NIST Tech Beat - August 16, 2007

A new process for adjusting the resistance of semiconductor devices by carpeting a small area of the device with tiny pits, like a yard dug up by demented terriers, may be the key to a new class of magnetic sensors, enabling new, ultra-dense data storage devices. The technique demonstrated by researchers at the National Institute of Standards and Technology (NIST)* allows engineers to tailor the electrical resistance of individual layers in a device without changing any other part of the processing or design.

The tiny magnetic sensors in modern disk drives are a sandwich of two magnetic layers separated by a thin buffer layer. The layer closest to the disk surface is designed to switch its magnetic polarity quickly in response to the direction of the magnetic “bit” recorded on the disk under it. The sensor works by measuring the electrical resistance across the magnetic layers, which changes depending on whether the two layers have matching polarities.

As manufacturers strive to make disk storage devices smaller and more densely packed with data, the sensors need to shrink as well, but current designs are starting to hit the wall. To meet the size constraints, prototype sensors measure sensor resistance perpendicular to the thin layers, but depending on the buffer material in the sensor, two different types of sensors can be made. Giant magneto-resistance (GMR) sensors use a low-resistance metal buffer layer and are fast, but plagued by very low, difficult to detect, signals. On the other hand, magnetic tunnel junction (MTJ) sensors use a relatively high-resistance insulating buffer that delivers a strong signal, but has a slower response time, too slow to keep up with a very high-speed, high-capacity drive.

What’s needed, says NIST physicist Josh Pomeroy, is a compromise. “Our approach is to combine these at the nanometer scale. We start out with a magnetic tunnel junction—an insulating buffer—and then, by using highly charged ions, sort of blow out little craters in the buffer layer so that when we grow the rest of the sensor on top, these craters will act like little GMR sensors, while the rest will act like an MTJ sensor.” The combined signal of the two effects, the researchers argue, should be superior to either alone.

The NIST team has demonstrated the first step—the controlled pockmarking of an insulating layer in a multi-layer structure to adjust its total resistance. The team uses small numbers of highly charged xenon ions that each have enormous potential energies—and can blast out surface pits without damaging the substrate. With each ion carrying more than 50 thousand electron volts of potential energy, only one impact is needed to create a pit—multiple hits in the same location are not necessary. Controlling the number of ions provides fine control over the number of pits etched, and hence the resistance of the layer—currently demonstrated over a range of three orders of magnitude. NIST researchers now are working to incorporate these modified layers into working magnetic sensors.

The new technique alters only a single step in the fabrication process—an important consideration for future scale-up—and can be applied to any device where it’s desirable to fine-tune the resistance of individual layers. NIST has a provisional patent on the work, number 60,905,125.

* J.M. Pomeroy, H. Grube, A.C. Perrella and J.D. Gillaspy. Selectable resistance-area product by dilute highly charged ion irradiation. Appl. Phys. Lett. 91, 073506 (2007).

The National Institute of Standards and Technology (NIST) has issued a suite of Standard Reference Materials (SRMs) for ginkgo biloba, one of the most popular dietary supplements in the marketplace, with annual worldwide sales estimated at $1 billion.

The NIST reference materials are designed to help researchers validate the accuracy of analytical methods for flavonoids and terpene lactones (plant constituents that may be associated with the perceived effectiveness of ginkgo) as well as toxic elements in ginkgo*. In addition to supporting measurements associated with clinical trials or verifying product label claims, the reference materials also can be used by dietary supplement manufacturers to improve product consistency.

The fruits and seeds of the female ginkgo are used for a variety of purposes in traditional Chinese medicine. In the West, dietary supplements are more commonly formulated from ginkgo leaves and standardized leaf extracts. They are used in the treatment of asthma, bronchitis, fatigue and tinnitus (ringing in the ears); for memory improvement and for the prevention and treatment of Alzheimer’s disease, although these uses have not been backed by rigorous clinical trials. Ginkgo biloba contains a family of chemical constituents known as ginkgolides which have been associated with reduced platelet aggregation. The National Institute of Health’s (NIH) National Center for Complementary and Alternative Medicine (NCCAM) notes promising results in a number of areas, but says “larger, well-designed research studies are needed.”

The new ginkgo reference materials include: SRM 3246 Ginkgo biloba (leaves); SRM 3247 Ginkgo biloba Extract; and SRM 3248 Ginkgo-Containing Tablets. In addition, the three ginkgo SRMs are available packaged together as SRM 3249. The reference materials come with certified values for five terpene lactones, three flavonoid aglycones and four potentially toxic trace elements (arsenic, cadmium, lead and mercury).

The goal of NIST’s ongoing effort with dietary supplements such as ginkgo biloba is to provide tools to the dietary supplement industry and measurement communities that will lead to improved quality of dietary supplements and the studies of their efficacy, as well as to ultimately reduce public health risks that could potentially be associated with the use of these products.

Support for the development of the gingko-related SRMs was provided in part by the National Institutes of Health (NIH) Office of Dietary Supplements (ODS) and the Food and Drug Administration (FDA) Center for Drug Evaluation and Research (CDER).

* C.A. Rimmer, S.B. Howerton, K.E. Sharpless, L.C. Sander, S.E. Long, K.E. Murphy, B.J. Porter, K. Putzbach, M.S. Rearick, S.A. Wise, L.J. Wood, R. Zeisler, D.K. Hancock, J.H. Yen, J.M. Betz, A.N. Pho, L. Yang, C. Scriver, S. Willie, R. Sturgeon, B. Schaneberg, C. Nelson, J. Skamarack, M. Pan, K. Levanseler, D. Gray, E.H. Waysek, A. Blatter and E. Reich. Characterization of a suite of ginkgo-containing standard reference materials. Analytical and Bioanalytical Chemistry. Published online: 7 July 2007. DOI 10.1007/s00216-007-1398-5.

Researchers from the American Dental Association Foundation (ADAF) and the National Institute of Standards and Technology (NIST) have developed a new method for layering two kinds of biomaterials into one strong, yet porous unit that may lead to improved reconstruction or repair of bones.

Currently, calcium phosphate cements (CPCs)—water-based pastes of powdered calcium and a phosphate compound that form hydroxyapatite, a material found in natural bone—are used for reconstructing or repairing skeletal defects, but only in bones that are not load-bearing (such as those in the face and skull). Macropores built into the CPCs make it easier for new bone cells to infuse and, eventually, solidify the implant. Until this happens, however, the macropores leave the implant brittle and susceptible to failure.

In the September 2007 issue of Biomaterials,* Hockin Xu and colleagues describe a unique approach for providing the strength needed to help an implant better survive its early stages. First, a macroporous CPC paste is placed into the area needing reconstruction or repair. Then, a strong, fiber-reinforced CPC paste is layered onto the first CPC to support the new implant. Once new bone has grown into the macroporous layer and increased its strength, the absorbable fibers in the strong layer dissolve and create additional macroporous channels that promote even more bone tissue ingrowth. This method mimics the natural bone structure in which a strong layer, called cortical bone, covers and strengthens a weaker, macroporous layer (spongy bone).

The two pastes used in the layered CPC method harden in the bone cavity to form an implant that for the first time has both the porosity needed for bone growth and the integrity required for reconstruction or repair of load-bearing bones (such as jaws).

NIST and the ADAF have conducted cooperative research on dental and medical materials since 1928. ADAF researchers focus on development of new dental and biomedical materials, while NIST specializes in the development of improved technologies and methods for measuring materials properties.

* H.K. Xu, E.F. Burguera and L.E. Carey. Strong, macroporous, and in situ-setting calcium phosphate cement-layered structures. Biomaterials 28 (September 2007), pp. 3786-3796.

If only the flame retardant chemicals routinely added to consumer products from carpets to cell phones just did their job and nothing more. Health officials, however, are concerned that one class of these chemicals called polybrominated diphenylethers (PBDEs), may be doing more than reducing fire-related injuries and property damage.

After several decades of use, PBDEs are widely distributed in the environment as contaminants, and trace levels of these chemicals can be measured in animal tissues and in the food chain (they can be found, for example, in bird eggs and human breast milk). To help scientists evaluate the risks of PBDEs by improving measurements of these pollutants in the environment, the National Institute of Standards and Technology (NIST) has re-evaluated several of its environmental reference materials to report PBDE concentrations in them.

Different commercial PBDE flame retardant formulations have been used, including pentaBDE in furniture foam; decaBDE in plastics for television cabinets, consumer electronics, draperies and upholstery; and octaDBE in plastics for personal computers and small appliances. Although human data on health effects are limited, the U.S. Environmental Protection Agency (EPA) cites animal tests as evidence that PBDEs are neurodevelopmental toxins, disruptors of thyroid functions, and liver toxins. The doses used in animal studies were slightly higher than PBDE levels found in some people in the United States.

U.S. production of pentaBDE and octaBDE formulations ended in 2004. DecaBDE (formulations which do not seem to be easily accumulated in humans, but can degrade to octaBDEs and pentaBDEs) are not banned. Pathways by which PBDEs enter the environment and humans are not yet known. Human exposure might come from food, manufacturing, or even from use of consumer product such as furniture.

To help investigators get a handle on the source and degree of PBDE contamination, NIST measured concentrations of selected PBDEs and other brominated flame retardants including hexabormocyclododecane (HBCD) in seven of the agency’s existing Standard Reference Materials (SRMs) that are considered benchmarks for measurements of environmental pollutants.

Concentration values for PBDEs are now available for NIST’s reference materials for house dust (SRM 2585), cod liver oil (SRM 1588b) and human blood serum (SRM 1589a). Newly certified values for PBDE concentrations in four other SRMs for whale blubber, mussel tissue and two types of fish tissue are expected to be available soon.

In collaboration with the Centers for Disease Control and Prevention (CDC), NIST also is developing four new SRMs based on human blood and milk. Two of these SRMs will have certified values for current PBDE concentrations to record the level of current human exposure. PBDEs will be added at higher levels for the other two materials to facilitate comparability of measurements among laboratories.

For further information, see H.M. Stapleton, J.M. Keller, M.M. Schantz, J.R.Kucklick, S.D. Leigh and S.A. Wise. Determination of polybrominated diphenyl ethers (PBDEs) in environmental standard reference materials. Analytical and Bioanalytical Chemistry. 387, 2365 (2007).

While the new calibration service for phasor measurement units (PMUs) offered by the National Institute of Standards and Technology (NIST) sounds like it would appeal to Star Trek fans, it’s actually the operators of America’s electrical power grid—and all of us who value uninterrupted current—who benefit.

The new NIST service provides calibrations for the instruments that measure the magnitude and phase of voltage and current signals in a power system—a combined mathematical entity called a phasor—and report the data in terms of Coordinated Universal Time (UTC, also known as “the official world atomic time”).

Use of absolute time enables measurements called phase angles taken at one location on a power grid to be comparable to others across different systems. Phase angles and their derivations allow grid managers to know the operating condition of their portion of the system and determine if action is needed to prevent a power blackout.

The new NIST calibration service has already yielded two additional benefits. First, a major PMU manufacturer reports that using the calibrations during the manufacture of its instruments has improved their accuracy by a factor of five. Secondly, some PMUs that have been calibrated using the NIST service have revealed incompatibilities in the message format they send out, leading to corrections that have improved interoperability between PMUs across power grids.

This project is partially funded by the U.S. Department of Energy (DoE), and is operated in conjunction with DoE and the North American Synchrophasor Initiative (NASPI). NASPI is a joint government and utility collaboration supporting the North American Electric Reliability Corporation’s efforts to improve the reliability of the nation’s power grids.

For more information on the NIST PMU calibration service, contact Jerry Stenbakken, gerard.stenbakken@nist.gov, (301) 975-2440.

On Aug. 9, the President signed the America COMPETES Act (Public Law Number 110-69), which authorizes funding for the National Institute of Standards and Technology (NIST) for the next three years. Several provisions have immediate consequences for NIST and related Department of Commerce agencies and programs.

The statute authorizes a NIST budget of $863 million for FY 2008. This includes funding for NIST’s portion of the President’s American Competitiveness Initiative, which puts NIST’s core programs (laboratories and facilities) and two other science and technology agencies on track to double their R&D budgets over 10 years. The FY 2007 budget for NIST was $676.9 million.

The act eliminates NIST’s Advanced Technology Program (ATP), but allows for continued support for previous and pending ATP awards. NIST plans to announce awards for the 2007 (and final) ATP competition by Sept. 30, 2007.

The same statute creates the Technology Innovation Program (TIP). NIST will work on details of implementing regulations for this new program.

The act also eliminates the Department of Commerce’s Technology Administration (TA).

The full title of the authorization bill is Public Law Number 110-69, The America Creating Opportunities to Meaningfully Promote Excellence in Technology, Education and Science Act (COMPETES).

Officials from the National Institute of Standards and Technology (NIST) and the University of Maryland Biotechnology Institute (UMBI) signed a Memorandum of Understanding on Aug. 10 designed to expand significantly the scope of joint research and educational activities in the biosciences between the two institutions.

The new MOU updates an existing relationship between NIST’s Chemical Science and Technology Laboratory and the University of Maryland that dates back to 1985, when they joined with Montgomery County, Md., to establish the Center for Advanced Research in Biotechnology (CARB), a joint research venture emphasizing work on the relationship between structure and function in biomolecules and the development of new technologies for the measurement, analysis and design of biomolecules.

“Our relationship with CARB over the past two decades has helped us to focus our significant investment in bioscience,” NIST Director William Jeffrey says, “Bioscience is one of the great frontiers of our time, and we look to this partnership to help us meet the challenges of that frontier.”

“UMBI researchers and our colleagues at NIST have produced many fruitful collaborations,” added UMBI President Jennie Hunter-Cevera. “As a partner with both the biotechnology industry and many federal agencies including NIST, UMBI is a key component in the continued growth of an important industrial sector for our region, nation and the world.”

Under the new agreement, the scope of the long-standing relationship will be broadened to include all four research centers under UMBI and all research laboratories at NIST. The MOU, which provides a general framework for future joint activities, allows for

In addition to CARB in Rockville, Md., the UMBI system includes the Center for Biosystems Research (College Park, Md.), the Center of Marine Biotechnology (Baltimore, Md.) and the Medical Biotechnology Center (Baltimore, Md.). NIST facilities include the NIST Center for Neutron Research, the Advanced Chemical Sciences Laboratory, and the Advanced Measurement Laboratory, in Gaithersburg, Md., and the Hollings Marine Laboratory in Charleston, S.C.

Secretary of Commerce Carlos Gutierrez will host a national meeting of private and public sector officials that will focus on promoting innovation and economic development across the United States. The “National Summit on American Competitiveness” will be held Sept. 18, 2007, in Washington, D.C., at the Ronald Reagan International Trade Center.

The summit will convene the nation’s premier leaders of business, government, academia and the research community to address the core components and lessons of the role of the private sector; education and workforce issues; energy independence; and partnerships in innovation. The agenda includes panel; discussions on “The Competitive Challenge for America in the 21st Century,” “Education & Workforce: Skillsets for the 21st Century,” “Innovation Partnerships: Best Practices,” and “Energy: The Technology Path Forward,” as well as a general townhall discussion.

CNBC’s Maria Bartiromo, White House Office of Science and Technology Policy Director John Marburger, and White House Council on Environmental Quality Chairman James Connaughton will join Gutierrez as moderators.

“America’s Most Wanted” meets Web 2.0 as researchers develop an additional implementation of a data format that allows disparate law enforcement agencies to exchange fingerprints and other biometric information by using XML, or “Extensible Markup Language,” a protocol which allows data to be exchanged easily across different computer platforms and mobile devices. On Sept. 18 and 19, 2007, the National Institute of Standards and Technology (NIST) and the Federal Bureau of Investigation (FBI) will co-sponsor a workshop in Gaithersburg, Md. On the first day, participants will discuss an XML version of the Data Format for the Interchange of Fingerprint, Facial and Other Biometric Information, an existing NIST standard that enables the interchange of fingerprints, palmprints, mugshots, tattoos, irises and other biometric information. The second day will be devoted to developing procedures and approaches for capturing biometric images and other information using mobile identification devices (Mobile ID). Issues associated with improving interoperability, or compatibility, between federal, state, local and international users of fingerprint and other biometric identification systems will be addressed on both days. For more details, go to www.nist.gov/public_affairs/confpage/070918.htm or contact ansi-nist-xml@nist.gov.

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Editor: Michael Baum

Date created: August 16, 2007
Date updated: August 16, 2007
Contact: inquiries@nist.gov