Stanford Synchrotron Radiation Lightsource

Gasoline cars are able to travel further between fill-ups than electric cars before recharge, which is a limiting factor for the widespread adoption of electric vehicles and utilization of renewable energy sources for transportation. Improving the energy density of the batteries could solve this problem, so researchers are developing lithium metal batteries to replace lithium-ion batteries. Lithium metal batteries can hold more charge per volume. However, they are not as stable and degrade over time. A team of researchers has studied the ways that the lithium metal electrode material degrades to cause capacity loss.

Switchable photovoltaic windows hold much promise as a new technology to mitigate greenhouse gases that cause climate change. These windows not only automatically and reversibly darken to decrease the need for air conditioning, they generate electricity. One promising active layer is based on metal halide perovskites (MHP), a crystalline material that can harness sunlight.

Physicists have been interested in crystalline materials where the quantum mechanical behavior of electrons is governed by topology, so-called topological quantum matter. Recently the community has been particularly excited about crystals which additionally exhibit magnetism, i.e. topological quantum magnets. What new topological behavior might such magnets exhibit? Can we find examples of such exotic quantum magnets in nature? And could magnetic topological phases of matter lead to insights about fundamental questions in science or pave the way to technological applications?
 

The field of superconductivity was surprised by the discovery of a manganese-based superconductor, published in 2015.  Because the electrons in manganese do not form couplets called Cooper pairs, it was not thought possible that manganese could have traits of superconductivity. This discovery necessitates a revised explanation for superconductivity, one not requiring Cooper pairing. The unconventional pairing of electrons in the manganese superconductor MnP provides a novel system to understand the phenomenon of superconductivity.

Many new electronic devices replace traditional silicon chips with silicon carbide (SiC) semiconductor chips, which are able to handle more power, function with less power loss, and operate at higher temperatures. Because these chips generate more heat, new materials that bond the chip to the heat sink are needed. A promising choice is sintered silver (Ag). However, detailed and quantitative information about the pore structure and evolution during aging of sintered Ag have not been well studied. A team of researchers quantitatively analyzed the pore structure of sintered silver at high temperatures over time. 

Metastable materials are materials that exist in their higher-energy configurations. They will eventually transform into their lowest energy form, given a certain amount of time. The classic example is diamond, which given enough time will change into graphite. They can have desired functionalities that make them useful in a variety of applications, such as in electronics, batteries, and catalysts. However, making metastable materials is not an easy job.

Local differences in a battery’s structure and chemistry can lead to problems with function, such local over-charging or under-charging, and can affect the ability to hold charge. Understanding these heterogeneities is important for engineering well-functioning batteries but they are difficult to measure and study.  Scientists usually use either an electrochemical process or a chemical process to prepare materials when studying lithium ion battery heterogeneity at different state of charge. Both of these have flaws: the electrochemical process is close to real-life behavior but experiments may be complicated by structural complexity, and the chemical delithiation process creates a simpler structure but may not properly reflect real-world applications.

Li-ion batteries (LIBs) are key components of portable electronic devices, as well as in electric vehicles, military and medical equipment, backup power supplies, and even grid storage. However, the energy storage capacity and rate capability of current LIBs is still too low to meet the increasing demand of key markets. For the latter, the properties of the electrolyte-electrode interface play a decisive role.

The materials and devices used in modern society are often structurally complex and chemically heterogeneous. The complexity in the material is usually caused by the desired functionality that has requirements in many different aspects of the material properties. Taking Li-ion battery as an example, the device is often evaluated by combining several different characteristics, including the energy density, capacity, cyclability, temperature stability, price etc.

Given our increasing dependence of rechargeable battery containing electronic devices, including electric cars, it is important to engineer these systems to mitigate potential for catastrophic battery failure. One possible source of lithium ion battery failure is over-discharge (over-lithiation) of the cathode, which can permanently damage the battery. Electronic battery management systems are programmed to prevent and identify such failures, but sometimes do not catch problems of over-lithiation when they occur. To better understand the characteristics of battery failure from over-discharging, a team of scientists studied the chemical and morphological changes that occur from over-lithiation of a lithium battery cathode.

Over the past three years a team of researchers has worked to understand the thermodynamic transitions in the antiferromagnetic ferroelectric BiFeO₃ with La substitutions in relation to a new strategy for finding the ultimate magnetoelectric single phase material. The researchers made the striking finding that structural, ferroelectric, and magnetic phases evolve due to strong spin-lattice coupling, thereby producing a multiferroic triple phase point where three competing multiferroic phases merge.

Rare earth magnetic materials have many applications, such as MRI scanners, Maglev trains, and electric vehicles. Scientists are researching improvements to these magnets through optimizing the component materials. Taking a different approach, a team of scientists have studied the effects of nano-scale heterogeneity in the chemistry and structure of Nd₂Fe₁₄B, a very strong and widely-used rare earth magnet. 

In materials science, the creation of composites by mixing of materials with different properties can lead to a new set of properties. To create a new type of nanocomposite material for semiconductors, a team of scientists chose to combine CdO and SnTe, materials with disparate optoelectric properties, one acting as an n-type (electron-rich) and the other a p-type (hole-rich) semiconductor.

Most solar panels use technology that employs a silver-silicon interface. Because silver is expensive and the lead used in the creation of this interface is toxic, researchers are interested searching for other materials that could work instead of these components. A team of scientists are working to understand the process involved in the silver-silicon contact formation so that alternatives that perform the same function can be found.

Current technologies of light emitting diodes (LEDs), photovoltaic systems (PVs), and other optical electronic devices typically use inorganic silicon-based semiconductors. However,  organic polymers could provide thinner, lighter and cheaper opto-electronic devices (like OLEDs and OPVs).

The heat that builds up in the shuttling of current in electronics is an important obstacle to packing more computing power into ever-smaller devices: Excess heat can cause them to fail or sap their efficiency.

Angle-resolved photoemission spectroscopy (ARPES) measurements taken at Beam Line 5-4 at SSRL and at the Advanced Light Source have observed an exotic property that could warp the electronic structure of a material in a way that reduces heat buildup and improves performance in ever-smaller computer components.

Rechargeable lithium-ion batteries are widely used in applications ranging from consumer electronics to electric vehicles. An important feature of a high-quality battery is a long lifetime, i.e. a large number of possible charge-discharge cycles. However, every cycle introduces changes in the battery’s electrode material, limiting its cyclability. A research collaboration has recently examined the occurring structural and chemical changes in the electrode material during cycling and linked them to the performance of lithium-ion batteries.

Carbon-based materials are extremely lightweight and have thermal, mechanical and electrical properties that are of great interest for use in functional devices. Carbon materials can be manufactured in virtually any shape and even with dimensions on the micro- and nanoscales. Recent research is now aimed at exploiting the spin and magnetism of carbon-based materials for data storage devices – a field called spintronics.

Topological insulators comprise a new state of quantum matter that has been predicted theoretically and realized experimentally in the past few years. Strong inversion asymmetry in topological insulators could lead to many interesting phenomena, such as pyroelectricity, intrinsic topological p-n junctions and topological magneto-electric effects.

Researchers using Beam Line 5-4 at SSRL and Beam Line 10.0.1 at the ALS have shown the compound BiTeCl to be the first topological insulator with a strong inversion asymmetric crystal structure.

Films of semiconducting organic polymers are major candidates for new materials, with industrial applications ranging from lighting equipment to solar cells to electronic devices. In order to fully exploit these materials, scientists must first understand how polymer films transport electric charge.

Perovskites are mineral oxides with unique properties of great interest to scientists. Many of these materials show remarkable transitions in their behavior. The perovskites lanthanum aluminium oxide (LAO) and strontium titanium oxide (STO), for instance, are insulators. However, when sandwiched together to an LAO/STO heterostructure, the material can conduct electricity at its interface. Researchers can tune conductivity and other emergent properties by doping the perovskites and hope to exploit heterostructures in future industrial applications such as new electronic devices.

Recently, scientists at the University of California, Berkeley and Lawrence Berkeley National Laboratory and their collaborators synthesized a series of metal-organic frameworks (MOFs) with pores up to 98 Å in diameter—large enough to house protein molecules. For the first time the researchers were able to design strategies to overcome three major obstacles to increasing pore capacity...

Olefins are the basic building blocks for many products from the petrochemical industry and are currently produced by steam cracking of naphtha or ethane, but increasing oil and gas prices are driving the industry toward producing olefins from syngas derived from cheaper feedstocks via the Fischer-Tropsch process instead. A team of scientists used full-field Transmission hard X-ray Microscopy (TXM) and a special reactor designed and built at SSRL and installed on SSRL Beam Line 6-2 to learn more about the catalyst at the heart of the Fischer-Tropsch-to-Olefins (FTO) process.

A new magnetic state called a quantum spin liquid has been observed by a large international team of investigators from ten institutions¹, including a group using SSRL. When magnetic ions are located within a crystal lattice there are usually strong local magnetic and electric forces between them. At low temperatures such forces lead to a preferred alignment of the atomic moments – in ferromagnets such as iron for example, the atomic magnets are aligned parallel to each other while in anti-ferromagnets they are antiparallel.

Much of our manufactured environment - many metals, plastics, glasses, ceramics, fiberglass and papers - consists of extrusion-molded products. To minimize waste, extrusion-molding plants must balance quality of product, speed of process and cost of production (primarily electricity) for each particular material. They need to know how fast each material can be processed at what energy cost while maintaining the quality of the finished bulk material. Fundamental changes in the macromolecular arrangement of materials occur at critical deformation rates.

A collaboration between scientists at SSRL and the department of Applied Physics at Stanford University has determined the phase diagram of a new family of prototypical charge density wave (CDW) compounds. These compounds have the chemical formula RTe₃, where R represents a rare earth element from La to Tm. In research, the collaborators have used X-ray diffraction and resistivity measurements to determine the factors affecting the symmetry of the CDW state, specifically whether the CDW runs in one direction or two.

Electrocatalysis is the science of modifying the overall rates of electrochemical reactions so that selectivity, yield and efficiency are maximized. Studies in electrocatalysis have resulted in tools such as highly selective multicomponent gas mixture sensors and better electrocatalysts for the fuel cells. Markovic and Lucas have been very active in studying the mechanisms by which these catalysts operate and developing in-situ surface x-ray scattering (SXS) techniques for their studies. 

Panoramic images are captivating in any form, with their wide field of view and extremely high resolution. Now, SSRL scientists have demonstrated a new x-ray holographic technique for imaging wide areas of a nanoscale sample without losing resolution. The results were published in the November 2007 edition of the journal Optics Letters.

The recent discovery of superconductivity in iron-based layered compounds known as iron oxypnictides has renewed interest in high-temperature superconductivity. Now, SLAC and Stanford researchers, using SSRL's angle resolved photoemission spectrometer at Beam Line 5-4, have furthered the quest to understand this iron-based compound. In a recent paper published in Nature, SSRL scientist Donghui Lu, with colleagues at SSRL and Stanford, reported on the mechanism behind the superconductivity of a lanthanum-oxygen-iron-phosphorus (LaOFeP) compound, one of the new iron-based superconducting materials.

However, the superconducting gap distributions in iron-based superconductors do not fall neatly into either of these two symmetries. Nodeless gap distributions, such as are associated with s-wave pairing symmetry have been directly observed in some members of the iron-based family of high-temperature superconductors, and the signatures of nodal superconducting gaps have been reported in others.

Nothing seems to move as fast as the field of consumer electronics. A browse through a technology store reveals the dizzying array of space-age -seeming products like flat screen TVs, touch screen phones, and mp3 players. A new development in electronics is on the horizon, one that may bring us roll-up flat screens and high-definition display clothing. These will be made possible using the thin and energy efficient organic light emitting diodes (OLEDs), which are based on organic semiconductor technology. Both a desire for less expensive, more convenient technologies and a concern for energy conservation have heightened interest in the field of organic semiconductors.

Discovering high performing organic semiconductors is a hot area of research, as we look for efficient, low-cost materials that can be used in inexpensive electronic devices, such as flexible solar cells and radio frequency ID tags. To design effective materials, the relationship between a material’s structure and its semiconductive properties must be found. Research on p-type (hole conducting) organic semiconductors has shown π-bond stacking to be important in determining the semiconducting properties. The newer,  n-type (electron conducting) class of organic semiconductors has not been as extensively studied.

Currently, organic or plastic solar cells are relatively inexpensive to make, yet they are also relatively inefficient. Researchers from Princeton University and SSRL recently studied the structure of organic solar cells that were manufactured and processed in different ways to better understand the causes of the inefficiencies.

Organic semiconductors could usher in an era of foldable smart phones, better high-definition television screens and clothing made of materials that can harvest energy from the sun needed to charge your iPod or iPad, but there is one serious drawback: Organic semiconductors, while inexpensive, do not conduct electricity very well.

Increasing the speed and complexity of semiconductor integrated circuits requires advanced processes that put extreme constraints on the level of metal contamination allowed on the surfaces of silicon wafers. Such contamination degrades for example the performance of the ultra thin SiO2 gate dielectrics (< 4nm) that form the heart of the individual transistors. Ultimately, reliability and yield are reduced to levels that must be improved before new processes can be put into production. Much of this metal contamination occurs during the wet chemical etching and rinsing steps required for the manufacture of integrated circuits and industry is actively developing new processes that have already brought the metal contamination to levels beyond the detection capabilities of conventional analytical techniques.

Many condensed matter systems can be described as large collections of microscopic entities, each of which can be in one of two possible states. For example, in many anisotropic magnets spins can point in one of two directions along a unique crystalline axis.  In a liquid-gas phase transition, molecules will be in either the gas or liquid phase.  When the microscopic entities interact, they may exhibit collective long-range order.  A collection of two-state particles with near-neigh bor interactions is known as an Ising system.  This simple system is very important because the behavior that an Ising system displays as it undergoes a transition to long-range order has universal features that are independent of the details of the two-state particles or their interaction.

Computer hard drives and other advanced electronic devices depend on layered stacks of magnetic and non-magnetic materials, but researchers don't fully understand why such layered materials exhibit new properties that cannot be predicted from the properties of the individual layers. In a recent publication a team working at SSRL and the ALS describes new methods, based on x-ray spectroscopy and x-ray microscopy, that reveal the magnetic structures at the boundaries between these layers. Their data show that the boundaries are not as clean as previously assumed but a new ultrathin interface layer may be formed by a chemical reaction. The thickness of the interfacial layer is found to change with temperature and this change can be directly correlated with the magnetic properties of the multilayer stack. The work provides the first magnetic images of a buried interface and gives direct experimental evidence for the existence and long-assumed importance of interfacial magnetic spins.

Extensive research efforts to study the novel electronic properties of high-Tc superconductors and their related materials by angle-resolved photoemission spectroscopy at a recently commissioned Beam Line 5-4 (led by Z.-X. Shen) continue to be successful, producing many important results. These results, which are highlighted by five articles recently published in Physical Review Letters and one in Science, brought our understanding steps closer to solving the mystery of the high-T_c superconductivity.