While complex transition metal oxides have for years held great promise for a variety of information and energy applications, the challenge has been to devise a method to reduce band gaps of those insulators without compromising the material's useful physical properties.
The band gap is a major factor in determining electrical conductivity in a material and directly determines the upper wavelength limit of light absorption. Thus, achieving wide band gap tunability is highly desirable for developing opto-electronic devices and energy materials.
Using a layer-by-layer growth technique for which Ho Nyung Lee of ORNL earned the Presidential Early Career Award for Scientists and Engineers, Lee and colleagues have achieved a 30 percent reduction in the band gap of complex metal oxides. The findings are outlined in the journal Nature Communications.
"Our approach to tuning band gaps is based on atomic-scale growth control of complex oxide materials, yielding novel artificial materials that do not exist in nature," Lee said. "This 'epitaxy' technique can be used to design entirely new materials or to specifically modify the composition of thin-film crystals with sub-nanometer accuracy."
While band gap tuning has been widely successful for more conventional semiconductors, the 30 percent band gap reduction demonstrated with oxides easily surpasses previous accomplishments of 6 percent – or 0.2 electron volt – in this area and opens pathways to new approaches to controlling band gap in complex-oxide materials.
With this discovery, the potential exists for oxides with band gaps to be continuously controlled over 1 electron volt by site-specific alloying developed by the ORNL team. "Therefore," Lee said, "this work represents a major achievement using complex oxides that offer a number of advantages as they are very stable under extreme and severe environments."
ORNL's Michelle Buchanan, associate lab director for the Physical Sciences Directorate, expanded on Lee's sentiment. "This work exemplifies how basic research can provide technical breakthroughs that will result in vastly improved energy technologies," she said.
Other authors of the paper, titled "Wide band gap tunability in complex transition metal oxides by site-specific substitution," are Woo Seok Choi, Matthew Chisholm, David Singh, Taekjib Choi and Gerald Jellison of ORNL's Materials Science and Technology Division. A patent is pending for this technology.
The research was funded initially by the Laboratory Directed Research and Development program and later by the Department of Energy's Office of Science. Optical measurements were performed in part at the Center for Nanophase Materials Sciences, a DOE-BES user facility at ORNL.
UT-Battelle manages ORNL for the Office of Science. The 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 http://science.energy.gov/
Ron Walli | EurekAlert!
Less is more to produce top-notch 2D materials
20.11.2017 | The Agency for Science, Technology and Research (A*STAR)
The stacked colour sensor
16.11.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
20.11.2017 | Earth Sciences
20.11.2017 | Earth Sciences
20.11.2017 | Life Sciences