(Press-News.org) OAK RIDGE, Tenn., Oct. 13, 2014 -- Researchers at the Department of Energy's Oak Ridge National Laboratory have obtained the first direct observations of atomic diffusion inside a bulk material. The research, which could be used to give unprecedented insight into the lifespan and properties of new materials, is published in the journal Physical Review Letters (06 October 2014, DOI: 10.1103/PhysRevLett.113.155501).
"This is the first time that anyone has directly imaged single dopant atoms moving around inside a material," said Rohan Mishra of Vanderbilt University who is also a visiting scientist in ORNL's Materials Science and Technology Division.
Semiconductors, which form the basis of modern electronics, are "doped" by adding a small number of impure atoms to tune their properties for specific applications. The study of the dopant atoms and how they move or "diffuse" inside a host lattice is a fundamental issue in materials research.
Traditionally, diffusion of atoms has been studied through indirect macroscopic methods or through theoretical calculations. Diffusion of single atoms has previously been directly observed only on the surface of materials.
The experiment also allowed the researchers to test a surprising prediction: Theory-based calculations for dopant motion in aluminum nitride predicted faster diffusion for cerium atoms than for manganese atoms. This prediction is surprising as cerium atoms are larger than manganese atoms.
"It's completely counterintuitive that a bigger, heavier atom would move faster than a smaller, lighter atom," said the Material Science and Technology Division's Andrew Lupini, a coauthor of the paper.
In the study, the researchers used a scanning transmission electron microscope to observe the diffusion processes of cerium and manganese dopant atoms. The images they captured showed that the larger cerium atoms readily diffused through the material, while the smaller manganese atoms remained fixed in place.
The team's work could be directly applied in basic material design and technologies such as energy-saving LED lights where dopants can affect color and atom movement can determine the failure modes.
"Diffusion governs how dopants get inside a material and how they move," said Lupini. "Our study gives a strategy for choosing which dopants will lead to a longer device lifetime."
See videos of manganese and cerium atom dopant jumps.
INFORMATION:
This research was conducted in part at ORNL and Lawrence Berkeley National Laboratory's National Energy Research Scientific Computing Center, a DOE Office of Science User Facility.
The study was funded by the DOE Office of Science, the Australian Research Council, Vanderbilt University and the Japan Society for the Promotion of Science Postdoctoral Fellowship for research abroad.
The project's authors include Ryo Ishikawa of Oak Ridge National Laboratory and the University of Tokyo; Scott Findlay of Monash University; Takashi Taniguchi of the National Institute for Materials Science; Sokrates Pantelides of Oak Ridge National Laboratory and Vanderbilt University; and Stephen Pennycook of the University of Tennessee.
UT-Battelle manages ORNL for the Department of Energy's 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/.
Image: http://www.ornl.gov/Image%20Library/Main%20Nav/ORNL/News/News%20Releases/2014/Atomic-Diffusion_hr.jpg?code=1d74da04-af08-48c6-93af-9f9afe9afde3
Caption: Selected frames from a sequence of scanning transmission electron microscope images showing the diffusion pathway of a Ce dopant (the bright atom highlighted with a white arrow) as it moves inside a bulk AlN crystal. The final frame overlays the Ce pathway on the Z-contrast image obtained by averaging each frame.
NOTE TO EDITORS: You may read other press releases from Oak Ridge National Laboratory or learn more about the lab at http://www.ornl.gov/news. Additional information about ORNL is available at the sites below:
Twitter - http://twitter.com/ornl
RSS Feeds - http://www.ornl.gov/ornlhome/rss_feeds.shtml
Flickr - http://www.flickr.com/photos/oakridgelab
YouTube - http://www.youtube.com/user/OakRidgeNationalLab
LinkedIn - http://www.linkedin.com/companies/oak-ridge-national-laboratory
Facebook - http://www.facebook.com/Oak.Ridge.National.Laboratory
ORNL researchers make first observation of atoms moving inside bulk material
2014-10-14
[Attachments] See images for this press release:
ELSE PRESS RELEASES FROM THIS DATE:
Charged graphene gives DNA a stage to perform molecular gymnastics
2014-10-14
CHAMPAIGN, Ill. — When Illinois researchers set out to investigate a method to control how DNA moves through a tiny sequencing device, they did not know they were about to witness a display of molecular gymnastics.
Fast, accurate and affordable DNA sequencing is the first step toward personalized medicine. Threading a DNA molecule through a tiny hole, called a nanopore, in a sheet of graphene allows researchers to read the DNA sequence; however, they have limited control over how fast the DNA moves through the pore. In a new study published in the journal Nature ...
Scientists sniff out unexpected role for stem cells in the brain
2014-10-14
For decades, scientists thought that neurons in the brain were born only during the early development period and could not be replenished. More recently, however, they discovered cells with the ability to divide and turn into new neurons in specific brain regions. The function of these neuroprogenitor cells remains an intense area of research. Scientists at the National Institutes of Health (NIH) report that newly formed brain cells in the mouse olfactory system — the area that processes smells — play a critical role in maintaining proper connections. The results ...
Light-activated drug could reduce side effects of diabetes medication
2014-10-14
Scientists have created a drug for type 2 diabetes that is switched on by blue light, which they hope will improve treatment of the disease.
Diabetes drugs that promote the release of insulin from the pancreas can in some cases cause side effects due to their actions on other organs such as the brain and heart. Some can also stimulate too much insulin release, causing blood sugar levels to drop too low.
To help create better drugs, researchers at Imperial College London and LMU Munich adapted an existing type of drug called a sulfonylurea so that it changes shape when ...
New forecasting method: Predicting extreme floods in the Andes mountains
2014-10-14
This might allow for improved disaster preparedness. As the complex systems technique builds upon a mathematical comparison that can be utilised for any time series data, the approach could be applied to extreme events in all sorts of complex systems.
"Current weather forecast models cannot capture the intensity of the most extreme rainfall events, yet these events are of course the most dangerous, and can have severe impacts for the local population, for example major floods or even landslides," says lead author Niklas Boers of the Potsdam Institute for Climate Impact ...
Teenage baseball pitchers at risk for permanent shoulder injury
2014-10-14
OAK BROOK, Ill. – Young baseball pitchers who throw more than 100 pitches per week are at risk for a newly identified overuse injury that can impede normal shoulder development and lead to additional problems, including rotator cuff tears, according to a new study published online in the journal Radiology.
The injury, termed acromial apophysiolysis by the researchers, is characterized by incomplete fusion and tenderness at the acromion. The acromion, which forms the bone at the top or roof of the shoulder, typically develops from four individual bones into one bone ...
New clues behind the resilience of a leading sexually transmitted pathogen, Chlamydia
2014-10-14
In the advanced online edition of Molecular Biology and Evolution, authors Domman, et al. have explored factors behind the resilience of the most common sexually transmitted disease in the U.S., chlamydia, with an estimated 1 million infected.
The research team sequenced 4 new strains of close genetic cousins of chlamydial pathogens, and examined these with existing DNA data. They found an extensive and robust shuffling of the genomic deck between chlamydia families has played a major role in the evolution of the pathogen, often serving to outwit and exploit its hosts. ...
Study sheds light on factors that may contribute to pancreatic cancer
2014-10-14
New research that provides a better understanding of pancreatic cancer may help identify individuals at increased risk. The findings are published early online in Cancer, a peer-reviewed journal of the American Cancer Society.
Pancreatic cancer is a stealthy cancer that is usually detected at very late stages and has a 5-year survival rate of less than 5 percent. Strategies that might help identify which individuals have an increased risk of developing the disease are sorely needed. Some cases seem to run in families, but the genes that are responsible for such inherited ...
Slow enteral feeding protocol can reduce instances of death in extreme preterm infants
2014-10-14
A standardized slow enteral feeding (SSEF) protocol significantly reduces the incidence of necrotizing enterocoltis (NEC), or death of intestinal tissue, and death in infants with extremely low birth weight, according to a new study.
The study, published today in the OnlineFirst version of the Journal of Parenteral and Enteral Nutrition (JPEN), the research journal of the American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.), found the use of SSEF resulted in a significant reduction in NEC and accompanying death in infants with a birth weight below 750 grams ...
Memories of pain during childbirth tied to intensity rather than length of labor
2014-10-14
Childbirth is physically intense and, for many women, it is the most painful experience they will have. And yet, new research shows that the amount of time a woman spends in labor doesn't seem to impact how she remembers her labor pain afterwards. The research, published in Psychological Science, a journal of the Association for Psychological Science, reveals that the peak and end levels of pain women experienced, and whether they received an epidural, impacted their recall of labor pain afterward.
"This phenomenon – called duration neglect – is particularly ...
Fly genome could help us improve health and our environment
2014-10-14
The house fly might be a worldwide pest, but its genome will provide information that could improve our lives. From insights into pathogen immunity, to pest control and decomposing waste, the 691 Mb genome has been sequenced and analyzed by a global consortium of scientists, and is published in the open access journal Genome Biology.
The genome highlights detoxification and immune system genes that are unique to the insect, and could be subjects of further study to help humans deal with toxic and disease causing environments.
The house fly (Musca domestica) lives on ...