Making something new is never easy. Scientists constantly theorize about new materials, but when the material is manufactured it doesn’t always work as expected. To create a new strategy for designing materials, scientists at the Department of Energy’s Argonne National Laboratory combined two different approaches at two different facilities to synthesize new materials.
This new strategy gives faster feedback on what growth schemes are best, thus shortening the timeframe to manufacture a new, stable material for energy transport and conversion applications.
A recent article in Nature Materials describes how researchers used X-ray scattering during a process called molecular beam epitaxy (MBE) to observe the behavior of atoms as a type of material known as layered oxides were being formed. These observations were then used as data for computational predictions of new materials, leading to insights on how to best combine atoms to form new, stable structures.
“MBE is the construction of new materials one layer at a time—and each layer is one-atom thick. We used a new type of MBE system to observe what happens during the growth of oxide thin films. We found that the layers spontaneously rearrange to reach a lower energy, preferred configuration—but not necessarily the configuration we intended,” said John Freeland, the Argonne physicist who led the team. “Most scientists would not expect layers to move around like this, but this is important information to know when designing new materials.”
In experimenting with a class of oxides known as strontium titanates, the research team found that when they layered titanium on top of two layers of Strontium, the titanium layer switched places with the second strontium layer, thus becoming the center layer. When titanium was layered on multiple layers of strontium, titanium always switched places with the strontium layer directly underneath it (Figures 1 and 2).
Argonne chemist June Hyuk Lee lead the experimental development of the in situ oxide MBE, and Guangfu Luo from the University of Wisconsin-Madison developed the theoretical approach to unraveling the energetics that drive the layer rearrangements.
The research team included expertise from Argonne’s Advanced Photon Source (APS), Center for Nanoscale Materials (CNM), Chemical Sciences and Engineering, and Materials Science, and partners from Northwestern University, the University of Connecticut-Storrs and the University of Wisconsin-Madison, who wanted to understand the driving force behind the rearrangements. Using density functional theory (DFT) and computational resources at the CNM, they calculated and compared the energies of different layer sequences, using the data collected from the MBE system. They found that the actual layer sequences corresponded to the lowest energy configuration. Their computations also showed that layer exchange was not unique to strontium and titanium; in fact, it was expected for many different materials systems. With this understanding, scientists can control—on an atomic level—the growth of oxide thin-films.
“What we have here is a new strategy for materials design and synthesis,” said Argonne materials scientist and article co-author Dillon Fong. “Our combination of in situ X-ray scattering with computational theory can be extended to other layered materials and structures, even theoretical ones that haven’t been made yet because they are challenging to manufacture.”
This new strategy gives faster feedback on what growth strategies are best, thus shortening the timeframe to actual manufacture of a new, stable material.
In the future, Argonne wants to make oxide MBE a tool available to APS facility users for synthesis science. “The APS was instrumental in making our findings possible,” explained Freeland. “The X-rays gave us the quantitative information we needed to plug into the theoretical framework, which in turn will allow us—and other APS users--to make new materials more efficiently.”
Films were grown in the in situ X-ray chamber at Sector 33ID-E of the APS. Calculations were carried out on the Fusion Cluster of Argonne's Laboratory Computing Resource Center at the National Energy Research Scientific Computing Center (NERSC) and on Argonne's Carbon Cluster.
The paper, “Dynamic layer rearrangement during growth of layered oxide films by molecular beam epitaxy,” was published in Nature Materials.
This work was supported by the U.S. Department of Energy Office of Science, and partially supported by the University of Wisconsin Materials Research Science and Engineering Center.
The Advanced Photon Source at Argonne National Laboratory is one of five national synchrotron radiation light sources supported by the U.S. Department of Energy's Office of Science to carry out applied and basic research to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels, provide the foundations for new energy technologies, and support DOE missions in energy, environment, and national security. To learn more about the Office of Science X-ray user facilities, visit the user facilities directory.
The Center for Nanoscale Materials at Argonne National Laboratory is one of the five DOE Nanoscale Science Research Centers (NSRCs), premier national user facilities for interdisciplinary research at the nanoscale, supported by the DOE Office of Science. Together the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative. The NSRCs are located at DOE’s Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge and Sandia and Los Alamos National Laboratories.
Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America's scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.
DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.
Tona Kunz | Eurek Alert!
Flying: Efficiency thanks to Lightweight Air Nozzles
23.10.2017 | Technische Universität Chemnitz
Strange but true: Turning a material upside down can sometimes make it softer
20.10.2017 | Universitat Autonoma de Barcelona
Salmonellae are dangerous pathogens that enter the body via contaminated food and can cause severe infections. But these bacteria are also known to target...
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
23.10.2017 | Event News
17.10.2017 | Event News
10.10.2017 | Event News
23.10.2017 | Life Sciences
23.10.2017 | Physics and Astronomy
23.10.2017 | Health and Medicine