Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ferroelectricity on the Nanoscale

11.07.2012
Berkeley Lab Researchers Say First Atomic-Scale Look at Ferroelectric Nanocrystals Points to Terabytes/Inch Storage

Promising news for those who relish the prospects of a one-inch chip storing multiple terabytes of data, some clarity has been brought to the here-to-fore confusing physics of ferroelectric nanomaterials.


Atomic-resolution images of germanium telluride nanoparticles from Berkeley Lab’s TEAM I electron microscope, and electron holographic images of barium titanate nanoparticles (below) from BNL yielded the first detailed experimental information on ferroelectric order at the nanoscale.

A multi-institutional team of researchers, led by scientists at the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) has provided the first atomic-scale insights into the ferroelectric properties of nanocrystals. This information will be critical for development of the next generation of nonvolatile data storage devices.

Working with the world’s most powerful transmission electron microscope, the researchers mapped the ferroelectric structural distortions in nanocrystals of germanium telluride, a semiconductor, and barium titanate, an insulator. This data was then combined with data from electron holographic polarization imaging to yield detailed information on the polarization structures and scaling limits of ferroelectric order on the nanoscale.

“As we scale down our device technology from the microscale to the nanoscale, we need a better understanding of how critical material properties, such as ferroelectric behavior, are impacted,” says Paul Alivisatos, director of Berkeley Lab and one of the principal investigators in this research. “Our results provide a pathway to unraveling the fundamental physics of nanoscale ferroelectricity at the smallest possible size scales.”

Alivisatos, who is also the Larry and Diane Bock Professor of Nanotechnology at the University of California (UC) Berkeley, is a corresponding author of a paper describing this work in the journal Nature Materials titled “Ferroelectric order in individual nanometrescale Crystals.” The other corresponding author is Ramamoorthy Ramesh, a senior scientist with Berkeley Lab’s Materials Sciences Division and the Plato Malozemoff Professor of Materials Science and Physics for UC Berkeley.

Ferroelectricity is the property by which materials can be electrically polarized, meaning they will be oriented in favor of either a positive or negative electrical charge. This polarization can be flipped with the application of an external electrical field, a property that could be exploited for nonvolatile data storage, similar to the use of ferromagnetic materials today but using much smaller, far more densely packed devices.

“Although much progress has been made towards understanding nanoscale photophysical magnetic and other functional properties, understanding the basic physics of ferroelectric nanomaterials remains far less advanced,” says co-principal investigator Ramesh, who attributes contradicting reports on nanoscale ferroelectricity in part to the lack of high-quality, nanocrystals of ferroelectric materials that feature well-defined sizes, shapes and surfaces.

“Another problem has been the reliance on ensemble measurements rather than single particle techniques,” he says. “Statistical-average measurement techniques tend to obscure the physical mechanisms responsible for profound changes in ferroelectric behavior within individual nanocrystals.”

The Berkeley Lab-led research team was able to map ferroelectric structural distortions within individual nanocrystals thanks to the unprecedented capabilities of TEAM I, which is housed at Berkeley Lab’s National Center for Electron Microscopy (NCEM). TEAM stands for “Transmission Electron Aberration-corrected Microscope.” TEAM I can resolve images of structures with dimensions as small as one half‑angstrom – less than the diameter of a single hydrogen atom.

The maps produced at TEAM I of ferroelectric distortion patterns within the highly conducting germanium telluride nanocrystals were then compared with electron holography studies of insulating nanocubes of barium titanate, which were carried out by collaborators at Brookhaven National Laboratory (BNL).

“Electron holography is an interferometry technique using coherent electron waves,” said BNL physicist and co-author of the Nature Materials paper Myung-Geun Han. “Firing focused electron waves through the ferroelectric sample creates what’s called a phase-shift, or an interference pattern that reveals details of the targeted structure. This produces an electron hologram, which we can use to directly see local electric fields of individual ferroelectric nanoparticles.”

These combined studies enabled the independent examination of depolarizing field and surface structure influences and thereby enabled the research team to identify the fundamental factors governing the nature of the ferroelectric polarized state at finite dimensions. The results indicate that a monodomain ferroelectric state with linearly ordered polarization remains stable in these nanocrystals down to dimensions of less than 10 nanometers. Also, room-temperature polarization flipping was demonstrated down to dimensions of about five nanometers. Below this threshold, ferroelectric behavior disappeared. This indicates that five nanometers is likely a size limit for data storage applications, the authors state.

“We also showed that ferroelectric coherence is facilitated in part by control of particle morphology, which along with electrostatic boundary conditions is found to determine the spatial extent of cooperative ferroelectric distortions,” Ramesh says. “Taken together, our results provide a glimpse of the structural and electrical manifestations of ferroelectricity down to its ultimate limits.”

Also co-authoring the Nature Materials paper in addition to Alivisatos, Ramesh and Han were Mark Polking, Amin Yourdkhani, Valeri Petkov, Christian Kisielowski, Vyacheslav Volkov, Yimei Zhu and Gabriel Caruntu.

This research was supported by the DOE Office of Science.

Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit www.lbl.gov.

One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by the Research Foundation for the State University of New York on behalf of Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization. Visit Brookhaven Lab’s electronic newsroom for links, news archives, graphics, and more at http://www.bnl.gov/newsroom, or follow Brookhaven Lab on Twitter, http://twitter.com/BrookhavenLab.

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.

Additional Information

For more information on the research of Ramamoorthy Ramesh, visit his Website at http://www.lbl.gov/msd/investigators/investigators_all/ramesh_investigator.html

For more information on the research of Paul Alivisatos visit his Website at http://www.cchem.berkeley.edu/pagrp/

For more about the National Center for Electron Microscopy and TEAM I visit the Website at http://ncem.lbl.gov/

Lynn Yarris | EurekAlert!
Further information:
http://www.lbl.gov
http://newscenter.lbl.gov/feature-stories/2012/07/10/ferroelectricity-on-the-nanoscale/

More articles from Materials Sciences:

nachricht An innovative high-performance material: biofibers made from green lacewing silk
20.01.2017 | Fraunhofer-Institut für Angewandte Polymerforschung IAP

nachricht Treated carbon pulls radioactive elements from water
20.01.2017 | Rice University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>