Thursday, December 28, 2006

"MEMS: Yesterday to tomorrow at Analog Devices"

Today, startup companies are touting microelectromechanical systems (MEMS) as a new growth area, but Analog Devices claims it has been pioneering MEMS chips since 1989. Since then, ADI has shipped hundreds of millions of accelerometers for automobile applications, and just this year broke into consumer electronics by shipping more than one million three-axis accelerometers for Nintendo's Wii video-game controller. The company's MEMS chips will also eventually take on applications as varied as microphones; acoustics; medical diagnostics; drug delivery; RF-switches, -resonators, "oscillators, and "filters. Hear ADI tell all in this question-and-answer session.

"MEMS: chips accelerate for drive to market"

Akustica Inc. (Pittsburgh)--the world's only digital MEMS microphone maker--put a second notch on its belt recently when it announced that Fujitsu Computer Systems Corp. will use its MEMS mics in an entry-level model of the LifeBook tablet PC line. The LifeBook has two AKU2000 CMOS MEMS microphone chips in its display bezel--one for horizontal operation and one for vertical. Meanwhile, quartz crystal makers are scrambling to keep up with the MEMS trend, with several manufacturers hedging their bets by jointly developing MEMS oscillators with startups like SiTime Corp.'s deal with Micro Crystal and Ecliptek. Discera has also been busy of late signing up quartz crystal maker Vectron as well as new distributors for its MEMS oscillators.

Thursday, December 21, 2006

"OPTICAL: IBM claims photonics speed record"

Silicon photonics could someday replace $10,000 optical-to-electrical-to-optical converters with $1 CMOS chips and enable on-chip data communications with photons, not the electrons used today. But the road to silicon photonics is fraught with peril. Doomsayers originally insisted that silicon's indirect bandgap forever favored direct bandgap materials like indium-gallium-arsenide (InGaAs), but history proved those compounds were too difficult to integrate. Now, researchers at IBM's Thomas J. Watson Research Center say they've clinched the case for silicon photonics by announcing new world's records for silicon photonics speed, density and bandwidth. IBM said its demonstration chip, a CMOS optical delay line, proves that silicon photonics will ultimately achieve the "holy grail" — optics on chips at integration levels rivaling those of electronic CMOS integration.

Monday, December 18, 2006

"MEMS: Best-practice definition varies by vendor"

To hear vendors tell it, the only right way to do microelectromechanical systems is "my way." So, what method of fabricating MEMS is really best? Which is preferable: MEMS-first or MEMS-last? Are proprietary processes best, or should MEMS methods be able to run on any foundry line? Are different approaches better for different applications? All vendors agree that the holy grail is seamless integration of MEMS structures onto the same CMOS chips as the circuitry to which they interface. But only one MEMS startup claims to be there already, though that vendor adds a step to the standard CMOS fabrication process.

"MEMS: Quartz, MEMS will meet"

A new entrant in the emerging timing-chip market plans to create the world's first hybrid timing chips that include both quartz crystals and MEMS components. Silicon Clocks Inc. is sampling its first timing chip, which is slated for mass production in 2007. The quartz crystal-based device will offer frequencies as high as 650 MHz, whereas existing quartz crystals peter out around 150 MHz. The chip has a unique architecture for which several patents have been filed, said company founder Andrew McCraith. In the future, the architecture will be extended to MEMS-based oscillators, he said, the first models of which will integrate multiple resonators on the same chip.

Monday, December 11, 2006

"CHIPS: Polymer slims wafer-level chip-scale packages"

Tessera Technologies Inc. (San Jose, Calif.) announced today (Dec. 11) what it says is one of the slimmest surface-mountable wafer-level chip-scale packages (WLCSPs) available for camera modules, microelectromechanical systems (MEMS) and optical detectors. The Shellcase Razor Thin (RT) package uses a thin polymer on one side, instead of the previous two-sided, glass sandwich, to decrease the package profile to 0.5 millimeter from the 0.9 mm of the previous Shellcase package. The RT version also sheds heat more easily than its predecessor, is insensitive to moisture and is more rugged overall, making it suitable for automotive, aerospace and military applications as well as consumer electronics, according to Tessera.

"CHIPS: Embedded superlattice slashes gate leakage"

CMOS devices isolate transistor gates from their channels with supposedly impenetrable oxides. But as chips scale below the 65-nanometer node, those oxides become so thin that applying enough voltage to turn on a transistor also enables a percentage of the electrons charging the gate to tunnel through the oxide into the channel. Mears Technologies addresses the leakage problem by adding an embedded superlattice during the construction of a transistor's channel to enhance current flow in the plane of the channel, while simultaneously blocking current flow perpendicular to the channel, thereby mitigating gate leakage. It claims its sili- con-on-silicon superlattice can reduce gate leakage by 70 to 90 percent, while increasing current drive in the channel.

"CHIPS: Doping ups OLED efficiency"

Organic LEDs promise to enable "spray on" displays covering entire walls and conforming to almost any form factor. But OLEDs' lower efficiency makes them dimmer and lower in contrast than conventional, inorganic LEDs. Now a chemist and an EE at the Massachusetts Institute of Technology claim to have hit upon a solution that increases OLED efficiency to 85 percent from 25 percent.

Monday, December 04, 2006

"CHIPS: Chip closes distance to real-time 3-D images"

The problem with machine vision is that the cameras are two-dimensional recorders of three-dimensional scenes. Objects in an image may be obscured by lighting, occluded by obstacles or camouflaged by similar colors in the background. Sophisticated software can sometimes piece together ob- jects from subtle cues, such as when two camera positions are used to reveal parallax. But such algorithms take time to run, making them inappropriate for real-time applications, like automobile collision avoidance. Now one company claims to have solved the problem with a real-time 3-D camera that uses pixel-level hardware to reveal the distance to any object in any scene, regardless of lighting, occlusion or blending. By integrating 3-D hardware into its SunShield CMOS 3-D time-of-flight imaging sensors, Canesta Inc. (Sunnyvale, Calif.) says it enables machine vision cameras that perceive objects, rather than just sense images, in a scene.

"CHIPS: Rival machine vision approaches take to the road"

Two companies are developing rival automotive machine vision solutions using inexpensive digital cameras. But while International Electronics & Engineering S.A. (IEE) has crafted a sensing system based on a combination of 2-D and 3-D cameras, Mobileye Inc. has opted to use a normal 2-D camera.

Friday, December 01, 2006

"CHIPS: CMOS image sensors aim for true machine vision"

Now that automobiles are beeping to alert you of obstacles while backing up, giving you directions on where to turn, and parallel-parking "hands free," you might have thought that machine vision had already been perfected. Such is not the case. In fact, all of the above applications are using make-shift technologies that substitute for true machine vision. New CMOS imager chips are emerging that directly sense depth—3D pixel-by-pixel—enabling machine vision to realize its goal of perceiving objects, and reacting appropriately. The automotive sensor market already tops $2.5 billion, according to ABI Research (Oyster Bay, N.Y.). Another $750 million is divided among security, industrial automation and videogaming uses of electronic sensors, according to Frost & Sullivan, the Automated Imaging Association and Piper Jaffray, respectively.

Thursday, November 30, 2006

"ALGORITHMS: Strontium scheme enters atomic clock race"

A candidate to be the next-generation atomic clock is based on the heavy metal strontium and uses a laser lattice to suspend super-cooled atoms. The result was a 430-THz time base—40,000 times faster than the current 9.19-GHz cesium-based atomic clocks. The strontium-based clock was demonstrated recently by the Commerce Department's National Institute of Standards and Technology (NIST) with help from the University of Colorado at Boulder and JILA (formerly the Joint Institute for Laboratory Astrophysics).
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Monday, November 27, 2006

"MEMS: Microfluidics is beginning to clear the lab"

While microfluidic devices that enable such popular applications as laboratories-on-a-chip are still mostly in the research stage, some companies are making strides toward commercial-grade applications. Microfluidics enables chips to pipe fluids around their surfaces in micron-sized channels, either to perform a test hitherto only possible in a lab, or just to remove heat and cool a chip. The premiere application--labs-on-a-chip--enables battery-powered sensor-based devices to quickly detect trace amounts of almost any substance. What are the blocks to volume production today? That depends on whom you ask, but three reasons loom large--a lack of chip-sized microfluidic pumps; a mismatch between micro-sized fluidic channels and the rest of a lab's equipment; and a lack of standards for interoperability among labs-on-a-chip from rival manufacturers. The first problem--a lack of chip-sized microfluidic pumps--was addressed recently by two new architectures for micropumps (see page 34). One from the University of Utah uses a "squeeze bottle" approach that houses the micropumps in a disposable polymer test card. The other from the Massachusetts Institute of Technology (Cambridge, Mass.) uses a novel photolithographic technique to gain electronic control over micropumping.

"MEMS: Battery-powered lab-on-chip may be near"

For a soldier in the field, a slight hand tremor, tic of the eye, sudden sore throat or whiff of a noxious odor could urgently put his battery-powered portable lab to work. Such microfluidic labs-on-a-chip could let soldiers test their own blood for exposure to many toxins simultaneously and in a matter of minutes. At least, that was the goal of a professor at the Massachusetts Institute of Technology when he landed a U.S. Army contract to pursue work on the tiny tool. Although commercially available "gene chips" can test blood for thousands of toxins simultaneously, it takes hours to diffuse a blood sample across the whole array and then scan for fluorescence. Laboratory high-voltage power supplies could speed the operation with the pumping action of an electric field, but a battery-powered device could not supply that much juice. Enter an MIT mathematician with friends in the engineering school and funding from the Army's Institute for Soldier Nanotechnologies has solved the problem with a low-voltage micropump. A new company, ICEO Technologies Inc., will commercialize the micropump technology.

"MEMS: Disposable biochip uses plastic"

Laboratories-on-a-chip pack the punch of an overnight testing facility, but get results in minutes by virtue of nanoliter-size chambers that speed up chemical reactions. Of the dozens of kinds of micropumps that can be used to fill those chambers, only a few avoid contaminating the nanoliter-size samples. Recently the University of Utah showed a design that avoids contamination via the use of vacuum-driven, plastic layered membranes. The beauty of the University of Utah design is that a tester the size of a deck of cards could contain hundreds or thousands of independent chambers, each prefilled with the reagents for an array of tests. Then, all the chambers could be supplied with the sample to be tested simultaneously, using nothing more that a battery-powered air pump. A reader no bigger than a deck of cards would accept blank, credit-card-size test cards. Its chambers would be filled with a sample from the patient, and the results of the test would be read out in minutes. After testing, the disposable card would be thrown away. Currently, patients have to wait overnight for a traditional medical lab to do the evening's batch run.

Wednesday, November 22, 2006

"ENERGY: Technology cutting final land-line links"

What with the Bluetooth headset crowd wandering the streets talking to the air, you might have thought the final tether to land lines had already been cut. You would be wrong. At least two vital functions have yet to be loosed: network routers, which must always be on and thus cannot be battery-powered, and the chargers for all those batteries powering the world's wireless network nodes, cell phones and laptops. Now developers and researchers are getting out the wire cutters. With half a dozen companies already touting battery-powered mesh networks as replacements for dedicated, wired routers in industrial and field environments, observers predict the technology will work its way into the mainstream. And researchers at the Massachusetts Institute of Technology are perfecting a technology that they say could recharge batteries wirelessly--and perhaps eliminate batteries altogether--by harnessing omnidirectional wireless power beacons

Monday, November 20, 2006

"CHIPS: 'Mote-on-chip' rolls for sensor nets"

Dust Networks Inc. (Hayward, Calif.) last week unveiled the world's first system-on-chip (SoC) for wireless sensor networks at Electronica in Munich, Germany. By integrating hardware and software functions to put distributed sensor networks on a single chip--called mote-on-chip--Dust Networks claims 5x lower power consumption than ZigBee, the elimination of the need for wired routers and a tenfold reduction in the overall price of adding new sensors to an existing network. Wireless sensor networks enable industrial users with distributed process control problems to quickly deploy new sensors without having to run cables to them, reducing their overall cost from thousands to hundreds of dollars. Emerson Process Management has launched a family of low-power wireless sensor networking systems that use Dust Networks' Time Synchronized Mesh Protocol (TSMP), including temperature sensors, pressure sensors, fluid-level sensors and fluid-flow sensors. British Petroleum (BP), Emerson's beta tester, now says that going wireless has reduced the cost of adding new sensors by 10x.

"ENERGY: Team claims midrange wireless energy transfer"

The hurdles to wireless power transfer through space have been perceived to be so great that the last serious work on the topic, reported in the 1920s, was inspired by Nikola Tesla's seminal demonstrations circa 1890. But now an MIT physicist claims the obstacles to wireless power transfer are surmountable, at least for distances under 12 feet. Nonradiative resonant energy transfer harnesses omnidirectional energy beacons without wasting energy, without requiring a clear line of sight and without damaging obstacles in the process. Power from such energy beacons would pass harmlessly through everything but their intended targets, by virtue of resonant power antennas that would be tuned to the power beacon's frequency in a lock-and-key approach.

Tuesday, November 14, 2006

"ENERGY: MIT claims advance in wireless power transfer"

Researchers are claiming that the obstacles to wireless power transfer can be overcome—at least at distances up to 12 feet. The Massachusetts Institute of Technology announced the development of wireless power beacons on Tuesday (Nov. 14) at the American Institute of Physics' Industrial Physics Forum in San Francisco. MIT claims that historical obstacles to wireless power transfer through space are surmountable, and perhaps enable the wireless recharging of batteries. Called "nonradiative resonant energy transfer," the technique harnesses omnidirectional energy beacons without the requirement for unobstructed line-of-sight. The technique wastes no energy and is eco-friendly, MIT claimed. In MIT's scheme, power from energy beacons would pass through everything but their intended targets by virtue of resonant power antennas tuned to the power beacon's frequency, ensuring that little energy is lost or would adversely affect the environment.

"MEMS: Discera, Vectron team for MEMS resonators"

Microelectromechanical system (MEMS) startup Discera Inc. said it is teaming with quartz crystal oscillator maker Vectron International Inc. to develop MEMS oscillators. Discera (San Jose, Calif.) said it will supply the MEMS resonator while Vectron (Hudson, N.H.) adds an ASIC containing a phase-locked loop (PLL) and conditioning circuitry. The result, the partners said at the Electronica exhibition this week in Munich, Germany, is the first MEMS oscillator from a quartz crystal oscillator maker.

Monday, November 13, 2006

"OPTICAL: Chips fill optical fiber cores"

Converting from optical to electrical signals, then back to optical, is the bane of modern networks, often requiring a $10,000 optical-to-electronic converter just to perform some simple signal processing, then another $10,000 electronic-to-optical converter to put the signal back on the fiber-optic cable. Now researchers have invented a method that merges electronics with optics by inserting semiconductor devices inside a hollow optical fiber, potentially integrating the electronic signal-processing functions into the cable carrying the signal. The technique coats the inside of the hollow cores of fiber-optic cables with semiconductors at a rate of tens of nanometers per minute. At the end of the process, the hollow cores--which may measure 100 nm to 5 microns in diameter--close down to as small as 10 nm. So far the researchers have successfully fabricated silicon germanium heterojunctions inside a fiber, demonstrated that the fiber still behaves as a waveguide, then implemented a field-effect transistor (FET) that could modulate the signal passing though the core.

Monday, November 06, 2006

"CHIPS: Spintronics approach advances toward live chips"

A research group at the State University of New York at Buffalo has announced a promising technique in spintronics that might be used in standard silicon chips in the near future. Spintronics combines today's charge-based data storage and communication with magnetic-based information using spin as the common coin. The experimental group has managed to inject electrons with spin into silicon chips by virtue of a ferromagnetic semiconductor junction with silicon. Spintronics marries electronics to magnetism by encoding electronic data with magnetic spin. Theorists recommend using techniques that have already been proved with gallium arsenide semiconductors to inject electrons with spin into silicon circuits. Their cookbook proposes techniques for spin injection and detection in silicon with colleagues at the U.S. Naval Research Laboratory. The researchers predict that the most promising technique, called the spin-voltaic effect, will bring spintronics to standard silicon chips within a year. They have already cast his spin-voltaic effect into experimental gallium arsenide chips and plan to have silicon devices working by 2007.

"ENERGY: Purified protein enables biofuel cell sans bacteria"

In experiments, biofuel cells have harnessed membranes of living bacteria to separate anode from cathode--enabling them to share an electrolyte chamber like a lead-acid battery. Now, researchers at the Pacific Northwest National Laboratory have purified the essential protein performing a fuel-cell membrane's electronic function, clearing the way to commercialize biofuel cells sans bacteria. The team purified the bacterium down to the essential protein in the cell wall--eliminating the need to keep the bacterium alive. The only missing element was a fuel source, which biomass could supply, lab scientists reasoned. Now they propose biofuel cell arrays to harvest biomass in tiny reactors. The reaction creates a mobile electron carrier that shuttles electrons to the protein-coated electrodes, generating electricity as it neutralizes the biomass. The proposed biofuel cells would use a cheap porous hematite electrode in which the bacteria's purified protein could be bound. The coated electrodes would catalyze the reaction, enabling electricity to flow from the anode to the cathode using nothing more than the biological agents in the biomass as fuel.

Monday, October 30, 2006

"QUANTUM: NIST demos quantum atom entanglement"

The National Institute of Standards and Technology (NIST) has demonstrated error-free quantum communication by pairs of entangled atoms, promising secure quantum computers. Entanglement is a quantum phenomenon in which two particles take on identical internal states in close proximity. If conditions are right, the synchronization persists even after the particles become separated, enabling the quantum information processed by one member of the pair to be simultaneously processed by the other. Now NIST has demonstrated a method that lets entangled atoms communicate information nondestructively, potentially enabling long quantum calculations in which intermediate results could be obtained without disturbing their quantum states. The algorithm traps charged ions in four electromagnetic traps spaced only a few microns apart on the surface of a chip. Ultraviolet lasers then entangle two pairs of ions.

"MATERIALS: Cloaking experiment taps split-ring resonators"

As recently as this summer, invisibility cloaks were only a theoretical possibility. Now the world's first cloaking demonstration has bent microwaves around a 7.2-cubic-inch enclosure, effectively hiding it from detection. The proof of concept suggests how engineers might pattern split-ring resonators to create "designer" metamaterials. Split-ring resonators--free-space rings of metal with a gap that prevents them from being a complete ring--are usually patterned on a fiberglass circuit board. When microwave radiation passes through them, they act as a dielectric whose magnetic permeability and electrical permittivity can be custom-tailored by adjusting the size and shape of the resonator. The cloak demonstrated earlier this month was designed to bend microwaves. But the researchers claim that with more engineering effort, EEs could create invisibility cloaks for any type of electromagnetic radiation, even visible light.

Monday, October 23, 2006

"MATERIALS: Science learns why size matters in capacitors"

If you look at the surface-mounted components on a typical printed-circuit board, the large ones are likely to be the capacitors. For reasons that were not previously verified, the smaller a capacitor gets, the less capacitance it exhibits, often necessitating the use of larger capacitors to achieve the desired capacitance. Now a materials science group at the University of California, Santa Barbara claims to have figured out why, and has concluded that using platinum or gold electrodes can allow a capacitor's depolarization layer's thickness to be reduced by a factor of four.

"MATERIALS: Self-isolating nanoparticles eyed for storage"

Supercomputer simulations running in the trillions of operations per second provide a virtual test tube for the nanoparticles to be used in a new generation of magnetic media for tomorrow's hard-disk drives. To prove that point, researchers at the Pittsburgh Supercomputing Center and Oak Ridge National Laboratory recently modeled a promising nanoparticle material exhibiting a hitherto hidden capability that the researchers say could enable densities of 1 terabit/square inch.

"QUANTUM: mechanical effects quell resonating bar"

Quantum mechanics predicts that measurements motivate mass--that the act of observing can affect the observed. Now a former National Security Agency scientist turned physics professor has demonstrated that motion can be elicited and quelled by quantum-level observations. Indeed, observations alone changed not only the physical motion of a device but also the motion's thermal consequence, according to Cornell University in a report on the largest device in which quantum mechanical effects have been observed. The device was an aluminum-on-silicon nitride resonating bar measuring 8.7 microns long by 200 nanometers wide, contained 10 trillion atoms.

"MEMS: microminiaturizing quartz crystal apps"

The last holdout against the microminiaturization of electronics--the quartz crystal--may be set to fall. Wielding oscillators based on microelectromechanical-system technology, two startups aim to break quartz crystals' monopoly on the mechanical time references used in virtually all electronic devices today. If the two are successful, larger competitors with established MEMS programs could be hot on their heels. But while the rivals envision a multibillion-dollar market for MEMS oscillators, the parts' price tag could confine them, at least at the outset, to niche markets.

Thursday, October 19, 2006

"QUANTUM: Spooky entanglement demonstrated"

The National Institute of Standards and Technology (NIST) said it has demonstrated what it claims is the world's first entangled atoms that could be used to communicate information nondestructively. By creating multiple pairings of entangled atoms, NIST scientist Dietrich Leibfried was able to transmit quantum data and verify its reception from one pair without destroying the information in the other pair. Entanglement—referred to by Albert Einstein as "spooky action at a distance"—is a quantum phenomenon in which two particles—atoms or photons in close proximity—take on identical internal states. The synchronization, if conditions are right, can persist even if the particles are separated so that information processed by one pair is simultaneously processed by the other. Researchers believe the phenomenon could serve as the basis for enabling quantum computing capabilities

Monday, October 16, 2006

"OPTICAL: Secure comms ride Internet stealth channel"

A secret communications channel hidden beneath the noise floor of existing Internet public fiber-optic networks could serve as a conduit for uncrackable data transmission, electrical engineers from Princeton University said last week. Even the presence of data in the stealth channel is hidden; it's impossible to know that anything is being transmitted. At the Optical Society of America's annual meeting in Rochester, N.Y., the EEs reported on their design for a physical-layer modification that hides a secure communications channel amid the clamor of public traffic. The technique could cheaply retrofit the existing Internet with a mechanism for secure transmission of confidential and sensitive data, the researchers said.

"OPTICAL: 'Backwards' approach leads to 1-pixel camera"

Remember how digital converters for audio started out at 8 bits, then went to 16 and 24 bits before resetting to 1 bit with oversampling? Engineers at Rice University will propose this week that we reset our megapixel cameras to 1 pixel and our video cameras to 1 voxel, both with oversampling. The 1-pixel camera takes tens of thousands of rapid-fire shots to capture the equivalent of 1 million pixels in an image. So instead of expensive megapixel sensors with separate detectors for red, green and blue, the Rice EEs' approach needs only a 1-pixel multispectral sensor, simplifying hardware resources while enabling images to be formed from spectra never before imaged. The enabling chip for the 1-pixel camera is not the detector used to sense an application-specific spectrum--that could use any technology. Instead, Texas Instruments Inc.'s digital micromirror array is used to project light from the lens onto the sensor. The micromirror array is the same chip that's used in Digital Light Processor televisions. Here, the lens focuses light onto the 1,024 x 768-pixel digital micromirror chip, which in turn projects all of its light into a single photodiode.

Monday, October 09, 2006

"OPTICAL: Technique brings high-def 3-D to small screen"

If you've seen any of the new IMAX 3-D movies, you surely noticed the jump in quality over the 3-D experience of yesteryear. Now a 3-D display maker has tapped an encoding technology that reproduces that cinematic experience on a 19-inch LCD for scientific visualization and medical diagnostics. The two LCDs are precision-aligned, then laminated on top of each other. The left and right images are separately displayed to the viewer's eyes, because the viewer wears passive glasses whose lenses are orthogonally polarized at 90° to each other.

Monday, October 02, 2006

"ENERGY: Future bright for solar energy plan"

A project to generate electricity from solar energy using a Stirling engine looks to create farms that will light and cool the households of millions of California customers, at a cost that by 2011 may rival what traditional sources are charging. The technology originated when Stirling Energy Systems Inc. agreed to supply Sandia National Laboratories with solar dishes in return for Sandia's addition of mechatronics to allow the dishes to track the sun. Together, Sandia (Albuquerque, N.M.) and Stirling Energy Systems (Phoenix) designed a 1-megawatt solar power substation capable of direct connections to the existing U.S. power grid. From 2007 to 2010, the Sandia program will perfect methods of ganging the substations into successively larger groups, operating at increasingly higher voltages. In California, the state government has mandated that utilities invest in renewable energy sources for at least 20 percent of their power by 2010.

"ENERGY: Turbines blowin' in the wind 100 miles offshore"

"You don't need a weather man to know which way the wind blows," Bob Dylan sang in "Subterranean Homesick Blues." That sentiment rings especially true if your turbine is blowin' in the wind more than 100 miles offshore, because there the breeze is always stiff. Now a designer of offshore drilling rigs for oil companies at MIT has validated the blueprints for an extra-large, 5-megawatt floating wind turbine with the National Renewable Energy Laboratory. Wind farms began on land, as eyesores familiar to anyone who drives much (for instance, from Los Angeles to Palm Springs). But the lack of constant wind onshore and the steady stream of complaints from the public have prompted a migration offshore. The public continues to complain about wind farms when they are visible from shore, prompting the newer projects to move even farther out. Last month, a consortium including oil company Talisman Energy Inc. and Scottish and Southern Energy began testing a 5-MW wind turbine almost 10 miles off the coast of Moray Firth, Scotland, where at 150 feet it is shallow enough to utilize an underwater foundation. For the United States, the engineers propose abandoning traditional rigid attachments to the ocean bottom, freeing the floating wind turbines to be located on the high seas, where the wind blows hardest. The Scottish project, if successful, will be a farm of 200 turbines. The U.S. plan is to up the ante by designing a farm twice as big--400 turbines, to power about 100,000 homes--located 100 miles off the New England coast.

"ALGORITHMS: Ultra-Wideband scheme banishes the delay line"

A new breed of ultrawideband radio that uses a mixer instead of a delay line could solve longstanding deployment problems, its developers say. The technique, invented by engineers at the University of Massachusetts (Amherst), was unveiled last week at the International Conference on Ultra-Wideband in Waltham, Mass. One of the most promising approaches to UWB was to send a nanosecond reference pulse before each data pulse, giving the radio a time frame in which to search its spectrum for data bits. However, after nearly a decade of attempting to use delay lines to synchronize data collection, most research into that approach has come to a halt. The new approach scraps the delay line idea for a mixer, which is easy to build even for ultrashort pulses. A reference pulse is still sent, but is mixed together with the data bit and multiplied by a cosine. On the receiving end is another mixer, with one input coming from the antenna and one from a sine wave generator.

"ALGORITHMS: Encryption technology makes quantum leap"

Using a superconducting detector, the National Institute of Standards and Technology has set a new world's distance record in quantum-key distribution--an uncrackable encryption technology that ensures absolute security by harnessing the quantum-physics principle that observations affect outcome. Until last week, Toshiba Research Europe Ltd. and Cambridge Research Laboratory held the record for the most sensitive detector with a prototype system that stretched 75 miles. Now NIST has upped the ante by more than 50 percent, reporting last week that it had transmitted over nearly 115 miles.

Monday, September 25, 2006

"CHIPS: Mobile ions may tailor organic ICs"

Looking to capitalize on the ability of organic semiconductors to host mobile ions, a Cornell University materials scientist propose bonding mobile ions to the surfaces of these semiconductors instead of doping. Circuitry made from organic polymers bonded to mobile ions can be optimized in ways that are impossible for doped semiconductors, opening the door to new functionality.

"OPTICAL: InP laser bonded to CMOS chip"

With optical processing migrating from exotic gallium arsenide devices to inexpensive silicon, Intel Corp. showed a research chip earlier this year that could do the world's first Raman lasing in a silicon waveguide. An all-silicon device, it had dynamically tunable wavelengths but was not very scalable, requiring an off-chip laser as an optical pump. Now, Intel is describing a scalable on-chip indium phosphide laser bonded to an all-silicon waveguide. Such an on-chip laser could supply the missing link between optics and electronics by performing both functions on the same photonic chips.

Monday, September 18, 2006

"SECURITY: Service reconstructs blurry video as sharp stills"

Ever wonder how blurry surveillance video images can be admissible as evidence in court? Software tools like Sarnoff Corp.'s VideoDetective mine the hidden data in such images to reconstruct their details clearly in still shots. But such tools are affordable only by large corporations and government agencies. Now a service called Sarensix permits private contractors to "farm out" the forensic evidence they gather from surveillance videos. The service was created by Sarnoff (Princeton, N.J.), a government contractor that fabricates custom ICs and ultrasmall video systems and software. Using data fused from video, infrared and other sensors, Sarnoff's security systems guard government installations and assist troops in the field. VideoDetective reconstructs video into stills that gather information from many frames, thereby creating sharp, telling still images from indistinct video. Smaller customers can use Sarensix to get their surveillance videos processed in VideoDetective by a Sarnoff-trained professional.

Monday, September 11, 2006

"SECURITY: Post-9/11, technology keeps us a step ahead"

Yes, we're safer--but. It's the answer, with a caveat, to the question that will be on everyone's mind today. But from a technologist's perspective, there are other questions to ask about where we stand five years after the 9/11 attacks. The country has spent billions on technology up- grades to detect and defuse new threats. Have we invested wisely? Are the technologies being deployed effectively? What more can be done? After 9/11, there was an explosion of research and development in sensor technologies, several of which have been deployed. But other technologies are languishing in red tape, according to analysts.

"CHIPS: Team demonstrates molecular-scale memory"

As chip dimensions shrink, picometer variability among nanoscale dimensions and the uneven distribution of dopants stand in the way of further miniaturization. Use of a precisely designed organic molecule as the memory storage element could provide one solution, because the molecules could be mass-produced to be identical. Recently, the IBM Research Laboratory (Zurich, Switzerland) demonstrated one such molecule, which it claims can be electrically programmed to store a bit in two bistable states.

Monday, September 04, 2006

"ALGORITHMS: Algorithm gives cameras a fly's-eye view"

By mimicking the way a fly's brain interprets images coming in through its eyes, an algorithm created by a researcher at Australia's University of Adelaide lets digital cameras "see" more clearly. Today, all cameras must be adjusted to take only a part of the range of available information. Scenes that involve large differences in brightness between their shadows and highlights are particularly difficult to capture. The photographer can adjust the camera to capture either shadows or highlights, but cannot optimally capture both simultaneously. The human eye is similarly hampered, but it compensates by quickly adjusting the diameter of the pupil when scanning a scene--making it larger to take in shadow details, then smaller for taking in highlight details--so that people do not often notice that they can't view both simultaneously. Insect eyes, on the other hand, appear to be able to record both shadows and highlights at the same time. At the University of Adelaide, postdoctoral research fellow Russell Brinkworth tested this theory by directly recording images from the brain cells of a fly, then crafting an algorithm to mimic the observed behaviors. The result is an algorithm that can accept inputs from a camera's sensor, process it and recover information that would otherwise be lost, enabling the camera to record clear scenes with detail in both the shadowed areas and the highlights.

"ALGORITHMS: Thimble-like digitizer doubles as input device"

Digitizing three-dimensional objects today is a tedious process requiring the user to trace an object's outlines using a tethered stylus. And even after laboriously running the stylus over every nook and cranny, the user captures only the object's shape; its other properties cannot be determined. Now researchers with the Virtual Reality Lab of the State University of New York at Buffalo have created a thimble-like fingertip digitizer that not only eliminates the stylus but also captures the viscosity (hardness, homogeneity, texture) as well as the shape of an object. Further, the digitizer can double as a universal input device, allowing a machine to interpret a user's gestures.

Monday, August 28, 2006

"OPTICAL: Displays may see full color"

Swiss researchers have found a way to directly make any color that can be perceived by the human eye on a computer screen. Instead of mixing red, green and blue, as is done today, electrical engineers at the Swiss Federal Institute of Technology (Zurich) have crafted an electrically controlled, flexible diffraction grating that can be tuned in real-time to any possible color. Though they have so far made only a single pixel, the EEs say that displays based on their technology could one day emit a unique color at each pixel by sending the appropriate electrical voltage to its deformable diffraction grating. Creating a spectrum of colors on a computer display is now accomplished by mixing RGB subpixels. But mixing three primary colors can represent only a fraction of the color space that the human eye can perceive. Now, the Swiss team believes it has found a way around the problem. Its electrically deformable diffraction grating is fabricated by sandwiching an electroactive-polymer dielectric--also called an artificial muscle--between two flexible conductors. The diffraction grating separates white light into a spectrum of colors in the same way that prisms do. When a voltage is applied, the conductors are attracted to each other, thereby squeezing the sandwiched polymer, which causes it to spread out.

"SECURITY: CT scanner to screen carry-on luggage in '07"

Since the British police foiled the plot to smuggle liquid explosives onto U.S.-bound commercial aircraft in carry-on baggage, the Transportation Security Administration (TSA) has been scrambling to develop technologies that could spot such items. Luckily, the best bet for identifying liquid explosives, according to its developer, is already in beta testing at Boston's Logan International Airport. Dubbed Cobra by developer Analogic Corp. (Peabody, Mass.), the scanner can detect objects of any shape that are massive enough to be a threat — including liquid explosives. If it passes certification by the TSA, Cobra could be deployed in airports nationwide by mid-2007. Both Cobra and a larger version called Exact, which has already been installed in more than half of the major airports in the United States, draw on Analogic's expertise in making medical scanners. By the late 1990s, Analogic was already adapting what was then called the "CAT" scanner--today called computed tomography (CT)--for use by airport security. After Sept. 11, the TSA mandated that all checked baggage be scanned, and Analogic's Exact was available to meet the need. The company quickly sold 525 Exact scanners, for sales of $525 million. The system, standing more than 7 feet tall and weighing 6,700 pounds, screens checked baggage automatically in an airport's private back room, diverting any suspicious bags to a side conveyer, where they are hand-checked with trace detectors. Cobra scales down Exact to a size and cost that makes it economical for use in screening carry-on bags.

Monday, August 21, 2006

"SECURITY: PC tool teams with X-rays to find explosives"

The revelation of a terrorist plot to smuggle liquid-explosive precursors onto airliners headed for the United States, then mix them together in the plane's bathroom, has sent the U.S. Transportation Security Administration and other anti-terrorism task forces worldwide scouring for systems that can detect liquid threats. The problem is that traditional, "sniffer" type sensors depend on detecting traces of explosives left on the outsides of the containers in which they are packed. Carefully sealed liquid containers, possibly fitting an unusual form factor or even shielded by metal, might get by a sniffer. And conventional X-ray detectors, which depend on human screeners to read the X-rays and identify weapons via shape recognition, cannot screen for liquids. Now Guardian Technologies International Inc. (Herndon, Va.) says it has devised PC-based software that can be used in tandem with conventional X-ray detectors in the field, acting as "a second set of eyes" to identify liquid-based compounds for explosives in scanned baggage.

"ENERGY: ORNL spin-off beta tests hybrid solar lighting"

The Department of Energy's Oak Ridge National Laboratory has transferred its hybrid solar/artificial-light technology to Sunlight Direct LLC (Oak Ridge, Tenn.), a company spun off from ORNL to commercialize the approach. Now in beta testing at five locations, with 20 more slated to be installed this fall, the technology could save utility customers $1 per square foot yearly on lighting costs, its inventors say. The adaptive, full-spectrum, solar collection and distribution platform, developed over a 10-year period with millions in Energy Department grants, collects sunlight via a mirrored dish on the roof that tracks the sun as it passes overhead each day. The mirror concentrates the resultant beam onto more than 120 fiber-optic cables, each measuring 3 mm in diameter, and distributes the fibers to 12 light fixtures covering 1,000 square feet in the building. The fixtures house two diffusion tubes (for dispersing the light from the fibers) alongside a high-temperature fluorescent tube. An electronic tracker adjusts the fluorescent tube's output so that the illumination level in the building does not vary with the strength of the sunlight. The system costs about $12 per square foot to install, but Sunlight Direct aims to reduce that to about $4. At the lower installed cost, the system would take only a few years to pay for itself. Besides the savings to the utility customer, hybrid solar lighting should ease overtaxed power grids during peak demand periods.

Thursday, August 17, 2006

"CHIPS: Atomic switch could yield higher-density memories"

A single-atom oscillator demonstrated by the Center for Nanoscale Science and Technology could become the basis for a future bistable atomic switch. Scientists at the Center, part of the Commerce Department's National Institute of Standards and Technology (NIST), injected a charge that switched a single cobalt atom between two locations on a crystalline substrate. The next step will be building a working device in a circuit. That will require a semiconducting or insulating substrate. Though they are years away, arrays of atomic-scale devices could provide the enhanced density needed for future memory devices.

Wednesday, August 16, 2006

"CHIPS: Diamond MEMS integrated with CMOS"

The world's first microelectromechanical systems (MEMS) directly integrated onto a CMOS chip is the aim of a new joint effort among U.S. laboratories, industry and academia.
Advanced Diamond Technologies Inc. (ADT), a spinoff from the U.S. Energy Department's Argonne National Laboratory, partnered last week with MEMS pioneer Innovative Micro Technology (Santa Barbara, Calif.) and the University of Wisconsin at Madison. They will supply the Defense Advanced Research Projects Agency (Darpa) with RF MEMS oscillators and resonators by next year. MEMS devices will be integrated with CMOS chips using the ultrananocrystalline diamond thin films patented by Argonne National Laboratory and licensed to ADT. Low-temperature processing required for diamond films enables MEMS circuit components to be fabricated in predesignated areas on finished CMOS chips.

Monday, August 14, 2006

"CHIPS: Nanotubes form vias in novel chip process"

Vias on printed-circuit boards are metal-clad holes that connect component leads on the top to component leads on the bottom. Similarly, on chips, semiconductor circuitry on one layer can be connected to a second layer via a hole, etched in the interlayer dielectric, which is then filled with metal. Now Purdue University engineers have demonstrated a semiconductor fabrication technique that uses tiny, 30- to 50-nanometer-pitch arrays of vertically grown carbon nanotubes for vias be- tween layers on semiconductor chips. The technique, devised by Timothy Fisher and Timothy Sands at Purdue's Birck Nanotechnology Center, works by virtue of "porous anodic alumina," which can form a network of evenly spaced pores in an aluminum oxide dielectric layer and then grow carbon nanotubes through the pores to form vias between layers. The technique produces both single- and double-walled carbon nanotubes. Each pore grows only a single tube, suggesting that the vias can be strictly controlled. That would make them easier to integrate with normal CMOS circuitry.

"MATERIALS: Metamaterials hold key to cloak of invisibility"

A "cloak of invisibility" sounds like the stuff of comic book superheroes. In fact, invisibility cloaks for any type of electromagnetic radiation--even visible light--are something Duke University postdoctoral fellow David Schurig believes are within grasp. Schurig and the professors directing his research--David Smith at Duke and Sir John Pendry at the Imperial College in London--maintain that by the end of 2007, metamaterials will enable an invisibility cloak that works in the microwave range. Further engineering effort will create such cloaks for other types of light, the researchers say. Metamaterials, or engineered composites, substitute macroscopic objects for atoms in a giant crystalline-like lattice, enabling the pitch of passive-component arrays to set the wavelengths affected. The design of these component arrays harks back to the first principles of electronics--simple R-C-L (resistor-capacitor-inductor) circuits. The electromagnetic waves passing through arrays of tiny resistors, capacitors, inductors and other dielectric materials positioned in free space can be bent down any designer-specified path. In 2000, Smith, who was then at the University of California- San Diego, and his colleagues demonstrated a composite metamaterial that used embedded passive resonators to bend microwaves backward. The circuit elements that the team used were based on the theoretical analysis provided by Pendry and his colleagues in London. Schurig recently sat down with technology editor R. Colin Johnson to describe how the cloaking device works, and what EEs can do to turn this science fiction idea into fact.

Monday, August 07, 2006

"MATERIALS: Phonons may drive high-Tc superconduction"

Just last month, an Oak Ridge National Laboratory team offered evidence that magnetic resonance was a more likely candidate than phonons as the mechanism behind high-temperature superconducting. But now a research team at Cornell University (Ithaca, N.Y.) has countered that careful characterization at the atomic scale reveals that the mechanism causing high-temperature superconducting may be phonons after all. Since the discovery of high-temperature superconducting materials, no one has convincingly explained why they work. Low-temperature superconducting is caused by a boson mode—a phonon—that interacts with electrons. But electron-phonon interaction in high-temperature superconductors has been elusive to observe, giving rise to the magnetic-resonance hypothesis. If the mechanism that enables high-temperature superconducting can be quantified, then designers worldwide could craft materials that eventually would enable room-temperature superconductivity.

Friday, July 28, 2006

"QUANTUM: Spintronics research targets GaAs"

Hole-rich semiconductors like gallium arsenide could harness the quantum effect called "electron spin" for a new era of spintronic devices which store information on magnetic atoms inserted into a semiconductor's crystalline lattice. But the current technique of random doping of magnetic atoms makes adding spintronics capabilities a hit-or-miss process. Now researchers claim to have perfected a method of brewing exactly the right molecular arrangement. Using a scanning tunneling microscope to substitute magnetic (manganese) atoms for individual gallium atoms, Princeton University researchers were able to experiment with different crystalline lattice architectures to optimize spintronic capabilities. The researchers confirmed the optimal lattice architecture for a new spintonic material: gallium manganese arsenide. The researchers claim this is the first time atomic-level manipulations were used to verify theoretical predictions about the optimal atomic arrangement in a semiconductor. Moreover, the arrangement was achieved one atom at a time in a crystalline lattice. GaAs is a candidate for next-generation spintronic devices because of its very high electron mobility compared to silicon. By incorporating magnetic atoms into a gallium manganese arsenide semiconductor, the team said it hopes to separately control spin and charge to enable highly energetic spintronic devices.

Wednesday, July 26, 2006

"QUANTUM: Quantum wires spin holes"

Researchers gathered this week to extend the use of quantum effects in semiconductors. Quantum effects result from the confinement of electrons, or holes, by restricting their free movement (perpendicular to the direction of crystal growth for quantum dots), thereby enabling their quantum effects to dominate. At the International Conference on the Physics of Semiconductors in Vienna, Austria, University of New South Wales (Sydney, Austrailia) claimed a world's first for quantum effects: successful fabrication of quantum wires from gallium arscenide. Dubbed "Hole Quantum Wires," the researchers reported on different aspects of their discovery. Other researchers discussed controlling spin in quantum dots, including those formed in graphene sheets and nanotube transport of holes with quantum spin to "q-bit" calculations of a quantum "Hall effect." Ballistic transport in quantum wires, bound electron-holes (excitons) in semiconductor quantum dots and optical control of spin polarization were also hot topics. New methods of handling nitrides, Bose condensates and quantum-effect optical devices such as quantum-cascade lasers and single-photon lasers are also emerging, researchers said.

"SENSORS: Biosensor tested on shuttle"

A recent Shuttle experiment could yield biosensors that harness living cells to detect harmful chemicals or biotoxins. Microbes encapsulated in biosensors by a nanoscale self-assembly method were genetically engineered to glow fluoresecent green when sensing specific toxins. After exposure to radiation and the cold vacuum of space, the biosensor prototype will return to Earth from the International Space Station on the next Shuttle flight for additional testing. If the biosensor continues to function, Sandia National Laboratories said it will develop rugged sensor technology that could be used for battlefield reconnaissance. Sandia earlier reported that it could direct the self-assembly of nanocyrstals into thin films. By controlling nanocystal structure so they self-organize to encapsulate the living cells, the researchers were able to seal them in a controlled environment that for use as biosensors. If the cells survive aboard the space station and continue functioning as biosensors when returned to Earth, then the reseachers expect to develop biosensor applications. For instance, the Defense Department is looking for a tiny biosensor carried by insects onto the battlefield. Unmanned aircraft could remotely detect any fluoresecent green generated by biological weapons or other biohazards.

Monday, July 24, 2006

"MATERIALS: Nanocrystalline circuitry gets sprayed on"

The future of semiconductors is not chips: Instead of fabricating circuits on chips and soldering them to printed-circuit boards, Canadian researchers propose painting transparent "solution processed" circuits directly onto a device's surface. Such semiconductor circuits--from emitters for large-area displays to detectors for spray-on solar cells--could drastically lower the cost of electronic devices, the group says. The first beneficiaries could be night vision goggles for the military that would be 10 times more sensitive, yet less expensive, than today's models. But that is just the beginning, according to the team at the University of Toronto, because now spray-on circuits no longer have to sacrifice performance to attain low cost. Besides being inexpensive to mass-produce, the photodetector material could post a tenfold sensitivity increase for military night vision systems, which image in infrared, as well as for biomedical imaging systems that use infrared to see through skin.

Thursday, July 20, 2006

"MATERIALS: 'MOMS' boost DLP applications"

A University of Delaware engineer claims to have solved a power issue that has prevented wider use of digital light processors (DLP) in power-sensitive applications. DLPs normally use microelectromechanical systems (MEMS) to control the angle of micromirror arrays. However, for power-sensitive applications such as space exploration, even the microamps required to tilt micromirrors make use of DLPs prohibitive. The University of Delaware engineering professor claims to have solved the problem using micro-optomechanical systems. MOMS use lasers to actuate tiny mirror-tipped cantilevers instead of electrical current to power pnematic, piezoelectric or electrostatic actuators. An optically-active nanotube film enables MOMs to be actuated by a ultralow-power laser rather than power-draining electrical current. The researcher claims power consumption is low enough for space exploration and new applications of field-emission displays and biomedical scanners. The technique patterns a carbon nanotube thin-film using standard CMOS processing steps, resulting in arrays of optically-actuated cantilevers measuring 300 microns long by 30 microns wide by 7 microns thick. The cantilevers deflected 23 microns when their base was illuminated by a 808-nm wavelength, 170 mW semiconductor laser.

Monday, July 17, 2006

"CHIPS: Magnetic resonance tied to superconduction"

Researchers believe they have unlocked the mystery to what makes high-temperature superconductors tick. According to a team from Oak Ridge National Laboratory and the University of Tennessee, the reason these materials superconduct at such high temperatures may be a magnetic resonance that causes their anti-ferromagnetic lattice to oscillate opposing-spin orientations in synchronization with the opposing-spin orientations of the so-called Cooper pairs passing through the superconductor's molecular lattice. Magnetic-resonance excitation is believed to be the mechanism that generates Cooper electron pairs in high-critical-temperature superconductors. Recent experiments at the National Institute of Standards and Technology have confirmed the theory in the superconductor called praseodymium lanthanum cerium copper oxide. The Oak Ridge-UT team also reported a universal law governing all high-temperature materials--their magnetic-resonance energy is proportional to their superconductivity transition temperature. If the researchers are correct that magnetic resonance serves the same function as phonon lattice vibrations in low-temperature superconductors, then room-temperature superconductors could be on the horizon.

Thursday, July 13, 2006

"ENERGY: Thermoelectric polymers could heat, cool buildings"

The National Science Foundation will fund research on a solar heating and cooling prototype that seeks to replace conventional systems. Details of the prototype technology called the Active Building Envelope (ABE) were disclosed this week at Solar 2006 in Denver. Rensselaer Polytechnic Institute (RPI) professor Steven Van Dessel described his group's work on the ABE system. He said ABE could allow the hitching of solar panels to thermoelectric heat pumps to reduce the cost of cooling and heating. The National Science Foundation will fund Van Dessel's next project to make ABE technology economically feasible by switching to low-cost thin-film materials. If successful, thin-films could then be used for other applications such as auto glass that heats or cools vehicle interiors. Thermoelectric heat pumps become cool on one end and hot on the other when electric current passes through them. By putting one end outside a container and the other inside, the thermoelectric device can pump heat into or out of the container. ABE combines the thermoelectric element with solar panels that can cover an entire building. Combined with a storage device, it could then heat or cool a building day or night. Van Dessel's group hopes to use low-cost, thin-film materials that allow both solar cells and thermoelectric heat pumps to be integrated into windows and other surfaces to enable climate control.

Monday, July 10, 2006

"SENSORS: Radar hides signal, penetrates concrete"

Two problems with conventional radar make it unsuitable for many applications: Anyone with a radar receiver can tell when you activate it, and it can't image objects closer than about 100 feet. Granted, radar automatically opens the door for you at the grocery store, and Stealth bombers are supposedly transparent to radar. But the grocery store radar uses a Doppler algorithm that can only sense movement, not make images, and an aircraft can only be made invisible to radar directed at it from the ground. Now Ohio State University electrical engineer Eric Walton claims to solve both problems with $100 worth of parts. Walton's "noise radar" hides its signal in wideband noise, making it undetectable by the enemy, and it can image objects right through concrete walls. By spreading low-level noise across gigahertz of radio spectrum, the noise radar signal becomes undetectable to normal radar receivers, which are designed to look for high-level signals and to filter out weak signals assumed to be noise. Spread-spectrum transmitters and receivers are widely used today, but spread-spectrum receivers cannot decode noise radar signals, because the signals are spread across gigahertz of bandwidth--simply too much territory for the receivers to cover when searching for correlations. In fact, even two of Walton's own noise radar transceivers, sitting side by side, cannot detect each other, because the signals they send out are random and unique. The only receiver that can detect the signal from a noise radar, Walton said, is the very device that sent out the signal in the first place, its unique code being the random signal itself.

Thursday, July 06, 2006

"CHIPS: Mechanism for high-Tc superconductivty probed"

Researchers said they have moved a step closer to understanding the mechanism behind high-temperature superconductivity. The discovery of a high-temperature superconductor (bismuth strontium calcium copper oxide) by IBM in 1986 made lower-cost devices feasible. Since then, researchers have been trying to understand why these materials superconduct at such a high temperature. Their aim is to design materials that superconduct at even higher temperatures—perhaps even at room temperature. Earlier this year, IBM confirmed that high-temperature superconduction results from a condensate of Cooper pairs—two electrons bound together with opposing spins. But the mechanism responsible for condensing the Cooper pairs remains a mystery. Working at NIST's Center for Neutron Research, the team claims to have observed what may be the mechanism that binds Cooper pairs, thereby explaining high-temperature superconductivity.

Monday, July 03, 2006

"ALGORITHMS: Microscope exposes atoms' inner mysteries"

A spherical-aberration corrector has enabled the transmission electron microscope at IBM's T.J. Watson Research Center (Yorktown Heights, N.Y.) to make the highest-resolution images in the world. Instead of blurry pictures of individual atoms, the researchers have obtained clear images of the individual molecular bonds among the different types of atoms in the crystalline lattice of a semiconductor surface. IBM recently installed a second-generation spherical-aberration correction system made by Nion Co. (Kirkland, Wash.) As a result, the world's highest-resolution images are now made on IBM's 120,000-electron-volt (eV) scanning-tunneling electron microscope (STEM). The researchers clearly imaged a crystalline aluminum nitride surface, showing the hexagonal "wurtzite" arrangement of atoms. The crystalline aluminum nitride layer was fabricated to experiment with storing charge in aluminum-nitride/gallium-nitride/aluminum-nitride quantum wells. The gallium nitride behaves as a semiconductor, storing as little as one charge carrier, while the aluminum-nitride sandwich insulates the quantum well from electrodes above and below it. The images clearly revealed for the first time the location and orientation of both the aluminum and the much tinier nitrogen atoms in the hexagonal wurtzite crystalline lattice pattern.

"ALGORITHMS: Spark spots short circuits early"

A diagnostic spark that finds defects in wiring systems as complex as those on aircraft has been developed by researchers at Sandia National Laboratories. The Pulsed Arrested Spark Discharge (PASD) enables engineers to pinpoint the location of future short circuits before they occur, by exposing weaknesses that would eventually cause the short, according to the researchers. Ordinarily, a 10,000 to 15,000-volt, 200-amp test signal would fry any electronics under test, but when it only lasts 10 nanoseconds, it can't damage wiring systems. Airplanes have miles of wiring harnesses, with many of the wires running hundreds of feet between connections. In the past, airlines have had to wait for shorts to develop before they could be diagnosed, possibly risking debilitating failures. Intermittent electrical short circuits in aging airliners often make cabin lights blink, but they have also caused fatal crashes, such as flights SwissAir 111 and TWA 800. If PASD had been used to precondition their wiring harnesses, then those aircraft could have been maintained short-free by replacing problem wires before they failed in flight. PASD pulses actually improve the performance of wiring harnesses, according to the laboratory, since they burn off any foreign matter that might be bridging a hot line to ground, thereby preconditioning the wiring system and raising its overall breakdown voltage.

Friday, June 30, 2006

"CHIPS: Silicon laser harnessed"

Continuous-wave silicon lasers were demonstrated for the first time last year by Intel Corp. But the new lasers generated too much heat to be practical for CMOS devices. Researchers at the University of California at Los Angeles now claim to have the solution: Harness the excess energy with a photovoltaic effect that converts heat back into electricity to power the chip. The researchers also beat Intel in the race for the world's first silicon laser in 2004, when they reported a pulsed silicon laser. The laser could not operate continuously because it produced excess hot electrons. In 2005, Intel followed up with a technique for sinking hot electrons, clearing the way for the first continuous-wave silicon laser. The first version did not use excess energy. The UCLA group has again topped Intel by showing how a Raman scattering architecture can be used in CMOS devices to harness excess energy from hot electrons. The mechanism, stimulated Raman scattering, sidesteps silicon's indirect bandgap that prevents normal lasing. However, Raman scattering works through double-photon absorption, which creates hot electrons as a byproduct and generates excess heat. The researchers claimed that a photovoltaic sink not only enables continuous operation of silicon laser chips, optical amplifiers and similar photonic devices, but it can now be economically incorporated into CMOS. Moreover, the excess energy can now be harvested to drive other CMOS circuitry.

Monday, June 26, 2006

"CHIPS: Defects spur light emission in nanotube FETs"

IBM Corp. researchers say they have characterized four types of carbon nanotube field-effect transistsor defects that can stimulate nanotube FETs to emit light. The first light-inducing defect was discovered on the end contacts, where a natural Schottky barrier exists at the semi- conducting nanotube interface with its metal electrode. The second was found anywhere that charge had been inadvertently trapped in the oxide-covered silicon wafer; trapped charge locally inverted the carriers in the nanotubes atop it by forming a light-emitting intratube npn or pnp junction. The third defect characterized was on a nanotube loop where the tube bent around and crossed over itself. At the crossover point, hot carriers could tunnel from one leg to the other, where they affected other carriers and caused light emission. The first three defects were studied by randomly laying down nanotubes on a substrate and looking for those anomalies. But the fourth type of defect was intentionally made by partially covering a nanotube with a polymer. Where the polymer ended, a voltage drop caused carriers to collide, inducing electroluminescence.

Wednesday, June 21, 2006

"CHIPS: Molecular switch promises to solve sticky situations"

Microfluidic devices sense and sort through molecules by channeling them down nanoscale pipes etched from polymer substrates. Unfortunately, the tiny channels often clog when biological materials stick to them, degrading performance. Researchers at the Rensselaer Polytechnic Institute (RPI, Troy, N.Y.) think they have found a remedy: a material that optically switches from slippery to sticky. When exposed to UV light, the polymer dislodges molecules stuck to its surfaces by becoming more slippery. The property enables even the most clogged microfluidic channels to be flushed clean. The researchers predicted that the polymer will be useful for filtering specific proteins from biological fluids, which often clog the pores of conventional filters.

Monday, June 19, 2006

"CHIPS: Record-low gate voltage for nanotube field emitters"

Scientists at the U.S. Naval Research Laboratory in Washington D.C., said they have fabricated arrays of high-current carbon nanotube field emitters with a record-low gate voltage of just 60 volts for emissions of up to 1.2 amps per square centimeter. Its low voltage-high current operation also yields the high transconductance--the rate of increase in current with increase in voltage--that is necessary for many electronic device applications. The arrays of carbon nanotube field emitters were grown by researchers David Hsu in the Chemistry Division and Jonathan Shaw of the Electronics Science and Technology Division, using chemical vapor deposition (CVD) on silicon substrates that had been prepatterned with 1-micron-diameter posts centered on 2.5-micron-diameter metal aperatures. Nickel or iron catalysts were deposited over the gated structures and then removed from the surfaces. The carbon nanotubes grew from the catalyst particles during CVD using ammonia and acetylene gas. By applying a relatively low voltage to the gate apertures, a relatively high electric field was produced at the nanotube tips, thereby causing electrons to spew out by field emission, the researchers reported. The proximity of the gates yielded the high local electric fields from the relatively low voltage input. The high-density field emitter arrays packed more than 75,000 emitters per square millimeter, according to the researchers. The scientists said their low-voltage emitters do not degenerate during extended usage as rapidly as high-voltage field emitters do. The low gate voltages avoid the damage typical in high-voltage devices, such as dielectric breakdown and residual ion aputtering, they said. The field emitters were said to perform well at temperatures up to 700°C and in the presence of water vapor and other common gases. The Navy researchers said that the 1.2 amps per square centimeter current density is more than adequate for applications such as spacecraft propulsion systems (ion thrusters and tethers), miniature x-ray sources, cathodoluminescent devices (flat-panel displays) and mass spectrometers. Another factor of ten to twenty higher current density is needed for high frequency electronics.

Thursday, June 15, 2006

"ALGORITHMS: Technique takes flight to quickly erase hard drives"

In 2001, an American spy plane collided in the air with a Chinese fighter and was forced to land on Chinese island. Since then, researchers have been looking for a way to quickly erase computer hard drives to deny access to sensitive intelligence data. Scientists at the Georgia Institute of Technology (Atlanta), working with L-3 Communications Corp. (New York), said they have developed a technique for quickly erasing hard-disk drives. The team reports development of a prototype fast-erasure system to prevent sensitive information from reaching enemy eyes. At the time of the U.S.-China incident, there was no way the U.S. crew could quickly erase hard drives on the surveillance aircraft before landing on Chinese soil. The Chinese eventually gained access to U.S. military secrets. Erasing a hard drive usually takes hours using special procedures that repeatedly scramble information on a disk drive. Still, given unlimited resources and time, special magnetic snooping techniques can often recover at least some of the original information. The researchers sought a method that not only securely erased information but also performed the erasure during emergency situations where minutes, not hours, were available. The researchers concluded that permanent magnets are the best solution. Other methods, including burning disks with heat-generating thermite, crushing drives in presses, chemically destroying the media or frying them with microwaves all proved susceptible to sensitive, patient, recovery efforts. Permanent magnets for erasing magnetic media have been available since the dawn of disk drives, but the team found that commercial systems were either magnetically too weak, too large and heavy or could not meet air-safety standards. Instead, the team crafted a new generation of super-powerful magnets to penetrate hard disk enclosures to quickly erase magnetic media. Special high-strength magnets as powerful as those in medical imaging equipment proved sufficient for permanently erasing all information on a disk drive in a single pass.

Tuesday, June 13, 2006

"CHIPS: Indium oxide may best GaAs for spintronics"

Harnessing electron spin for optomagneto-electronic devices will depend on materials that, like silicon, can separately adjust their densities and dopant levels to designer specifications. Indium oxide doped with chromium may fill the bill, according to a research team from the Massachusetts Institute of Technology and Boise State University. Lacking the limitations of gallium arsenide-based ferromagnetic materials, chromium-doped indium oxide could enable durable, transparent thin-film spintronic devices, said researchers at MIT's Francis Bitter Magnet Lab. According to the researchers, ferromagnetic memories will need to harness spintronic approaches within a decade as they scale down into molecular-sized magnetic domains to store information. Chromium-doped indium oxide and similar formulations could enable the magnetic spin of even individual molecules to be flipped from "up" to "down," potentially packing a bit of data into every atom. By the time FRAMs scale down to molecular-sized domains, MIT researchers hope to have chromium-doped indium oxides fully characterized and ready to build spintronic devices. For now, they are merely reporting that they have overcome the basic limitations of other ferromagnetic formulations, especially those using GaAs, by adjusting the location of molecules in the crystalline lattice of indium oxide and by setting the dopant levels separately.

"CHIPS: Decoupling capacitors return to simpler times"

AVX Corp. has made what it claims is a revolutionary step backward with its invention of a patented new land-grid array (LGA) architecture for decoupling capacitors. Decoupling capacitors provide on-demand power reserves that can keep the edges sharp on the quickly changing signals from high-speed microprocessors, graphics coprocessors, digital signal pro- cessors and field-programmable gate arrays. Unfortunately, as clock frequencies have climbed, capacitor designers have quelled the parasitic inductance that can limit switching speed by resorting to hard-to-use multilayer architectures that require terminals that exit from the side. AVX has lowered parasitic inductance by returning to the simpler design of old-school capacitors, which feed directly into the printed-circuit board from the bottom. Most capacitors are just parallel metal plates separated by an insulator, and hence have essentially no inductance. In working capacitors, however, parasitic inductance is a fact of life. When current flows, the flux creates a magnetic field that loops around the internal electrodes of the capacitor and its external termination, the power planes, vias, mounting pads and solder fillets of the printed-circuit board. AVX's LGA capacitors solve the parasitic inductance problem through a reorientation of the internal electrodes. Instead of a horizontal orientation, in which the electrodes are parallel to the substrate, the electrodes are given a vertical orientation. The LGA architecture enables multilayer capacitors to gang together their multiple electrodes internally, with only two terminals exiting the capacitor from the bottom of the package. This allows printed-circuit-board makers to use a single two-terminal component with bottom exits, rather than using multiple small capacitors, each of which might have up to eight terminals exiting from the sides.

Monday, June 05, 2006

"MATERIALS: Team posits 'cloaking' nanomaterial"

The researcher who introduced the concept of negative-index-of-refraction metamaterials in 2000 is now positing that materials with a variable refractive index could enable such fantastic applications as a Harry Potteresque "invisibility cloak." Sir John Pendry, a physicist at Imperial College in London, predicted six years ago that metals could be engineered to make electrical fields behave oppositely to normal, yielding negative-index-of-refraction metamaterial composites. Since his prediction, such metamaterials have been created and demonstrated from gigahertz to optical frequencies. Now Pendry has teamed with Duke University EEs David Schurig and David Smith to predict that both the electrical and the magnetic properties of an inhomogeneous composite with embedded nanoparticles could be altered to create a variable-index-of-refraction material. They postulate that such a material could adapt at the nanoscale to conceal what's under it by preventing electromagnetic energy from entering an area. Light hitting the material would "flow" around it and continue, undistorted, on the other side. The material thus would neither reflect light nor cast a shadow.

Monday, May 29, 2006

"ENERGY: Here comes the sun"

Sticker shock at the gas pumps combined with concerns over the diminishing supply of nonrenewable energy sources like coal, oil and natural gas have added new urgency to the search for alternatives. Riding to the rescue are technology-based resources that will never run out, because they are renewable; are environmentally friendly, and do not add to the greenhouse effect; and are increasingly cheap to harvest, thanks to continuing technical breakthroughs. Solar is here today, but at about three times the cost of conventionally generated electricity (18 to 22 cents per kilowatt, compared with 5 to 10 cents/ kW for conventional). However, thanks to advances including the use of "plastic" solar cells to replace the more expensive silicon versions, the U.S. Department of Energy believes the cost of solar will be on par with that of conventional electricity within 10 years. By that time, two other contenders--hydrogen fuel cells and nanoscale electric generators--will be at about the same stage of development as solar cells are today. Photovoltaic solar cells work by absorbing units of light, or photons, in a semiconductor, thereby energizing its electrons enough to drive circuitry. Japan holds just 20 percent of the $3 billion to $4 billion world solar cell market today, according to Solarbuzz LLC (San Francisco). Germany has the greatest number of solar installations, accounting for 57 percent of the total in 2005, with the United States at only 7 percent, the rest of Europe at 6 percent and the rest of the world at 10 percent. Of the various solar cells available, efficiencies range from about 6 percent for the least expensive amorphous-silicon models on glass or plastic substrates to as high as 30 percent for multijunction gallium arsenide cells on monocrystalline wafers, which cost up to 100 times more. Monocrystalline and polycrystalline silicon solar cells, the most popular types, have efficiencies ranging from about 10 to 18 percent. Ready-to-install modules sell for about $4 per watt. Devices with lower conversion efficiency than mono- or polycrystalline silicon cells include amorphous silicon, cadmium telluride, copper indium diselenide and other, similar alloys. Monocrystalline and polycrystalline silicon solar cells hold 93 percent of the worldwide market today

"CHIPS: Single-chip microphone on the road to digital"

Akustica Inc. announced last week that Fujitsu's LifeBook Q2010--a notebook aimed at no-holds-barred "road warriors" like traveling executives--will include two AKU2000 single- chip microphones located on the display's bezel. This design win indicates that high-end laptop computers are switching from analog to digital microphones, according to Akustica (Pittsburgh). At the same time, the company introduced a chip, the AKU2001, that permits multiple microphones to share a single interface wire. Codec maker SigmaTel Inc. (Austin, Texas) simultaneously announced support for the AKU2001 microphones. The compatible codec will permit designers to multiplex multiple microphones on a single interface wire without using any other supporting circuitry. Market research firm Yole Development (Lyon, France) puts the silicon microphone market last year at nearly 100 million units and predicts it will grow to 800 million units by 2010. Most of those, today, are analog MEMS microphones made for analog cell phones by Knowles Electronics LLC (Itasca, Ill.) and Sonion MEMS A/S (Roskilde, Denmark). In contrast, Akustica's silicon microphone has the analog-to-digital converter on the same chip, greatly simplifying integration into notebook PCs and other digital devices, such as PDAs, Bluetooth headsets and the increasing number of ports for voice-over-Internet Protocol (VoIP).

Monday, May 22, 2006

"ENERGY: U.S. funding photovoltaic development"

The Department of Energy has begun funding solutions to the engineering and infrastructure problems that must be solved before widespread commercialization of current photovoltaic technologies can become a reality. Called the Solar America Initiative, the 2007 DOE Budget set aside $148 million to accelerate the development of photovoltaic cells ranging from those made from monocrystalline, polycrystalline and amorphous silicon structures, as well as those based on thin films, organic polymers and quantum wells. The U.S. Department of Energy has issued a Notice of Program Interest to the industry, universities and other potential partners to help plan topics, program phases, technologies and procurement strategies to meet its goal. To start, Solar America will try to see what obstacles remain to commercialization, then enlist EEs and others to solve those problems. The program aims to develop multiple competing solar cell technologies by 2015 to provide electricity at a cost per kilowatt-hour that equals or exceeds what the grid offers.

"ROBOTICS: Robots march (well, walk) in land of Disney"

Humanoid robots seized the spotlight at the IEEE's International Conference on Robotics and Automation here last week. All told, more than 1,200 engineers explored all the angles and scales of robots in upwards of 750 sessions covering everything from nanobots to full-sized robotic automobiles. But humanoid robots dominated a host of sessions at the Disney World Hilton, ranging from pure theoretical studies to end-user applications. In the latter category was a report by Waseda University (Tokyo) and Kanagawa University (Yokohama, Japan) that described a new robot designed to help senior citizens walk. If a robot bumps into something or is pushed from behind, say researchers at the University of Tokyo and City University of Hong Kong, they'll need a special algorithm to maintain stability. The researchers used video cameras and force plates to capture human responses to sudden disturbances, then extracted the parameters relevant to their solution. If all that "walking" worked up an appetite in Orlando, one of the more realistic humanoids, designed by the University of Tokyo, aims at conquering one of the most ubiquitous tasks facing any human: cooking meals.

Wednesday, May 17, 2006

"ROBOTICS: Biorobotics challenges engineers"

While enabling better robots, biorobotics are also encouraging engineers to become neuroscientists, an expert told the IEEE's International Conference on Robotics and Automation. Keynote speaker Paolo Dario's team is validating new principles which integrate "bio-inspired" control and learning strategies with human/robot interfaces and mechanisms. They are also pursuing biomechatronics, or prosthetics, technical aids for physical rehabilitation and humanoid robots for assisting the elderly. For humanoid robotics applications, the new paradigm includes three computer models running simultaneously: a model of the world, a model of the human and a model of their interaction. The engineer/scientist first studies biological systems and formulates hypothesizes for how it succeeds. The resulting robot mimics the hypothesized procedures. Once the robot is debugged, biological systems are reevaluated to determine where a model went wrong and a new hypothesis is developed for correcting errors. Finally, the robot is rebuilt. Dario predicted that robotic surgery would benefit from biorobotic advances. Robo-surgery is designed to "steady the hand" of surgeons, and has progressed to delicate neurological procedures that are nearly impossible to perform without robotic assistance.
Biorobotics are also enabling new procedures that would be impossible to perform manually.

Monday, May 15, 2006

"CHIPS: Carbon-nanotube arrays take heat off chips"

A carbon-nanotube-based thermal material has been crafted by researchers at Purdue University to transfer heat away from the densely packed transistors that are increasingly being crammed onto silicon chips. The researchers claim that the material transfers heat away from chips to any heat sink faster than the liquid-cooled method used by many of today's manufacturers. Heat sinks traditionally use metal fins to dissipate heat into the air. Even liquid-cooling fins, which circulate water through their inside channels to an externally cooled reservoir, still need to transfer the heat from the silicon chip to the heat sink. Ordinarily, an electrical insulator like mica, which nevertheless conducts heat, is used between the silicon chip and the heat sink. A thermal-transfer paste is applied to both sides of the mica before it is inserted between the chip and heat sink. The Purdue researchers contend that a carbon nanotube can transfer heat from the chip through the mica and to the sink more that three times more efficiently than paste.

Wednesday, May 10, 2006

"ALGORITHMS: Iowa State claims highest resolution VR room"

A virtual reality installation sporting 100 million pixels is being touted as offering the world's highest resolution, and could aid medical and military research. The $4 million upgrade to Iowa State University's "C6" VR room will employ 24 Sony digital projectors to back-illuminate all four walls, floor and celling of the installation. Operators of the C6 room claimed it was the highest resolution VR installation when it was first unveiled in 2000. Since then, other VR rooms have been built with higher resolution, including a five-sided room recently installed by Fakespace Systems Inc. (Marshalltown, Iowa) and at the at Los Alamos National Laboratories' Strategic Computing Complex. Fakespace worked with Iowa State to upgrade its current C6 installation to regain the highest resolution: 100 million pixels compared to 43 million pixels at Los Alamos. The six-sided10- by 10- by 10-foot room back-projects 3D computer- generated scenes on walls, floor and ceiling. The images will be generated by a Hewlett-Packard computer with 96 parallel graphics processing units feeding the 24 digital projectors, plus an eight-channel 3D audio system and an ultrasonic motion-tracking system that changes the scene as a user turns his head.

Monday, May 08, 2006

"CHIPS: Dip-pen technique drives molecular-scale litho"

IBM Corp. has found a way to electrically control the deposition rate of materials--the ink--from a dip-pen lithography system without lifting it from the substrate on which it is writing, thereby enabling molecular-scale nanolithography. Dip-pen lithography harnesses an atomic-force microscope (AFM) to ink virtually any chemical compound onto a substrate with nanometer control. Unfortunately, there was no way to control the deposition rate, because the molecules were deposited on a surface by diffusion--like a quill pen. The only thing that could be controlled was the speed at which the tip was scanning, and the only way to stop and start deposition was to lift and touch the pen to the substrate--a lengthy and error-prone procedure. IBM's trick was to add a reservoir to the AFM's tip at the place where it connects to a cantilever. Thus, the new cone-shaped tip directly ties into a material reservoir that can convey molecules up or down to a substrate with an electric field of a million volts per meter. By changing the strength and duration of the field, IBM has demonstrated millisecond-level control of deposition--a thousandfold faster than today's best methods. Like all dip-pen approaches, IBM's electronically controlled, direct-writing method uses AFM positioning accuracy to define complex patterns in a variety of materials with features down to 10 nm. That's five times smaller than today's e-beam lithography equipment and 10 times smaller than photolithography. The twist lies in adding control by an electric field, and in setting up the right conditions to make that work. Besides use in nanoscale lithography for electronic circuits, IBM predicts the method will enable nanoscale-size microfluidic devices, such as those that perform electrophoresis assays for everything from DNA fingerprinting to routine blood tests.

"SECURITY: Screener promises safer airports"

U.S. airports have invested billions in security since the 9/11 terrorist attacks. Still, the Government Accountability Office managed to sneak bomb-making components onto planes at 21 U.S. airports--every one it tested--over a recent four-month period. Now, an Israeli technology called CarrySafe has been licensed to a U.S. company that insists it could have detected those bomb-making components with 100 percent accuracy. In the security trial, conducted from last October until January, GAO investigators were able to smuggle explosives past screeners in their carry-on luggage in 21 out of the 21 U.S. airports. TraceGuard Technologies Inc. (New York), says its CarrySafe would have detected traces from every one of those carry-on bags. CarrySafe is a retrofit that collects traces of explosives that it passes to existing analysis equipment. Instead of manually swabbing a bag and putting the swab into an analyzer, hoping the single swabbed spot had residue on it, CarrySafe automatically collects residue from every part of the luggage. Originally designed to screen air cargo, CarrySafe wraps an active membrane around bags to detect trace amounts of explosives TraceTrack Technology Ltd. (Tel Aviv, Israel) has developed the technology for seven years, then last year licensed it to TraceGuard Technologies Inc., a U.S. corporation. The Israeli Security Agency is certifying CarrySafe for use in Israeli airports, and the U.S. Transportation Security Administration is expected to follow suit with certification in early 2007 for use in U.S. airports.

Monday, May 01, 2006

"ENERGY: Nanogenerator takes charge from motion"

The first nanoscale piezoelectric generator, which could one day use environmental motion to provide unlimited electricity for small devices, has been demonstrated by researchers in Georgia. For the demonstration, the researchers grew arrays of nanoscale zinc-oxide piezoelectric nanowires perpendicular to a sapphire substrate and coupled the material's piezoelectric and semiconducting properties. While the group has not yet created a batteryless device, it did use an atomic-force microscope (AFM) to demonstrate how mechanical motion of the arrays of piezoelectric semiconductors could initiate a charge cycle for future batteryless devices. While the demonstration shows that the piezoelectric nanogenerator remains years away from powering commercial devices, the talk focused on its great potential. Converting mechanical energy into electricity with nanoscale piezoelectric materials could provide the foundation for future wireless applications, the researchers suggested. Besides simplifying medical implants, piezoelectric nanogenerators could also power remote sensors or even recharge conventional batteries. For instance, the researchers envision soldiers in the field with nanogenerators built into their uniforms so that their normal body movements can automatically recharge their communication devices' batteries.

Monday, April 24, 2006

"CHIPS: Coating lets nanotube transistors self-assemble on chips"

Next-generation semiconductors aim to harness the ballistic electron transport capabilities of pure carbon nanotubes, but until now there has been no easy way to integrate the tubes with silicon chips. Now IBM Corp. researchers think they have the solution--coat nanotubes with a ligand that only sticks to high-k dielectrics, then lithographically pattern the wafer with high-k dielectrics wherever transistor channels are wanted. The researchers showed that carbon nanotubes would self-assemble on the lithographically defined channels and that annealling boiled off their ligand coating, leaving behind arrays of carbon nanotube transistors. Normally, when used as the channel for a transistor, carbon nanotubes are many times smaller than the source and drain electrodes--less than 1 nanometer, compared with tens or hundreds of nm. This makes it difficult to fabricate them using traditional lithographic techniques. The process runs on any standard CMOS semiconductor fabrication line. In their proof-of-concept demonstration chip, the IBM researchers fabricated an array of nanotube transistors by patterning 40-nm-deep x 300-nm-wide aluminum lines on a silicon dioxide wafer, placing them where transistor channels were supposed to be. The aluminum was then oxidized to turn it into a high-k dielectric. Next, the chemically treated nanotubes, in an ethanol solution, were applied to the wafer. At this point, the nanotubes stuck only to the high-k dielectric pattern and not to the silicon dioxide substrate. Finally, the IBM team patterned electrodes for the source and drains of the transistors. The resultant demonstration transistors had a 400-nm channel length.