crystalline to amorphous has been investigated in the past as the result of laser processing strongly depends on the crystal orientation. Moreover, SIE is capable of determining the properties of buried a-Si interfaces with micrometer lateral and sub-nanoneter vertical precision. Additionally, the growth of native and laser-induced oxides can be revealed. T2 - ICSE10 - 10th International Conference on Spectroscopic Ellipsometry CY - Boulder, CO, USA DA - 08.06.2025 KW - Laser surface ablation KW - Amorphous Carbon KW - Silicon KW - Correlative Imaging Ellipsometry PY - 2025 AN - OPUS4-63633 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -