A Self-Correcting Crystal May Unleash the Next Generation of Advanced Communications


mix-id328072.jpgResearchers from the National Institute of Standards and Technology (NIST) have joined with an international team to engineer and measure a potentially important new class of nanostructured materials for microwave and advanced communication devices.

 

Based on NIST’s measurements, the new materials—a family of multilayered crystalline sandwiches—might enable a whole new class of compact, high-performance, high-efficiency components for devices such as cellular phones.*

strontium bricks
Not a brick wall. Electron microscope image of a cross section of the newly characterized tunable microwave dielectric clearly shows the thick layers of strontium titanate “bricks” separated by thin “mortar lines” of strontium oxide that help promote the largely defect-free growth of the bricks.
Credit: TEM image courtesy David Mueller. Color added for clarity by Nathan Orloff. high resolution version

“These materials are an excellent example of what the Materials Genome Initiative refers to as ‘materials-by-design’,” says NIST physicist James Booth, one of the lead researchers. “Materials science is getting better and better at engineering complex structures at an atomic scale to create materials with previously unheard-of properties.”

The new multilayer crystals are so-called “tunable dielectrics,” the heart of electronic devices that, for example, enable cell phones to tune to a precise frequency, picking a unique signal out of the welter of possible ones.

Tunable dielectrics that work well in the microwave range and beyond—modern communications applications typically use frequencies around a few gigahertz—have been hard to make, according to NIST materials scientist Nathan Orloff. “People have created tunable microwave dielectrics for decades, but they’ve always used up way too much power.” These new materials work well up to 100 GHz, opening the door for the next generation of devices for advanced communications.

Modern cellphone dielectrics use materials that suffer from misplaced or missing atoms called “defects” within their crystal structure, which interfere with the dielectric properties and lead to power loss. One major feature of the new materials, says Orloff, is that they self-correct, reducing the effect of defects in the part of the crystal where it counts. “We refer to this material as having ‘perfect faults’,” he says. “When it’s being grown, one portion accommodates defects without affecting the good parts of the crystal. It’s able to correct itself and create perfect dielectric bricks that result in the rare combination of high tuning and low loss.”

The new material has layers of strontium oxide, believed to be responsible for the self-correcting feature, separating a variable number of layers of strontium titanate. Strontium titanate on its own is normally a pretty stable dielectric—not really tunable at all—but another bit of nanostructure wizardry solves that. The sandwich layers are grown as a thin crystalline film on top of a substrate material with a mismatched crystal spacing that produces strain within the strontium titanate structure that makes it a less stable dielectric—but one that can be tuned. “It’s like putting a queen-sized sheet on a king-sized bed,” says Orloff. “The combination of strain with defect control leads to the unique electronic properties.”

One key discovery by the research team was that, in addition to adding strain to the crystal sandwich, adding additional layers of strontium titanate in between the strontium oxide layers increased the room-temperature “tunability” performance of the structure, providing a new mechanism to control the material response. The material they reported on recently in the journal Nature has six layers of strontium titanate between each strontium oxide layer.

The new sandwich material performs so well as a tunable dielectric, over such a broad range of frequencies, that the NIST team led by Booth had to develop a new measurement technique—an array of test structures fabricated on top of the test film—just to measure its electronic characteristics. “We were able to characterize the performance of these materials as a function of frequency running from 10 hertz all the way up to 125 gigahertz. That’s the equivalent of measuring wavelengths from kilometers down to microns all with the same experimental set-up,” says Orloff, adding, “This material has a much lower loss and a much higher tunability for a given applied field then any material that we have seen.”

An international team of researchers contributed to the recent paper, representing, in addition to NIST, Cornell University, the University of Maryland, Pennsylvania State University, the Institute of Physics ASCR (Czech Republic), Universitat Politècnica de Catalunya (Spain), the Kavli Institute at Cornell for Nanoscale Science, Oak Ridge National Laboratory, the Leibniz Institute for Crystal Growth (Germany), The University of Texas at Austin and Temple University.

Contact: Michael Baum 301-975-2763

For additional perspective, see the Cornell University news story, “Tunable antenna could end dropped cell phone calls” at www.news.cornell.edu/stories/2013/10/tunable-antenna-could-end-dropped-cell-phone-calls. For more on the MGI at NIST, see www.nist.gov/mgi/index.cfm.

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NIST seeks proposals to establish new Center of Excellence on Advanced Materials Research


(Nanowerk News) The National Institute of Standards and  Technology (NIST) has announced a competition to create an Advanced Materials  Center of Excellence to foster interdisciplinary collaborations between NIST  researchers and scientists and engineers from academia and industry. The new  center will focus on accelerating the discovery and development of advanced  materials through innovations in measurement science and in new modeling,  simulation, data and informatics tools.        
Block Copolymer
Computer models of polymer mixtures studied at NIST can help develop  improved lithography resists for nanomanufacturing.
NIST anticipates funding the new center at approximately $5  million per year for five years, with the possibility of renewing the award for  an additional five years. Funding is subject to the availability of funds  through NIST’s appropriations. The competition is open to accredited  institutions of higher education and nonprofit organizations located in the  United States and its territories. The proposing institution may work as part of  a consortium that could include other academic institutions; nonprofit  organizations; companies; or state, tribal or local governments.                      
Advanced materials, such as new high-performance alloys or  ceramics, polymers, glasses, nanocomposites or biomaterials, are a key factor in  global competitiveness. They drive the development of new products and new  technical capabilities, and can create whole new industries. However, currently,  the average time from laboratory discovery of a new material to its first  commercial use can take up to 20 years. Reducing that lag by half is one of the  primary goals of the administration’s Materials Genome Initiative, announced in 2011.                      
In many cases, the lengthy time for materials development is due  to a repetitive process of trial and error experimentation that would be  familiar to Thomas Edison. The Materials Genome Initiative and the new NIST  center focus on dramatically reducing this through the use of measurement and  data-based research tools: massive materials databases, computer models and  computer simulations. The new center will provide a mechanism to merge NIST  expertise and resources in materials science, materials characterization,  reference data and standards with leading research capabilities in industry and  academia for designing, producing and processing advanced materials.                      
Full details of the solicitation, including eligibility  requirements, selection criteria, legal requirements and the mechanism for  submitting proposals are found in an announcement of Federal Funding Opportunity  (FFO) posted at Grants.gov under funding opportunity number  2013-NIST-ADV-MAT-COE-01.                     
Applications will only be accepted through the Grants.gov  website. The deadline for applications is 11:59 p.m. Eastern time, Aug. 12,  2013.                     
NIST will offer a webinar presentation on the Advanced Materials  Center of Excellence on July 15, 2013, at 2 p.m. Eastern time. The webinar will  offer general guidance on preparing proposals and provide an opportunity to  answer questions from the public about the program. Participation in the webinar  is not required to apply. There is no cost for the webinar, but participants  must register in advance. Information on, and registration for the webinar is  available at www.nist.gov/mgi.  
Source: NIST

Read more: http://www.nanowerk.com/news2/newsid=31095.php#ixzz2XeHbclDW

Vaporware: Scientists Use Cloud of Atoms as Optical Memory Device


QDOTS imagesCAKXSY1K 8Talk about storing data in the cloud. Scientists at the Joint Quantum Institute (JQI) of the National Institute of Standards and Technology (NIST) and the University of Maryland have taken this to a whole new level by demonstrating* that they can store visual images within quite an ethereal memory device—a thin vapor of rubidium atoms. The effort may prove helpful in creating memory for quantum computers.

This brief animation (click link to launch mp4) by the NIST/JQI team shows the NIST logo they stored within a vapor of rubidium atoms and three different portions of it that they were able to extract at will. Animation combines three actual images from the vapor extracted at different times.

Their work builds on an approach developed at the Australian National University, where scientists showed that a rubidium vapor could be manipulated in interesting ways using magnetic fields and lasers. The vapor is contained in a small tube and magnetized, and a laser pulse made up of multiple light frequencies is fired through the tube. The energy level of each rubidium atom changes depending on which frequency strikes it, and these changes within the vapor become a sort of fingerprint of the pulse’s characteristics. If the field’s orientation is flipped, a second pulse fired through the vapor takes on the exact characteristics of the first pulse—in essence, a readout of the fingerprint.

“With our paper, we’ve taken this same idea and applied it to storing an image—basically moving up from storing a single ‘pixel’ of light information to about a hundred,” says Paul Lett, a physicist with JQI and NIST’s Quantum Measurement Division. “By modifying their technique, we have been able to store a simple image in the vapor and extract pieces of it at different times.”

It’s a dramatic increase in the amount of information that can be stored and manipulated with this approach. But because atoms in a vapor are always in motion, the image can only be stored for about 10 milliseconds, and in any case the modifications the team made to the original technique introduce too much noise into the laser signal to make the improvements practically useful. So, should the term vaporware be applied here after all? Not quite, says Lett—because the whole point of the effort was not to build a device for market, but to learn more about how to create memory for next-generation quantum computers.

“What we’ve done here is store an image using classical physics. However, the ultimate goal is to store quantum information, which a quantum computer will need,” he says. “Measuring what the rubidium atoms do as we manipulate them is teaching us how we might use them as quantum bits and what problems those bits might present. This way, when someone builds a solid-state system for a finished computer, we’ll know how to handle them more effectively.”

*J.B. Clark, Q. Glorieux and P.D. Lett. Spatially addressable readout and erasure of an image in a gradient echo memory. New Journal of Physics, doi: 10.1088/1367-2630/15/3/035005, 06 March 2013.

Feds enlist Rice for nanocarbon project


Rice News

National Institute of Standards and Technology grant supports measurement and characterization of nanomaterials

The nascent industry of carbon-based nanomanufacturing will benefit from a new cooperative venture between scientists at Rice University and its Richard E. Smalley Institute for Nanoscale Science and Technology and scientists at the National Institute of Standards and Technology (NIST) in Gaithersburg, Md.

NIST announced a $2.7 million, five-year cooperative research agreement to study how nanoparticles – particularly fullerenes (aka buckyballs), nanotubes and graphene – operate and interact with other materials at the molecular, even atomic, scale.

“The payoff will be grand,” said Rice engineering professor Matteo Pasquali, the principal investigator of the new cooperative agreement to advance methods of measurement and characterization of nanomaterials. The goal is to enable the manufacture of high-end products that incorporate carbon-based nanomaterials for enhanced optical, electrical, mechanical and thermal properties.

“With this agreement, we’re building and expanding on several successful years of collaboration between NIST and Rice,” said Pasquali, a professor of chemical and biomolecular engineering and of chemistry at Rice. “Up to now, the research has focused primarily on the separation, spectroscopy and rheology of carbon nanotubes, but we will now go further to enable products and devices to be manufactured that include many types of carbon nanomaterials.”

“A lot of the research we’ve already done we can map onto the long-term goal of benefiting U.S. manufacturing,” he said.

The range of products that could benefit from advanced nanomaterials is vast, Pasquali said. The new research will help kick start advances in energy, health care, materials science and national security.

“We look forward to leveraging our combined scientific, engineering and standards leadership in nanomaterials to help the U.S. lead in the race toward commercialization and manufacturing,” said Kalman Migler, leader of the Complex Fluids Group of the Materials Science and Engineering Division at NIST.

“The opportunity to work closely with Rice faculty will quicken the pace of realizing carbon-based nanoelectronics,” said Angela Hight Walker, project leader in the Semiconductor and Dimensional Metrology Division at NIST.

Migler and Hight Walker are technical leads from NIST on the joint project.

The Rice grant will be administered by Pasquali and his colleagues, Vice Provost for Research Vicki Colvin, the Kenneth S. Pitzer-Schlumberger Professor of Chemistry and a professor of chemical and biomolecular engineering, and Junichiro Kono, a professor of electrical and computer engineering and of physics and astronomy.

The agreement builds on two earlier cooperative research agreements and a series of NIST workshops at which industry, government and academic researchers were polled about obstacles that remain in the path of efficient manufacturing with nanoscale carbon, from production of components to integration.

The agreement allows Rice to hire a team of postdoctoral associates and researchers who will study ways to disperse and characterize nanomaterials for specific uses, control and measure nano-network structures and create systems for in-line measurements during manufacturing. The new team will be primarily based at NIST headquarters in Maryland, where they will work closely with NIST scientists while also drawing on Rice expertise as they develop new methods.

Carbon at the nanoscale has become one of the most-studied materials by labs around the world since the discovery of the buckyball at Rice in 1986, which brought the Nobel Prize to Rice’s Richard Smalley and Robert Curl. Since then, nanocarbon has taken on new forms with the discovery of the carbon nanotube in the late ’90s and graphene, the single-atomic-layer form of carbon that won a Nobel for its discovers two years ago.

Pasquali’s lab has deep experience working on the dispersal and characterization of carbon nanotubes and graphene, which group members are working toward extruding into fibers that could become essential components in the advanced energy grid envisioned by Smalley.

Kono’s lab focuses on the physics and applications of carbon nanomaterials, with recent breakthroughs on the fabrication of devices based on aligned carbon nanotubes and graphene to control terahertz waves. “We’ve been working closely with NIST scientists Ming Zheng, Jeffery Fagan and Angela Hight Walker on the chirality separation and spectroscopy of single-wall carbon nanotubes,” Kono said. “Their successful enrichment of armchair carbon nanotubes has led to a significant advancement in our understanding of the electronic and optical properties of these one-dimensional metals.”

Colvin’s group has expertise in how nanoparticles interact with the environment and living systems and has recently demonstrated nano-based technology to remove arsenic from drinking water in Mexico.

 

Nobel physics prize highlights weird world of quantum optics


By Karl Ritter and Louise Nordstrom

Image: Atomic clock

STOCKHOLM — A French-American duo shared the 2012 Nobel Prize in physics Tuesday for inventing methods to observe the bizarre properties of the quantum world — research that has led to the construction of extremely precise clocks and helped scientists take the first steps toward building superfast computers.

Serge Haroche of France and American David Wineland opened the door to new experiments in quantum physics by showing how to observe individual quantum particles without destroying them.

A quantum particle is one that is isolated from everything else. In this situation, an atom or electron or photon takes on strange properties. It can be in two places at once, for example. It behaves in some ways like a wave. But these properties are instantly changed when it interacts with something else, such as when somebody observes it.

Working separately, the two scientists, both 68, developed “ingenious laboratory methods” that allowed them to manage and measure and control fragile quantum states, the Royal Swedish Academy of Sciences said.

“Their ground-breaking methods have enabled this field of research to take the very first steps towards building a new type of superfast computer based on quantum physics,” the academy said. “The research has also led to the construction of extremely precise clocks that could become the future basis for a new standard of time.”

Background: Nobel-winning physics explained

Haroche is a professor at the College de France and Ecole Normale Superieure in Paris. Wineland is a physicist at the National Institute of Standards and Technology and the University of Colorado in Boulder, Colorado.

The two researchers use opposite approaches to examine, control and count quantum particles, the academy said. Wineland traps ions — electrically charged atoms — and measures them with light. Haroche controls and measures photons, or light particles, by sending atoms through a specially prepared trap.

Haroche said he was out walking with his wife when he got the call from the Nobel judges.

“I was in the street and passing a bench so I was able to sit down,” Haroche told a news conference in Stockholm by telephone. “It’s very overwhelming.”

He said his work in the realm of quantum physics could ultimately lead to unimaginably fast computers, with atoms that can essentially be in two different states at the same time. “You can do things which are prohibited by the laws of classical physics,” he told The Associated Press.

Haroche also said quantum research could help make GPS navigating systems more accurate.

‘Field of Dweebs’

NIST spokesman Jim Burrus said Wineland was asleep at home in Boulder when the call came in early Tuesday notifying him that he won; his wife answered the phone. Burrus said Wineland described the news as overwhelming and wonderful.

He said Wineland was a humble person who never expected to win prizes. He also doesn’t take himself very seriously: Wineland once played first base on a NIST softball team called “Field of Dweebs.”

Christopher Monroe, who does similar work at the Joint Quantum Institute at the University of Maryland, said the awarding of the prize to the two men “is not a big surprise to me. … It was sort of obvious that they were a package.”

Monroe said that thanks to the bizarre properties of the quantum world, when he and Wineland worked together in the 1990s, they were able to put a single atom in two places simultaneously.

At that time, it wasn’t clear that trapping single atoms could help pave the way to superfast quantum computers, he said. That whole field “just fell into our laps,'” Monroe said.

In an ordinary computer, information is represented in bits, each of which is either a zero or a one. But in a quantum computer, an individual particle can essentially represent a zero and a one at the same time — that is, until the result is read out. If scientists can make quantum bits, or “qubits,” work together, certain kinds of calculations could be done with blazing speed.

One example is prime factorization, the process of discovering which two prime numbers can be multiplied together to produce a given number. That has implications for breaking the encryption codes that provide the foundation for today’s secure financial transactions. However, quantum encryption could open the way for a new generation of secure communication tools as well.

Quantum computers could radically change people’s lives in the way that classical computers did last century, but a full-scale quantum computer is still decades away, the Nobel judges said. “The calculations would be incredibly much faster and exact, and you would be able to use it for areas like meteorology and for measuring the climate of the earth,” said Lars Bergstrom, the secretary of the prize committee.

The physics prize was the second of the 2012 Nobel Prizes to be announced, with the medicine prize going Monday to stem cell pioneers John Gurdon of Britain and Japan’s Shinya Yamanaka. Each award is worth 8 million kronor, or about $1.2 million.

The prizes are always handed out on Dec. 10, the anniversary of prize founder Alfred Nobel’s death in 1896.

Researchers Determine Critical Factors for Improving Performance of a Solar Fuel Catalyst


October 3, 2012

Contact: Veronika Szalai

False-color SEMs of cross-sectioned hematite films. 
False-color scanning electron micrographs of cross-sectioned hematite films grown by sputter deposition and then annealed at two different temperatures.  The physical structure and the tin dopant atom distributions in the hematite films differ depending on the annealing temperature.  Hematite annealed at higher temperatures has better catalytic performance for splitting water.

Hydrogen gas that is created using solar energy to split water into hydrogen and oxygen has the potential to be a cost-effective fuel source if the efficiency of the catalysts used in the water-splitting process can be improved. By controlling the placement of key additives (dopant atoms) in an iron oxide catalyst, researchers from the NIST Center for Nanoscale Science and Technology have found that the final location of the dopants and the temperature at which they are incorporated into the catalyst crystal lattice determine overall catalytic performance in splitting water.* The iron oxide hematite is a promising catalyst for water splitting because it is stable in water and absorbs a large portion of the solar spectrum. It is also abundant in the earth’s crust, making it inexpensive. Unfortunately, pure hematite has only modest catalytic activity, falling well short of its predicted theoretical maximum efficiency. Incorporating dopants such as tin atoms into hematite’s lattice improves performance, but it is a challenge to accurately measure the dopant concentration, making it difficult to understand and optimize their effects on catalyst performance. Using thin films of hematite doped with tin, the researchers produced highly active samples that enabled them to measure and characterize the spatial distribution of dopants in the material and their role in catalysis. The researchers determined that as a result of the sample preparation protocol they followed, a dopant gradient extends from the interface with the dopant source to the catalyst surface, where the measured concentration is low compared with previous estimates from similarly prepared samples. Contrary to prior results, they found that only a small dopant concentration is needed to improve catalytic activity. The researchers believe this study creates a path for improving the rational design of inexpensive catalysts for splitting water using solar energy.

*Effect of tin doping on α-Fe2O3 photoanodes for water splitting, C. D. Bohn, A. K. Agrawal, E. C. Walter, M. D. Vaudin, A. A. Herzing, P. M. Haney, A. A. Talin, and V. A. Szalai, The Journal of Physical Chemistry C 116, 15290–15296 (2012).
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