Tech Beat - August 3, 2010

• JILA Frequency Comb System Detects Gas Impurities to Aid Semiconductor Manufacturing
• Beware the Dim Laser Pointer: NIST Researchers Measure High Infrared Power Levels from Some Green Lasers
• NIST Nanofluidic 'Multi-tool' Separates and Sizes Nanoparticles
• New NIST Report Advises: Securing Critical Computer Systems Begins at the Beginning
• NIST Seeks New Members for Nine Advisory Committees
• Commerce Department Seeks Comments on Cybersecurity and Its Impact on Innovation

JILA Frequency Comb System Detects Gas Impurities to Aid Semiconductor Manufacturing

Purity of ingredients is a constant concern for the semiconductor industry, because a mere trace of contaminants can damage or ruin tiny devices. In a step toward solving a long-standing problem in semiconductor manufacturing, scientists at JILA and collaborators have used their unique version of a “fine-toothed comb” to detect minute traces of contaminant molecules in the arsine gas used to make a variety of photonics devices.

A NIST invention may help purify a process for making semiconductors used in devices such as light-emitting diodes (LEDs). ©Igor Stepovik/courtesy Shutterstock

JILA is a joint institute of the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder (CU). The research was conducted with collaborators from NIST’s Boulder campus and Matheson Tri-Gas (Longmont, Colo.).

The research, described in a new paper,* used a NIST/CU invention called cavity-enhanced direct frequency comb spectroscopy (CE-DFCS).** It consists of an optical frequency comb—a tool for accurately generating different colors, or frequencies, of light—adapted to analyze the quantity, structure and dynamics of various atoms and molecules simultaneously. The technique offers a unique combination of speed, sensitivity, specificity and broad frequency coverage.

The semiconductor industry has long struggled to find traces of water and other impurities in arsine gas used in manufacturing of III-V semiconductors for light-emitting diodes (LEDs), solar-energy cells and laser diodes for DVD players. The contaminants can alter a semiconductor’s electrical and optical properties. For instance, water vapor can add oxygen to the material, reducing device brightness and reliability. Traces of water are hard to identify in arsine, which absorbs light in a complex, congested pattern across a broad frequency range. Most analytical techniques have significant drawbacks, such as large and complex equipment or a narrow frequency range.

The JILA comb system, previously demonstrated as a “breathalyzer” for detecting disease***, was upgraded recently to access longer wavelengths of light, where water strongly absorbs and arsine does not, to better identify the water. The new paper describes the first demonstration of the comb system in an industrial application.

In the JILA experiments, arsine gas was placed in an optical cavity where it was “combed” by light pulses. The atoms and molecules inside the cavity absorbed some light energy at frequencies where they switch energy levels, vibrate or rotate. The comb’s “teeth” were used to precisely measure the intensity of different shades of infrared light before and after the interactions. By detecting which colors were absorbed and in what amounts—matched against a catalog of known absorption signatures for different atoms and molecules—the researchers could measure water concentration to very low levels.

Just 10 water molecules per billion molecules of arsine can cause semiconductor defects. The researchers detected water at levels of 7 molecules per billion in nitrogen gas, and at 31 molecules per billion in arsine. The researchers are now working on extending the comb system even further into the infrared and aiming for parts-per-trillion sensitivity.

The research was funded by the Air Force Office of Scientific Research, Defense Advanced Research Projects Agency, Defense Threat Reduction Agency, Agilent Technologies, and NIST.

Media Contact: Laura Ost, laura.ost@nist.gov, 303-497-4880

  Comment on this article.back to top

Beware the Dim Laser Pointer: NIST Researchers Measure High Infrared Power Levels from Some Green Lasers

Green laser pointers have become a popular consumer item, delivering light that’s brighter to the eye than red lasers, but stories have circulated on the Web about the potential hazards of inexpensive models. Now, a team led by physicist Charles Clark at the National Institute of Standards and Technology (NIST) puts some numbers to the problem. In one case, the group found that a green laser pointer emitted almost twice its rated power level of light—but at invisible and potentially dangerous infrared wavelengths rather than green. A new NIST technical note* describes the nature of the problem as well as a home test using an inexpensive webcam that can detect excess infrared light from green lasers.

IR leakage: (Top) Photo from an ordinary camera shows light from a green laser diffracted into several spots. The green laser pointer is visible in the foreground. (Bottom) The same vignette photographed by a webcam with no infrared-blocking filter reveals intense diffraction spots from 808nm infrared light, invisible to the eye. View hi-resolution image Credit: NIST

Late last year, the research team purchased three low-cost green laser pointers advertised to have a power output of 10 milliwatts (mW). Measurements showed that one unit emitted dim green light but delivered infrared levels of nearly 20 mW—powerful enough to cause retinal damage to an individual before he or she is aware of the invisible light. NIST’s Jemellie Galang and her colleagues repeated the tests with several other laser pointers and found similarly intense infrared emissions in some but not all units.

The problem stems from inadequate procedures in manufacturing quality assurance, according to the research team. Inside a green laser pointer, infrared light from a semiconductor diode laser pumps infrared light at a wavelength of 808 nm into a transparent crystal of yttrium orthovanadate doped with neodymium atoms (Nd:YVO4), causing the crystal to lase even deeper in the infrared, at 1064 nm. This light passes through a crystal of potassium titanyl phosphate (KTP), which emits light of half the wavelength: 532 nm, the familiar color of the green laser pointer.

However, if the KTP crystal is misaligned, little of the 1064 nm light is converted into green light, and most of it comes out as infrared. Excess infrared leakage can also occur if the coatings at both ends of the crystal that act as mirrors for the infrared laser light are too thin.

The NIST team says this problem could be solved by incorporating an inexpensive infrared filter at the end of the laser, which could reduce infrared emissions by 100-1000 times depending on quality and cost. Although these filters exist in modern digital cameras and more expensive green laser pointers, they often are left out of the inexpensive models.

The team demonstrates a home test that laser hobbyists could conduct to detect excessive infrared leakage, by using a common digital or cell phone camera, a compact disc, a webcam and a TV remote control. Regardless, they say owners of the devices should never point the lasers at the eyes or aim them at surfaces such as windows, which can reflect infrared light back to the user—a particularly subtle hazard because many modern energy-saving windows have coatings designed specifically to reflect infrared.

The researchers are all members of the Joint Quantum Institute, a collaboration of NIST and the University of Maryland. Co-author Edward W. Hagley is also at Acadia Optronics in Rockville, MD.

Media Contact: Ben Stein, ben.stein@nist.gov, 301-975-3097

  Comment on this article.back to top

NIST Nanofluidic 'Multi-tool' Separates and Sizes Nanoparticles

A wrench or a screwdriver of a single size is useful for some jobs, but for a more complicated project, you need a set of tools of different sizes. Following this guiding principle, researchers at the National Institute of Standards and Technology (NIST) have engineered a nanoscale fluidic device that functions as a miniature “multi-tool” for working with nanoparticles—objects whose dimensions are measured in nanometers, or billionths of a meter.

A 3D nanofluidic "staircase" channel with many depths was used to separate and measure a mixture of different-sized fluorescent nanoparticles. Larger (brighter) and smaller (dimmer) particles were forced toward the shallow side of the channel (fluorescence micrograph on left). The particles stopped at the "steps" of the staircase with depths that matched their sizes. View hi-resolution image Credit: S.M. Stavis, NIST

First introduced in March 2009 (see “NIST-Cornell Team Builds World’s First Nanofluidic Device with Complex 3-D Surfaces”, the device consists of a chamber with a cascading “staircase” of 30 nanofluidic channels ranging in depth from about 80 nanometers at the top to about 620 nanometers (slightly smaller than an average bacterium) at the bottom. Each of the many “steps” of the staircase provides another “tool” of a different size to manipulate nanoparticles in a method that is similar to how a coin sorter separates nickels, dimes and quarters.

In a new article in the journal Lab on a Chip*, the NIST research team demonstrates that the device can successfully perform the first of a planned suite of nanoscale tasks—separating and measuring a mixture of spherical nanoparticles of different sizes (ranging from about 80 to 250 nanometers in diameter) dispersed in a solution. The researchers used electrophoresis—the method of moving charged particles through a solution by forcing them forward with an applied electric field—to drive the nanoparticles from the deep end of the chamber across the device into the progressively shallower channels. The nanoparticles were labeled with fluorescent dye so that their movements could be tracked with a microscope.

As expected, the larger particles stopped when they reached the steps of the staircase with depths that matched their diameters of around 220 nanometers. The smaller particles moved on until they, too, were restricted from moving into shallower channels at depths of around 110 nanometers. Because the particles were visible as fluorescent points of light, the position in the chamber where each individual particle was stopped could be mapped to the corresponding channel depth. This allowed the researchers to measure the distribution of nanoparticle sizes and validate the usefulness of the device as both a separation tool and reference material. Integrated into a microchip, the device could enable the sorting of complex nanoparticle mixtures, without observation, for subsequent application. This approach could prove to be faster and more economical than conventional methods of nanoparticle sample preparation and characterization.

The NIST team plans to engineer nanofluidic devices optimized for different nanoparticle sorting applications. These devices could be fabricated with tailored resolution (by increasing or decreasing the step size of the channels), over a particular range of particle sizes (by increasing or decreasing the maximum and minimum channel depths), and for select materials (by conforming the surface chemistry of the channels to optimize interaction with a specific substance). The researchers are also interested in determining if their technique could be used to separate mixtures of nanoparticles with similar sizes but different shapes—for example, mixtures of tubes and spheres.

Media Contact: Michael E. Newman, michael.newman@nist.gov, 301-975-3025

  Comment on this article.back to top

New NIST Report Advises: Securing Critical Computer Systems Begins at the Beginning

Nothing beats the feeling of starting up a new computer – be it a laptop, desktop or a major, custom-designed computing system. A new system is a blank slate with no worry of botnets, viruses or any other cybersecurity hazards.

©Romanchuck Dimitry/courtesy Shutterstock

Not so, explains computer researcher Marianne Swanson at the National Institute of Standards and Technology (NIST), lead author of a draft report, Piloting Supply Chain Risk Management for Federal Information Systems. Information systems and components are under attack throughout the supply chain from the design phase—including specification and acquisition of custom products—through disposal. "Computer systems are under attack before installation by adversaries enabled by growing technological sophistication and facilitated by the rapid globalization of our information system infrastructure, suppliers and adversaries," Swanson says.

NIST has released a public draft of the new report for comment.

The supply chain report is geared to information systems that are categorized as "high-impact level," systems for which the loss of confidentiality, integrity or availability could be expected to have a "severe or catastrophic adverse effect on organizational operations, organizational assets or individuals."* The report provides an array of practices designed to help mitigate supply chain risk throughout the life cycle, not just on accepting systems and products "as they are" and managing risks after delivery. The practices are based on security procedures found in NIST special publications, and those from the National Defense University and the National Defense Industry Association, and these are expanded to include implementations specific to mitigating supply chain risk.

Typical examples of good practices recommended in the report include integrating information security and supply chain requirements from inception of the project, protecting the supply chain environment, hardening the supply chain delivering mechanisms and configuring the product to limit access and exposure.

Other recommendations:

• Ensure your information system security, acquisition personnel, legal counsel, and other appropriate advisors and stakeholders are participating in decision making from system concept definition through review and are involved or approving each milestone decision.
• Ensure the proper funding is allocated for information system security and supply chain risk management
• Follow consistent, well-documented processes for system engineering and acquisition
• Provide oversight of suppliers
• Audit the development process
• Perform quality assurance and control of security features
• Assign roles and responsibilities and follow them
• Fully implement the tailored set of baseline security controls in NIST Special Publication 800-53** appropriate to the system's impact level.

The supply chain security report is intended for information system owners, acquisition staff, information security personnel and systems engineers.

NIST is requesting comments on the draft document to be sent to scrm-nist@nist.gov by August 15.

The Comprehensive National Cybersecurity Initiative 11, "Develop Multi-Pronged Approach for Global Supply Chain Risk Management," currently is pilot testing many of the practices. To get a more thorough sample, the writers of this draft report are asking readers to consider testing a few of the practices and to provide comments and lessons learned to the same e-mail address by Dec. 30, 2010.

Media Contact: Evelyn Brown, evelyn.brown@nist.gov, 301-975-5661

  Comment on this article.back to top

NIST Seeks New Members for Nine Advisory Committees

The National Institute of Standards and Technology (NIST) is requesting nominations of qualified individuals for its nine existing Federal Advisory Committees. Nominations for all committees will be accepted on an ongoing basis and will be considered as and when vacancies arise. A July 27, 2010, Federal Register notice* details each committee, including the number of members serving on the committee, its objectives and duties, the nomination procedure and committee contacts.

New to the list of NIST advisory committees this year is the NIST Smart Grid Advisory Committee. The Energy Independence and Security Act (EISA) of 2007 charges NIST with primary responsibility to coordinate development of technical protocols and standards necessary for interoperability of smart grid devices and systems. This advisory committee provides guidance to the NIST Director on the overall direction, status and health of the Smart Grid implementation and identifies issues and needs.  Input from the committee will be used to help guide Smart Grid Interoperability Panel activities and assist NIST in directing research and standards activities.

The other NIST advisory committees described in the Federal Register notice are: the Board of Overseers of the Malcolm Baldrige National Quality Award, the Judges Panel of the Malcolm Baldrige National Quality Award, the Information Security and Privacy Advisory Board, the Manufacturing Extension Partnership Advisory Board, the National Construction Safety Team Advisory Board, the Advisory Committee on Earthquake Hazards Reduction, the Technology Innovation Program Advisory Board, and the Visiting Committee on Advanced Technology.

Media Contact: Michael E. Newman, michael.newman@nist.gov, 301-975-3025

  Comment on this article.back to top

Commerce Department Seeks Comments on Cybersecurity and Its Impact on Innovation

Media Contact: Evelyn Brown, evelyn.brown@nist.gov, 301-975-5661

  Comment on this article.back to top