Germanium telluride’s hidden properties revealed

Germanium Telluride is an interesting candidate material for spintronic devices. In a comprehensive study at BESSY II, a Helmholtz-RSF Joint Research Group has now revealed how the spin texture switches by ferroelectric polarization within individual nanodomains.

Germanium telluride (GeTe) is known as a ferrolectric Rashba semiconductor with a number of interesting properties. The crystals consist of nanodomains, whose ferrolectric polarization can be switched by external electric fields. Because of the so-called Rashba effect, this ferroelectricity can also be used to switch electron spins within each domain. Germanium telluride is therefore an interesting material for spintronic devices, which allow data processing with significantly less energy input.

Russian German Cooperation

Now a team from HZB and the Lomonosov Moscow State University, which has established a Helmholtz-RSF Joint Research Group, has provided comprehensive insights into this material at the nanoscale. The group is headed by physical chemist Dr. Lada Yashina (Lomonosov State University) and HZB physicist Dr. Jaime Sánchez-Barriga. “We have examined the material using a variety of state-of-the-art methods to not only determine its atomic structure, but also the internal correlation between its atomic and electronic structure at the nanoscale,” says Lada Yashina, who produced the high-quality crystalline samples in her laboratory.

Read more on the BESSY II website

Image: The Fermi surface of multidomain GeTe (111) bulk single crystal measured with high-resolution angle-resolved photoemission at BESSY II. © HZB

Dust travelled thousands of miles to enrich hawaiian soils

With its warm weather and sandy beaches, Hawaii is a magnet for tourists every year. This unique ecosystem also attracts soil scientists interested in what surprises may lie beneath their feet.

In a recent paper published in Geoderma, European researchers outline how they used the rich soils of Hawaii to study the critical movement of phosphorous through the environment. By better understanding the amount and type of phosphorus in the soil, they can help crops become more successful and maintain the health of our ecosystems for years to come.

The project was led by Agroscope scientist Dr. Julian Helfenstein, Prof. Emmanuel Frossard with the Institute of Agricultural Sciences, ETH Zurich; and Dr. Christian Vogel, a researcher at the Federal Institute for Materials Research and Testing in Berlin.

The team used the Canadian Light Source (CLS) at the University of Saskatchewan to help analyze the different types of phosphorus in their samples and track their origins.

Read more on the Canadian Light Source website

Image: Dr. Christian Vogel using the VLS-PGM beamline to analyze a sample at the CLS.

A new approach for studying electric charge arrangements in a superconductor

X-ray scattering yields new information on “charge density waves”

High-temperature superconductors are a class of materials that can conduct electricity with almost zero resistance at temperatures that are relatively high compared to their standard counterparts, which must be chilled to nearly absolute zero—the coldest temperature possible. The high-temperature materials are exciting because they hold the possibility of revolutionizing modern life, such as by facilitating ultra-efficient energy transmission or being used to create cutting-edge quantum computers.

One particular group of high-temperature superconductors, the cuprates, has been studied for 30 years, yet scientists still cannot fully explain how they work: What goes on inside a “typical” cuprate?

Piecing together a complete picture of their electronic behavior is vital to engineering the “holy grail” of cuprates: a versatile, robust material that can superconduct at room temperature and ambient pressure.

Read more on the NSLS-II website

Image: Brookhaven Lab scientist Mark Dean used the Soft Inelastic X-Ray (SIX) beamline at the National Synchrotron Light Source II (NSLS-II) to unveil new insights about a cuperates, a particular group of high-temperature superconductors. Credit: BNL

Get out your vacuum: Scientists find harmful chemicals in household dust

Since the 1970s, chemicals called brominated flame retardants (BFRs) have been added to a host of consumer and household products, ranging from electronics and mattresses to upholstery and carpets. While they were intended to improve fire safety, one form — polybrominated diphenyl ethers, or PBDEs — has proved harmful to human health, specifically our hormonal systems.

Although the use of PBDEs has been restricted in Canada since 2008, older household electronics and furniture with these compounds are still in use. Additionally, the process used to add this chemical to manufactured goods attached the particles very loosely. As a result, the compound tends to shed over time through normal wear and tear.

A growing body of evidence suggests that concentrations of this chemical are higher indoors and that it is present in dust. A team of researchers from the Canadian Light Source (CLS) at the University of Saskatchewan and Memorial University set out to determine whether they could find bromine in household dust using synchrotron X-ray techniques.

Read more on the Canadian Light Source website

Image: Dr. Peter Blanchard, CLS Associate Scientist, standing in the HXMA beamline at the CLS.

Hybrid photoactive perovskites imaged with atomic resolution for the first-time

A huge step towards better performing solar cells – a collaboration identified information previously invisible using Diamond’s ePSIC microscopes of Oxford University’s Departments of Materials and Physics

A new technique has been developed allowing reliable atomic-resolution images to be taken, for the first time, of hybrid photoactive perovskite thin films.- highly favourable materials for efficient photovoltaic and optoelectronic applications. These images have significant implications for improving the performance of solar cell materials and have unlocked the next level of ability to understand these technologically important materials. The breakthrough was achieved by a joint team from the University of Oxford and Diamond who have just released a new paper published in Science.

Using the ePSIC (the Electron Physical Science Imaging Centre) E02 microscope and the ARM200 microscope in at the Department of Materials, University of Oxford, the team developed a new technique which allowed them to image the hybrid photoactive perovskites thin films with atomic resolution. This gave them unprecedented insights into their atomic makeup and provided them with information that is invisible to every other technique.

Read more on the Diamond website

Image: An example of one of the images obtained using the new protocol, which illustrates several of the phenomena that the team has been able to describe for the first time, including a range of grain boundaries, extended planar defects, stacking faults, and local inclusions of non-perovskite material.

Order in the disorder: density fluctuations in amorphous silicon discovered

For the first time, a team at HZB has identified the atomic substructure of amorphous silicon with a resolution of 0.8 nanometres using X-ray and neutron scattering at BESSY II and BER II. Such a-Si:H thin films have been used for decades in solar cells, TFT displays, and detectors. The results show that three different phases form within the amorphous matrix, which dramatically influences the quality and lifetime of the semiconductor layer. The study was selected for the cover of the actual issue of Physical Review Letters.

Silicon does not have to be crystalline, but can also be produced as an amorphous thin film. In such amorphous films, the atomic structure is disordered like in a liquid or glass. If additional hydrogen is incorporated during the production of these thin layers, so-called a-Si:H layers are formed. “Such a-Si:H thin films have been known for decades and are used for various applications, for example as contact layers in world record tandem solar cells made of perovskite and silicon, recently developed by HZB” explains Prof. Klaus Lips from HZB. “With this study, we show that the a-Si:H is by no means a homogeneously amorphous material. The amorphous matrix is interspersed with nanometre-sized areas of varying local density, from cavities to areas of extremely high order,” the physicist comments.

Read more on the BESSY II website

Image: Structural model of highly porous a-Si:H, which was deposited very quickly, calculated based on measurement data. Densely ordered domains (DOD) are drawn in blue and cavities in red. The grey layer represents the disordered a-Si:H matrix. The round sections show the nanostructures enlarged to atomic resolution (below, Si atoms: grey, Si atoms on the surfaces of the voids: red; H: white) © Eike Gericke/HZB

In search of the perfect system

Researchers take a new approach to improve widely used biotechnology tool

The unique relationship between an essential vitamin and a purified bacterial protein has been used as a valuable tool in science and medicine for several decades. Together these two molecules, known as streptavidin and biotin, form a very strong and specific interaction that is invaluable for many biotechnological applications.

Labeling molecules with biotin and detecting them with streptavidin is a common part of many lab tests and has enabled many scientific discoveries in medicine. Streptavidin and biotin are as essential to lab technicians as hammers and nails are to a carpenter. The two molecules combine to form “molecular glue” for many of the tests used to diagnose infectious diseases like HIV, Hepatitis C and Lyme disease, to discover new proteins, viruses and bacteria, and to explore how molecules function in living organisms.

Read more on the Canadian Light Source website

Image: Trapped biotin: A crystal structure of the M88 mutein, determined at the CMCF beamline at CLS, reveals how the engineered disulphide formed between Cys49 and Cys86 (green spheres) partially block the exit pathway for biotin (magenta spheres). Credit: CLS

Experimental drug targets HIV in a novel way

SCIENTIFIC ACHIEVEMENT

Using the Advanced Light Source (ALS), researchers from Gilead Sciences Inc. solved the structure of an experimental HIV drug bound to a novel target: the capsid protein that forms a shield around the viral RNA.

SIGNIFICANCE AND IMPACT

The work could lead to a long-lasting treatment for HIV that overcomes the problem of drug resistance and avoids the need for burdensome daily pill-taking.

Progress in HIV treatment still needed

Over the past couple of decades, safe and effective treatment for HIV infection has turned what was once a death sentence into a chronic disease. Today, people on the latest HIV drugs have near-normal life expectancy.

However, many people are still living with multidrug-resistant HIV, unable to control their virus loads with currently available HIV drugs. The virus develops resistance when people take their pills inconsistently due to forgetfulness, side effects, or a complex schedule. To some, taking a pill every day is a burden: they schedule their lives around it for fear of missing a dose. To others, it is a stigma, as it makes it difficult to hide one’s HIV status from close friends and family.

Read more on the Advanced Light Source website

Image: An experimental small-molecule drug (GS-6207) targets the protein building blocks of the HIV capsid—a conical shell (colored red in this artistic rendering) that encloses and protects the viral RNA—making the virus unable to replicate in cells. Credit Advanced Light Source

How deadly parasites ‘glide’ into human cells

X-ray analysis reveals structure of molecular machinery of malaria and toxoplasmosis pathogens

An investigation at DESY’s X-ray source PETRA III provides new insights into the molecular machinery by which certain parasites travel through the human organism. The study, led by Christian Löw from the Hamburg branch of the European Molecular Biology Laboratory EMBL, analyzed the so-called gliding movement of the malaria and toxoplasmosis parasites. The results, which the interdisciplinary team presents in the journal Communications Biology, can aid the search for new drugs against the pathogens.

In biological terms, gliding refers to the type of movement during which a cell moves along a surface without changing its shape. This form of movement is unique to parasites from the phylum Apicomplexa, such as Plasmodium and Toxoplasma. Both parasites, which are transmitted by mosquitoes and cats, have an enormous impact on global heath. Plasmodium causes 228 million malaria infections and around 400 000 deaths per year. Toxoplasma, which infects even one third of the human population, can cause severe symptoms in some people, and is particularly dangerous during pregnancy.

Read more on the DESY PETRA III website

Image: Molecular structure of essential light chain (ELC) protein in Plasmodium glideosome. Blue represents the electron density of the protein, with bonds between atoms indicated in yellow and water molecules indicated in red. The crystal structure at a resolution of 1.5 Ångström (0.15 millionths of a millimetre) was obtained at the EMBL beamlines at DESY’S X-ray source PETRA III. Credit: EMBL, Samuel Pazicky

Red and black ink from Egyptian papyri unveil ancient writing practices

Scientists led by the ESRF and the University of Copenhagen have discovered the composition of red and black inks in ancient Egyptian papyri from circa 100-200 AD, leading to different hypotheses about writing practices. The analysis shows that lead was probably used as a dryer rather than as a pigment, similar to its usage in 15th century Europe during the development of oil paintings. They publish their results today in PNAS.

The earliest examples of preserving human thought by applying ink on a flexible and durable material, papyrus, are found in ancient Egypt at the dawn of recorded history (c. 3200 BCE). Egyptians used black ink for writing the main body of text, while red ink was often used to highlight headings, instructions or keywords. During the last decade, many scientific studies have been conducted to elucidate the invention and history of ink in ancient Egypt and in the Mediterranean cultures, for instance ancient Greece and Rome.

Read more on The European Synchrotron website

Image: Detail of a medical treatise (inv. P. Carlsberg 930) from the Tebtunis temple library with headings marked in red ink. Credit: The Papyrus Carlsberg Collection and the ESRF.

Powering the future of clean energy

Hydrogen gas can be used to power vehicles and has the potential to provide electricity to homes

The global quest for clean energy is championed by researchers in Canada who are focused on harnessing the potential of hydrogen.

The idea of the hydrogen economy was first proposed 50 years ago as a way to combat the negative effects of fossil fuels. Its future is the focus of new research from the University of Toronto’s Thermofluids for Energy and Advanced Materials (TEAM) lab, whose work relied on the Canadian Light Source (CLS) at the University of Saskatchewan to visualize performance.

Read more on the Canadian Light Source website

Image: Adam Webb (CLS), Sergey Gasilov (CLS), Manojkumar Balakrishnan (U of T), Jason Keonhag Lee (U of T), Denise Miller (CLS), Kieran Fahy (U of T) on the BMIT beamline at CLS.

Electron and X‑ray Focused Beam-Induced Cross-Linking in Liquids:

Toward Rapid Continuous 3D Nanoprinting and Interfacing using Soft Materials

Modern additive fabrication of three-dimensional (3D) micron to centimeter size constructs made of polymers and soft materials has immensely benefited from the development of photocurable formulations suitable for optical photolithography,holographic,and stereolithographymethods. Recent implementation of multiphoton laser polymerization and its coupling with advanced irradiation schemes has drastically improved the writing rates and resolution, which now approaches the 100 nm range. Alternatively, traditional electron beam lithography and its variations such as electron-beam chemical lithography, etc. rely on tightly focused electron beams and a high interaction cross-section of 0.1−10 keV electrons with the matter and have been routinely used for complex patterning of polymer resists, self-assembled monolayers, and dried gel films with up to a few nanometers accuracy.

Similarly, a significant progress has been made in deep X-ray lithography, direct writing with zone plate focused X-ray beams for precise, and chemically selective fabrication of high aspect ratio microstructures. Reduced radiation damage within the so-called “water window” has spurred wide biomedical X-ray spectroscopy, microscopy, and tomography research including material processing, for example, gels related controlled swelling and polymerization inside live systems, particles encapsulations,and high aspect ratio structures fabrication.The potential of focused X-rays for additive fabrication through the deposition from gas-phase precursors or from liquid solutions is now well recognized and is becoming an active area of research.

Read more on the Elettra website

Image: The electron/X-ray beam gelation in liquid polymer solution through a SiN ultrathin membrane. Varying the energy and focus of the soft X-rays smaller or larger excitation volumes and therefore finer or wider feature sizes and patterns can be generated.

IBM Investigates Microelectronics at NSLS-II

IBM researchers used the Hard X-ray Nanoprobe at NSLS-II to visualize strain in a new architecture for next-generation microelectronics

From smartphones to laptops, the demand for smaller and faster electronics is ever increasing. And as more everyday activities move to virtual formats, making consumer electronics more powerful and widely available is more important than ever.

IBM is one company at the forefront of this movement, researching ways to shrink and redesign their microelectronics—the transistors and other semiconductor devices that make up the small but mighty chips at the heart of all consumer electronics.

“As devices get smaller, it becomes more challenging to maintain electrostatic control,” said Conal Murray, a scientist at IBM’s T.J. Watson Research Center. “To ensure we can deliver the same level of performance in smaller devices, we’ve been employing new semiconductor materials and designs over the last decade.”

Read more on the NSLS-II website

Image: NSLS-II scientist Hanfei Yam is shown at the Hard X-ray Nanoprobe beamline, where IBM researchers visualised strain in a new architecture for next-generation microelectronics.

Orbital angular momentum carried by an optical field can be imprinted onto a propagating electron wave

Photons have fixed spin and unbounded orbital angular momentum (OAM). While the former is manifested in the polarization of light, the latter corresponds to the spatial phase distribution of its wavefront. The distinctive way in which the photon spin dictates the electron motion upon light–matter interaction is the basis for numerous well-established spectroscopies. By contrast, imprinting OAM on a matter wave, specifically on a propagating electron, is generally considered very challenging and the anticipated effect undetectable.

We carried out an experiment at the LDM beam line at the FERMI free-electron laser, with the aim of inducing an OAM-dependent dichroic photoelectric effect on photo-electrons emitted by a sample of He atoms. The experiment involved a large international collaboration and surprisingly confirmed that the spatial distribution of an optical field with vortex phase profile can be imprinted coherently on a photoelectron wave packet that recedes from an atom. Our results explore new aspects of light–matter interaction and point to qualitatively novel analytical tools, which can be used to study, for example, the electronic structure of intrinsic chiral organic molecules. The results have been published in Nature Photonics.

Read more on the Elettra website

Image: A VUV free-electron laser (violet) is used to ionize a sample of He atoms, and an infrared beam (red) to imprint orbital angular momentum on photo-emitted electrons. Credit: J. Wätzel (Halle university)

Producing less costly, greener hydrogen peroxide

Australian researchers led by the University of New South Wales have used the Australian Synchrotron to understand how the chemical structure of an advanced catalytic material contributes to its stability and efficiency. The approach has the potential to produce hydrogen peroxide (H2O2) in a process that is cost-effective with less harm to the environment.

Hydrogen peroxide is an important chemical that used widely in a range of applications, including wastewater treatment, disinfection, paper/pulp bleaching, semi-conductor cleaning, mining and metal processing, fuel cells and in chemical synthesis.

According to an international market research group, IMARC, the global hydrogen peroxide market size was valued at US$4.0 billion in 2017 and is increasing.

Read more on the ANSTO website

Image: The optimized geometry structures of bare CoN4 moiety and CoN4 moieties with different coverages of epoxy oxygen. The gray, blue, orange and red balls represent C, N, Co and O atoms, respectively [Reprinted with permission by Creative Commons License: Attribution 4.0 International (CC BY 4.0)]

Secrets of spider web strength revealed

An international collaboration between the University of MelbourneUniversity of Bayreuth and ANSTO’s Australian Synchrotron provides the first insights into how the rare silk of the Australian basket-web spider retains its strength and resilient structure— allowing the spider to make a robust and rather exquisite silken basket.  

The silk is so firm and remarkable that it enables the basket web to maintain its structural integrity without any support from the surrounding vegetation.

The insights into physical and chemical properties of this basket-web silk may be useful for the production of artificial spider silks, which have already shown strong potential as an advanced biomimetic material in textile and medical applications.

“The biochemical makeup of the silk thread cross-section, particularly secondary protein structures and complex carbohydrates, was examined on the Infrared Microspectroscopy (IRM) beamline at the Australian Synchrotron,” said beamline scientist and co-author, Dr Pimm Vongsvivut.

Read more on the ANSTO website

Image: Credit:  Hanyl et al, “Free-standing spider silk webs of the thomisid Saccodomus Formivorus are made of composites comprising micro- and submicron fibers,” Scientific Reports10, 17624 (2020)