Scientific Highlights

X-ray nanotomography aids the production of eco-friendly solar cells

Polymer solar cells are in the spotlight for sustainable energy production of the future. Characterization of these devices by X-ray nanotomography helps to improve their production using environmentally friendly materials.

Hydrogen atoms are light and can tunnel through a barrier. Tunnelling can be quenched by substituting them with deuterium, a twice as heavy isotope of H.

Controlling tunnelling in methane loss from acetone ions by deuteration

At the imaging Photoelectron Photoion Coincidence (iPEPICO) endstation of the VUV beamline evidence of H-atom tunneling was shown.

Top: High-pressure CH4 adsorption isotherms (AIs). The usable capacity for a classical Langmuir-type AI (top left) and a ‘stepped’ AI (top middle), with the minimum desorption pressure and the maximum adsorption pressure indicated by the vertical lines. Right, CH4 AIs for Co(bdp)  at 25 °C with Pdes = 5.8 bar and Pads = 35 bar indicated by dashed lines and filled/open circles representing adsorption/desorption.  Middle: The crystal structures of the collapsed (0bar) and CH4- expanded (30bar CH4) phases of …

Methane storage in flexible metal–organic frameworks with intrinsic thermal management

As a cleaner, cheaper, and more globally evenly distributed fuel, natural gas has considerable environmental, economic, and political advantages over petroleum as a source of energy for the transportation sector. Despite these benefits, its low volumetric energy density at ambient temperature and moderate pressure presents substantial challenges, particularly for light-duty vehicles with little space available for on-board fuel storage.

Figure caption: Sketch of the 3D Fermi surface of d-AlNiCo (left) and its experimental cross-sections in the indicated planes (right) showing vanishing pseudogap in the quasiperiodic directions.

Fermi states and anisotropy of Brillouin zone scattering in the decagonal Al–Ni–Co quasicrystal

Quasicrystals (QCs) are intermetallic alloys where excellent long-range order coexists with lack of translational symmetry in one or more dimensions. These materials have a high potential in application as a material for a solar cells, hydrogen storage applications, heat insulating layers, and others.

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2015 Otto Kratky award

Marianne Liebi was awarded the 2015 Otto Kratky award by the Helmholtz-Centre Berlin for excellence in the field of small-angle X-ray scattering (SAXS) analysis. The award was bestowed in the last SAS2015 conference in Berlin. Marianne is a postdoctoral fellow in the coherent X-ray scattering group (CXS) in PSI, carrying out research in scanning SAXS measurement and analysis in 2D and 3D. Image credit ©HZB/Michael Setzpfandt

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In Situ Serial Crystallography Workshop at the SLS

The Macromolecular Crystallography group at SLS is organizing a three days workshop on in situ serial crystallography (http://indico.psi.ch/event/issx) between November 17 and 19, 2015. It will be dedicated in the presentation of a novel method facilitating the structure determination of membrane proteins, which are highly important pharmaceutical targets but are difficult to handle using 'classical' crystallographic tools. Designed for 20 Ph.D. students, postdocs and young scientists from both academia and industry, the workshop will consist of introductory lectures, followed by hands-on practicals on in meso or lipidic cubic phase (LCP) crystallization, on in situ serial crystallography data collection using a micro-sized beam and on data processing.

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New insight into receptor signalling

A team of 72 investigators across 25 institutions including researchers from the Paul Scherrer Institut obtained the X-ray structure of a rhodopsinàarrestin complex, which represents a major milestone in the area of G-protein-coupled-receptor (GPCR), a protein family recognized in the award of the 2012 Nobel Prize in Chemistry.

3D image of the buckyball structure investigated. In the right picture the distribution of Cobalt is shown in orange. (The solid line corresponds to 1 micrometre or 1 thousandth of a millimetre).

Element-Specific X-Ray Phase Tomography of 3D Structures at the Nanoscale

Recent advances in fabrication techniques to create mesoscopic 3D structures have led to significant developments in a variety of fields including biology, photonics, and magnetism. Further progress in these areas benefits from their full quantitative and structural characterization.

Schematic diagram of vortex core reversal process. The vortex core magnetisation reverses its orientation when crossing a domain boundary (black down arrow to white up arrow).

Nanoscale switch for vortex polarization mediated by Bloch core formation in magnetic hybrid systems

Vortices are fundamental magnetic topological structures characterized by a curling magnetization around a highly stable nanometric core.

Figure: Left top, one of the XRPD measured patterns and the corresponding fit. Left bottom, the fitted size distribution (green bars) with the maghemite (shell) and magnetite (core) weight fractions as a function of diameter. Right, the corresponding saturation magnetization as a function of shell relative thickness for samples with the same average diameter. Inset, a sketch of a core-shell nanoparticle as modeled.

Correlating the Core-Shell Composition and the Surface Structure to the Magnetic Properties for Magnetite-Maghemite Nanoparticles in the 5-15 nm Range

Very small superparamagnetic iron oxide nanoparticles were characterized by innovative synchrotron X-ray total scattering methods and Debye function analysis, developed at the X04SA Materials Science beamline of SLS.

View of a Mn19 molecule on the gold surface. The surface-induced changes of the oxidation state and magnetic properties of the constituent Mn ions have been probed by X-ray absorption spectroscopy and X-ray magnetic circular dichroism.

Reduction of Mn19 Coordination Clusters on a Gold Surface

The surface-induced changes of the oxidation state and magnetic properties of Mn ion clusters have been probed by X-ray absorption spectroscopy and X-ray magnetic circular dichroism.

Schematics of the iMott spin detector attached to an ARPES analyzer.

Concept of a multichannel spin-resolving electron analyzer based on Mott scattering

The spin of electron plays a crucial role in many physical phenomena, ranging from the obvious example of magnetism, via novel materials for spintronics applications, to high-temperature superconductivity. Spin- and angle-resolved photoelectron spectroscopy (SARPES) gives the most direct access to the spin aspects of the electronic structure, but the one-channel detection principle of all presently available SARPES spectrometers severely limits their efficiency. A team of Swiss and Russian scientists has developed a revolutionary concept of a multichannel electron spin detector based on Mott scattering as the spin selective process and imaging-type electron optics.

(a) Rhombohedral distortion of the pseudocubic La1−xSrxMnO3 lattice; (b) GGA+U theoretical FS; (c,d) Experimental FS cross-sections, with the shadow contours manifesting the lattice distortion.

Fermi Surface of Three-Dimensional La1−xSrxMnO3 Explored by Soft-X-Ray ARPES: Rhombohedral Lattice Distortion and its Effect on Magnetoresistance

A research team led by scientists from the Swiss Light Source has for the first time established three-dimensional (3D) electronic structure of the perovskite compound La1−xSrxMnO3 connected with its colossal magnetoresistance. Instrumental for this study has been the use of the new experimental technique of soft-x-ray ARPES, available at the ADRESS beamline, with its intrinsically sharp definition of 3D electron momentum.

Multiresolution X-ray tomography, getting a clear view of the interior

Researchers at PSI have developed a technique that combines tomography measurements at different resolution levels to allow quantitative interpretation for nanoscale tomography on an interior region of interest of the sample. In collaboration with researchers of the institute AMOLF in the Netherlands and ETH Zurich in Switzerland they showcase their technique by studying the porous structure within a section of an avian eggshell. The detailed measurements of the interior of the sample allowed the researchers to quantify the ordering and distribution of an intricate network of pores within the shell.

Left: Structure of BaFe2As2 with the motion pattern of the A1g phonon mode (red arrows). 
Right: Pump-induced change of diffraction intensity of the (1 0 5) reflection

Ultrafast structural dynamics of the Fe-pnictide parent compound BaFe2As2

Understanding the interplay of the various degrees of freedom such as the electrons, spins and lattice is essential for many complex materials, including the high-temperature superconductors.

Magnetization dynamics inside a 5 µm x 5 µm structure.(a) Time-resolved PEEM images using XMCD as a magnetic contrast mechanism recorded at a given time delay t after the laser pulse and (b) extracted XMCD contrast as a function of the time delay t for three different ROI, defined in the inset image by the coloured area superimposed on the non-dichroic X-ray absorption of the structure. The 0° incoming laser direction with respect to the structure edge is indicated in the inset by the laser in-plane wave v…

Nanoscale sub-100 picosecond all-optical magnetization switching in GdFeCo microstructure

Ultrafast magnetization reversal driven by femtosecond laser pulses has been shown to be a promising way to write information. Seeking to improve the recording density has raised intriguing fundamental questions about the feasibility of combining ultrafast temporal resolution with sub-wavelength spatial resolution for magnetic recording. Here we report on the experimental demonstration of nanoscale sub-100 ps all-optical magnetization switching, providing a path to sub-wavelength magnetic recording.

ARPES spectra revealing the electronic structure of a metallic surface state on SrTiO3.

A revealing mixture: The surface of an oxide insulator can host two distinct types of conducting electrons

Strontium titanate, SrTiO3, is an important material for the realization of next-generation electronic devices. A famous example is the interface of LaAlO3 grown on SrTiO3, which is metallic and magnetic at its interface, even though the individual compounds are insulating and nonmagnetic in bulk form. The physics behind how novel interface states form on SrTiO3 - and how they become endowed with such surprising properties - is not well understood.

Square dance of the atoms: Shedding light on ultrafast phase transitions

The exploration of the interaction of structural and electronic degrees of freedom in strongly correlated electron systems on the femtosecond time scale is an emerging area of research. One goal of these studies is to advance our understanding of the underlying correlations, another to find ways to control the exciting properties of these materials on an ultrafast time scale.