Search Results
The patterning toolbox FIB-o-mat: Exploiting the full potential of focused helium ions for nanofabrication
2021, Deinhart, Victor, Kern, Lisa-Marie, Kirchhof, Jan N., Juergensen, Sabrina, Sturm, Joris, Krauss, Enno, Feichtner, Thorsten, Kovalchuk, Sviatoslav, Schneider, Michael, Engel, Dieter, Pfau, Bastian, Hecht, Bert, Bolotin, Kirill I., Reich, Stephanie, Höflich, Katja
Focused beams of helium ions are a powerful tool for high-fidelity machining with spatial precision below 5 nm. Achieving such a high patterning precision over large areas and for different materials in a reproducible manner, however, is not trivial. Here, we introduce the Python toolbox FIB-o-mat for automated pattern creation and optimization, providing full flexibility to accomplish demanding patterning tasks. FIB-o-mat offers high-level pattern creation, enabling high-fidelity large-area patterning and systematic variations in geometry and raster settings. It also offers low-level beam path creation, providing full control over the beam movement and including sophisticated optimization tools. Three applications showcasing the potential of He ion beam nanofabrication for two-dimensional material systems and devices using FIB-o-mat are presented.
Quantification of silver nanoparticle uptake and distribution within individual human macrophages by FIB/SEM slice and view
2017-3-21, Guehrs, Erik, Schneider, Michael, Günther, Christian M., Hessing, Piet, Heitz, Karen, Wittke, Doreen, López-Serrano Oliver, Ana, Jakubowski, Norbert, Plendl, Johanna, Eisebitt, Stefan, Haase, Andrea
Background: Quantification of nanoparticle (NP) uptake in cells or tissues is very important for safety assessment. Often, electron microscopy based approaches are used for this purpose, which allow imaging at very high resolution. However, precise quantification of NP numbers in cells and tissues remains challenging. The aim of this study was to present a novel approach, that combines precise quantification of NPs in individual cells together with high resolution imaging of their intracellular distribution based on focused ion beam/ scanning electron microscopy (FIB/SEM) slice and view approaches. Results: We quantified cellular uptake of 75 nm diameter citrate stabilized silver NPs (Ag 75 Cit) into an individual human macrophage derived from monocytic THP-1 cells using a FIB/SEM slice and view approach. Cells were treated with 10 μg/ml for 24 h. We investigated a single cell and found in total 3138 ± 722 silver NPs inside this cell. Most of the silver NPs were located in large agglomerates, only a few were found in clusters of fewer than five NPs. Furthermore, we cross-checked our results by using inductively coupled plasma mass spectrometry and could confirm the FIB/SEM results. Conclusions: Our approach based on FIB/SEM slice and view is currently the only one that allows the quantification of the absolute dose of silver NPs in individual cells and at the same time to assess their intracellular distribution at high resolution. We therefore propose to use FIB/SEM slice and view to systematically analyse the cellular uptake of various NPs as a function of size, concentration and incubation time.
In situ single-shot diffractive fluence mapping for X-ray free-electron laser pulses
2018, Schneider, Michael, Günther, Christian M., Pfau, Bastian, Capotondi, Flavio, Manfredda, Michele, Zangrando, Marco, Mahne, Nicola, Raimondi, Lorenzo, Pedersoli, Emanuele, Naumenko, Denys, Eisebitt, Stefan
Free-electron lasers (FELs) in the extreme ultraviolet (XUV) and X-ray regime opened up the possibility for experiments at high power densities, in particular allowing for fluence-dependent absorption and scattering experiments to reveal non-linear light-matter interactions at ever shorter wavelengths. Findings of such non-linear effects are met with tremendous interest, but prove difficult to understand and model due to the inherent shot-to-shot fluctuations in photon intensity and the often structured, non-Gaussian spatial intensity profile of a focused FEL beam. Presently, the focused beam is characterized and optimized separately from the actual experiment. Here, we present the simultaneous measurement of XUV diffraction signals from solid samples in tandem with the corresponding single-shot spatial fluence distribution on the actual sample. Our in situ characterization scheme enables direct monitoring of the sample illumination, providing a basis to optimize and quantitatively understand FEL experiments.
Spatial distribution of electric-field enhancement across the gap of terahertz bow-tie antennas
2020, Runge, Matthias, Engel, Dieter, Schneider, Michael, Reimann, Klaus, Woerner, Michael, Elsaesser, Thomas
The electric-field enhancement in terahertz (THz) antennas designed for nonlinear THz spectroscopy of soft matter is characterized by spatially resolved electrooptic sampling. To mimic the relevant interaction geometry, metallic, resonant bow-tie antennas are deposited on a thin zinc telluride crystal of 10 µm thickness. The THz electric field transmitted through the antenna gap is recorded by electrooptic sampling. By focusing the 800 nm, sub-20 fs sampling pulses, we achieve a spatial resolution of some 3 µm, which is 1/3 to 1/8 of the antenna-gap width. The THz field in the gap displays an enhancement by a factor of up to 4.5 with a pronounced spectral variation, depending sensitively on the antenna-arm length and the gap width. By scanning the 800 nm probe spot laterally through the antenna gap, the spatial variation of the enhancement is determined, reaching the highest values at the edges of the gap. The results are in agreement with simulations of the electric-field distributions by finite-element calculations. © 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Enabling time-resolved 2D spatial-coherence measurements using the Fourier-analysis method with an integrated curved-grating beam monitor
2020, Bagschik, Kai, Schneider, Michael, Wagner, Jochen, Buss, Ralph, Riepp, Matthias, Philippi-Kobs, Andre, Müller, Leonard, Roseker, Wojciech, Trinter, Florian, Hoesch, Moritz, Viefhaus, Jens, Eisebitt, Stefan, Grübel, Gerhard, Oepen, Hans Peter, Frömter, Robert
Direct 2D spatial-coherence measurements are increasingly gaining importance at synchrotron beamlines, especially due to present and future upgrades of synchrotron facilities to diffraction-limited storage rings. We present a method to determine the 2D spatial coherence of synchrotron radiation in a direct and particularly simple way by using the Fourier-analysis method in conjunction with curved gratings. Direct photon-beam monitoring provided by a curved grating circumvents the otherwise necessary separate determination of the illuminating intensity distribution required for the Fourier-analysis method. Hence, combining these two methods allows for time-resolved spatial-coherence measurements. As a consequence, spatial-coherence degradation effects caused by beamline optics vibrations, which is one of the key issues of state-of-the-art X-ray imaging and scattering beamlines, can be identified and analyzed. © 2020 Optical Society of America.
Experimental evaluation of signal-to-noise in spectro-holography via modified uniformly redundant arrays in the soft x-ray and extreme ultraviolet spectral regime
2017-05-08, Günther, Christian M., Guehrs, Erik, Schneider, Michael, Pfau, Bastian, von Korff Schmising, Clemens, Geilhufe, Jan, Schaffert, Stefan, Eisebitt, Stefan
We present dichroic x-ray lensless magnetic imaging by Fourier transform holography with an extended reference scheme via a modified uniformly redundant array (mURA). Holographic images of magnetic domains simultaneously generated by a single pinhole reference as well as by a mURA reference are compared with respect to the signal-to-noise ratio (SNR) as a function of exposure time. We apply this approach for spectro-holographic imaging of ferromagnetic domain patterns in Co/Pt multilayer films. Soft x-rays with wavelengths of 1.59 nm (Co L3 absorption edge) and 20.8 nm (Co M2,3 absorption edges) are used for image formation and to generate contrast via x-ray magnetic circular dichroism. For a given exposure time, the mURA-based holography allows to decouple the reconstruction SNR from the spatial resolution. For 1.59 nm wavelength, the reconstruction via the extended reference scheme shows no significant loss of spatial resolution compared to the single pinhole reference. In contrast, at 20.8 nm wavelength the single pinhole reveals some very intricate features which are lost in the image generated by the mURA, although overall a high-quality image is generated. The SNR-advantage of the mURA scheme is most notable when the hologram has to be encoded with few photons, while errors associated with the increased complexity of the reconstruction process reduce the advantage for high-photon-number experiments.
Singleshot polychromatic coherent diffractive imaging with a high-order harmonic source
2020, Malm, Erik, Wikmark, Hampus, Pfau, Bastian, Villanueva-Perez, Pablo, Rudawski, Piotr, Peschel, Jasper, Maclot, Sylvain, Schneider, Michael, Eisebitt, Stefan, Mikkelsen, Anders, L’Huillier, Anne, Johnsson, Per
Singleshot polychromatic coherent diffractive imaging is performed with a high-intensity high-order harmonic generation source. The coherence properties are analyzed and several reconstructions show the shot-to-shot fluctuations of the incident beam wavefront. The method is based on a multi-step approach. First, the spectrum is extracted from double-slit diffraction data. The spectrum is used as input to extract the monochromatic sample diffraction pattern, then phase retrieval is performed on the quasi-monochromatic data to obtain the sample’s exit surface wave. Reconstructions based on guided error reduction (ER) and alternating direction method of multipliers (ADMM) are compared. ADMM allows additional penalty terms to be included in the cost functional to promote sparsity within the reconstruction. © 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.
Reference shape effects on Fourier transform holography
2022, Malm, Erik, Pfau, Bastian, Schneider, Michael, Günther, Christian M., Hessing, Piet, Büttner, Felix, Mikkelsen, Anders, Eisebitt, Stefan
Soft-x-ray holography which utilizes an optics mask fabricated in direct contact with the sample, is a widely applied x-ray microscopy method, in particular, for investigating magnetic samples. The optics mask splits the x-ray beam into a reference wave and a wave to illuminate the sample. The reconstruction quality in such a Fourier-transform holography experiment depends primarily on the characteristics of the reference wave, typically emerging from a small, high-aspect-ratio pinhole in the mask. In this paper, we study two commonly used reference geometries and investigate how their 3D structure affects the reconstruction within an x-ray Fourier holography experiment. Insight into these effects is obtained by imaging the exit waves from reference pinholes via high-resolution coherent diffraction imaging combined with three-dimensional multislice simulations of the x-ray propagation through the reference pinhole. The results were used to simulate Fourier-transform holography experiments to determine the spatial resolution and precise location of the reconstruction plane for different reference geometries. Based on our findings, we discuss the properties of the reference pinholes with view on application in soft-x-ray holography experiments.
Non-invasive prospection techniques and direct push sensing as high-resolution validation tools in wetland geoarchaeology – Artificial water supply at a Carolingian canal in South Germany?
2020, Rabiger-Völlmer, Johannes, Schmidt, Johannes, Linzen, Sven, Schneider, Michael, Werban, Ulrike, Dietrich, Peter, Wilken, Dennis, Wunderlich, Tina, Fediuk, Annika, Berg, Stefanie, Werther, Lukas, Zielhofer, Christoph
The prospection of (geo-)archaeological sites yield important knowledge about the concept and the utilisation of pre-historical and historical infrastructure. The satisfactory conduction of classical prospection methods like archaeological excavations or geoarchaeological vibra-coring might be challenging in the case of large sites or difficult underground conditions. This is particularly problematic in wetlands featuring a high groundwater table and high compaction rates of organic layers. In this study, we provide an alternative and non- to minimal-invasive exploration approach to discover hydro-engineering structures for artificial water supply in the surrounding of a Carolingian summit canal in South Germany. The Early Medieval Fossa Carolina was intended 792/793 CE to bridge the Central European watershed between Rhine-Main and Danube catchments. As the canal was constructed as a summit canal, an artificial water supply at the highest levels seemed very likely or even obligatory. In order to explore these obligatory hydro-engineering features, we use a wide range of on-site and off-site tools in a spatial hierarchical way. Our approach includes the large-scale SQUID magnetic survey and the sighting of historical maps. Furthermore, we integrate high-resolution direct push colour logs, and subsequent vibra-coring for small-scale stratigraphical verification and sedimentological analyses. The SQUID magnetic survey and related depth models discover two pronounced linear anomalies that might represent potential artificial water inlets in the North-Eastern and Northern Sections of the canal. I) In the North-Eastern Section, direct push colour logs, vibra-coring and 14C dating provide no evidence for a Carolingian hydro-engineering feature but reveal a natural lenticular structure of Early Holocene age. II) The linear magnetic anomaly in the Northern Section can be excluded with high probability as a hydro-engineering structure as well. Here, direct push colour logs, vibra-coring, 14C dating and the comparison with a historic map reveal evidence for a historic gravel road. Thus, we have nicely verified the magnetic information but have no prove for an artificial Carolingian water inlet from the Swabian Rezat River that contradicts with assumptions of former studies. © 2020 The Authors
Real-time spatial characterization of micrometer-sized X-ray free-electron laser beams focused by bendable mirrors
2022, Mercurio, Giuseppe, Chalupský, Jaromír, Nistea, Ioana-Theodora, Schneider, Michael, Hájková, Věra, Gerasimova, Natalia, Carley, Robert, Cascella, Michele, Le Guyader, Loïc, Mercadier, Laurent, Schlappa, Justine, Setoodehnia, Kiana, Teichmann, Martin, Yaroslavtsev, Alexander, Burian, Tomáš, Vozda, Vojtĕch, Vyšín, Luděk, Wild, Jan, Hickin, David, Silenzi, Alessandro, Stupar, Marijan, Torben Delitz, Jan, Broers, Carsten, Reich, Alexander, Pfau, Bastian, Eisebitt, Stefan, La Civita, Daniele, Sinn, Harald, Vannoni, Maurizio, Alcock, Simon G., Juha, Libor, Scherz, Andreas
A real-time and accurate characterization of the X-ray beam size is essential to enable a large variety of different experiments at free-electron laser facilities. Typically, ablative imprints are employed to determine shape and size of μm-focused X-ray beams. The high accuracy of this state-of-the-art method comes at the expense of the time required to perform an ex-situ image analysis. In contrast, diffraction at a curved grating with suitably varying period and orientation forms a magnified image of the X-ray beam, which can be recorded by a 2D pixelated detector providing beam size and pointing jitter in real time. In this manuscript, we compare results obtained with both techniques, address their advantages and limitations, and demonstrate their excellent agreement. We present an extensive characterization of the FEL beam focused to ≈1 μm by two Kirkpatrick-Baez (KB) mirrors, along with optical metrology slope profiles demonstrating their exceptionally high quality. This work provides a systematic and comprehensive study of the accuracy provided by curved gratings in real-time imaging of X-ray beams at a free-electron laser facility. It is applied here to soft X-rays and can be extended to the hard X-ray range. Furthermore, curved gratings, in combination with a suitable detector, can provide spatial properties of μm-focused X-ray beams at MHz repetition rate.