TY - CONF A1 - Hertwig, Andreas T1 - Hochempfindliche Detektion von Gasen mittels SPR-Sensoren mit ellipsometrischen Messprinzip T2 - EFDS-Workshop "Analyse von Spurenverunreinigungen auf Oberflächen und in Gasen" CY - Dresden, Germany DA - 2013-12-02 PY - 2013 AN - OPUS4-30312 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Accurate determination of film thickness and optical constants with ellipsometry T2 - Congrès International de Métrologie CY - Paris, France DA - 2013-10-07 PY - 2013 AN - OPUS4-30313 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Vergleichbarkeit, Zuverlässigkeit und Genauigkeit der Bestimmung von Schichtdicken und optischen Konstanten mit Ellipsometrie an nicht-idealen Proben T2 - Seminar Messunsicherheit, PTB Berlin CY - Berlin, Germany DA - 2013-03-20 PY - 2013 AN - OPUS4-30314 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Methoden zur optischen Analyse von dünnen Schichten mittels Ellipsometrie: Auswerteverfahren und Referenzmaterialien T2 - 7. VDI Fachtagung Messunsicherheit CY - Braunschweig, Deutschland DA - 2015-11-19 PY - 2015 AN - OPUS4-35111 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - IR ellipsometry - a new sampling technique in thin film analysis and nanotechnologies T2 - Sentech-Seminar on Thin Film Analysis CY - Dortmund, Germany DA - 2013-06-25 PY - 2013 AN - OPUS4-30594 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Accuracy, traceability, and standardization in spectroscopic ellipsometry N2 - Ellipsometry has been an extremely successful and fast expanding method in the past decades along with other related techniques using polarisation sensitive measurements. Opening new fields of application for a successful measurement technique brings some requirements and issues that have to be solved. From a metrological point of view, ellipsometry has the problem that uncertainties are difficult to determine for model-based analysis techniques in general. In this presentation, we will explore how the usefulness of polarimetric methods like ellipsometry can be increased. Ellipsometry as a method could profit from several current developments which will be discussed in this presentation: • Standardisation initiatives on national and international level developing standards for best practice when using ellipsometry. A series of at least six standards is currently developed on national German and international level covering different levels of sample complexity. • Projects on traceability of ellipsometry and structured surface spectrometry as well as new dielectric function database initiatives. • Metadata handling and data ontology providing a better framework for exchange and collaborative use of research data. We will also explore the quantification of measurement uncertainty using examples from projects in which BAM is involved. Examples will be presented of multilayer and non-ideal materials as well as the determination of layer properties for technical applications such as thin layer catalysts and complex polymers. The definition of reference materials will be discussed. T2 - 11th Workshop Ellipsometry (WSE 11) CY - Steyr, Austria DA - 06.09.2021 KW - Ellipsometry KW - Uncertainty KW - Surface analytics KW - Data science PY - 2021 AN - OPUS4-53295 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Characterisation of thin layers of Polydopamine used as functional coatings in X-Ray optics N2 - Polydopamine (PDA) is a biological / biomimetic polymer which has spiked considerable interest in recent years. Its monomer is an important neurotransmitter and it is one of the strongest glues produced by biological organisms. Polydopamine is a candidate for several applications, mainly in the field of biology and medicine, but also - recently - for layer coatings with optical, electrical, and mechanical function. In this work, we investigate PDA layers intended as reflectivity enhancers for mirror surfaces in X-ray astronomical observatories. It has previously been shown, that such X-ray telescopes can be improved by a coating of PDA in the thickness range of several nm. Accurate thickness determination is required to monitor and optimise the coating process. We use spectroscopic ellipsometry to determine first the dielectric function of the polydopamine layers using model coatings of sufficient thickness. This data is then used to accurately determine the layer thickness of much thinner PDA layers. This study resulted in data on the thickness and dielectric function of PDA layers that could lead to a better understanding of the correlation of layer thickness and layer properties depending on the process parameters. T2 - Deutsche Physikalische Gesellschaft - Frühjahrstagung CY - Berlin, Germany DA - 17.03.2024 KW - Ellipsometry KW - Polydopamine KW - Thin Polymer Layers KW - X-Ray Reflectometry KW - Biopolymers PY - 2024 AN - OPUS4-59760 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas A1 - Osterwald, Stephan A1 - Gerhold, Stefan T1 - Mess- und Prüfverfahren für Schichten und Schichtsysteme - Der DIN-Normausschuss 062-01-61 N2 - Die Funktionalität von modernen technischen Komponenten liegt meist in der Oberfläche und in Beschichtungen. Das Design und die Herstellungsqualität von Beschichtungen ist essenziell für die optischen, elektrischen, mechanischen und chemischen Eigenschaften von Bauteilen, sowie für den Korrosions- und Verschleißschutz. In diesem Gremium bearbeiten wir Normen für die Qualitätssicherung von dünnen Schichten verschiedener Art. Dabei betrachten wir Eigenschaften wie Schichtdicke, Zusammensetzung, Haltbarkeit, Korrosionsbeständigkeit und physikalische Parameter von dünnen Schichten mit sehr vielfältigen Techniken. Neben klassischen Verfahren aus der Galvanik und Schichtmesstechnik, werden dabei auch neuere spektroskopische Verfahren wie Ellipsometrie und THz-Reflektion bedeutend. Unser Gremium ist offen für neue Mitglieder aus der Oberflächen- und Beschichtungsgemeinschaft. T2 - ZVO Oberflächentage 2023 CY - Berlin, Germany DA - 13.09.2023 KW - Dünne Schichten KW - Galvanotechnik KW - Metallschichten KW - Messtechnik PY - 2023 AN - OPUS4-58432 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Omar, Hassan A1 - Hertwig, Andreas A1 - Szymoniak, Paulina A1 - Schönhals, Andreas T1 - Signature of the Adsorbed Layer on the glass transition of thin polymer Films: Broadband Dielectric spectroscopy and related techniques N2 - In well annealed thin polymer films with non-repulsive polymer/substrate interaction with a substrate an irreversibly adsorbed layer is expected to form. These adsorbed layers have shown a great potential for technological applications [1]. However, the growth kinetics and the molecular mobility of the adsorbed layer is still not fully understood. This concerns also the influence of the adsorbed layer on the thickness dependence of the glass transition temperature of thin films. This is partly due to the difficult accessibility of these layers in thin films. Here, the irreversibly adsorbed layers of semi-rigid mail chain polymers like polycarbonate or polysulfone are revealed by solvent-leaching experiments. First, the growth kinetics of these layers is investigated as a function of annealing time. The film thickness, topography and the quality of the adsorbed layer is controlled by Atomic Force Microscopy (AFM). Secondly, the molecular mobility of the adsorbed layer is investigated by Broadband Dielectric Spectroscopy (BDS). A developed nanostructured capacitor arrangement is employed to measure the layer with a free surface. In addition to the dielectric experiments, spectroscopic Ellipsometry measurements are carried out to estimate the glass transition of the thin films. The thickness dependence of the glass transition of the thin films is correlated with the adsorbed layer [2,3]. Acknowledgments D. Hülagü and G. Hidde thanked for the help with the ellipsometry measurements. T2 - 12. Conference on Broabband Dielectric Spectroscopy and its Application CY - Lisbon, Portugal DA - 01.09.2024 KW - Thin films PY - 2024 AN - OPUS4-60959 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Determination of the glass transition region of thin PVME films by means of spectroscopic ellipsometry N2 - In this presentation, we report on the Determination of the glass transition temperature of thin layers of Polyvinylmethylether (PVME) depending on the thickness of the polymer layer. The glass Transition of thin polymer layers is currently under much investigation due to the nano-confinement effects proposed to appear in dependence on the layer thicknesses in the nm range. The properties of the polymer, the temperature range, as well as the thicknesses range of the polymer layers pose a serious challenge to the investigation by means of spectroscopic ellipsometry. By careful choice of experimental parameters, we were able to investigate the thickness change by temperature of PVME layers in the range between 2 and 300 nm and in the temperature range between 200 K and 340 K. By optimizing the analysis process, we were able to determine Tg values within this parameter range with sufficient accuracy to investigate the Tg change due to confinement effects. Alongside the change of position of the glass transition with thickness, we discuss the details of the ellipsometric analysis and its implications for the resulting thermal properties of the thin polymer layers as well as the accuracy of the Tg value with respect to the method used in the analysis process. T2 - Workshop Ellipsometry 2018 CY - Chemnitz, Germany DA - 19.03.2018 KW - Polymers KW - PVME KW - Temperature dependent ellipsometry KW - Glass transition PY - 2018 AN - OPUS4-44672 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Standardised and referenced surface analysis with ellipsometry - Is ellipsometry a metrological tool? N2 - Ellipsometry is a valuable surface analysis tool with an unmatched sensitivity towards surface layer properties. In this presentation, an initiative is discussed to make ellipsometry also a metrological tool. This is usually seen as very difficult due to the model-based nature of the analysis process. By establishing standardisation and reference materials, ellipsometry can be made traceable and can also become a valuable part of the traceable thin film metrology landscape. This is important because this technique has much potential to determine complex material parameters much needed in the production of high-tech products. T2 - University (UNL), Engineering Department CY - Lincoln, Nebraska, USA DA - 06.11.2017 KW - Metrology KW - Spectroscopic Ellipsometry KW - Reference Materials KW - Traceability KW - Measurement Uncertainty PY - 2017 AN - OPUS4-43412 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Multi-methods surface analysis involving spectroscopic ellipsometry: New measurements for optical and energy applications N2 - Surface analysis is still gaining importance, as most modern technology is in essence surface and thin film technology. In microelectronics and optics but also in many fields of energy storage and conversion, thin surface layers or structured surfaces are key components. Optical surface measurements are useful because of their reliability, robustness, and scalability – properties, which are especially desirable in a production environment. However, many of these methods take require considerable effort in data analysis. Spectroscopic ellipsometry (SE) is maybe the prime example of this class of methods. To combine the advantages of SE with metrological trueness and traceability, we combine it in a group of other methods, such as electron microscopy, instrumental surface analysis, X-ray diffraction. This presentation will give an overview on the principles of SE, its available quantities and the general properties of this measurement technique. Several examples from current and past projects of BAM-6.7 will show how a measurement community involving ellipsometry can benefit many fields of interest, from polymer science to energy applications. In the context of creating a “measurement landscape”, standardisation and standard compliance play an important role. The efforts of BAM in standardisation and accrediting of ellipsometry will be shown demonstrating the possible impact on quality assurance in different fields of technology. T2 - Abteilungskolloquium 2018, BAM CY - BAM, Berlin, Germany DA - 12.12.2018 KW - Spectroscopic ellipsometry KW - Surface analysis KW - Thin film technology KW - Reference materials PY - 2018 AN - OPUS4-47671 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - ELENA: a European project for electrical nanoscale metrology in industry N2 - A competitive advantage in the semiconductors industry is gained through the exploitation of new materials and processes, translating into improved components’ performances. This requires a metrological infrastructure allowing reliable nanoscale characterisation of new materials and devices, particularly in terms of their electrical parameters and properties. Traceability and reliability of nanoscale measurements stand as a major challenge for electrical properties (i.e. resistance, impedance) using conductive atomic force microscopy (C-AFM) and scanning microwave microscopy (SMM) techniques. The non-destructive analysis nature of these two methods is of paramount importance for the characterization of devices and components. However, the state of the art still lacks established measurement protocols, easy to use reference standards, well-defined best practice guides and easy to use 3D models to assess environmental and external stimulation effects. Moreover, costly instrumentation, particularly for high-frequency measurements, still hinders efficient advancements in these directions. ELENA is a 3-years European project that aims at bringing solutions to the aforementioned difficulties. To achieve this goal, the project uses a combination of nanoscale electrodynamic scanning probe methods in combination with optical tools such as spectroscopic ellipsometry on several lateral length scales to determine the electrical properties of layers and small structures. T2 - ICSE-9: The 9th International Conference on Spectroscopic Ellipsometry CY - Beijing, China DA - 2022-05-21 KW - Imaging Ellipsometry KW - Electrical thin layers KW - Scanning Probe methods KW - Hybrid metrology PY - 2022 AN - OPUS4-55464 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - New analytic ways to characterise mesoporous thin layers used in electrocatalytic water splitting N2 - Mesoporous materials are needed in many applications where a high specific surface area and adsorptive behaviour is needed. Important examples are separation techniques and barrier layers and catalysts. Electrochemical water splitting is the key technology for producing green hydrogen and there is no foreseeable alternative to this process for producing elementary hydrogen from green electrical power. Water electrolysis can be divided into the anodic Oxygen Evolution Reaction (OER) and the cathodic Hydrogen Evolution Reaction (HER). Both processes have to be heavily optimised to a large extent to avoid energy losses caused by overvoltage. The development of electrodes for these processes is especially difficult due to the many boundary conditions. Water splitting is a catalytic as well as electrochemical process. The contact area between the electrolyte and the electrode must be maximised maintaining the stability of the surface. Side reactions must be suppressed, and effective gas transport must be ensured. The whole process has to be tolerant with respect to temperature, harsh chemical conditions from the electrolyte as well as high current densities. We present a hybrid analytical method combining several analytical techniques for determining the properties of thin layers of mixed oxides of the general composition Ir:TiOx. These materials are promising candidates for electrocatalytical top coatings of OER electrodes. To lower the costs of the electrolysers, the main goal is to lower the Ir content retaining the system efficiency. The main properties which are hard to determine are the porous volume fraction and the Ir:Ti element ratio. By a combination of electron microscopy, spectroscopic operando ellipsometry, ellipsometric porosimetry, and other techniques, we can determine key features of mesoporous thin layer materials. We aim to develop operando capable techniques used in process monitoring as well as measurement techniques optimised for accuracy. By developing reference materials, we support long term uptake of our methodology. This work can directly be used for optimising electrocatalytic layers and is a good example for the power of hybrid metrology for improving materials design. T2 - International Conference on Resource Chemistry CY - Alzenau, Germany DA - 11.03.2024 KW - Ellipsometry KW - Electrocatalytic Water Splitting KW - Mesoporous Materials KW - Electron Probe Microanalysis KW - Hydrogen Generation PY - 2024 AN - OPUS4-59764 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Ellipsometry as a tool for electrical metrology - Referencing electrical properties of thin layers with TCO materials N2 - Ellipsometry is a highly valuable technology for bridging different measurement methods. As a fast, highly sensitive, and non-destructive optical technique with low environmental requirements, it is ideal for transporting measurement accuracy and for up-scaling measurements in the production environment. It can be used for highly precise determination of properties, material identity and correctness confirmation, as well as defect detection. Comparable, traceable, and accurate electrical measurements, especially at small scales are one of the biggest challenges in the development of the electrical and electronic devices of the future. In this project, we develop structured thin layer systems of the transparent conductive material indium tin oxide (ITO) to prove the concept of using these systems as standards for conductivity and permittivity. The layers are produced in a reactive magnetron sputtering process from raw ITO targets with additional oxidation achieved by oxygen injection. We present results of a study correlating the coating process conditions with the properties of the final layer material. We found that especially the temperature development during coating is of key importance and determines the layer properties to a large extent. We will discuss questions of homogeneity and reproducibility of the coating processes used. The finished layers undergo lithographic structuring and etching to produce patterns to serve as reference structures for scanning probe electrical measurements. TCOs have a large variety of applications. In this work we also study the usability of ITO for other purposes and investigate the stability of this material under application conditions. T2 - 12th Workshop Ellipsometry 2023 CY - Prague, Czech Republic DA - 18.09.2023 KW - Thin Films KW - Transparent Conductive Oxides KW - Ellipsometry KW - Electrical Properties KW - Nanoelectronics PY - 2023 AN - OPUS4-58410 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - On the use of spectroscopic imaging ellipsometry for quantification and characterisation of defects in thin films for power electronics N2 - Compound semiconductors (CS) are promising materials for the development of high-power electrical applications. They have low losses, can withstand high temperatures and can operate at very high voltages and currents. This makes them a key technology for the electrification of many high energy applications, especially electromobility and HVDC power lines. The challenge with CS technology is that most of the process technology has to be developed anew to the high standards required by electronic applications. Today, compound semiconductors can be produced in thin layers on top of substrates fabricated from classical crystal growth processes that are already well established. A promising method for this is metal organic vapour phase epitaxy (MOVPE). With this method, many different compounds with semiconducting properties can be synthesized. Additionally, this process technology is a direct thin layer deposition method. Therefore, complex multilayer systems can be generated directly by the deposition process and without the need of doping after growing. There are a number of critical defects that can originate from the deposition process of these thin film devices. Within this project, we intend to develop new correlative imaging and analysis techniques to determine defect types, to quantify defect size and number density, as well as to characterise defects for process optimisation. We report here on the use of spectroscopic ellipsometry and imaging ellipsometry to investigate defects in several different compound semiconductor materials used in high-power electronic devices. The materials we investigated are β-Ga2O3, SiC, GaN, AlN, and AlGaN materials as well as oxidised SiC surfaces. All of these materials have their typical defects and require optimised measurement and analysis schemes for reliable detection and analysis. Spectroscopic ellipsometry is a highly sensitive method for determining the thicknesses and dielectric function of thin layers, yielding potentially a high number of microscopic properties. The combined method between ellipsometry and optical microscopy is called imaging ellipsometry and is especially powerful for the large amount of data it produces. We have analysed defects in SiC- and AlN-based thin film semiconductors as well as characterised the properties of different types of SiO2 layers created on top of SiC monocrystals. We developed ellipsometric models for the data analysis of the different semiconductor materials. If the defects have geometric features, it is useful to combine the ellipsometric analysis with topometry method like interference microscopy and scanning probe microscopy. We have successfully characterised function-critical defects in MOVPE SiC layers and correlated the findings with topography from WLIM measurements. We have developed an imaging ellipsometric measurement methodology that allows to estimate the relative defect area on a surface by a statistical raw data analysis. T2 - EMRS Spring Meeting 2024 - ALTECH 2024 CY - Strasbourg, France DA - 27.05.2024 KW - compound semiconductors KW - Ellipsometry KW - Layer Materials KW - Defect Analysis PY - 2024 AN - OPUS4-61005 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas A1 - François, P. T1 - ELENA Project: Creating a simplified uncertainty calculation for industrial applications N2 - In this workpackage of the ELENA project, we develop a way to express the measurement uncertainty of nanoscale determination of electrical propserties. The method developed aims to be usable for industrial contexts and described in technical documents and standards drafts. Standards and reference samples are used to make traceable measurements available for the end user. T2 - Congrès International de Metrologie CY - Lyon, France DA - 06.03.2023 KW - Nanoscale measurements KW - Electrical properties KW - Optical measurements KW - Surfaces KW - Scanning probe measurements PY - 2023 AN - OPUS4-57155 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Characterisation of thin layers of Polydopamine used as functional coatings in X-Ray optics N2 - Polydopamine (PDA) is a biological / biomimetic polymer which has spiked considerable interest in recent years. Its monomer is an important neurotransmitter and it is one of the strongest glues produced by biological organisms. Polydopamine is a candidate for several applications, mainly in the field of biology and medicine, but also - recently - for layer coatings with optical, electrical, and mechanical function. In this work, we investigate PDA layers intended as reflectivity enhancers for mirror surfaces in X-ray astronomical observatories. It has previously been shown, that such X-ray telescopes can be improved by a coating of PDA in the thickness range of several nm. Accurate thickness determination is required to monitor and optimise the coating process. We use spectroscopic ellipsometry to determine first the dielectric function of the polydopamine layers using model coatings of sufficient thickness. This data is then used to accurately determine the layer thickness of much thinner PDA layers. This study resulted in data on the thickness and dielectric function of PDA layers that could lead to a better understanding of the correlation of layer thickness and layer properties depending on the process parameters. T2 - Deutsche Physikalische Gesellschaft - Frühjahrstagung CY - Berlin, Germany DA - 17.03.2024 KW - Polydopamine KW - Thin Solid Layers KW - X-ray optics KW - Spectroscopic Ellipsometry PY - 2024 AN - OPUS4-60955 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Neue Methoden in der Dünnschichtmesstechnik für mikroelektronische Anwendungen durch Mapping- und Imaging-Ellipsometrie T2 - OptecBB Handlungsfeldkonferenz CY - Berlin, Deutschland DA - 2014-06-27 PY - 2014 AN - OPUS4-32030 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Metrologie für die Dünnschicht- und Nanotechnologie Neue Anwendungen für optische Oberflächenmessungen T2 - Göttinger Messtechnisches Symposium CY - Göttingen, Deutschland DA - 2014-07-16 PY - 2014 AN - OPUS4-32031 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Optical vs. mivroscopic properties of ECR and RF bias generated amoephous hydrogenated carbon films T2 - PSE CY - Garmisch-Partenkirchen, Germany DA - 2010-09-13 PY - 2010 AN - OPUS4-20869 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Optische Messtechnik an Mikrotopografien T2 - OptecBB Veranstaltungsreihe MPK CY - Potsdam, Germany DA - 2010-05-19 PY - 2010 AN - OPUS4-21275 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Gas Monitoring with the SPR Effect and Ellipsometric Detection T2 - Third NanoCharm Workshop an Non-Destructive Real Time Process Control CY - Berlin, Germany DA - 2010-10-13 PY - 2010 AN - OPUS4-22110 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Interaction area dependence of the ablation threshold of ion doped glass T2 - EMRS Spring Meeting 2003 CY - Strasbourg, France DA - 2003-06-10 PY - 2003 AN - OPUS4-4323 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Surface damage and color centers generated by femtosecond pulses in borosilicate glass and silica T2 - 7th International Conference on Laser Ablation (COLA' 03) CY - Hersonissos, Greece DA - 2003-10-05 PY - 2003 AN - OPUS4-4324 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Qualitätssicherung für Schichtsysteme aus Ionenstrahl- und Plasmaprozessen mit optischen Methoden T2 - 12. Bundesdeutsche Plasmatagung CY - Braunschweig, Germany DA - 2005-03-21 PY - 2005 AN - OPUS4-7292 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Laser Safety: Ablation thresholds of fs-Pulses vs. optical constants evaluated by spectroscopic ellipsometry T2 - 4. Workshop Ellipsometry CY - Berlin, Germany DA - 2006-02-20 PY - 2006 AN - OPUS4-10885 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Ultra-short Pulse Laser Safety - a Challenge to Materials Science T2 - Optical Systems Design CY - Jena, Germany DA - 2005-09-12 PY - 2005 AN - OPUS4-7894 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 - International Symposium on Fluorine Chemistry CY - Bremen, Germany DA - 2006-07-30 PY - 2006 AN - OPUS4-12524 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 - ICSE - 4 CY - Stockholm, Sweden DA - 2007-06-11 PY - 2007 AN - OPUS4-14711 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Qualitätssicherung mit Optischen Methoden T2 - OptecBB Jahrestreffen CY - Mittenwalde, Germany DA - 2007-12-06 PY - 2007 AN - OPUS4-16473 LA - deu 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 - OPUS4-25686 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - On the use of plasma-deposited thin films for gas sensors with read-out based on the SPR effect T2 - PSE 2012, 13th International Conference on Plasma Surface Engineering CY - Garmisch-Partenkirchen, Germany DA - 2012-09-10 PY - 2012 AN - OPUS4-25971 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Charakterisierung von Oberflächen und dünnen Schichten mit Ellipsometrie T2 - BLiX-Seminar, TU Berlin CY - Berlin, Germany DA - 2012-07-10 PY - 2012 AN - OPUS4-26147 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 - OPUS4-28803 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - Gasdetektion mit komplexen SPR-Sensoren und ellipsometrischem Messprinzip T2 - Bunsentagung 2013 CY - Karlsruhe, Germany DA - 2013-05-09 PY - 2013 AN - OPUS4-28804 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hertwig, Andreas T1 - On the use of spectroscopic imaging ellipsometry for quantification and characterisation of defects in thin films for power electronics N2 - Compound semiconductors (CS) are promising materials for the development of high-power electrical applications. They have low losses, can withstand high temperatures and can operate at very high voltages and currents. This makes them a key technology for the electrification of many high energy applications, especially electromobility and HVDC power lines. The challenge with CS technology is that most of the process technology has to be developed anew to the high standards required by electronic applications. Today, compound semiconductors can be produced in thin layers on top of substrates fabricated from classical crystal growth processes that are already well established. A promising method for this is metal organic vapour phase epitaxy (MOVPE). With this method, many different compounds with semiconducting properties can be synthesized. Additionally, this process technology is a direct thin layer deposition method. Therefore, complex multilayer systems can be generated directly by the deposition process and without the need of doping after growing. There are a number of critical defects that can originate from the deposition process of these thin film devices. Within this project, we intend to develop new correlative imaging and analysis techniques to determine defect types, to quantify defect size and number density, as well as to characterise defects for process optimisation. We report here on the use of spectroscopic ellipsometry and imaging ellipsometry to investigate defects in several different compound semiconductor materials used in high-power electronic devices. The materials we investigated are β-Ga2O3, SiC, GaN, AlN, and AlGaN materials as well as oxidised SiC surfaces. All of these materials have their typical defects and require optimised measurement and analysis schemes for reliable detection and analysis. Spectroscopic ellipsometry is a highly sensitive method for determining the thicknesses and dielectric function of thin layers, yielding potentially a high number of microscopic properties. The combined method between ellipsometry and optical microscopy is called imaging ellipsometry and is especially powerful for the large amount of data it produces. We have analysed defects in SiC- and AlN-based thin film semiconductors as well as characterised the properties of different types of SiO2 layers created on top of SiC monocrystals. We developed ellipsometric models for the data analysis of the different semiconductor materials. If the defects have geometric features, it is useful to combine the ellipsometric analysis with topometry method like interference microscopy and scanning probe microscopy. We have successfully characterised function-critical defects in MOVPE SiC layers and correlated the findings with topography from WLIM measurements. We have developed an imaging ellipsometric measurement methodology that allows to estimate the relative defect area on a surface by a statistical raw data analysis. Compound semiconductors (CS) are promising materials for the development of high-power electrical applications. They have low losses, can withstand high temperatures and can operate at very high voltages and currents. This makes them a key technology for the electrification of many high energy applications, especially electromobility and HVDC power lines. The challenge is that most of the process technology has to be developed specifically and tailored to the high standards required by electronic applications. Today, many different CS materials can be produced in thin layers on top of substrates fabricated from classical crystal growth processes that are already well established. A promising method for this is metal organic vapour phase epitaxy (MOVPE). This technology is a direct thin layer deposition method capable of producing complex multilayer systems directly from one deposition process without the need of doping after growing. There are a number of critical defects that can originate from the deposition process when targeting electronic thin film devices. Within this project, we intend to develop new correlative imaging and analysis techniques to determine defect types, to quantify defect size and density, as well as to characterise defects for further process optimisation. We report here on the use of spectroscopic and multispectral imaging ellipsometry to investigate defects in several different compound semiconductor materials used in high-power electronic devices. The materials we investigated are β-Ga2O3, SiC, GaN, AlN, and AlGaN as well as oxidised SiC. All of these materials have their typical defects and require optimised measurement and analysis schemes for reliable detection and analysis. Spectroscopic ellipsometry is a highly sensitive method for determining the thicknesses and dielectric function of thin layers, yielding potentially a high number of microscopic properties. The combined method between ellipsometry and optical microscopy is known as imaging ellipsometry and is especially powerful for the large amount of data it produces. We have analysed defects in SiC- and AlN-based thin film semiconductors as well as characterised the properties of different types of SiO2 layers created on top of SiC monocrystals. We developed ellipsometric models for the data analysis of the different semiconductor materials. If the defects have geometric features, it is useful to combine the ellipsometric analysis with topometry methods like interference microscopy and scanning probe microscopy. We have successfully characterised function-critical defects in MOVPE SiC layers and correlated the findings with topography from WLIM measurements. We have developed an imaging ellipsometric measurement methodology that allows to estimate the relative defect area on a surface by a statistical raw data analysis. T2 - EMRS Spring Meeting 2024 - ALTECH 2024 CY - Strasbourg, France DA - 27.05.2024 KW - Ellipsometry KW - Power Electronics KW - Layer Materials KW - Defect Analysis PY - 2024 AN - OPUS4-60266 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 - 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 - 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 - 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 - TY - CONF A1 - Hertwig, Andreas T1 - Towards hydrogen economy: multimethod analysis and operando investigation of mesoporous iridium oxides films for electrocatalysis, EMPIR/EURAMET Project HyMet 16ENG03 N2 - In the face of rising energy demand and the impending climate change the development of a sustainable, fossil-free fuel and chemical production is of global importance. One possible goal is the development of electrochemical conversion processes using catalysts. Porous materials play an important role in such energy applications. The key to the development of improved catalysts is a better understanding of the relations between their performance, stability and physico-chemical properties. However, the complex morphology of such catalysts constitutes a challenge even for modern analytical techniques. Spectroscopic ellipsometry (SE) is a versatile method for studying material properties by using appropriate models (e.g. film thickness, optical and electronic properties). The fact that the material properties cannot be taken directly from the measured spectra, the developed models have to be validated. In a first step, the model for the ellipsometric fit studies of a calcination series of mesoporous iridium oxide films (300 – 600 °C) was investigated and validated with respect to their material properties. Moreover, the electronic structures of the catalysts reveal a direct correlation with electrochemical activities. The development of an environmental cell offers the possibility of investigations under real conditions. This will allow changes in the optical and electronic properties during the electrocatalytic oxygen evolution reaction. T2 - HyMet dissemination event CY - Online meeting DA - 17.11.2020 KW - Correlative ex-situ ellipsometric analysis KW - Ellipsometric operando investigation KW - Hydrogen economy KW - Mesoporous iridium oxides films KW - Oxygen evolution reaction PY - 2020 AN - OPUS4-51629 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 -