Materials scientists watch electrons 'melt'

November 22, 2011 By Jared Sagoff, Argonne National Laboratory

Electrons in a grid pattern. Credit: University of Pittsburgh
( -- When a skier rushes down a ski slope or a skater glides across an ice rink, a very thin melted layer of liquid water forms on the surface of the ice crystals, which allows for a smooth glide instead of a rough skid. In a recent experiment, scientists have discovered that the interface between the surface and bulk electronic structures of certain crystalline materials can act in much the same way.

Materials scientists often face the challenge of finding ways to move electrons across interfaces and through a material, according to John Mitchell, a at the U.S. Department of Energy's Argonne National Laboratory. However, the organization of the crystalline surface of a material does not always correlate with the organization of the below. In fact, in the between the surface and the bulk can be quite rough.

"You can think about the fidelity of an interface chemically—how well the atoms are arranged, or how neatly and properly they're distributed," Mitchell said. "Below that, however, there's a second level of organization, which is electronic fidelity."

While the crystal structure of the material can look nearly perfectly organized over large length scales, researchers at Argonne and Brookhaven National Laboratory showed a dividing line of "roughness" between the crystal surface and the bulk. "The electronic structure there is not perfect; instead, it's disturbed. That has implications for how might transport within that layer or across that surface. We tried to explore how this rough intermediary layer evolves as a function of temperature compared to the bulk of the crystal. Looking towards future devices, structures and new materials, we'd like to think about this in a three-dimensional way, moving not just in a plane but across different interfaces," he added. "How well you're going to communicate information across interfaces depends on how well organized they are."

Using surface X-ray scattering techniques at Sector 6-ID of Argonne's Advanced Photon Source, the research team studied the electronic order of an oxide material just below the temperature at which it would begin to "melt"—that is, to become electronically disorganized—in the bulk. "You want to operate in a temperature window just below this bulk ordering temperature because that's where you get the biggest bang for your buck in terms of signal, but the potential problem we're seeing here is that it's exactly in this regime that the electronic surface might be in its worst condition."

"It's the same principle that we see in ice skating, just shrunk down much smaller," Mitchell added. "The electronic surface pre-melted while the bulk remained frozen."

According to Mitchell, the findings have important implications for future electronic devices that require well-defined electronic interfaces. This could be particularly true for nanoscale devices, whose performance is dominated by their surface electronic behavior. "The challenge is to figure out how to engineer these materials to try to make this surface a little more electronically robust," he said.

Explore further: Expanding the degrees of surface freezing

Related Stories

Expanding the degrees of surface freezing

March 31, 2011

( -- As part of the quest to form perfectly smooth single-molecule layers of materials for advanced energy, electronic, and medical devices, researchers at the U.S. Department of Energy's Brookhaven National Laboratory ...

Metal oxide 'can transform'

February 15, 2010

( -- A team including Oxford University scientists has been investigating what happens to the top layer of atoms on the surface of a material that splits water and has potential uses in nanoelectronics.

Unexpected magnetism discovered

October 18, 2010

Theoretical work done at the Department of Energy's Oak Ridge National Laboratory has provided a key to understanding an unexpected magnetism between two dissimilar materials.

Experiments Prove Existence of Atomic Chain Anchors

February 3, 2005

Atoms at the ends of self-assembled atomic chains act like anchors with lower energy levels than the “links” in the chain, according to new measurements by physicists at the National Institute of Standards and Technology ...

Graphene: What projections and humps can be good for

April 19, 2010

At present, graphene probably is the most investigated new material system worldwide. Due to its astonishing mechanical, chemical and electronic properties, it promises manifold future applications - for example in microelectronics. ...

Recommended for you

A quantum magnet with a topological twist

February 22, 2019

Taking their name from an intricate Japanese basket pattern, kagome magnets are thought to have electronic properties that could be valuable for future quantum devices and applications. Theories predict that some electrons ...

Sculpting stable structures in pure liquids

February 21, 2019

Oscillating flow and light pulses can be used to create reconfigurable architecture in liquid crystals. Materials scientists can carefully engineer concerted microfluidic flows and localized optothermal fields to achieve ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.