Advanced Light Source (ALS) – Page 4

Tuning material properties with laser light

2019/07/262019/08/01

The research results suggest the possibility of creating microelectronic devices that use a laser beam to erase and rewrite bits of information in materials engineered for random-access memory and data storage.

Many semiconductor-based devices use electric currents to control and manipulate bits of information encoded into tiny magnetic domains. However, this approach is reaching the physical limits of thermally stable feature sizes, and scientists are actively searching for the next generation of materials and processes that could lead to smaller, faster, more powerful devices.
One possible path forward has been opened up by the emergence of materials that can be engineered, layer by layer, to theoretical specifications. Multiferroics, for example, are designed materials with technologically useful properties that can be controlled by external fields. While many studies have been performed on the effects of electric and magnetic fields on multiferroics, very few studies have explored the use of optical modulation (i.e., laser light) as a way to tune magnetic and electronic ordering in such materials.

Images: They are taken at the same illuminated region using PFM, PEEM with linearly polarized x-rays, and PEEM with circularly polarized x-rays. The strong black and white contrast in the linear dichroism image indicates the antiferromagnetic order; the red/blue contrast in the circular dichroism image shows the existence of ferromagnetic moments that lie parallel/antiparallel to the incident x-rays, respectively.

Research on how light-harvesting bacteria toggle off and on

2019/07/232019/07/31

The results could have long-range implications for artificial photosynthesis and optogenetics—the use of light to selectively activate biological processes.

Cyanobacteria are water-dwelling microbes capable of absorbing sunlight and converting it into chemical energy through photosynthesis. Long ago, ancient versions of these bacteria were incorporated into plant cells, where they eventually evolved into chloroplasts, the organelles responsible for carrying out photosynthesis in green plants. Today, in seeking to develop artificial photosynthesis to harness the sun’s abundant energy, scientists look to cyanobacteria to better understand the nuts and bolts of how natural photosynthesis works.

Cyanobacterial “off switch”

One topic of interest is how cyanobacteria respond to too much light. If a sunlight-harvesting system becomes overloaded with absorbed solar energy, it most likely will suffer some form of damage. Nature has solved the problem in cyanobacteria through a protective mechanism—an energy-quenching “off switch” in which excess solar energy is safely dissipated as heat.

Illustration: X-ray footprinting provides time-resolved information about where key conformational changes occur. On the left is the overall OCP structure. The two structures on the right highlight local areas with increasing protein packing over time (blue shading) and areas with decreasing protein packing over time (red shading). The changes in accessibility are initiated by the movement of the carotenoid molecule (magenta chain).

Natural defense against red tide toxin found in bullfrogs

2019/06/262019/06/27

A team led by Berkeley Lab faculty biochemist Daniel Minor has discovered how a protein produced by bullfrogs binds to and inhibits the action of saxitoxin, the deadly neurotoxin made by cyanobacteria and dinoflagellates that causes paralytic shellfish poisoning.
The findings, published this week in Science Advances, could lead to the first-ever antidote for the compound, which blocks nerve signaling in animal muscles, causing death by asphyxiation when consumed in sufficient quantities.
“Saxitoxin is among the most lethal natural poisons and is the only marine toxin that has been declared a chemical weapon,” said Minor, who is also a professor at the UCSF Cardiovascular Research Institute. About one thousand times more potent than cyanide, saxitoxin accumulates in tissues and can therefore work its way up the food chain – from the shellfish that eat the microbes to fish, turtles, marine mammals, and us.

>Read more on the ALS website

Image: A photo illustration showing the atomic structures of saxiphilin and saxitoxin, a red tide algal bloom, and an American bullfrog (R. catesbeiana).
Credit: Daniel L. Minor, Jr., and Deborah Stalford/Berkeley Lab.

Catalyst improves cycling life of magnesium/sulfur batteries

2019/06/242019/06/27

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 MgS₈and MgS₄at a fast reaction rate, reduction of MgS₄to Mg₃S₈, and a sluggish further reduction of Mg₃S₈to MgS. The in situ XAS analysis revealed that Mg₃S₈and 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.

Electric dipoles form chiral skyrmions

2019/06/142019/06/27

Control of such phenomena could one day lead to low-power, nonvolatile data storage as well as to high-performance computers.

A group of researchers, led by scientists from Berkeley Lab’s Materials Sciences Division and UC Berkeley’s Materials Science and Engineering Department, set out to find ways to control how heat moves through materials. They fabricated a material with alternating layers of strontium titanate, which is an electrical insulator, and lead titanate, a ferroelectric material with a natural electrical polarization that can be reversed by the application of an external electric field.

When the group took the material to Berkeley Lab’s Molecular Foundry for atomic-resolution scanning transmission electron microscope (STEM) measurements, however, they found something completely unexpected: bubble-like formations had appeared throughout the material, even at room temperature.

>Read more on the ALS website

Image: (a) Hard x-ray studies showed the presence of two sets of ordering: regular peaks along the out-of-plane direction (Q_z), related to superlattice periodicity (about 12 nm), and satellite peaks in the in-plane direction (Q_y), corresponding to the in-plane skyrmion periodicity (about 8 nm). (b) RSXD studies were performed at the in-plane satellite peaks, which correspond to the periodic polarization texture of the skyrmions’ Bloch components. (c) Spectra from a satellite peak for right- (red) and left- (blue) circularly polarized light. (d) The same spectra with background fluorescence subtracted. (e) The difference spectrum shows a clear circular dichroism peak at the titanium L₃ t_2g edge.

‘A day in the light’ Videos highlight how scientists use light in experiment

2019/05/162019/05/16

In recognition of the International Day of Light (@IDL2019) on May 16, the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) is highlighting how scientists use light in laboratory experiments. From nanolasers and X-ray beams to artificial photosynthesis and optical electronics, Berkeley Lab researchers tap into light’s many properties to drive a range of innovative R&D.
In the three videos displayed below, you will learn how light drives the science of Berkeley Lab’s Advanced Light Source (ALS), a synchrotron that produces many forms of light beams. These light beams are customized to perform a variety of experimental techniques for dozens of simultaneous experiments conducted by researchers from across the nation and around the world.

Image: Shambhavi Pratap, ALS Doctoral Fellow in Residence and a Ph.D. student at the Technical University of Munich, discusses how she studies thin-film solar energy materials using X-rays at the ALS.
Credit: Marilyn Chung/Berkeley Lab

Research on sand near Hiroshima shows fallout debris from A-Bomb blast

2019/05/132019/05/14

X-ray studies at Berkeley Lab provide evidence for source of exotic assortment of melt debris

Mario Wannier, a career geologist with expertise in studying tiny marine life, was methodically sorting through particles in samples of beach sand from Japan’s Motoujina Peninsula when he spotted something unexpected: a number of tiny, glassy spheres and other unusual objects.
Wannier, who is now retired, had been comparing biological debris in beach sands from different areas in an effort to gauge the health of local and regional marine ecosystems. The work involved examining each sand particle in a sample under a microscope, and with a fine brush, separating particles of interest from grains of sediment into a tray for further study.

Image: Researchers collected and studied beach sands from locations near Hiroshima including Japan’s Miyajima Island, home to this torii gate, which at high tide is surrounded by water. The torii and associated Itsukushima Shinto Shrine, near the city of Hiroshima, are popular tourist attractions. The sand samples contained a unique collection of particles, including several that were studied at Berkeley Lab and UC Berkeley.
Credit: Ajay Suresh/Wikimedia Commons

Superconductor exhibits “glassy” electronic phase

2019/04/232019/05/08

The study provides valuable insight into the nature of collective electron behaviors and how they relate to high-temperature superconductivity.

At extremely low temperatures, superconductors conduct electricity without resistance, a characteristic that’s already being used in cryogenically cooled power lines and quantum-computer prototypes. To apply this characteristic more widely, however, it’s necessary to raise the temperature at which materials become superconducting. Unfortunately, the exact mechanism by which this happens remains unclear.

Recently, scientists found that electrons in cuprate superconductors can self-organize into charge-density waves—periodic modulations in electron density that hinder the flow of electrons. As this effect is antagonistic to superconductivity, tremendous effort has been devoted to fully characterizing this charge-order phase and its interplay with high-temperature superconductivity.

Image: At low doping levels, the charge correlations in the copper–oxide plane possess full rotational symmetry (C_inf) in reciprocal space (left), in marked contrast to all previous reports of bond-oriented charge order in cuprates. In real space (right), this corresponds to a “glassy” state with an apparent tendency to periodic ordering, but without any preference in orientation (scale bar ~5 unit cells).

Electric skyrmions charge ahead for next-generation data storage

2019/04/182019/04/22

Berkeley Lab-led research team makes a chiral skyrmion crystal with electric properties; puts new spin on future information storage applications.

When you toss a ball, what hand do you use? Left-handed people naturally throw with their left hand, and right-handed people with their right. This natural preference for one side versus the other is called handedness, and can be seen almost everywhere – from a glucose molecule whose atomic structure leans left, to a dog who shakes “hands” only with her right.

Handedness can be exhibited in chirality – where two objects, like a pair of gloves, can be mirror images of each other but cannot be superimposed on one another. Now a team of researchers led by Berkeley Lab has observed chirality for the first time in polar skyrmions – quasiparticles akin to tiny magnetic swirls – in a material with reversible electrical properties. The combination of polar skyrmions and these electrical properties could one day lead to applications such as more powerful data storage devices that continue to hold information – even after a device has been powered off. Their findings were reported this week in the journal Nature.

Image: Simulations of skyrmion bubbles and elongated skyrmions for the lead titanate/strontium titanate superlattice.
Credit: Berkeley Lab.

A new twist in soft x-ray beams

2019/03/262019/04/03

Light waves, when generated a certain way, can exert twisting forces on matter. In the visible-light regime, such beams have been used as “optical tweezers” to trap and manipulate tiny particles (like a tractor beam) or to detect rotational motion in targets. Now, the ability to generate beams with a specific type of rotational character, known as orbital angular momentum (OAM), has been extended to the soft x-ray regime. The work lays the foundation for a new type of soft x-ray contrast mechanism that could provide access to previously hidden material properties.
In a recently published Nature Photonics paper, researchers from the Advanced Light Source (ALS) and the University of Oregon reported on the fabrication and testing of specialized diffraction gratings that, when placed in the coherent light of ALS Beamline 12.0.2, produce OAM soft x-ray beams of exceptionally high quality.

Image: A flower-like interference pattern generated by a special diffraction grating that superposes two different orbital angular momentum (OAM) modes on a soft x-ray beam.

Absorber captures excess chemotherapy drugs

2019/03/222019/04/10

The work opens up a new route to fighting cancer that minimizes drug toxicity and enables personalized, targeted, high-dose chemotherapy.

Most anticancer drugs are poisonous, so doctors walk a delicate line when administering chemotherapy. A dose must be sufficient to kill or stop the growth of cancer cells in the target organ, but not high enough to irreparably damage a patient’s other organs. To avoid this, doctors can thread catheters through the bloodstream to deliver chemotherapy drugs directly to the site of the tumor—a method known as intra-arterial chemotherapy. Still, typically more than half of the dose injected into the body escapes the target organ. Several years ago, researchers began working on a major improvement: placing a device “downstream” of the targeted organ to filter out excess chemo so that much less of the drug reaches the body as a whole.

>Read more on the Advanced Light Source

Image: (extract, see here the full image)
(a) Diagram of the proposed approach for drug capture using a 3D-printed cylindrical absorber. (b) Chemical structure of doxorubicin, the chemotherapy drug used in this study. (c) Schematic of the endovascular treatment of liver cancer. Excess drug molecules are captured by the absorber in the vein draining the organ. An introducer sheath guides the absorber to the desired location via a guide wire.

The best topological conductor yet: spiraling crystal is the key to exotic discovery

2019/03/202019/03/22

X-ray research at Berkeley Lab reveals samples are a new state of matter

The realization of so-called topological materials – which exhibit exotic, defect-resistant properties and are expected to have applications in electronics, optics, quantum computing, and other fields – has opened up a new realm in materials discovery.
Several of the hotly studied topological materials to date are known as topological insulators. Their surfaces are expected to conduct electricity with very little resistance, somewhat akin to superconductors but without the need for incredibly chilly temperatures, while their interiors – the so-called “bulk” of the material – do not conduct current.
Now, a team of researchers working at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has discovered the strongest topological conductor yet, in the form of thin crystal samples that have a spiral-staircase structure. The team’s study of crystals, dubbed topological chiral crystals, is reported in the March 20 edition of the journal Nature.

Image: This illustration shows a repeated 2D patterning of a property related to electrical conductivity, known as the surface Fermi arc, in rhodium-silicon crystal samples.
Credit: Hasan Lab/Princeton University

Reversible lattice-oxygen reactions in batteries

2019/03/152019/03/25

The results open up new ways to explore how to pack more energy into batteries with electrodes made out of low-cost, common materials.

For a wide range of applications, from mobile phones to electric vehicles, the reversibility and cyclability of the chemical reactions occurring inside a rechargeable battery are key to commercial viability. Conventional wisdom had held that involving oxygen in a battery’s electrochemical operation spontaneously triggers irreversible oxygen losses and parasitic surface reactions, reducing reversibility and safety. Recently however, the idea emerged that reactions involving lattice oxygen (i.e., oxygen that’s part of the crystal-lattice structure vs oxygen on the surface) could be useful for improving battery capacity. Here, researchers report the first direct quantification of a strong, beneficial, and highly reversible chemical reaction involving lattice oxygen in electrodes made with low-cost elements.

>Read more on the Advanced Light Source

Image: Advanced spectroscopy at the ALS clearly resolves the activities of cations and anions (known in Chinese as “yin” and “yang” ions) in battery electrodes.

A deep dive into the imperfect world of 2D materials

2019/03/082019/03/12

Berkeley Lab-led team combines several nanoscale techniques to gain new insights on the effects of defects in a well-studied monolayer material

Nothing is perfect, or so the saying goes, and that’s not always a bad thing. In a study at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), scientists learned how nanoscale defects can enhance the properties of an ultrathin, so-called 2D material. They combined a toolbox of techniques to home in on natural, nanoscale defects formed in the manufacture of tiny flakes of a monolayer material known as tungsten disulfide (WS₂) and measured their electronic effects in detail not possible before. “Usually we say that defects are bad for a material,” said Christoph Kastl, a postdoctoral researcher at Berkeley Lab’s Molecular Foundry and the lead author of the study, published in the journal ACS Nano. “Here they provide functionality.”

Tungsten disulfide is a well-studied 2D material that, like other 2D materials of its kind, exhibits special properties because of its atomic thinness. It is particularly well-known for its efficiency in absorbing and emitting light, and it is a semiconductor.

Image: This image shows an illustration of the atomic structure of a 2D material called tungsten disulfide. Tungsten atoms are shown in blue and sulfur atoms are shown in yellow. The background image, taken by an electron microscope at Berkeley Lab’s Molecular Foundry, shows groupings of flakes of the material (dark gray) grown by a process called chemical vapor deposition on a titanium dioxide layer (light gray).
Credit: Katherine Cochrane/Berkeley Lab

How to catch a magnetic monopole in the act

2019/03/042019/03/08

Berkeley Lab-led study could lead to smaller memory devices, microelectronics, and spintronics

A research team led by the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has created a nanoscale “playground” on a chip that simulates the formation of exotic magnetic particles called monopoles. The study – published recently in Science Advances – could unlock the secrets to ever-smaller, more powerful memory devices, microelectronics, and next-generation hard drives that employ the power of magnetic spin to store data.

Follow the ‘ice rules’
For years, other researchers have been trying to create a real-world model of a magnetic monopole – a theoretical magnetic, subatomic particle that has a single north or south pole. These elusive particles can be simulated and observed by manufacturing artificial spin ice materials – large arrays of nanomagnets that have structures analogous to water ice – wherein the arrangement of atoms isn’t perfectly symmetrical, leading to residual north or south poles.

Image: Full image here. This nanoscale “playground” on a chip uses nanomagnets to simulate the formation of exotic magnetic particles called “monopoles.” Credit: Farhan/Berkeley Lab

Meteorites suggest galvanic origins for martian organic carbon

2019/02/252019/02/26

The nature of carbon on Mars has been the subject of intense research since NASA’s Viking-era missions in the 1970s, due to the link between organic (carbon-containing) molecules and the detection of extraterrestrial life. Analyses of Martian meteorites marked the first confirmation that macromolecular carbon (MMC)—large chains of carbon and hydrogen—are a common occurrence in Mars rocks. More recently, researchers have applied the lessons taken from studies of meteorites to the data being gathered by the Curiosity rover, finding similar MMC signatures on Mars itself. Now, the central question is “what is the synthesis mechanism of this abiotic organic carbon?”

>Read more about on the Advanced Light Source website

Image: A high-resolution transmission electron micrograph (scale bar = 50 nm) of a grain from a Martian meteorite. Reminiscent of a long dinner fork, organic carbon layers were found between the intact “tines.” This texture was created when the volcanic minerals of the Martian rock interacted with a salty brine and became the anode and cathode of a naturally occurring battery in a corrosion reaction. This reaction would then have enough energy—under certain conditions—to synthesize organic carbon.
Credit: Andrew Steele