"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.
Text: http://www.eetimes.com/showArticle.jhtml?articleID=191504070

"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.
Text: http://www.eetimes.com/showArticle.jhtml?articleID=191204807

"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.
Text: http://www.eetimes.com/showArticle.jhtml?articleID=191201394

"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.
Text: http://www.eetimes.com/showArticle.jhtml?articleID=190500733

"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.
Text: http://www.eetimes.com/showArticle.jhtml?articleID=190900171

"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.
Text: http://www.eetimes.com/showArticle.jhtml?articleID=190302307

"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.
Text: http://www.eetimes.com/showArticle.jhtml?articleID=190303034

"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.
Text: http://www.eetimes.com/showArticle.jhtml?articleID=190301115