Nanotechnology Now







Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Promising Ferroelectric Materials Suffer From Unexpected Electric Polarizations: Brookhaven Lab scientists find surprising locked charge polarizations that impede performance in next-gen materials that could otherwise revolutionize data-driven devices

Electrostatic potential landscapes reconstructed from electron holography data with 15 volts of positive or negative current applied to the substrate (Nb-STO). The much steeper potential drop from the +15 V signifies a higher electric field, whereas the -15 V yielded a much flatter curve—indicating the charge asymmetry within the material.
Electrostatic potential landscapes reconstructed from electron holography data with 15 volts of positive or negative current applied to the substrate (Nb-STO). The much steeper potential drop from the +15 V signifies a higher electric field, whereas the -15 V yielded a much flatter curve—indicating the charge asymmetry within the material.

Abstract:
Electronic devices with unprecedented efficiency and data storage may someday run on ferroelectrics—remarkable materials that use built-in electric polarizations to read and write digital information, outperforming the magnets inside most popular data-driven technology. But ferroelectrics must first overcome a few key stumbling blocks, including a curious habit of "forgetting" stored data.

Promising Ferroelectric Materials Suffer From Unexpected Electric Polarizations: Brookhaven Lab scientists find surprising locked charge polarizations that impede performance in next-gen materials that could otherwise revolutionize data-driven devices

Upton, NY | Posted on August 18th, 2014

Now, scientists at the U.S. Department of Energy's Brookhaven National Laboratory have discovered nanoscale asymmetries and charge preferences hidden within ferroelectrics that may explain their operational limits.

"The positive or negative polarizations in these ferroelectric materials should be incredibly easy to switch, but the reality is much stranger," said Brookhaven Lab physicist Myung-Geun Han, lead author on the new study. "To our surprise, opposing electronic configurations only allowed for polarization in one direction—a non-starter for reading and writing data."

The researchers used a suite of state-of-the-art techniques—including real-time electrical biasing, electron holography, and electron-beam-induced current measurements—to reveal never-before-seen electric field distributions in ferroelectric thin films, which were custom-grown at Yale University. The results, published in Nature Communications, open new pathways for ferroelectric technology.

Physics of Flipping

Most electronic devices rely on ferromagnetism to read and write data. Each so-called ferromagnetic domain contains a north or south magnetic polarity, which translates into the flipping 1 or 0 of the binary code underlying all digital information. But ferromagnetic operations not only require large electric current, but the magnets can flip each other like dominoes when packed together too tightly—effectively erasing any data.

Ferroelectrics, however, use positive or negative electric charge to render digital code. Crucially, they can be packed together with domains spanning just a few atoms and require only a tiny voltage kick to flip the charge, storing much more information with much greater efficiency.

"But ferroelectric commercialization is held up by material fatigue, sudden polarization reversal, and intrinsic charge preferences," said Brookhaven Lab physicist and study coauthor Yimei Zhu. "We suspected that the origin of these issues was in the atomic interactions along the material's interface—where the ferroelectric thin film sits on a substrate."

Interface Exploration

The scientists examined ferroelectric films of lead, zirconium, and titanium oxide grown on conductive substrates of strontium, and titanium oxide with a small amount of niobium—chosen because it exhibits large polarization values with well-defined directions, either up or down. The challenge was mapping the internal electric fields in materials thousands of times thinner than a human hair under actual operating conditions.

Brookhaven scientists hunted down the suspected interface quirks using electron holography. In this technique, a transmission electron microscope (TEM) fired 200,000-volt electron wave packets through the sample with billionth-of-a-meter precision. Negative and positive electric fields inside the ferroelectric film then attracted or repelled the electron wave and slightly changed its direction. Tracking the way the beam bent throughout the ferroelectric film revealed its hidden charges.

"Rather than an evenly distributed electric field, the bending electron waves revealed non-uniform and unidirectional electric fields that induced unstable, head-to-head domain configurations," Han said. "For the first time, we could see these unusual and jagged polarizations mapped out in real space and real time."

These opposing polarizations—like rival football teams squaring off aggressively at the line of scrimmage—surprised scientists and challenged assumptions about the ferroelectric phenomenon.

"These results were totally unexpected based on the present understanding of ferroelectrics," Han said.

The asymmetries were further confirmed by measurements of electron-beam-induced current. When a focused electron beam struck the ferroelectric sample, electric fields within the film-substrate interface revealed themselves by generating additional current. Other techniques, including piezoresponse force microscopy—in which a sub-nanometer tip induces a reaction by pressing against the ferroelectric—also confirmed the strange domains.

"Each technique demonstrated this intrinsic polarization preference, likely the origin of the back-switching and poor coding performance in these ferroelectrics," Han said. "But these domain structures should require a lot of energy and thus be very unstable. The interface effect alone cannot explain their existence."
Missing Oxygen

The scientists used another ultra-precise technique to probe the material's interface: electron energy loss spectroscopy (EELS). By measuring the energy deposited by an electron beam in specific locations—a kind of electronic fingerprint—the scientists determined the material's chemical composition.

"We suspect that more oxygen could be missing near the surface of the thin films, creating electron pockets that may neutralize positive charges at the domain walls," Han said. "This oxygen deficiency naturally forms in the material, and it could explain the stabilization of head-to-head domains."

This electron-swapping oxygen deficiency—and its negative effects on reliably storing data—might be corrected by additional engineering, Han said. For example, incorporating a "sacrificial layer" between the ferroelectric and the substrate could help block the interface interactions. In fact, the study may inspire new ferroelectrics that either exploit or overcome this unexpected charge phenomenon.

Other authors include Lijun Wu and Marvin A. Schofield of Brookhaven Lab; Matthew S. J. Marshall, Jason Hoffman, Frederick J. Walker, and Charles H. Ahn of the Yale University Department of Applied Physics and Center for Research on Interfaces Structures and Phenomena; Toshihiro Aoki of JEOL USA Inc.; and Ray Twesten of Gatan Inc.

The samples used for transmission electron microscopy (TEM) were prepared by Kim Kisslinger at Brookhaven Lab's Center for Functional Nanomaterials, a U.S. Department of Energy user facility.

The research was supported by the U.S. Department of Energy's Office of Science.

Brookhaven National Laboratory is supported by the Office of Science of the U.S. Department of Energy. 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 science.energy.gov.

####

About Brookhaven National Laboratory
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.

For more information, please click here

Contacts:
Justin Eure

631-344-2347

Copyright © Brookhaven National Laboratory

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

onic Present breakthrough in CMOS-based Transceivers for mm-Wave Radar Systems March 1st, 2015

Graphene Shows Promise In Eradication Of Stem Cancer Cells March 1st, 2015

Novel Method to Determine Optical Purity of Drug Components March 1st, 2015

Scientific breakthrough in rechargeable batteries: Researchers from Singapore and Québec Team Up to Develop Next-Generation Materials to Power Electronic Devices and Electric Vehicles February 28th, 2015

Laboratories

First detailed microscopy evidence of bacteria at the lower size limit of life: Berkeley Lab research provides comprehensive description of ultra-small bacteria February 28th, 2015

Physics

Moving molecule writes letters: Caging of molecules allows investigation of equilibrium thermodynamics February 27th, 2015

Real-time observation of bond formation by using femtosecond X-ray liquidography February 26th, 2015

Warming up the world of superconductors: Clusters of aluminum metal atoms become superconductive at surprisingly high temperatures February 25th, 2015

Quantum many-body systems on the way back to equilibrium: Advances in experimental and theoretical physics enable a deeper understanding of the dynamics and properties of quantum many-body systems February 25th, 2015

Govt.-Legislation/Regulation/Funding/Policy

First detailed microscopy evidence of bacteria at the lower size limit of life: Berkeley Lab research provides comprehensive description of ultra-small bacteria February 28th, 2015

Warming up the world of superconductors: Clusters of aluminum metal atoms become superconductive at surprisingly high temperatures February 25th, 2015

SUNY Poly CNSE Researchers and Corporate Partners to Present Forty Papers at Globally Recognized Lithography Conference: SUNY Poly CNSE Research Group Awarded Both ‘Best Research Paper’ and ‘Best Research Poster’ at SPIE Advanced Lithography 2015 forum February 25th, 2015

European roadmap for graphene science and technology published February 25th, 2015

Chip Technology

onic Present breakthrough in CMOS-based Transceivers for mm-Wave Radar Systems March 1st, 2015

New nanowire structure absorbs light efficiently: Dual-type nanowire arrays can be used in applications such as LEDs and solar cells February 25th, 2015

SUNY Poly CNSE Researchers and Corporate Partners to Present Forty Papers at Globally Recognized Lithography Conference: SUNY Poly CNSE Research Group Awarded Both ‘Best Research Paper’ and ‘Best Research Poster’ at SPIE Advanced Lithography 2015 forum February 25th, 2015

Ultra-thin nanowires can trap electron 'twisters' that disrupt superconductors February 24th, 2015

Memory Technology

Insight into inner magnetic layers: Measurements at BESSY II have shown how spin filters forming within magnetic sandwiches influence tunnel magnetoresistance -- results that can help in designing spintronic component- February 17th, 2015

Dance of the nanovortices February 2nd, 2015

Nano - "Green" metal oxides ... January 13th, 2015

Quantum optical hard drive breakthrough January 8th, 2015

Discoveries

Graphene Shows Promise In Eradication Of Stem Cancer Cells March 1st, 2015

Novel Method to Determine Optical Purity of Drug Components March 1st, 2015

First detailed microscopy evidence of bacteria at the lower size limit of life: Berkeley Lab research provides comprehensive description of ultra-small bacteria February 28th, 2015

Moving molecule writes letters: Caging of molecules allows investigation of equilibrium thermodynamics February 27th, 2015

Materials/Metamaterials

Moving molecule writes letters: Caging of molecules allows investigation of equilibrium thermodynamics February 27th, 2015

Graphene shows potential as novel anti-cancer therapeutic strategy: University of Manchester scientists have used graphene to target and neutralise cancer stem cells while not harming other cells February 26th, 2015

In quest for better lithium-air batteries, chemists boost carbon's stability: Nanoparticle coatings improve stability, cyclability of '3DOm' carbon February 25th, 2015

Learning by eye: Silicon micro-funnels increase the efficiency of solar cells February 25th, 2015

Announcements

onic Present breakthrough in CMOS-based Transceivers for mm-Wave Radar Systems March 1st, 2015

Graphene Shows Promise In Eradication Of Stem Cancer Cells March 1st, 2015

Novel Method to Determine Optical Purity of Drug Components March 1st, 2015

Scientific breakthrough in rechargeable batteries: Researchers from Singapore and Québec Team Up to Develop Next-Generation Materials to Power Electronic Devices and Electric Vehicles February 28th, 2015

Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers

Novel Method to Determine Optical Purity of Drug Components March 1st, 2015

Moving molecule writes letters: Caging of molecules allows investigation of equilibrium thermodynamics February 27th, 2015

Untangling DNA with a droplet of water, a pipet and a polymer: With the 'rolling droplet technique,' a DNA-injected water droplet rolls like a ball over a platelet, sticking the DNA to the plate surface February 27th, 2015

Graphene shows potential as novel anti-cancer therapeutic strategy: University of Manchester scientists have used graphene to target and neutralise cancer stem cells while not harming other cells February 26th, 2015

Research partnerships

onic Present breakthrough in CMOS-based Transceivers for mm-Wave Radar Systems March 1st, 2015

Scientific breakthrough in rechargeable batteries: Researchers from Singapore and Québec Team Up to Develop Next-Generation Materials to Power Electronic Devices and Electric Vehicles February 28th, 2015

Moving molecule writes letters: Caging of molecules allows investigation of equilibrium thermodynamics February 27th, 2015

European roadmap for graphene science and technology published February 25th, 2015

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More










ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2015 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE