New monochromator optics for tender X-rays
Schematic drawing of the novel monochromator concept at the U41-PGM1 beamline at BESSY-II based on a multilayer coated blazed plane grating and mirror to improve the photon flux in the tender X-ray photon energy range (1.5 – 5.0 keV). The inset shows a TEM image of the cross-section of the Cr/C multilayer blazed grating structures. For better visualization of the grating period, the image was horizontally compressed 10 fold. © HZB / Small Methods 2022
X-ray microscopy images of a 400 nm thick lamella cut out of a modern microchip device. The individual images were taken from a microspectrocopic energy series at the Si-K absorption edge. The NEXAFS spectra were extracted from the acquired energy series for SiCN and OSG materials. The corresponding energy peaks are related to the dominating Si-C bonds for SiCN and the dominating Si-O bonds for OSG dielectrics.
© HZB / Small Methods 2022
Until now, it has been extremely tedious to perform measurements with high sensitivity and high spatial resolution using X-ray light in the tender energy range of 1.5 - 5.0 keV. Yet this X-ray light is ideal for investigating energy materials such as batteries or catalysts, but also biological systems. A team from HZB has now solved this problem: The newly developed monochromator optics increase the photon flux in the tender energy range by a factor of 100 and thus enable highly precise measurements of nanostructured systems. The method was successfully tested for the first time on catalytically active nanoparticles and microchips.
A climate-neutral energy supply requires a wide variety of materials for energy conversion processes, for example catalytically active materials and new electrodes for batteries. Many of these materials have nanostructures that increase their functionality. When investigating these samples, spectroscopic measurements to detect the chemical properties are ideally combined with X-ray imaging with high spatial resolution at the nanoscale. However, since key elements in these materials, such as molybdenum, silicon or sulphur, react predominantly to X-rays in the so-called tender photon energy range, there has been a major problem until now.
This is because in this "tender" energy range between soft and hard X-rays, conventional X-ray optics from plane grating or crystal monochromators deliver only very low efficiencies. A team from HZB has now solved this problem: "We have developed novel monochromator optics. These optics are based on an adapted, multilayer-coated sawtooth grating with a plane mirror," says Frank Siewert from the HZB Optics and Beamlines Department. The new monochromator concept increases the photon flux in the tender X-ray range by a factor of 100 and thus enables highly sensitive spectromicroscopic measurements with high resolutions for the first time. "Within a short time we were able to collect data from NEXAFS spectromicroscopy on the nanoscale. We have demonstrated this on catalytically active nanoparticles and modern microchip structures," says Stephan Werner, first author of the publication. "The new development now enables experiments that would otherwise have required months of data collection," Werner emphasises.
"This monochromator will become the method of choice for imaging in this X-ray energy range, not only at synchrotrons worldwide, but also at free-electron lasers and laboratory sources," says Gerd Schneider, who heads the X-ray Microscopy Department at HZB. He expects enormous effects on many areas of materials research: Studies in the tender X-ray range could significantly advance the development of energy materials and thus contribute to climate-neutral solutions for electricity and energy supply.
- Battery research with the HZB X-ray microscopeNew cathode materials are being developed to further increase the capacity of lithium batteries. Multilayer lithium-rich transition metal oxides (LRTMOs) offer particularly high energy density. However, their capacity decreases with each charging cycle due to structural and chemical changes. Using X-ray methods at BESSY II, teams from several Chinese research institutions have now investigated these changes for the first time with highest precision: at the unique X-ray microscope, they were able to observe morphological and structural developments on the nanometre scale and also clarify chemical changes.
- BESSY II: New procedure for better thermoplasticsBio-based thermoplastics are produced from renewable organic materials and can be recycled after use. Their resilience can be improved by blending bio-based thermoplastics with other thermoplastics. However, the interface between the materials in these blends sometimes requires enhancement to achieve optimal properties. A team from the Eindhoven University of Technology in the Netherlands has now investigated at BESSY II how a new process enables thermoplastic blends with a high interfacial strength to be made from two base materials: Images taken at the new nano station of the IRIS beamline showed that nanocrystalline layers form during the process, which increase material performance.
- Hydrogen: Breakthrough in alkaline membrane electrolysersA team from the Technical University of Berlin, HZB, IMTEK (University of Freiburg) and Siemens Energy has developed a highly efficient alkaline membrane electrolyser that approaches the performance of established PEM electrolysers. What makes this achievement remarkable is the use of inexpensive nickel compounds for the anode catalyst, replacing costly and rare iridium. At BESSY II, the team was able to elucidate the catalytic processes in detail using operando measurements, and a theory team (USA, Singapore) provided a consistent molecular description. In Freiburg, prototype cells were built using a new coating process and tested in operation. The results have been published in the prestigious journal Nature Catalysis.