Transmission Soft X-ray Microscopy Research Articles

Soft x-ray ptychography studies of nanoscale magnetic and structural correlations in thin SmCo5 films

High spatial resolution magnetic x-ray spectromicroscopy at x-ray photon energies near the cobalt L3 resonance was applied to probe an amorphous 50 nm thin SmCo5 film prepared by off-axis pulsed laser deposition onto an x-ray transparent 200 nm thin Si3N4 membrane. Alternating gradient magnetometry shows a strong in-plane anisotropy and an only weak perpendicular magnetic anisotropy, which is confirmed by magnetic transmission soft x-ray microscopy images showing over a field of view of 10 μm a primarily stripe-like domain pattern but with local labyrinth-like domains. Soft x-ray ptychography in amplitude and phase contrast was used to identify and characterize local magnetic and structural features over a field of view of 1 μm with a spatial resolution of about 10 nm. There, the magnetic labyrinth domain patterns are accompanied by nanoscale structural inclusions that are primarily located in close proximity to the magnetic domain walls. Our analysis suggests that these inclusions are nanocrystalline Sm2Co17 phases with nominally in-plane magnetic anisotropy.

Quantitative X-ray microscopic analysis of individual thermoresponsive microgel particles in aqueous solution

The temperature dependent phase transition of individual thermoresponsive microgel particles in aqueous solution has been studied by high resolution soft X-ray transmission microscopy (STXM).

Evidence of cell surface iron speciation of acidophilic iron-oxidizing microorganisms in indirect bioleaching process.

While indirect model has been widely accepted in bioleaching, but the evidence of cell surface iron speciation has not been reported. In the present work the iron speciation on the cell surfaces of four typically acidophilic iron-oxidizing microorganism (mesophilic Acidithiobacillus ferrooxidans ATCC 23270, moderately thermophilic Leptospirillum ferriphilum YSK and Sulfobacillus thermosulfidooxidans St, and extremely thermophilic Acidianus manzaensis YN25) grown on different energy substrates (chalcopyrite, pyrite, ferrous sulfate and elemental sulfur (S(0))) were studied in situ firstly by using synchrotron-based micro- X-ray fluorescence analysis and X-ray absorption near-edge structure spectroscopy. Results showed that the cells grown on iron-containing substrates had apparently higher surface iron content than the cells grown on S(0). Both ferrous iron and ferric iron were detected on the cell surface of all tested AIOMs, and the Fe(II)/Fe(III) ratios of the same microorganism were affected by different energy substrates. The iron distribution and bonding state of single cell of A. manzaensis were then studied in situ by scanning transmission soft X-ray microscopy based on dual-energy contrast analysis and stack analysis. Results showed that the iron species distributed evenly on the cell surface and bonded with amino, carboxyl and hydroxyl groups.

Binary pseudo-random patterned structures for modulation transfer function calibration and resolution characterization of a full-field transmission soft x-ray microscope.

We present a modulation transfer function (MTF) calibration method based on binary pseudo-random (BPR) one-dimensional sequences and two-dimensional arrays as an effective method for spectral characterization in the spatial frequency domain of a broad variety of metrology instrumentation, including interferometric microscopes, scatterometers, phase shifting Fizeau interferometers, scanning and transmission electron microscopes, and at this time, x-ray microscopes. The inherent power spectral density of BPR gratings and arrays, which has a deterministic white-noise-like character, allows a direct determination of the MTF with a uniform sensitivity over the entire spatial frequency range and field of view of an instrument. We demonstrate the MTF calibration and resolution characterization over the full field of a transmission soft x-ray microscope using a BPR multilayer (ML) test sample with 2.8 nm fundamental layer thickness. We show that beyond providing a direct measurement of the microscope's MTF, tests with the BPRML sample can be used to fine tune the instrument's focal distance. Our results confirm the universality of the method that makes it applicable to a large variety of metrology instrumentation with spatial wavelength bandwidths from a few nanometers to hundreds of millimeters.

Ballistic rectification of vortex domain wall chirality at nanowire corners

The interactions of vortex domain walls with corners in planar magnetic nanowires are probed using magnetic soft X-ray transmission microscopy. We show that when the domain walls are propagated into sharp corners using applied magnetic fields above a critical value, their chiralities are rectified to either clockwise or anticlockwise circulation depending on whether the corners turn left or right. Single-shot focused magneto-optic Kerr effect measurements are then used to demonstrate how, when combined with modes of domain propagation that conserve vortex chirality, this allows us to dramatically reduce the stochasticity of domain pinning at artificial defect sites. Our results provide a tool for controlling domain wall chirality and pinning behavior both in further experimental studies and in future domain wall-based memory, logic and sensor technologies.

Spatial Distributions of Discharged Products of Lithium-Oxygen Batteries Revealed by Synchrotron X-ray Transmission Microscopy.

The discharge products of ether-based Li-O2 cells were grown directly on common carbon-coated TEM grids and observed by oxidation-state-sensitive full field transmission soft X-ray microscopy (TXM). The acquired data have permitted to quantify and localize with spatial resolution the distribution of the oxygen discharge products in these samples (i.e., lithium superoxide, peroxide, and carbonates) and appreciate several compositional, structural, and morphological aspects. Most of the peroxide particles had a toroidal shape, often with a central hole usually open on only one side, and which included significant amounts of superoxide-like phases (LiO2/Li2O2 ratio between 0.2 and 0.5). Smaller particles had smaller or no superoxide content, from which we infer that abundance of soluble LiO2 may have a role in toroid formation. Significant amount of carbonates were found irregularly distributed on the electrode surface, occasionally appearing as small particles and aggregates, and mostly coating lithium peroxide particles. This suggests the formation of a barrier that, similar to the solid electrolyte interface (SEI) critical in Li-ion batteries, requires an appropriate management for a reversible operation.

Phase Separated Morphology of Ferroelectric–Semiconductor Polymer Blends Probed by Synchrotron X-ray Methods

Control of the domain size and morphology of ferroelectric-semiconductor polymer blend thin films is essential for producing working organic ferroelectric resistive switches that can be used for low-cost, flexible memory applications. However, improvements in characterization techniques that can selectively probe these polymers are still needed. The unique core-level absorption profiles of these polymers make synchrotron based soft X-ray techniques ideal to achieve contrast and chemical sensitivity between polymers and characterize thin film morphology. Transmission soft X-ray microscopy and scattering reveal that a phase separated structure exists through the bulk for a blend of a semicrystalline semiconducting polythiophene with a functionalized side chain and a well-studied ferroelectric polymer. Surface sensitive soft X-ray spectroscopy and wide-angle X-ray scattering suggest a potential enhancement of polythiophene at the film surface, and that the surface layer is more amorphous in character. This w...

MISTRAL: a transmission soft X-ray microscopy beamline for cryo nano-tomography of biological samples and magnetic domains imaging.

The performance of MISTRAL is reported, the soft X-ray transmission microscopy beamline at the ALBA light source (Barcelona, Spain) which is primarily dedicated to cryo soft X-ray tomography (cryo-SXT) for three-dimensional visualization of whole unstained cells at spatial resolutions down to 30 nm (half pitch). Short acquisition times allowing for high-throughput and correlative microscopy studies have promoted cryo-SXT as an emerging cellular imaging tool for structural cell biologists bridging the gap between optical and electron microscopy. In addition, the beamline offers the possibility of imaging magnetic domains in thin magnetic films that are illustrated here with an example.

Quantitative x-ray magnetic circular dichroism mapping with high spatial resolution full-field magnetic transmission soft x-ray spectro-microscopy

The spectroscopic analysis of X-ray magnetic circular dichroism (XMCD), which serves as strong and element-specific magnetic contrast in full-field magnetic transmission soft x-ray microscopy, is shown to provide information on the local distribution of spin (S) and orbital (L) magnetic moments down to a spatial resolution of 25 nm limited by the x-ray optics used in the x-ray microscope. The spatially resolved L/S ratio observed in a multilayered (Co 0.3 nm/Pt 0.5 nm) × 30 thin film exhibiting a strong perpendicular magnetic anisotropy decreases significantly in the vicinity of domain walls, indicating a non-uniform spin configuration in the vertical profile of a domain wall across the thin film. Quantitative XMCD mapping with x-ray spectro-microscopy will become an important characterization tool for systems with topological or engineered magnetization inhomogeneities.

High pressure treated Bacillus subtilis spores — Structural analysis by means of synchrotron and laboratory based soft X-ray microscopy

Abstract Measurements were carried out on high pressure treated (HPT) bacterial endospores of the Bacillus subtilis strain PS832 by means of laboratory (LTXM) and synchrotron based transmission soft X-ray microscopy (SynchTXM). Using LTXM at 500 eV HPT spores could be identified by a higher transparency, due to dipicolinic acid (DPA) release from the spore's core, and their shriveled appearance caused by air-drying. Dormant spores were investigated at different photon energies at SynchTXM. Inner structures were visualized and it was shown that at a photon energy of 280 eV the micrographs yielded bigger absorption differences, and thus better contrast between the core/coat and the peptidoglycan-rich cortex. Tilt series of dormant and HPT spores were reconstructed. Virtual sections revealed the dormant spores' core, cortex and coat without the need to physically slice the sample. It was also possible to visualize the inside of the HPT spores, which proved to be void of DPA. Industrial relevance Isostatic high pressure processing (HPP) is often regarded as the major recent technological innovation in food preservation. However, this technology is only applied in large scale for pasteurization and not for sterilization, which is largely due to the unknown inactivation mechanisms of highly resistant bacterial endospores. The structural analysis of high pressure treated endospores by X-ray microscopy could be used to study the progress of spore germination and inactivation under pressure and may add to the information already gathered in previous studies such as (Reineke et al., 2013) to establish the high pressure thermal sterilization at industrial scale. This technology in combination with different extrinsic factors like chemical or thermal preservation may open up new possibilities for a multi-target spore inactivation strategy for food sterilization.

Dynamics and efficiency of magnetic vortex circulation reversal

Author(s): Urbanek, M; Uhliř, V; Lambert, CH; Kan, JJ; Eibagi, N; Vaňatka, M; Flajsman, L; Kalousek, R; Im, MY; Fischer, P; Sikola, T; Fullerton, EE | Abstract: Dynamic switching of the vortex circulation in magnetic nanodisks by fast-rising magnetic field pulse requires annihilation of the vortex core at the disk and reforming a new vortex with the opposite sense of circulation. Here we study the influence of pulse parameters on the dynamics and efficiency of the vortex core annihilation in permalloy (Ni80Fe20) nanodisks. We use magnetic transmission soft x-ray microscopy to experimentally determine a pulse rise time-pulse amplitude phase diagram for vortex circulation switching and investigate the time-resolved evolution of magnetization in different regions of the phase diagram. The experimental phase diagram is compared with an analytical model based on Thiele's equation describing high-amplitude vortex core motion in a parabolic potential. We find that the analytical model is in good agreement with experimental data for a wide range of disk geometries. From the analytical model and in accordance with our experimental finding we determine the geometrical condition for dynamic vortex core annihilation and pulse parameters needed for the most efficient and fastest circulation switching. The comparison of our experimental results with micromagnetic simulations shows that the micromagnetic simulations of ideal disks with diameters larger than ∼250 nm overestimate nonlinearities in susceptibility and eigenfrequency. This overestimation leads to the core polarity switching near the disk boundary, which then in disagreement with experimental findings prevents the core annihilation and circulation switching. We modify the micromagnetic simulations by introducing the boundary region of reduced magnetization to simulate the experimentally determined susceptibility and in these modified micromagnetic simulations we are able to reproduce the experimentally observed dynamic vortex core annihilation and circulation switching.

The soft x-ray transform

Several new forward models are introduced as mathematical formalizations of the processes that take place during image formation in transmission soft x-ray microscopy, which has the unique capability of imaging whole cells in their native environment with high resolution. Mathematical solutions of some of the associated inverse problems are provided by deriving closed-form formulas specifying the inverse transforms. Numerical experimental results are presented to demonstrate how the inverse transforms can be used to improve the reconstructions computed from data acquired according to the forward models.

Biological soft X-ray tomography on beamline 2.1 atthe Advanced Light Source.

Beamline 2.1 (XM-2) is a transmission soft X-ray microscope in sector 2 of the Advanced Light Source at Lawrence Berkeley National Laboratory. XM-2 was designed, built and is now operated by the National Center for X-ray Tomography as a National Institutes of Health Biomedical Technology Research Resource. XM-2 is equipped with a cryogenic rotation stage to enable tomographic data collection from cryo-preserved cells, including large mammalian cells. During data collection the specimen is illuminated with `water window' X-rays (284-543 eV). Illuminating photons are attenuated an order of magnitude more strongly by biomolecules than by water. Consequently, differences in molecular composition generate quantitative contrast in images of the specimen. Soft X-ray tomography is an information-rich three-dimensional imaging method that can be applied either as a standalone technique or as a component modality in correlative imaging studies.

Extreme ultraviolet and soft X-ray imaging using compact laser-plasma sources based on a double stream gas-puff target

New developments in science and technology require imaging tools and techniques capable of imaging with increased contrast and high spatial resolution, such as an extreme ultraviolet (EUV) and soft X-ray (SXR) microscopy. In this paper, we report on our recent activities related to various imaging techniques in the EUV and SXR region of electromagnetic spectrum, employing a double stream gas-puff target source. Those techniques has been successfully used for studies of morphology of thin silicon membranes coated with NaCl crystals, samples composed of ZnO nanofibers and biological samples. Full Text: PDF References D. Attwood, Soft X-Rays and Extreme Ultraviolet Radiation, Cambridge University, Cambridge, England, 1999. CrossRef W. Chao, J. Kim, S. Rekawa, P. Fischer and E. H. Anderson, "Demonstration of 12 nm Resolution Fresnel Zone Plate Lens based Soft X-ray Microscopy", Opt. Express 17, 20, 17669 (2009) CrossRef G. Vaschenko, et al., "Sub- 38nm resolution tabletop microscopy with 13nm wavelength laser light", Opt.Lett. 31, 1214?1216 (2006) CrossRef C. A. Brewer, et al., "Single-shot extreme ultraviolet laser imaging of nanostructures with wavelength resolution", Opt. Lett. 33, 5, 518, (2008) CrossRef K. W. Kim, et al., "Compact soft x-ray transmission microscopy with sub-50 nm spatial resolution", Phys. Med. Biol. 51, N99-N107 (2006) CrossRef L. Juschkin, R. Freiberger, and K. Bergman, "EUV microscopy for defect inspection by dark-field mapping and zone plate zooming", J. Phys.: Conf. Ser. 186, 012030 (2009) CrossRef P. W. Wachulak, A. Bartnik and H. Fiedorowicz, "Sub-70 nm resolution tabletop microscopy at 13.8 nm using a compact laser?plasma EUV source", Opt. Lett. 35, 14, 2337-2339 (2010) CrossRef P. W. Wachulak, A. Bartnik, H. Fiedorowicz, and J. Kostecki, "A 50nm spatial resolution EUV imaging?resolution dependence on object thickness and illumination bandwidth", Opt. Exp. 19, 10, 9541?9550 (2011) CrossRef P. W. Wachulak, et al., "A compact, quasi-monochromatic laser-plasma EUV source based on a double-stream gas-puff target at 13.8 nm wavelength", Applied Physics B 100, 3, 461-469, (2010) CrossRef R. L. Kelly, Journal of Physical and Chemical Reference Data, 16, supplement 1 (1987) DirectLink The ZP was fabricated by Zone Plates Ltd., using electron beam lithography in 220nm thick PMMA (polymethyl methacrylate) layer spin- coated on top of a 50nm thick silicon nitride Si3N4 membrane. P. W. Wachulak, A. Bartnik, H. Fiedorowicz, D. Panek, P. Bruza, "Imaging of nanostructures with sub-100 nm spatial resolution using a desktop EUV microscope", Appl. Phys. B 109, 105-111 (2012) CrossRef P.W. Wachulak, et al., "Study of crystalline thin films and nanofibers by means of the laser?plasma EUV-source based microscopy", Radiation Physics and Chemistry 93, 54-58 (2013) CrossRef L.B. Da Silva, et al., "X-ray laser microscopy of rat sperm nuclei", Science 258, 269 (1992) CrossRef P. W. Wachulak, et al., "Water-window microscopy using a compact, laser-plasma SXR source based on a double-stream gas-puff target", Appl. Phys. B 111, 2, 239-247 (2013) CrossRef P. W. Wachulak, et al., "Sub 1-?m resolution ?water-window? microscopy using a compact, laser-plasma SXR source based on a double stream gas-puff target", Nucl. Instr. and Meth. B 311, 42-46(2013) CrossRef H. Wolter, "Verallgemeinerte Schwarzschildsche Spiegelsysteme streifender Reflexion als Optiken für Röntgenstrahlen", Ann. Physik 10, 286 (1952) CrossRef

Rapid Prototyping of Fresnel Zone Plates via Direct Ga+ Ion Beam Lithography for High-Resolution X-ray Imaging

A significant challenge to the wide utilization of X-ray microscopy lies in the difficulty in fabricating adequate high-resolution optics. To date, electron beam lithography has been the dominant technique for the fabrication of diffractive focusing optics called Fresnel zone plates (FZP), even though this preparation method is usually very complicated and is composed of many fabrication steps. In this work, we demonstrate an alternative method that allows the direct, simple, and fast fabrication of FZPs using focused Ga(+) beam lithography practically, in a single step. This method enabled us to prepare a high-resolution FZP in less than 13 min. The performance of the FZP was evaluated in a scanning transmission soft X-ray microscope where nanostructures as small as sub-29 nm in width were clearly resolved, with an ultimate cutoff resolution of 24.25 nm, demonstrating the highest first-order resolution for any FZP fabricated by the ion beam lithography technique. This rapid and simple fabrication scheme illustrates the capabilities and the potential of direct ion beam lithography (IBL) and is expected to increase the accessibility of high-resolution optics to a wider community of researchers working on soft X-ray and extreme ultraviolet microscopy using synchrotron radiation and advanced laboratory sources.

Linear transport of domain walls confined to propagating 1-D potential wells

We present a method of controllably propagating domain walls (DWs) in magnetic nanowires over extended linear distances by confining them to geometrically defined energy minima. Using simple models, magnetic transmission soft x-ray microscopy and magneto-optic Kerr effect measurements, we show that the technique allows DWs to be moved at arbitrary, user-defined velocities and be positioned with micrometer precision. Our approach is expected to be of utility in applications where the precise transport and positioning of DWs take precedent over the absolute speed of propagation, for example, where the fields produced by DWs are used to trap and transport magnetized particles.

Magnetic Microstructure of Rolled‐Up Single‐Layer Ferromagnetic Nanomembranes

The magnetic microstructure of rolled-up magnetic nanomembranes is revealed both theoretically and experimentally. Two types of nanomembranes are considered, one with a non-magnetic spacer layer and the other without. Experimentally, by using different materials and tuning the dimensions of the rolled-up nanomembranes, domain patterns consisting of spiral-like and azimuthally magnetized domains are observed, which are in qualitative agreement with the theoretical predictions.

STXM Characterization of Nanostructured Thin Film Anode Before and After Start-Up Shutdown and Reversal Tests

Nanostructured thin film (NSTF) catalysts are promising for proton exchange membrane fuel cell applications. We have used synchrotron based scanning transmission soft X-ray microscopy (STXM) to evaluate composition and structure of NSTF anodes prepared by decaling and the changes that occur after start-up shut-down and reversal testing. We find the metal decorated perylene red support material is mechanically compressed, so that there is very little penetration of the catalyst into the membrane. Such a structure exhibits little or no chemical modification upon generating the PEM-FC structure. In contrast, after the testing there is essentially no perylene red material detected. However, there is no evidence that the loss of the perylene red support affects the catalytic properties of the anode NSTF structure.

New insights into the effects of the herbicide imazethapyr on Cu(II) ecotoxicity to the aquatic unicellular alga Scenedesmus obliquus

Interactions between heavy metals and organic contaminants can result in speciation changes of heavy metals. Therefore, it is unknown whether organic contaminants in aquatic environments act as selective agents to mediate the toxicity of heavy metals. To elucidate these interactions, the effects of the herbicide imazethapyr (IM) on Cu(II) ecotoxicity to the aquatic unicellular alga Scenedesmus obliquus were investigated. It was found that the toxicity of Cu could be mediated by IM. To explore the mechanisms involved, complex formation, the catalytic activity of the complex, the Cu species and the distribution of Cu and Fe in the algal cell were characterized. The results showed that Cu(II) and IM formed an octahedral complex with an IM:Cu molar ratio of 2:1. These complexes also catalyzed the disproportionation of hydrogen peroxide. Analysis of the K-edge of Cu using XAFS spectroscopy indicated that when treated with Cu, the Cu was bound to polygalacturonic acid (on the cell wall), and once inside the cell, Cu may complex with the reduced glutathione (GSH) (in the cell). When the cell is treated with IM and Cu simultaneously, IM–Cu may be the primary complex formed. Once Cu combines with IM, it is difficult for it to interact with the cell wall. In addition, using scanning transmission soft X-ray microscopy, it was found that Cu could induce changes in the distribution of the essential trace element Fe, whereas IM–Cu cannot. This finding demonstrates the importance of interactions between heavy metals and organic contaminants, which are able to mediate the toxicity of heavy metals and should be considered in future risk assessments.

Dynamic switching of the spin circulation in tapered magnetic nanodisks

Magnetic vortices are characterized by the sense of in-plane magnetization circulation and by the polarity of the vortex core. With each having two possible states, there are four possible stable magnetization configurations that can be utilized for a multibit memory cell. Dynamic control of vortex core polarity has been demonstrated using both alternating and pulsed magnetic fields and currents. Here, we show controlled dynamic switching of spin circulation in vortices using nanosecond field pulses by imaging the process with full-field soft X-ray transmission microscopy. The dynamic reversal process is controlled by far-from-equilibrium gyrotropic precession of the vortex core, and the reversal is achieved at significantly reduced field amplitudes when compared with static switching. We further show that both the field pulse amplitude and duration required for efficient circulation reversal can be controlled by appropriate selection of the disk geometry.