- M-26
Eißendorfer Straße 42
21073 Hamburg
Deutschland - Tel.: +49 (0) 40 - 428 78 3543
Martin Ritter
Hamburg University of Technology (TUHH), Electron Microscopy Division, Department Member
The combination of focused ion beam (FIB) with scanning electron microscopy (SEM), also known as FIB-SEM tomography, has become a powerful 3D imaging technique at the nanometer scale. This method uses an ion beam to mill away a thin slice... more
The combination of focused ion beam (FIB) with scanning electron microscopy (SEM), also known as FIB-SEM tomography, has become a powerful 3D imaging technique at the nanometer scale. This method uses an ion beam to mill away a thin slice of material, which is then block-face imaged using an electron beam. With consecutive slicing along the z-axis and subsequent imaging, a volume of interest can be reconstructed from the images and further analyzed. Hierarchical nanoporous gold (HNPG) exhibits unique structural properties and has a ligament size of 15–110 nm and pore size of 5–20 nm. Accurate reconstruction of its image is crucial in determining its mechanical and other properties. Slice thickness is one of the most critical and uncertain parameters in FIB-SEM tomography. For HNPG, the slice thickness should be at least half as thin as the pore size and, in our approach, should not exceed 10 nm. Variations in slice thickness are caused by various microscope and sample parameters, e....
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Titanium nitride (TiN) has emerged as one of the most promising refractory materials for plasmonic and photonic applications at high temperatures due to its prominent optical properties along with mechanical and thermal stability. From a... more
Titanium nitride (TiN) has emerged as one of the most promising refractory materials for plasmonic and photonic applications at high temperatures due to its prominent optical properties along with mechanical and thermal stability. From a high temperature standpoint, TiN is a substitution for Au and Ag in the visible to near‐infrared wavelength range, with potential applications including thermophotovoltaics, thermoplasmonics, hot‐electron and high temperature reflective coatings. However, the optical properties and thermal stability of TiN films strongly depend on the growth conditions, such as temperature, partial pressure of the reactive ion gas, ion energy, and substrate orientation. In this work, epitaxial TiN films are grown at 835 °C on an Al2O3 substrate using a radio frequency sputtering method. The oxidization behavior of TiN is investigated at 1000 °C under a medium vacuum condition of 2 × 10–3 mbar, which is relevant for practical technical applications, and the thermal s...
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Commercial deployment of thermophotovoltaics (TPV) is lacking behind the implementation of solar PV technology due to limited thermal stability of the selective emitter structures. Most of the TPV emitters demonstrated so far are designed... more
Commercial deployment of thermophotovoltaics (TPV) is lacking behind the implementation of solar PV technology due to limited thermal stability of the selective emitter structures. Most of the TPV emitters demonstrated so far are designed to operate under high vacuum conditions (~10−6 mbar vacuum pressure), whereas under medium vacuum conditions (~10−2 mbar vacuum pressure), which are feasible in technical implementations of TPV, these emitters suffer from oxidation due to significant O2 partial pressure. In this work, the thermal stability of 1D refractory W-HfO2 based multilayered metamaterial emitter structure is investigated under different vacuum conditions. The impact of the O2 partial pressure on thermal stability of the emitters is experimentally quantified. We show that, under medium vacuum conditions, i.e. ~10−2 mbar vacuum pressure, the emitter shows unprecedented thermal stability up to 1300 °C when the residual O2 in the annealing chamber is minimized by encapsulating t...
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Silica encapsulation dramatically enhances the thermal stability of zirconia submicron particles by grain growth inhibition and tetragonal phase stabilization.
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Focused ion beam (FIB) tomography is a destructive technique used to collect three-dimensional (3D) structural information at a resolution of a few nanometers. For FIB tomography, a material sample is degraded by layer-wise milling. After... more
Focused ion beam (FIB) tomography is a destructive technique used to collect three-dimensional (3D) structural information at a resolution of a few nanometers. For FIB tomography, a material sample is degraded by layer-wise milling. After each layer, the current surface is imaged by a scanning electron microscope (SEM), providing a consecutive series of cross-sections of the three-dimensional material sample. Especially for nanoporous materials, the reconstruction of the 3D microstructure of the material, from the information collected during FIB tomography, is impaired by the so-called shine-through effect. This effect prevents a unique mapping between voxel intensity values and material phase (e.g., solid or void). It often substantially reduces the accuracy of conventional methods for image segmentation. Here we demonstrate how machine learning can be used to tackle this problem. A bottleneck in doing so is the availability of sufficient training data. To overcome this problem, w...
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Herein we report on how to render Ti3C2Tx (MXene) monolayers deposited on SiO2/Si wafers, with different SiO2 thicknesses, visible. Inputting the effective thickness of a Ti3C2Tx monolayer (1 ± 0.2 nm) measured by atomic force microscopy,... more
Herein we report on how to render Ti3C2Tx (MXene) monolayers deposited on SiO2/Si wafers, with different SiO2 thicknesses, visible. Inputting the effective thickness of a Ti3C2Tx monolayer (1 ± 0.2 nm) measured by atomic force microscopy, and its refractive index into a Fresnel-law-based simulation software, we show that the optical contrast of Ti3C2Tx monolayers deposited on SiO2/Si wafers depends on the SiO2 thickness, number of MXene layers, and the light's wavelength. The highest contrast was found for SiO2 thicknesses around 220 nm. Simulations for other substrates, namely, Al2O3/Si, HfO2/Si, Si3N4/Si and Al2O3/Al, are presented as supplementary information.
We investigate spectrally selective high temperature stable metamaterial emitters for thermophotovoltaics. We demonstrate band-edge emitters based on a W-Hf02 multilayer metamaterial stable up to 1400°C. Conditions for improved... more
We investigate spectrally selective high temperature stable metamaterial emitters for thermophotovoltaics. We demonstrate band-edge emitters based on a W-Hf02 multilayer metamaterial stable up to 1400°C. Conditions for improved selectivity and thermal stability are discussed. © 2019 The Author(s)
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Precise sample stage positioning plays an important role for various FIB (Focused Ion Beam) and SEM (scanning electron microscope) applications in microand nanotechnology. During the last few years, FIB instruments have become an... more
Precise sample stage positioning plays an important role for various FIB (Focused Ion Beam) and SEM (scanning electron microscope) applications in microand nanotechnology. During the last few years, FIB instruments have become an indispensable tool for sample preparation, prototyping and micro-machining. Modern FIB devices are equipped with an additional electron column. Such combined SEM/FIB devices not only offer the possibility of forming structures by the focused ion beam, but also to almost instantly image the results in a non-destructive manner with the electron probe. Because of the fact that the ion column and the electron column are located at different positions in respect to each another, the sample has to be orientated normal to the beam by a positioning stage. Within a joint project we investigated the accuracy of SEM/FIB positioning stage operations. Therefore, the repetition uncertainty of the positioning stage was determined by applying photogrammetric methods that w...
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In view of the growing demand for sustainable and lightweight concrete structures, the use of ultra-high-performance concrete (UHPC) is becoming increasingly important. However, fatigue loads occur more frequently in nature than static... more
In view of the growing demand for sustainable and lightweight concrete structures, the use of ultra-high-performance concrete (UHPC) is becoming increasingly important. However, fatigue loads occur more frequently in nature than static loads. Despite the impressive mechanical properties of UHPC, a reduced tolerance for cyclic loading is known. For this reason, our paper deals with experimental and numerical investigations regarding the main causes for crack initiation on the meso, micro, and nanoscale. After mechanical fatigue tests, we use both scanning (SEM) and transmission electron microscopy (TEM) to characterize microstructural changes. A new rheological model was developed to apply those changes to the mesoscopic scale. The origins of fatigue damaging can be traced back to a transformation of nanoscale ettringite, resulting in a densification of the surrounding binder matrix. Additionally, a higher content of unhydrated cement clinker in the matrix benefits fatigue resistance...
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Zirconia nanoceramics are interesting materials for numerous high-temperature applications. Because their beneficial properties are mainly governed by the crystal and microstructure, it is essential to understand and control these... more
Zirconia nanoceramics are interesting materials for numerous high-temperature applications. Because their beneficial properties are mainly governed by the crystal and microstructure, it is essential to understand and control these features. The use of co-stabilizing agents in the sol-gel synthesis of zirconia submicro-particles should provide an effective tool for adjusting the particles’ size and shape. Furthermore, alumina-doping is expected to enhance the particles’ size and shape persistence at high temperatures, similar to what is observed in corresponding bulk ceramics. Dispersed alumina should inhibit grain growth by forming diffusion barriers, additionally impeding the martensitic phase transformation in zirconia grains. Here, alumina-doped zirconia particles with sphere-like shape and average diameters of ∼ 300 n m were synthesized using a modified sol-gel route employing icosanoic acid and hydroxypropyl cellulose as stabilizing agents. The particles were annealed at temper...
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In this work the fabrication of hard, stiff and strong nanocomposites based on polybutadiene and iron oxide nanoparticles is presented. The nanocomposites are fabricated via a general concept for mechanically superior nanocomposites not... more
In this work the fabrication of hard, stiff and strong nanocomposites based on polybutadiene and iron oxide nanoparticles is presented. The nanocomposites are fabricated via a general concept for mechanically superior nanocomposites not based on the brick and mortar structure, thus on globular nanoparticles with nanosized organic shells. For the fabrication of the composites oleic acid functionalized iron oxide nanoparticles are decorated via ligand exchange with an α,ω-polybutadiene dicarboxylic acid. The functionalized particles were processed at 145 °C. Since polybutadiene contains double bonds the nanocomposites obtained a crosslinked structure which was enhanced by the presence of oxygen or sulfur. It was found that the crosslinking and filler percolation yields high elastic moduli of approximately 12-20 GPa and hardness of 15-18 GPa, although the polymer volume fraction is up to 40%. We attribute our results to a catalytically enhanced crosslinking reaction of the polymer chai...
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ABSTRACT The 4-quadrant-large-angles-BSE-analysis (4Q-analysis) is well known for the fast analysis of the 3D sample morphology of catalysts, fracture surfaces and semiconductor devices in the scanning electron microscope (SEM) using... more
ABSTRACT The 4-quadrant-large-angles-BSE-analysis (4Q-analysis) is well known for the fast analysis of the 3D sample morphology of catalysts, fracture surfaces and semiconductor devices in the scanning electron microscope (SEM) using backscattered electrons (BSE). As reported previously [1–3] the 4Q-analysis works well for the qualitative reconstruction of the sample morphology, i.e. the relative heights of surface structures are measured properly with respect to each other. The method can resolve heights down to 10 nm.
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1. ABSTRACT Several measurement methods provide spatial information of micro-structured objects, e.g., confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM) in combination with photogrammetry. Our goal is to... more
1. ABSTRACT Several measurement methods provide spatial information of micro-structured objects, e.g., confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM) in combination with photogrammetry. Our goal is to correlate the specific details revealed by each method in a quantitative manner. Therefore, we developed a new method for the geometrical calibration of scanning microscopes by applying 3D nano-, and micrometer sized reference structures. This new calibration procedure makes use of landmarks, a concept which is already well-established in calibration strategies used at the millimeter, or meter scale. The landmarks used here are of sub-micrometer size and, therefore, are called "nanomarkers" (1). The multi-step pyramidal reference structures were produced by focused ion beam (FIB) induced metal deposition. FIB deposition allows the flexible fabrication of versatile spatial objects in order to fit best the needs for the chosen microscopy techn...
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ABSTRACT The fusion of spatial data generated by different microscopes allows an integrative and comprehensive characterization of 3D geometries and their characteristics.
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ABSTRACT Because electric cars are manufactured in high quantities, the influence of punching of nonoriented electrical steel with respect to tool wear becomes an important topic for the automotive industry. With regard to quality... more
ABSTRACT Because electric cars are manufactured in high quantities, the influence of punching of nonoriented electrical steel with respect to tool wear becomes an important topic for the automotive industry. With regard to quality assurance, it is necessary to investigate the local degradation of the magnetic properties due to the plastic deformation caused by the cutting process. In this contribution, both the local changes of the microstructure of the material and the magnetic properties will be considered. Different methods for analyzing the manufactured electrical steel laminations were applied. Cutting edges generated under different states of tool wear were examined by means of optical microscopy and electron backscatter diffraction to visualize the influence of plastic deformations. The magnetic properties of punched electrical steel laminations as a function of increasing tool wear have been determined by hysteresis measurements of stacked ring cores. With respect to quality assurance purposes spatially resolved measurements have been carried out to determine local magnetic properties and find a suitable correlation to application-relevant quantities.
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The high-temperature stability of thermal emitters is one of the critical properties of thermophotovoltaic (TPV) systems to obtain high radiative power and conversion efficiencies. W and HfO2 are ideal due to their high melting points and... more
The high-temperature stability of thermal emitters is one of the critical properties of thermophotovoltaic (TPV) systems to obtain high radiative power and conversion efficiencies. W and HfO2 are ideal due to their high melting points and low vapor pressures. At high temperatures and given vacuum conditions, W is prone to oxidation resulting in instantaneous sublimation of volatile W oxides. Herein, we present a detailed in-situ XRD analysis of the morphological changes of a 3-layer-system: HfO2/W/HfO2 layers, in a high-temperature environment, up to 1520 °C. These samples were annealed between 300 °C and 1520 °C for 6 h, 20 h, and 40 h at a vacuum pressure below 3 × 10–6 mbar using an in-situ high-temperature X-ray diffractometer, which allows investigation of crucial alterations in HfO2 and W layers. HfO2 exhibits polymorphic behavior, phase transformations and anisotropy of thermal expansion leads to formation of voids above 800 °C. These voids serve as transport channels for the...
Titanium aluminides based on the L10 ordered g-phase are promising structural light-weight materials for applications in aircraft engines. Typical compositions for γ-TiAl alloys lie in the range Ti-(44-48)Al (at.-%). For high creep... more
Titanium aluminides based on the L10 ordered g-phase are promising structural light-weight materials for applications in aircraft engines. Typical compositions for γ-TiAl alloys lie in the range Ti-(44-48)Al (at.-%). For high creep resistance, a two-phase microstructure based on lamellar (α2+γ)-colonies is desirable that may be tuned towards better ductility by introducing pure γ-grains (near lamellar or duplex microstructure).γ-TiAl alloys are often alloyed with niobium for increased oxidation resistance and improved mechanical properties. HEXRD and TEM studies of the alloy Ti-42Al-8.5Nb revealed that the orthorhombic O-phase forms during annealing at 500-650°C. This orthorhombic phase has been known in Nb-rich, Al-lean, α2-based Ti-aluminides since the late 1980ies (Nb> 12.5 at.-%, Al< 31 at.-%) but the finding in γ-based alloys is new.TEM imaging showed that the O-phase is located within α2 lamellae of lamellar (α2+γ)-colonies. O-phase domains and α2 phase form small column...
Precise sample stage positioning plays an important role for various FIB (Focused Ion Beam) and SEM (scanning electron microscope) applications in micro- and nanotechnology. During the last few years, FIB instruments have become an... more
Precise sample stage positioning plays an important role for various FIB (Focused Ion Beam) and SEM (scanning electron microscope) applications in micro- and nanotechnology. During the last few years, FIB instruments have become an indispensable tool for sample preparation, prototyping and micro-machining. Modern FIB devices are equipped with an additional electron column. Such combined SEM/FIB devices not only offer the possibility of forming structures by the focused ion beam, but also to almost instantly image the results in a non-destructive manner with the electron probe. Because of the fact that the ion column and the electron column are located at different positions in respect to each another, the sample has to be orientated normal to the beam by a positioning stage. Within a joint project we investigated the accuracy of SEM/FIB positioning stage operations. Therefore, the repetition uncertainty of the positioning stage was determined by applying photogrammetric methods that...
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2007 Herausgeber: Bundesanstalt für Materialforschung und -prüfung (BAM) Unter den Eichen 87 12205 Berlin Telefon: +49 30 8104-0 Telefax: +49 30 8112029 E-Mail: info@bam.de Internet: www.bam.de Copyright © 2007 by Bundesanstalt für... more
2007 Herausgeber: Bundesanstalt für Materialforschung und -prüfung (BAM) Unter den Eichen 87 12205 Berlin Telefon: +49 30 8104-0 Telefax: +49 30 8112029 E-Mail: info@bam.de Internet: www.bam.de Copyright © 2007 by Bundesanstalt für Materialforschung und - ...
In this paper we present the calibration of a scanning electron microscope, using a high precision tilting sample stage and a new microscopic calibration pyramid. Difficulties when using extremely high magnifications will be stated and... more
In this paper we present the calibration of a scanning electron microscope, using a high precision tilting sample stage and a new microscopic calibration pyramid. Difficulties when using extremely high magnifications will be stated and means of solutions are presented and evaluated. Since the scanning electron microscope cannot be moved around the object, the object has to be tilted instead. By this movement, the object can be seen in several virtual points of view, which is a necessity for any three dimensional reconstruction. As for generating the virtual views, the first difficulty encountered is to position the sample into the eucentric axis. Only when positioned in the rotation axis, the sample remains within the field of view, instead of being moved outside. Therefore, a special tilting table was required, which provided maximum precision and accuracy. Furthermore, an object had to be found, which met the requirements of a calibration object. Here, a new microscopic cascade py...
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Merging information from different measurement procedures enables consistent and extensive characterization of 3D geometries and features. Methods of processing, merging, and analyzing multimodal measurement data are shown and used with... more
Merging information from different measurement procedures enables consistent and extensive characterization of 3D geometries and features. Methods of processing, merging, and analyzing multimodal measurement data are shown and used with exemplary ...
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Im Bereich der Mikrometer- und Nanometer-Messtechnik werden immer neue Normale benötigt und bereitgestellt. Bei deren Design, Herstellung und Einsatz werden zum Teil neue Wege beschritten, um den Anforderungen und Randbedingungen der... more
Im Bereich der Mikrometer- und Nanometer-Messtechnik werden immer neue Normale benötigt und bereitgestellt. Bei deren Design, Herstellung und Einsatz werden zum Teil neue Wege beschritten, um den Anforderungen und Randbedingungen der Mikro- und Nanotechnik gerecht zu werden. Im Folgenden werden diese Aspekte und Entwicklungen anhand ausgewählter Beispiele verdeutlicht.
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Abstract We introduce the application of a new 3D calibration method for the calibration of scanning probe microscopes (SPM) in order to be able to obtain faster and better quantitative topography measurements for the determination of... more
Abstract We introduce the application of a new 3D calibration method for the calibration of scanning probe microscopes (SPM) in order to be able to obtain faster and better quantitative topography measurements for the determination of technical, dimensional and geometrical surface ...