Study reveals new characteristics of complex oxide surfaces

Jul 24, 2014
An Oak Ridge National Laboratory study combined microscopy and data processing to provide an unprecedented look at the surface of a magnanite material known for its unusual properties. The resulting "distortion maps" (right) brought into view structural areas called domains that were not easily identified in the raw images (left). Credit: ORNL

A novel combination of microscopy and data processing has given researchers at the Department of Energy's Oak Ridge National Laboratory an unprecedented look at the surface of a material known for its unusual physical and electrochemical properties.

The research team led by ORNL's Zheng Gai examined how oxygen affects the surface of a perovskite manganite, a complex material that exhibits dramatic magnetic and electronic behavior. The new avenue to understand surface behavior could benefit researchers who are interested in using a wide range of correlated oxide materials for applications such as solid fuel cells or .

"Surface properties are key for any sensitive application, because the surface controls the interaction with the outside world," said coauthor Art Baddorf.

The team's results, published in Nature Communications, underscore why the materials are called "strongly correlated:" Because the chemical and physical functionalities are coupled, any minor change can influence the entire system.

"It's like the material has many knobs, and if you turn one, all the properties change," Gai said. "You turn a different knob and the whole thing changes again. It turns out the surface is another knob—you can use it to change the properties."

The researchers used high-resolution scanning tunneling microscopy to generate images of the manganite surface—down to the level of 30 picometers. A picometer is one trillionth of a meter. They then processed the imaging data to determine the position of each atom and calculate the angles between the atoms.

"Knowing where the atoms are positioned shows how they are interacting," Baddorf said.

The resulting "distortion maps" brought into view structural areas called domains that were not easily identified in the raw images. The maps clearly showed how the presence of forced the atoms into a checkerboard pattern known as a Jahn-Teller distortion. Gai says the team's study is the first time the phenomenon has been observed on a material's surface.

"The oxygen totally changes the surface energy," Gai said. "Once you introduce oxygen, the electrons don't like to form a straight line; they zigzag to get to a lower energy state. This distortion is a very common concept in bulk materials, but nobody has been able to show this effect on the surface before."

The study is published as "Chemically induced Jahn–Teller ordering on manganite surfaces." Coauthors are ORNL's Wenzhi Lin, Paul Snijders, Thomas Ward, J. Shen, Stephen Jesse, Sergei Kalinin, and Arthur Baddorf; University of Nebraska's J.D. Burton and Evgeny Tsymbal; and IHI Corporation's K. Fuchigami.

This research was conducted in part at the Center for Nanophase Materials Sciences, a DOE Office of Science user facility. The DOE's Office of Science supported the research. Work at the University of Nebraska-Lincoln was supported by the National Science Foundation.

Explore further: Researchers create stable 2-D electron gas in strontium titanate, open door to new kind of electronics

add to favorites email to friend print save as pdf

Related Stories

ORNL finding goes beyond surface of oxide films

Aug 13, 2013

(Phys.org) —Better batteries, catalysts, electronic information storage and processing devices are among potential benefits of an unexpected discovery made by Oak Ridge National Laboratory scientists using ...

Tiny step edges, big step for surface science

Apr 09, 2014

An interesting effect could help build better solar cells and create better chemical catalysts: If a titanium oxide surface is completely flat, the electrons inside the material can move freely. But if there ...

Researchers probe invisible vacancies in fuel cell materials

Aug 22, 2012

(Phys.org) -- Knowing the position of missing oxygen atoms could be the key to cheaper solid oxide fuel cells with longer lifetimes. New microscopy research from the Department of Energy's Oak Ridge National Laboratory is ...

A 'sponge' path to better catalysts and energy materials

Sep 10, 2013

Scientists from the U.S. Department of Energy (DOE) Office of Science's Oak Ridge (ORNL) and Argonne National Laboratories, Northwestern University, and Hokkaido University (Japan) have developed a new oxygen ...

Recommended for you

Researchers develop world's thinnest electric generator

Oct 15, 2014

Researchers from Columbia Engineering and the Georgia Institute of Technology report today that they have made the first experimental observation of piezoelectricity and the piezotronic effect in an atomically ...

User comments : 0