Electronix Express Newsletter

June 2010 Issue

Welcome to the June 2010 Issue of the Electronix Express Newsletter

STORIES

Green Machine: Could Cars Run on Sunlight and CO2?

Redefining Electrical Current Law With the Transistor Laser

Computers That Use Light Instead of Electricity? First Germanium Laser Created

The Coming Data Explosion

Chinese Supercomputer Is Ranked World's Second-Fastest, Challenging U.S. Dominance

Solar Cell Sets World Efficiency Record At 40.8 Percent

New 'Electronic Glue' Promises Less Expensive Semiconductors

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1. Green machine: Could Cars Run on Sunlight and CO2?

Greenhouse-gas-pumping cars are, let's face it, never going to be green. But innovative sunlight-powered fuel production techniques could inch motor vehicles towards carbon neutrality. A team at Sandia National Laboratories in Albuquerque, New Mexico, is developing a technique to create some of the ingredients for synthetic fuels from carbon-containing gases. Their cerium-oxide-based system can convert CO2 into carbon monoxide, and can also turn water into hydrogen.

The machine, called the Counter Rotating Ring Receiver Reactor Recuperator (CR5) consists of two chambers separated by rotating rings of cerium oxide. As the rings spin, a large parabolic mirror concentrates solar energy onto one side, heating it to 1500 °C and causing the cerium oxide there to release oxygen gas into one of the chambers, whence it is pumped away. As the ring rotates further it takes the deoxygenated ring off the heat and allows it to cool before it swings round to the other chamber. CO2 is pumped into the second chamber, causing the cooled cerium to steal back an oxygen molecule, producing carbon monoxide and cerium oxide. The process also works with water instead of CO2, with the reaction this time producing hydrogen.

The team is now working to improve reliability while building a bigger reactor with 28 rotating rings. Once the reactor is producing a steady stream of hydrogen and carbon monoxide, the gases can be converted into a synthetic liquid fuel using a technique such as the Fischer-Tropsch process developed in Germany in the 1920s. In this process the two gases are heated in the presence of an iron-based catalyst to produce hydrocarbon fuels. Initially, the team plan to use CO2 captured from power-plant exhaust flues to produce their synthetic fuel. Ultimately, however, they hope to use CO2 extracted directly from the air.

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2. Redefining Electrical Current Law With the Transistor Laser

While the laws of physics weren't made to be broken, sometimes they need revision. A major current law has been rewritten thanks to the three-port transistor laser, developed by Milton Feng and Nick Holonyak Jr. at the University of Illinois. With the transistor laser, researchers can explore the behavior of photons, electrons and semiconductors. The device could shape the future of high-speed signal processing, integrated circuits, optical communications, supercomputing and other applications. However, harnessing these capabilities hinges on a clear understanding of the physics of the device, and data the transistor laser generated did not fit neatly within established circuit laws governing electrical currents.

"We were puzzled. How did that work? Is it violating Kirchhoff's law? How can the law accommodate a further output signal, a photon or optical signal?", said Feng, the Holonyak Chair Professor of Electrical and Computer Engineering. Kirchhoff's current law, described by Gustav Kirchhoff in 1845, states charge input at a node is equal to the charge output. In other words, all the electrical energy going in must go out again. The transistor laser adds a third port for optical output, emitting light. This posed a conundrum for researchers working with the laser: How were they to apply the laws of conservation of charge and conservation of energy with two forms of energy output?

"The optical signal is connected and related to the electrical signals, but until now it's been dismissed in a transistor," said Holonyak. "Kirchhoff's law takes care of balancing the charge, but it doesn't take care of balancing the energies. The question is, how do you put it all together, and represent it in circuit language?" The unique properties of the transistor laser required Holonyak, Feng and graduate student Han Wui to re-examine and modify the law to account for photon particles as well as electrons, effectively expanding it from a current law to a current-energy law. They published their model and supporting data in the Journal of Applied Physics, available online May 10.

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3. Computers That Use Light Instead of Electricity? First Germanium Laser Created

MIT researchers have demonstrated the first laser built from germanium that can produce wavelengths of light useful for optical communication. It's also the first germanium laser to operate at room temperature. Unlike the materials typically used in lasers, germanium is easy to incorporate into existing processes for manufacturing silicon chips. So the result could prove an important step toward computers that move data and maybe even perform calculations using light instead of electricity. But more fundamentally, the researchers have shown that, contrary to prior belief, a class of materials called indirect-band-gap semiconductors can yield practical lasers.

As chips' computational capacity increases, they need higher-bandwidth connections to send data to memory. But conventional electrical connections will soon become impractical, because they'll require too much power to transport data at ever higher rates. Transmitting data with lasers -- devices that concentrate light into a narrow, powerful beam -- could be much more power-efficient. However, it requires a cheap way to integrate optical and electronic components on silicon chips.

In a forthcoming paper in the journal Optics Letters, Kimerling, Michel and three other researchers in the group describe how they coaxed excited germanium electrons into the higher-energy, photon-emitting state. According to Miao, one member of the group, "high-speed optical circuits like germanium in general is a good marriage and a good combination." Miao points out that the germanium lasers need to become more power-efficient before they're a practical source of light for optical communications systems. "But on the other hand, the promise is exciting, and the fact that they got germanium to lase at all is very exciting", he says. So their laser research is very, very promising.

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4. The Coming Data Explosion

One of the key aspects of the emerging Internet of things, where real-world objects are connected to the Internet, is the massive amount of new data on the Web that will result. As more and more things in the world are connected to the Internet, it follows that more data will be uploaded to and downloaded from the cloud. And this is in addition to the burgeoning amount of user-generated content which has increased 15-fold over the past few years, according to a presentation that Google VP Marissa Mayer made last August at Xerox PARC. Mayer said in that presentation that this data explosion is bigger than Moore's law.

Like Mayer, Parthasarathy Ranganathan, a distinguished technologist at HP Labs, compared the online data growth rate to Moore's Law. According to Ranganathan, it's rising significantly faster than Moore's Law. HP CEO Mark Hurd put it this way in June 2009: "more data will be created in the next four years than in the history of the planet." In her presentation at PARC, intriguingly entitled 'The Physics of Data,' Marissa Mayer noted that there have been 3 big changes to Internet data in recent times-- speed (real-time data), scale (unprecedented processing power), and sensors (new kinds of data).

Marissa Mayer talked about "a sensor revolution," including data from mobile phones which she remarked that "today's phones are almost like people," in that they have senses such as eyes (a camera), ears (a microphone) and skin (a touch screen). Mayer went on to say that there were 5 exabytes of data online in 2002, which had risen to 281 exabytes in 2009. That's a growth rate of 56x over 7 years. What will be the future impact of such data explosion? Mayer states, "We don't know yet which computing or Internet companies will be most successful over the next 5-10 years, but one thing is for sure. They'll have to know how to process and make sense of massive quantities of data flowing through the Web - and do it in real-time."

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5. Chinese Supercomputer Is Ranked World's Second-Fastest, Challenging U.S. Dominance

A Chinese supercomputer has been ranked as the world's second-fastest machine, surpassing European and Japanese systems and underscoring China's aggressive commitment to science and technology. The Dawning Nebulae, based at the National Supercomputing Center in Shenzhen, China, has achieved a sustained computing speed of 1.27 petaflops - the equivalent of one thousand trillion mathematical operations a second - in the latest semiannual ranking of the world's fastest 500 computers.

Supercomputers are used for scientific and engineering problems as diverse as climate simulation and automotive design. The Chinese machine is actually now ranked as the world's fastest in terms of theoretical peak performance, but that is considered a less significant measure than the actual computing speed achieved on a standardized computing test. The world's fastest computer remains the Cray Jaguar supercomputer, based at the Oak Ridge National Laboratory in Tennessee. Last November it was measured at 1.75 petaflops. But China appears intent on challenging American dominance. There had been some expectation that China would make an effort to complete a system based on Chinese-designed components in time for the June ranking. The Nebulae is based on chips from Intel and Nvidia. The new system, which is based on a microprocessor that has been designed and manufactured in China, is now expected later this year. A number of supercomputing industry scientists and engineers said that it was possible that the new machine would claim the title of world's fastest.

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6. Solar Cell Sets World Efficiency Record At 40.8 Percent

Scientists at the U.S. Department of Energy's National Renewable Energy Laboratory (NREL) have set a world record in solar cell efficiency with a photovoltaic device that converts 40.8 percent of the light that hits it into electricity. This is the highest confirmed efficiency of any photovoltaic device to date. The inverted metamorphic triple-junction solar cell was designed, fabricated and independently measured at NREL. The 40.8 percent efficiency was measured under concentrated light of 326 suns. One sun is about the amount of light that typically hits Earth on a sunny day. The new cell is a natural candidate for the space satellite market and for terrestrial concentrated photovoltaic arrays, which use lenses or mirrors to focus sunlight onto the solar cells.

The new solar cell differs significantly from the previous record holder, also based on a NREL design. Instead of using a germanium wafer as the bottom junction of the device, the new design uses compositions of gallium indium phosphide and gallium indium arsenide to split the solar spectrum into three equal parts that are absorbed by each of the cell's three junctions for higher potential efficiencies. This is accomplished by growing the solar cell on a gallium arsenide wafer, flipping it over, then removing the wafer. The resulting device is extremely thin and light and represents a new class of solar cells with advantages in performance, design, operation and cost.

NREL's Mark Wanlass invented the original inverted cell, which recently won a R&D 100 award. His design was modified by a team led by John Geisz that further optimized the junction energies by making the middle junction metamorphic as well as the bottom junction. Metamorphic junctions are lattice mismatched - their atoms don't line up. The material properties of the mismatched semiconductors allows for greater potential conversion of sunlight.

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7. New 'Electronic Glue' Promises Less Expensive Semiconductors

Researchers at the University of Chicago and Lawrence Berkeley National Laboratory have developed an electronic glue that could accelerate advances in semiconductor-based technologies, including solar cells and thermoelectric devices that convert sun light and waste heat, respectively, into useful electrical energy. Semiconductors have served as choice materials for many electronic and optical devices because of their physical properties. Commercial solar cells, computer chips and other semiconductor technologies typically use large semiconductor crystals. But that is expensive and can make large-scale applications such as rooftop solar-energy collectors way out of reach.

However, engineers see great potential in semiconductor nanocrystals, sometimes just a few hundred atoms each. Nanocrystals can be readily mass-produced and used for device manufacturing via inkjet printing and other solution-based processes. But a problem remains: The crystals are unable to efficiently transfer their electric charges to one another due to surface ligands-bulky, insulating organic molecules that cap nanocrystals.

The electronic glue developed in Dmitri Talapin's laboratory at the University of Chicago solves the ligand problem. The team describes in the journal Science how substituting the insulating organic molecules with novel inorganic molecules dramatically increases the electronic coupling between nanocrystals. The University of Chicago licensed the underlying technology for thermoelectric applications to Evident Technologies in February.

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