NIST Tech Beat - November 21, 2003

A super-cold collection of molecules behaving in perfect unison has been created for the first time from a sea of “fermion” atoms by researchers at JILA, a joint institute of the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder (CU-Boulder).

Fermions are a class of particles that are inherently difficult to coax into a uniform quantum state. The ability to meld fermions into this state—a soup of particles that acts like one giant, super molecule—may lead to better understanding of superconductivity, in which electricity flows through certain metals with no resistance.

The work was described in a paper posted Nov. 7 on the informal physics archival Web site at http://arxiv.org and will be published online by the journal Nature on Nov. 26. Researchers Deborah S. Jin of NIST and Markus Greiner and Cindy A. Regal of CU-Boulder reported that they created a Bose-Einstein condensate (BEC) of weakly bound molecules starting with a gas of fermionic potassium atoms cooled to 150 nanoKelvin above absolute zero (about minus 273 degrees Celsius or minus 459 degrees Fahrenheit).

Jin describes her team’s work as the “first molecular condensate” and says it is closely related to “fermionic superfluidity,” a hotly sought after state in gases that is analogous to superconductivity in metals. “Fermionic superfluidity is superconductivity in another form,” says Jin. Quantum physicists are in a worldwide race to produce fermionic superfluidity because gases would be much easier to study than solid superconductors and such work could lead to more useful superconducting materials.

X-ray Inspection May Meet Computer Chip-Making Need

A decades-old, X-ray-based method for studying the atomic structure of materials may be the answer to a looming semiconductor industry need—a rugged, high-throughput technology for measuring dimensions of chip circuitry packed with devices approaching molecular proportions.

A team led by National Institute of Standards and Technology (NIST) scientists recently reported* their initial success in adapting small-angle X-ray scattering (SAXS) to rapidly characterize the size and shape of grid-like patterns with nanometer-scale linewidths. With better than one nanometer (billionth of a meter) precision, the team determined the average size of periodically repeating features arrayed on three chemically different samples much like the intricately patterned polymer masks used to print integrated-circuit designs.

With the size of on-chip devices soon to shrink to below 100 nanometers, current dimensional measurement tools are approaching their limits. The versatile SAXS method, the team suggests, could be an able substitute. It can be used on a wide range of materials to evaluate the quality of surface and subsurface patterns consisting of features considerably smaller than 100 nanometers.

In proof-of-concept experiments supported by the Defense Advanced Research Projects Agency, NIST, and the U.S. Department of Energy, essential data were gathered, within a second, over an area about 40 micrometers on a side—a large swath, nanotechnologically speaking. Images assembled from X-rays deflected by electrons in the samples yielded high-precision measurements of linewidths, spaces, line-edge roughness, and feature geometry.

Implementing the SAXS method actually should become easier as feature sizes decrease and near molecular dimensions, explains NIST’s Ronald Jones.

In addition to NIST polymer scientists, the team included researchers from ExxonMobil Research Co., Argonne National Laboratory’s Advanced Photon Source, and the Shipley Co. For more details, see www.nist.gov/public_affairs/newsfromnist_says.htm.

*Ronald L. Jones, Tengijao Hu, Eric K. Lin, Wen-Li Wu, Rainer Kolb, Diego M. Casa, Patrick J. Bolton, and George G. Barclay, “Small angle X-ray scattering for sub-100 nm pattern characterization,” Applied Physics Letters, Vol. 83, Issue 19, pp. 4059-4061.

Radio Waves Help See Moisture Inside Walls

The building community soon may have radio vision—a new way to “see” moisture inside walls. Building researchers at the National Institute of Standards and Technology (NIST) have joined forces with Intelligent Automation Inc. in Rockville, Md., to develop a way to use ultra wide-band radio waves to non-destructively detect moisture within the walls of a building. As any homeowner who’s suffered with leaky plumbing or mold problems will tell you, the current state of the art for pinpointing moisture problem areas relies mostly on guesswork and a drywall saw.

Based on hardware developed by Intelligent Automation, the new NIST technique involves sending a broad range of radio frequencies through typical drywall construction to look for a “moisture” signature in the signal that is reflected back. Laboratory experiments conducted with a simplified wall section made of gypsum board, fiberglass insulation, and oriented strand board (similar to plywood), demonstrated that the new method can locate moisture pockets to within one centimeter.

The presence of water within the model wall produced a stronger reflection of radio waves at specific frequencies. The elapsed time between transmission of the waves and their arrival at a receiving antenna helps determine the location of the water. By processing the reflected signals with computer software, the researchers can create detailed three-dimensional maps that highlight wet areas.

Research is continuing to see how well the apparatus performs with real walls that include studs, wires, pipes and windows that may complicate the readings. A paper describing the research has been accepted for publication in an upcoming issue of ASHRAE Transactions.

Prospects Brighten for Future Superconductor Power Cables

New research from the National Institute of Standards and Technology (NIST) suggests that next-generation, high-temperature superconductor (HTS) wire can withstand more mechanical strain than originally thought. As a result, superconductor power cables employing this future wire may be used for transmission grid applications. Projected to become available in three to four years, the advanced superconductor wire (known in the industry as second generation HTS wire) is expected to cost less than the HTS wire used in today’s superconductor power cables. The NIST research is described in the Nov. 17 issue of Applied Physics Letters.

Superconductor power cables can carry three to five times the power of conventional copper cables. Compact, underground superconductor cables can be used to expand capacity and direct power flows at strategic points on the electric power grid and can be used in city centers where there is enormous demand, but little space under the streets for additional copper cables. One important challenge in using this next-generation HTS wire in such applications is the need for sufficient strength and resiliency to withstand the stretching and bending that occurs during power cable fabrication and installation.

Using superconductor ceramic coatings on metallic substrates fabricated by American Superconductor Corp. and Oak Ridge National Laboratory, the NIST researchers tested the material’s electromechanical properties. According to lead author Najib Cheggour, they found that these advanced wires could stretch almost twice as much as previously believed without any cracking of the superconductor coating and with almost no loss in the coating’s ability to carry electricity.

Moreover, the NIST team found that strain-induced degradation of the superconductors’ ability to carry electricity is reversible up to a certain critical strain value. That is, the materials return to their original condition once the strain is relieved. The strain tolerance of this future HTS wire was found to be high enough for even the most demanding electric utility applications. The discovered reversible strain effect also opens new opportunities for better understanding of the mechanisms governing the conduction of electricity in this class of superconductors.

Interactive CD-ROM Provides Mass Metrology Training

Accurate weights and measures are critical for commerce in everything from animal feed to gasoline. The National Institute of Standards and Technology (NIST) trains many state and industry laboratory metrologists who verify the accuracy of standards used to test the measuring equipment used in commercial transactions. To alleviate a training backlog of officials from government and industrial mass calibration laboratories, NIST has just released an electronic mass measurement training course.

Three years in the making, the free multimedia CD-ROM covers NIST’s basic one-week mass metrology courses. It includes interactive activities, knowledge quizzes, examples, video demonstrations, and specialty graphics and photos for specific products. The CD-ROM is designed to introduce mass metrology to newcomers to the field; offer supplementary training for those who have recently attended a metrology course and want to review their knowledge before entering the laboratory environment; and act as a refresher for long-time laboratory staff unfamiliar with the latest measuring techniques.

The Basic Mass Metrology CD-ROM (NIST Special Publication 1001) is available from NIST at (301) 975-4004 or by e-mail at owm@nist.gov. A Spanish version of the CD-ROM is under development.

Measuring RNA—Quantitative measurements of RNA for gene expression assays give information about what genes are “turned on,” or being expressed, in a cell. What genes are being expressed, and when, gives key information about what proteins are being made and leads to conclusions about the biological function. NIST is hosting a workshop on Dec. 2 to invite comments and discussion on a new specification for materials used to validate measurements of RNA.

Researchers Create Bose-Einstein 'Super Molecule'

X-ray Inspection May Meet Computer Chip-Making Need

Radio Waves Help See Moisture Inside Walls

Prospects Brighten for Future Superconductor Power Cables

Interactive CD-ROM Provides Mass Metrology Training