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Energy now lost as heat during the production of electricity could be harnessed through the use of silicon nanowires synthesized via a technique developed by researchers with the U.S. Department of Energy’s (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) at Berkeley.

 The far-ranging potential applications of this technology include DOE’s hydrogen fuel cell-powered “Freedom CAR,” and personal power-jackets that could use heat from the human body to recharge cell-phones and other electronic devices.

Continue reading ‘Researchers Make Thermoelectric Breakthrough In Silicon Nanowires’ »

Energy now lost as heat during the production of electricity could be harnessed through the use of silicon nanowires synthesized via a technique developed by researchers with the U.S. Department of Energy’s (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) at Berkeley.

Continue reading ‘Researchers Make Thermoelectric Breakthrough In Silicon Nanowires’ »

Nanophotonics is living up to the hype. The study of light on the nanoscale might have been a ‘buzzword’ within optics circles a couple of years ago, but this tiny science is now moving away from the world of theoretical science and new research facilities are popping up in laboratories around the world.

And, with it, nanophotonics brings a myriad of new nano-prefixed buzzwords, including nanocapacitors, nanoforests, nanorice and nanoshells. But the real buzz is around the applications that using light as a tool on the submicron scale could open up.

Continue reading ‘Nanophotonics is moving out of the computational simulations and taking over the labs’ »

WEST LAFAYETTE, Ind. -

Engineers have created the first “active matrix” display using a new class of transparent transistors and circuits, a step toward realizing applications such as e-paper, flexible color monitors and “heads-up” displays in car windshields.

The transistors are made of “nanowires,” tiny cylindrical structures that are assembled on glass or thin films of flexible plastic. The researchers used nanowires as small as 20 nanometers - a thousand times thinner than a human hair - to create a display containing organic light emitting diodes, or OLEDS. The OLEDS are devices that rival the brightness of conventional pixels in flat-panel television sets, computer monitors and displays in consumer electronics.

Continue reading ‘Engineers make first ‘active matrix’ display using nanowires’ »

Scientists have created silicon nanowires that are perfect—at least atomically. Down at the single-atom level, the identical wires have no bumps, bends, or other imperfections. They are perfectly crystalline, even more so than bulk silicon. The full array of nanowires is also highly parallel, and each wire is an excellent metallic conductor.

This research may be an important step forward for nanotechnology. Nanowires play a key role in developing nanoelectronics applications, and silicon nanowires are particularly important because of the central function that silicon plays in the semiconductor industry and current technologies. Some scientists believe that silicon nanowires will overtake carbon nanotubes in popularity, and they are being eyed for a variety of electronics applications and even quantum computing.

Therefore, the ability to create straight, identical, parallel, and atomically smooth nanowires could lead to new developments in nanoelectronics.

Berkeley, CA — Energy now lost as heat during the production of electricity could be harnessed through the use of silicon nanowires synthesized via a technique developed by researchers with the U.S. Department of Energy’s (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) at Berkeley. The far-ranging potential applications of this technology include DOE’s hydrogen fuel cell-powered “Freedom CAR,” and personal power-jackets that could use heat from the human body to recharge cell-phones and other electronic devices.

“This is the first demonstration of high performance thermoelectric capability in silicon, an abundant semiconductor for which there already exists a multibillion dollar infrastructure for low-cost and high-yield processing and packaging,” said Arun Majumdar, a mechanical engineer and materials scientist with joint appointments at Berkeley Lab and UC Berkeley, who was one of the principal investigators behind this research.

“We’ve shown that it’s possible to achieve a large enhancement of thermoelectric energy efficiency at room temperature in rough silicon nanowires that have been processed by wafer-scale electrochemical synthesis,” said chemist Peidong Yang, the other principal investigator behind this research, who also holds a joint Berkeley Lab and UC Berkeley appointment.

Continue reading ‘Feeling The Heat: Berkeley Researchers Make Thermoelectric Breakthrough In Silicon Nanowires’ »

Gaithersburg, MD — Nanowires grown at the National Institute of Standards and Technology (NIST) have a mechanical “quality factor” at least 10 times higher than reported values for other nanoscale devices such as carbon nanotubes, and comparable to that of commercial quartz crystals. Because a high-Q factor indicates a capacity for stable vibrations, the nanowires might be used as oscillators in nano-electromechanical systems for future nano-sensors and communications devices.“We think the most interesting thing about these wires is the very high quality factor observed for such a small object,” says NIST researcher and co-author Kris Bertness, who grew the nanowires.The photo at right depicts an electron micrograph of a NIST-grown nanowire with a high “quality factor” vibrating more than 1 million times per second. At photo’s lower right, a stationary nanowire shows the typical hexagonal shape of the gallium nitride structures.NIST has developed a unique way of growing hexagonal gallium nitride (GaN) nanowires featuring low defect density and high luminescence intensity. In a new paper, researchers at NIST and the University of Colorado at Boulder report high-Q factors in wires that are 30 to 500 nanometers in diameter and 5 to 20 micrometers long, vibrating between 400,000 and 2.8 million times per second. (For comparison, the quartz crystals used in watches usually vibrate about 32,000 times a second.) The nanowires vibrated when placed on a piezoelectric device stimulated by an electrical signal. The nanowires also oscillated when excited directly by an electron beam, apparently due to the GaN material’s intrinsic piezoelectric ability to covert voltage to mechanical force.

Q measures the damping of oscillations in a mechanical system as a function of frequency—the higher its Q, the longer a bell rings after being struck. Ordinarily, Q factors of mechanical resonators tend to drop as their diameters shrink. But GaN nanowires have a number of properties that may boost their Q and make them suitable as practical oscillators. They have extremely flat and smooth surfaces (irregularities have reduced performance in other oscillators.) GaN also has a resonant frequency similar to silicon (commonly used in microelectronics) but is less susceptible to some sources of “noise.” Finally, GaN has high heat capacity and thermal conductivity, reducing sensitivity to temperature fluctuations. Another practical advantage is that NIST’s GaN nanowires are grown on silicon, making them compatible with existing microelectronics processing methods.

To measure the resonance properties of the nanowires, researchers observed clumps of nanowires using a scanning electron microscope. As the frequency of the applied signal was varied across a range, the nanowires seen in micrographs appear to blur or fan out at or near the resonance frequency. For the nanowire shown in the image, the Q value (about 38,000) is at least 10 times higher than previously reported values for other GaN nanowires, carbon nanotubes, and single-crystal silicon microstructures of similar surface-to-volume ratio. The researchers have measured Q values of more than 1 million in resonating GaN nanowires using feedback (like continuous striking of a bell to keep it ringing), as would occur in a real device.

Continue reading ‘NIST Developed GaN Nanowires May Be Practical Oscillators’ »