Tag: XAS

Researchers identify new material for creating electronic devices

Researchers identify new material for creating electronic devices

A multidisciplinary research team is developing more efficient and environmentally friendly processes to build light-emitting diodes with the help of the Canadian Light Source (CLS) at the University of Saskatchewan.

Dr. Simon Trudel, professor in chemistry at the University of Calgary and director of the university’s Nanoscience Program, said his team has been studying ways to use amorphous materials to build better “optoelectronic devices” such as organic photovoltaic cells or organic light-emitting diodes (OLEDs), which make possible digital display TV screens, computer monitors and smartphones.

By using a technique called X-ray Absorption Spectroscopy (XAS) at the CLS, Trudel’s team was able to precisely examine the structure of the materials they were experimenting with to create more efficient electronic cells.

Trudel’s team focused on one of the interior layers of the diode called the hole-transport layer, which regulates the movement of electrons — and electrical energy — in a device. They identified an amorphous vanadium oxide compound that could be used for the hole-transfer layer but did not require the standard-but-intense heat treatments to crystallize the material.

Read more on the Canadian Light Source website

Image: Digital displays

Unveiling finer details in the physics of materials

Unveiling finer details in the physics of materials

Scientists at the European XFEL’s SCS instrument routinely use a technique called transient X-ray absorption spectroscopy (XAS) to investigate materials that have applications in data storage and processing, catalysis, or in the search for room temperature superconductors. Investigating very small changes in the motion of electrons within a material’s structure on ultrashort timescales provides scientists with fingerprints of the complex processes at play within them. This helps them characterise samples that are important for energy and materials research.

Using the European XFEL’s brilliant pulses, researchers can overcome some of the issues of conventional transient XAS—such as long measurement times—but the varying intensity of European XFEL’s pulses provides its own challenges. Now, scientists at SCS have implemented a new sampling scheme for improving the efficiency of such measurements.

Read more on the European XFEL website

Image: The X-ray beam is split into three copies. Two of these copies are passed through identical samples of the material under investigation, with one of these samples also being illuminated by a laser (‘optical laser’ in the figure). This transforms it into a new state, interesting to researchers. From this, scientists are able to ‘subtract’ detrimental noise, revealing the finest details of the sample under investigation.

Researchers reproduce the learning and forgetting functions of the brain with magnetic systems

Researchers reproduce the learning and forgetting functions of the brain with magnetic systems

A research led by the UAB has managed to emulate learning neuromorphic abilities using thin layers of cobalt oxide. The experiment, performed at the ALBA Synchrotron, is a new step towards brain-inspired computers.

  • The experiment, performed at the ALBA Synchrotron, is a new step towards brain-inspired computers

With the advent of Big Data, current computational architectures are proving to be insufficient. Difficulties in decreasing transistors’ size, large power consumption and limited operating speeds make neuromorphic computing a promising alternative.

Neuromorphic computing, a new brain-inspired computation paradigm, reproduce the activity of biological synapses by using artificial neural networks. Such devices work as a system of switches, so that the ON position corresponds to the information retention or ‘learning’, while the OFF position corresponds to the information deletion or ‘forgetting’.

In a recent publication, scientists from the Universitat Autònoma de Barcelona (UAB), the CNR-SPIN (Italy), the Catalan Institute of Nanoscience and Nanotechnology (ICN2), the Institute of Micro and Nanotechnology (IMN-CNM-CSIC) and the ALBA Synchrotron have explored the emulation of artificial synapses using new advanced material devices. The project was led by Serra Húnter Fellow Enric Menéndez and ICREA researcher Jordi Sort, both at the Department of Physics of the UAB, and is part of Sofia Martins PhD thesis.

A new approach to mimic synapse functions

Until now, most systems used for this purpose were ultimately controlled by electric currents, involving significant energy loss by heat dissipation. Here, researchers’ proposal was to use magneto-ionics, the non-volatile control of the magnetic properties of materials by voltage-driven ion migration, which drastically decreases power consumption and makes data storage energy-efficient.

Although heat dissipation decreases with ion migration effects, magneto-ionic motion of oxygen at room temperature is usually slow for industrial applications, involving several seconds or even minutes to toggle the magnetic state. To solve this problem, the team investigated the use of target materials whose crystal structure already contained the ions to be transported. Such magneto-ionic targets can undergo fully reversible transformations from a non-ferromagnetic (switch OFF) to a ferromagnetic (switch ON) state and vice versa just by the voltage-driven oxygen motion from the target towards a reservoir (ON) and vice versa (OFF).

Given their crystalline structures, cobalt oxides were the chosen materials for the fabrication of the films, ranging from 5nm to 230nm thick. They investigated the role of thickness on the resulting magneto-ionic behaviour, revealing that the thinner the films, the faster the generation of magnetization was reached.

X-ray absorption spectra (XAS) of the samples were performed at the BOREAS beamline of the ALBA Synchrotron. XAS was used to characterize, at room temperature, the elemental composition and oxidation state of the cobalt oxide films, which resulted to be different for the thinner and thickest films. These findings were crucial to understand the differences in the magneto-ionic motion of oxygen between the films.

Read more on the ALBA website

Image: BOREAS beamline of the ALBA Synchrotron

Observation of Magnetoelectric Coupling

Observation of Magnetoelectric Coupling

Multiferroic materials with coexisting ferroelectric and ferromagnetic orders have attracted much attention due to the magnetoelectric (ME) coupling opening prospects for alternative multifunctional electronic devices.  Switching magnetization by applied electric rather than magnetic field or spin-polarized current requires much less energy, making multiferroics promising for memory and logic applications. Due to a limited number of single-phase multiferroic compounds operating at room temperature, composite multiferroics containing ferroelectric and ferromagnetic components have been considered as viable alternatives. Moreover, it was shown that composite multiferroic materials often have much larger magnetoelectric coupling effect compared to their single-phase counterparts.

The recently emerged class of polycrystalline doped HfO2-based ferroelectric thin films, which are compatible with the modern Si technology, is a promising ferroelectric component in composite multiferroic heterostructures and it is therefore crucial to explore the ME effect at the ferroelectric/ferromagnetic interface in the heterostructures comprising doped HfO2. In this respect, a strong charge-mediated magnetoelectric coupling at the interface between classical ferromagnetic metal – Ni and ferroelectric HfO2has been recently predicted by theoretical modelling.

Read more on the Elettra Website

Image: Schematic drawing of a single capacitor device structure used in operando XAS/XMCD and HAXPES/MCDAD measurements with EELS (Electron energy loss spectroscopy) map of Co, Ni and O. Polarization vs. voltage hysteresis loop at RT and LT (left) and  MOKE (right) of Au/Co/Ni/HZO/W sample are also shown in figure.

Credit: Elettra

New insights into the photochemical activity of titanium dioxide

New insights into the photochemical activity of titanium dioxide

Not so many compounds are as important to industry and medicine today as titanium dioxide (TiO2). The electronic structure of transition metal oxides is an important factor determining the chemical and optical properties of materials. Specifically for metal-oxide structures, the crystal-field interaction determines the shape and occupancy of electronic orbitals. Consequently, the crystal-field splitting and resulting unoccupied state populations can be foreseen as modeling factors of the photochemical activity. The research on titanium dioxide inaugurated the presence of IFJ PAN scientists in research programs carried out at the SOLARIS synchrotron. The measurements, co-financed by the National Science Center, were carried out at the XAS beamline.

In many chemical reactions, TiO2 appears as a catalyst. As a pigment, it occurs in plastics, paints, and cosmetics, while in medical implants, it guarantees their high biocompatibility. A group of scientists from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Krakow, led by Dr. Jakub Szlachetka, engaged in research on the oxidation processes of the outer layers of titanium samples and related changes in the electronic structure of this material. Scientists from the IFJ PAN conducted their latest measurements, co-financed by the National Science Center, at the XAS beamline. They analyzed how X-rays are absorbed by the surface layers of titanium samples previously produced at the Institute under carefully controlled conditions.

Read more on the SOLARIS website

Riverine iron survives salty exit to sea

Riverine iron survives salty exit to sea

Iron organic complexes in Sweden’s boreal rivers significantly contribute to increased iron concentration in open marine waters, X-ray spectroscopy data shows. A Lund University study in Biogeosciences characterizes the role of salinity for iron-loading in estuarine zones, a factor which underpins intensifying seasonal algal blooms in the Baltic Sea.

The study ties in with a reported trend of increased riverine iron concentrations over the last decade in North America, northern Europe and in particular, Swedish and Finnish rivers. This, in conjunction with a predicted rise in extreme weather events in Scandinavia due to climate change, provides momentum for more bioavailable iron to enter marine environments such as the Baltic Sea.

“The consequences of increasing riverine iron for the receiving [marine] system depend first and foremost on the fate of iron in the estuarine salinity gradient. We had questions on what factors determine the movement and transport capacity of iron in these boreal rivers,” said Simon Herzog, postdoctoral researcher at Lund University.

The research group investigated the iron discharge in eight boreal rivers in Sweden which drain into the Baltic Sea, a brackish marine system. Water samples were taken upstream and at the river mouths, the latter just before estuarine mixing and stronger saline conditions occur. Spring and autumn specimens enabled the comparative analysis of flow conditions. To determine the type and amounts of iron species, measurements with X-ray absorbance spectroscopy (XAS) were taken at beamline I811 at Max-lab in Lund, Sweden and X-ray Absorption Near-Edge Structure (XANES) spectra at beamline ID26 at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France.

Read more on the MAX IV website

Image: A view of the Ore River in northern Sweden

Credit: Simon Herzog

Transition-metal dichalcogenide NiTe2: an ambient-stable material for catalysis and nanoelectronics

Transition-metal dichalcogenide NiTe2: an ambient-stable material for catalysis and nanoelectronics

Recently, transition-metal dichalcogenides hosting topological states have attracted considerable attention for their potential implications for catalysis and nanoelectronics. The investigation of their chemical reactivity and ambient stability of these materials is crucial in order to assess the suitability of technology transfer. With this aim, an international team of researchers from Italy, Russia, China, USA, India, and Taiwan has studied physicochemical properties of NiTe2 by means of several experimental techniques and density functional theory. Surface chemical reactivity and ambient stability were followed by x-ray photoemission spectroscopy (XPS) and x-ray absorption spectroscopy (XAS) experiments at the BACH beamline, while the electronic band structure was probed by spin- and angle-resolved photoelectron spectroscopy (spin-ARPES) at the APE-LE beamline. 

Read more on the Elettra website

Image:  a) Ni-3p and b) Te-4d XPS core-level spectra collected from as-cleaved NiTe2 (black curves) and from the same surface exposed to 2·104 L of CO (red curves), H2O (green curves) and O2 (blue curves). Adapted from “S. Nappini et al., Adv. Funct. Mater. 30, 2000915 (2020); DOI: 10.1002/adfm.202000915” with permission from Wiley (Copyright 2020) with license 4873681106527

Unexpected rise in ferroelectricity as material thins

Unexpected rise in ferroelectricity as material thins

SCIENTIFIC ACHIEVEMENT

Researchers working at the Advanced Light Source (ALS) showed that hafnium oxide surprisingly exhibits enhanced ferroelectricity (reversible electric polarization) as it gets thinner.

SIGNIFICANCE AND IMPACT

The work shifts the focus of ferroelectric studies from more complex, problematic compounds to a simpler class of materials and opens the door to novel ultrasmall, energy-efficient electronics.

Ferroelectric lower limit?

Distortions in the atomic geometries of certain materials can lead to ferroelectricity—the presence of electric dipoles (charge separations) with switchable polarizations. The ability to control this polarization with an external voltage offers great promise for ultralow-power microprocessors and nonvolatile memory.

As electronic devices become smaller, however, the materials used to store and manipulate electronic data are being pushed to low-dimensional extremes. Properties that function reliably in bulk materials often diminish in ultrathin films just a few atomic units thick. Therefore, exploring the critical thickness limit in “polar” materials (i.e., materials having spontaneous electric polarization) is not only a fundamental issue for nanoscale ferroelectric research, it also has extensive implications for the future of high-density ferroelectric-based electronics.

Read more on Advanced Light Source (ALS) website

Image : A thin layer of hafnium oxide (two unit-cell thicknesses, or about 1 nm) has an electric polarization that’s reversible by an external electric field, making it attractive for use in next-generation low-power microelectronics.

Credit: Ella Maru Studio

Electronics of future: magnetic properties of InSb-Mn

Electronics of future: magnetic properties of InSb-Mn

The recent volume of “ACS Nano Letters” presented the results of research conducted at the SOLARIS National Synchrotron Radiation Centre and at the Academic Centre for Materials and Nanotechnology of the University of Science and Technology in Kraków.

The research was led by Dr Katarzyna Hnida-Gut and demonstrated that the magnetic properties of indium antimonide nanowires with an addition of manganese (InSb-Mn) can be controlled by the concentration of the dopants. The ground-breaking aspect of this research was that for the first time in the pulse electrosynthesis process in AAO pores (anodic aluminium oxide) high quality InSb-Mn nanowires were obtained, making use of previously determined optimum conditions for the synthesis of the semiconductor indium antimonide.

Some of the measurements conducted as part of the research project were performed using synchrotron radiation at the SOLARIS Centre in Kraków. Thanks to an experiment conducted on PEEM/XAS beamline, it was possible to determine the local structure in the vicinity of manganese atoms. This allowed for the confirmation of the hypothesis that “the manganese atoms in the studied nanowires form small clusters, such as Mn3. It is precisely these clusters that are the source of the magnetic response at room temperature,” explains Dr. Marcin Sikora, one of the co-authors of the paper.

>Read more on the SOLARIS website

Operando X-ray diffraction during laser 3D printing

Operando X-ray diffraction during laser 3D printing

Additive manufacturing, a bottom-up approach for manufacturing components layer by layer from a 3D computer model, plays a key role in the so-called “fourth” industrial revolution. Selective laser melting (SLM), one of the more mature additive manufacturing processes, uses a high power-density laser to selectively melt and fuse powders spread layer by layer. The method enables to build near full density functional parts and has viable economic benefits. Despite significant progress in recent years, the relationship between the many processing parameters and final microstructure is not well understood, which strongly limits the number of alloys that can be produced by SLM for commercial applications.

>Read more on the Swiss Light Source (PSI) website

Image: Rendered 3D model of the MiniSLM device.

Multimodal study of ion-conducting membranes

Multimodal study of ion-conducting membranes

Using multiple x-ray characterization tools, researchers showed how chemical and structural changes improve the performance of a novel ion-conducting polymer (ionomer) membrane from 3M Company.

In fuel cells (which generate clean power from hydrogen fuel) and electrolyzers (water-splitting devices that produce hydrogen fuel), positive and negative electrodes are separated by membranes composed of ion-conducting polymers (ionomers). These membranes prevent contact between the electrodes—thus avoiding catastrophic failure—while allowing selective passage of ions to complete the circuit.

Generally, such membranes are based on a class of perfluorosulfonic acid (PFSA) ionomers with remarkable proton conductivity and stability. Recently, however, companies such as 3M have been developing new ionomers with improved performance. In this work, researchers took a closer look at the structural and chemical properties of these materials at the nanometer scale. The resulting insights provide valuable guidance on design strategies for optimally performing ionomers.

>Read more on the Advanced Light Source website

Image: Resonant x-ray scattering (RXS) and x-ray absorption spectroscopy (XAS) with elemental sensitivity unravel structural features and chemical factors affecting morphology and ion transport in proton-conducting membranes.

Synergistic Co−Mn oxide catalyst for oxygen reduction reactions

Synergistic Co−Mn oxide catalyst for oxygen reduction reactions

Researchers employed synchrotron-based X-ray absorption spectroscopy (XAS) at CHESS to investigate the synergistic interaction of bimetallic Co1.5Mn1.5O4/C catalysts… under real-time operando electrochemical conditions.

Identifying the catalytically active site(s) in the oxygen reduction reaction (ORR) is critical to the development of fuel cells and other technologies. Researchers employed synchrotron-based X-ray absorption spectroscopy (XAS) at CHESS to investigate the synergistic interaction of bimetallic Co1.5Mn1.5O4/C catalysts – which exhibit impressive ORR activity in alkaline fuel cells – under real-time operando electrochemical conditions. Under steady state conditions, both Mn and Co valences decreased at lower potentials, indicating the conversion from Mn-(III,IV) and Co(III) to Mn(II,III) and Co(II), respectively. Changes in the Co and Mn valence states are simultaneous and exhibited periodic patterns that tracked the cyclic potential sweeps.

>Read more on the CHESS website

Image: Schematic of the in situ XAS electrochemical cell. Working electrode (WE, catalyst on carbon paper) and counter electrode (CE, carbon rod) were immersed in 1 M KOH solution. The reference electrode was connected to the cell by a salt bridge to minimize IR drops caused by the resistance in the thin electrolyte layer within the X-ray window.

Catalyst improves cycling life of magnesium/sulfur batteries

Catalyst improves cycling life of magnesium/sulfur batteries

Comprising earth-abundant elements, cathodes made of magnesium/sulfur compounds could represent the next step in battery technology. However, despite being dendrite free and having a high theoretical energy density compared with lithium batteries, magnesium/sulfur batteries have suffered from high polarization and extremely limited recharging capabilities. To gain electrochemical insights into magnesium/sulfur batteries during charge–discharge cycles, researchers used the Advanced Light Source (ALS) to investigate and optimize battery chemistry.

The in situ x-ray absorption spectroscopy (XAS) capabilities at ALS Beamlines 5.3.1 and 10.3.2 provided information on the oxidation state of sulfur under real operating conditions. The group found that the conversion of sulfur in the first discharging process was divided into three stages: formation of MgS8 and MgS4 at a fast reaction rate, reduction of MgS4 to Mg3S8, and a sluggish further reduction of Mg3S8 to MgS. The in situ XAS analysis revealed that Mg3S8 and MgS are more electrochemically inert and cannot revert to the active forms of sulfur, thereby dramatically reducing the battery’s cycling life.

>Read more on the ALS website

Image: Efforts to develop magnesium/sulfur batteries have been stymied by a loss of capacity after the first discharging process. In situ XAS revealed the accumulation of Mg3S8 and MgS during the discharging process, which are inert forms of the magnesium/sulfur compounds. Introducing a titanium-sulfide catalyst activated the compounds, reversing the chemical mechanism so that the battery could be recharged multiple times.

 

Cause of cathode degradation identified for nickel-rich materials

Cause of cathode degradation identified for nickel-rich materials

Combination of research methods reveals causes of capacity fading, giving scientists better insight to design advanced batteries for electric vehicles

A team of scientists including researchers at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory and SLAC National Accelerator Laboratory have identified the causes of degradation in a cathode material for lithium-ion batteries, as well as possible remedies. Their findings, published on Mar. 7 in Advanced Functional Materials, could lead to the development of more affordable and better performing batteries for electric vehicles.

Searching for high-performance cathode materials
For electric vehicles to deliver the same reliability as gas vehicles they need lightweight yet powerful batteries. Lithium-ion batteries are the most common type of battery found in electric vehicles today, but their high cost and limited lifetimes are limitations to the widespread deployment of electric vehicles. To overcome these challenges, scientists at many of DOE’s national labs are researching ways to improve the traditional lithium-ion battery.

>Read more on the NSLS-II at Brookhaven Lab website

Image: Members of the Brookhaven team are shown at NSLS-II’s ISS beamline, where part of the research was conducted. Pictured from front to back are Eli Stavitski, Xiao-Qing Yang, Xuelong Wang, and Enyuan Hu.

Copper mobilization and immobilization

Copper mobilization and immobilization

… along an organic matter and redox gradient- insights from a mofette site.

The metal copper (Cu) is known to be an essential trace element for many organisms but it is also considered a severe contaminant at higher concentrations. Especially in soils with changing redox conditions, Cu binding mechanisms and, thus, Cu mobility are hard to predict. The metal is known to have a high affinity to soil organic matter (SOM), i.e., it can either be sequestered by adsorption to solid-phase organic matter or mobilized by complexation with dissolved organic matter. Under reducing conditions, Cu(II) can also be reduced to Cu(I) via biotic and abiotic processes and precipitate in the form of sulfidic minerals.
>Read more on the SSRL website
Image: Picture of the investigated mofette site (left) and Cu sorption isotherms determined for mofette, transitions, and reference soil in a Cu spike experiment (right).
Credit: Reprinted with permission from Mehlhorn et al. 2018, ES&T, DOI: 10.1021/acs.est.8b02668, Copyright 2018 American Chemical Society

Tunable ferromagnetism in a 2D material at room temperature

Tunable ferromagnetism in a 2D material at room temperature

Breakthroughs in next-generation spintronic logic and memory devices could hinge on our ability to control spin behavior in two-dimensional materials—stacks of ultrathin layers held together by relatively weak electrostatic (van der Waals) forces. The reduced dimensionality of these so-called “van der Waals materials” often leads to tunable electronic and magnetic properties, including intrinsic ferromagnetism. However, it remains a challenge to tune this ferromagnetism (e.g. spin orientation, magnetic domain phase, and magnetic long-range order) at ambient temperatures.

In this work, researchers performed a study of Fe3GeTe2, a van der Waals material that consists of Fe3Ge layers alternating with two Te layers. The material’s magnetic properties were characterized using a variety of techniques, including x-ray absorption spectroscopy (XAS) with x-ray magnetic circular dichroism (XMCD) contrast at Beamline 6.3.1 and photoemission electron microscopy (PEEM) at Beamline 11.0.1.

>Read more on the Advanced Light Source (ALS) at LBNL website

Image: PEEM images for unpatterned and patterned Fe3GeTe2 samples at 110 K and 300 K. The unpatterned samples formed stripe domains at 110 K, which disappeared at 300 K. The patterned samples formed out-of-plane stripe domains at 110 K and transitioned to in-plane vortex states at 300 K, demonstrating control over magnetism at room temperature and beyond.