December '06 Newsletter

With transistors set to reach their smallest possible size in the next two decades, CITRIS researchers are among those searching for the next big computing substrate.<!-- InstanceEndEditable -->

by <!-- InstanceBeginEditable name="Feature1Author" -->Jenn Shreve<!-- InstanceEndEditable -->

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With transistors set to reach their smallest possible size in the next two decades, the silicon chip is likely to change dramatically. CITRIS researchers are among a worldwide body of engineers, physicists, and chemists racing to find which new computing substrate will allow the industry to continue on its current path.

That path has been largely shaped by Gordon Moore's famous prediction that the number of transistors on a silicon chip would double approximately every eighteen months. "Moore's Law" has served as a brass ring for the semiconductor industry, moving innovation at a steady clip for decades. Indeed, it is the basis for the International Technology Roadmap for Semiconductors, which the industry uses to lay out its plans for the next fifteen years. But, as Jeffrey Bokor, an EECS professor at UC Berkeley, explains, major roadblocks are just around the corner.

UC Berkeley EECS Professor Jeffrey Bokor.

"The current 2005 version of the Roadmap has as the final node on there transistors that are as small as six nanometers," Bokor explains. "The new Roadmap is going to come out soon, and it may push a little further. Who knows? There may be a four-nanometer transistor on there. But everybody knows they are not going to get much smaller than that. That is getting pretty close to the absolute limit for standard conventional transistors as we know them now."

Make transistors much smaller than that on a silicon chip, and you run up against numerous difficulties. For example, shrinking the distance between the two output terminals in a silicon transistor makes it harder to switch the transistor off, an operation that is crucial to the operation of logic circuits. Power is another problem. Just because you can add more transistors does not mean you can scale the amount of power each transistor uses. "Putting more and more transistors onto the chips just causes these chips to use up more and more power," says Bokor.

An emerging field called spintronics is addressing the power issue by exploring ways to use electron spin rather than electric charge to process information. Spintronics is the main focus of the newly formed Western Institute of Nanoelectronics, of which Bokor is a leader. At this time, silicon is one of several materials being considered for manipulating electronic spin. "In the WIN center we have many investigators looking at all sorts of materials," Bokor says.

Spintronics is also relevant to the field of quantum computing, which operates on a molecular level. Classical computing relies on bits, which can be in a state of 0 or 1. In quantum computing, bits are replaced by quantum bits, or qubits, which can be in both states at once. That superposition means more complex processing can occur at much higher speeds. "You can do many operations at once by operating on a quantum state rather than a classical state," explains Birgitta Whaley, a professor of chemistry at UC Berkeley and co-director of the Berkeley Quantum Information & Computation (BQIC). That could eventually lead to major breakthroughs in cryptography, search engines, and modeling of complex biological and physical systems.

This diagram depicts a system of qubits, the building blocks of quantum computers. Image Courtesy of KB Whaley.

But quantum states are also highly sensitive to interference and readily revert to classical systems, a reaction called decoherence. Some isotopes in silicon have nuclear spin, which interferes with electron spin, causing decoherence to occur, making silicon a less than ideal substrate for this kind of computing.

If not silicon, then what? Right now, that is anyone's guess. Whaley says her group is basing its quantum computing models on a variety of promising materials, including gallium arsenide and superconductors. She has seen proposals that use lasers to manipulate ions in the gas phase, and others "using atoms trapped in potential fields created by light." She says, "I don't think it is clear right now which material is going to be best. My view is we need to continue to investigate many different proposals for these different ideas."

Of course, one need not reach quantum states to see that better materials are required. "There is already a clear recognition that the transistors that are made down there at the end of the Roadmap certainly will not be pure silicon. There are already materials that allow you to make a better transistor, such as carbon nanotubes," says Bokor.

Tens of thousands times thinner than a human hair, yet remarkably strong and flexible, these thin cylinders of carbon could form the basis for future nanoelectronics. "The advantage of carbon nanotubes is that they can be formed as perfect single molecules of pure carbon, so electrons can move along them in a perfect one-dimensional line without being jostled side-to-side as they are when they move in silicon. This makes it possible to build faster transistors," Bokor explains.

None of this is to say that silicon has been ruled out entirely. Bokor's group has already successfully incorporated carbon nanotubes into a functioning integrated silicon circuit. Both Bokor and Whaley are collaborating with Thomas Schenkel's group at Lawrence Berkeley Laboratory to implement quantum computing in silicon. In addition, Bokor is working with Schenkel on implementing classical spintronics in silicon.

Both Bokor and Whaley point out that there are compelling reasons to keep silicon around. "There is a huge industry built up that understand how to work with silicon. So the more you can take advantage of that infrastructure, the better off you are," says Bokor. Industry giants like IBM, HP, and Intel are not taking any chances; all have announced programs to explore alternative computing substrates.

Whatever the integrated circuit look like, a lot of the research going towards building it will take place in CITRIS's NanoLab Center, which is currently under construction—from housing research equipment to enabling researchers to manufacture and try out new materials and approaches.

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For more information:

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International Technology Roadmap for Semiconductors

Berkeley Quantum Information & Computation Center

Giant leap in small technology: Milestone in the field of nanoelectronics by David Pescovitz (Forefront, Spring, 2004)

Jeffrey Bokor Home Page Whaley Group Home Page Exploration and Control of Condensed Matter Qubits (CITRIS Research Projects)

Focus Center in Materials, Structures, and Devices (CITRIS Research Projects)

Making Quantum Computing Work in Silicon, by Paul Preuss (Science at Berkeley Lab, May 2006)

A Nano-Scale Lab with Societal-Scale Impact by Jenn Shreve (CITRIS Newsletter, August 2006)

Beyond Silicon: Intel is exploring different materials for computer chips. by Kate Green (Technology Review , March 15, 2006

IBM researchers look beyond silicon technology (PhysOrg.com, August 3, 2006)

Beyond Silicon: HP Outlines Comprehensive Strategy for Molecular-scale Electronics (PhysOrg.com, March 14, 2005)

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With a set of major new initiatives and grants, CITRIS campus UC Davis is taking its energy research to the next level. <!-- InstanceEndEditable -->

by <!-- InstanceBeginEditable name="Feature2Author" -->Jenn Shreve<!-- InstanceEndEditable -->

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UC Davis, one of the four CITRIS campuses, has long been known for the depth and breadth of its research into alternative fuels and energy. But three new initiatives—the Energy Efficiency Center, a major grant for biofuel research, and the campus-wide Energy for the Future Initiative—are adding more juice to these endeavors.

Spearheaded by the College of Engineering, the Energy for the Future Initiative is an attempt to integrate and focus the campus’ energy research into a single interdisciplinary research, education, and outreach program. Fifteen new faculty members specializing in energy are being recruited in a wide variety of departments across the campus, with the initial focus on research into transportation systems energy, renewable energy and energy at the molecular frontier.

Professor Daniel Sperling: director of the Institute of Transportation Studies and Associate Director of the Energy Efficiency Center at UC Davis.

"Clean energy could be the next major industrial revolution, following information technology and biotechnology. We, that is, California, the United States and the world are confronting a huge challenge and opportunity. We need to do something about it. We need to replace oil and reduce greenhouse gases. We need to find new ways of supplying energy, which many at Davis are focused on, and need to use it more efficiently—which is what the Energy Efficiency Center (EEC) is all about," says Professor Daniel Sperling, who is the director of Davis's Institute of Transportation Studies, Associate Director of the EEC, and co-director of the campus Energy Initiative. "The campus has decided at the highest levels that this is a top priority," he adds.

As Chancellor Larry Vanderhoef, right, looks on, Gov. Arnold Schwarzenegger congratulates UC Davis for being the winner in a competitive grant process for an energy efficiency center. (Karin Higgins/UC Davis photo)

Launched in April 2006 at a ceremony attended by Governor Arnold Schwarzenegger, the EEC is a perfect example of the Energy Initiative in action. Its focus is on developing business models around energy efficiency research in the areas of transportation, buildings, and agriculture and food processing in order to make energy efficiency central to our economy.

"Energy efficiency technologies are among the best and lowest-cost options for reducing greenhouse gas emissions, for reducing exposure to fluctuating energy costs, and even for increasing the value of investments in alternative energies. Yet energy efficient technologies often face difficulties in moving from research laboratories to the marketplace. The Energy Efficiency Center is focused on helping researchers and entrepreneurs successfully launch new ventures that promote energy efficiency. In essence, our goal is to build sustainable businesses around sustainable technologies," says the Center's director Andrew Hargadon.

Andrew Hargadon: director of the Energy Efficiency Center at UC Davis

Using a model developed at the Center for Entrepreneurship, which Hargadon also directs, the EEC is pairing up business students and industry partners with researchers through meetings and workshops. In some cases, they might make researchers aware of marketplace needs, in order to help them focus their research accordingly. In other cases, they might make industry aware of a new technology that has a lot of potential, effectively creating a new market.

For example, the EEC recently facilitated a partnership between the Innovative Mobility Research (IMR) group at UC’s California Partners for Advanced Transit and Highways (PATH) program and the Bay Area startup ParkingCarma™ to do a "smart parking" pilot program and outreach workshop in Sacramento. Smart parking technology uses information technology and sensor networks to let drivers know when parking spots are available, thus reducing fuel and pollution caused by drivers circling lots. Another initiative is aimed at developing business models around an infrared food-processing technology developed at Davis for efficiently blanching and drying fruits and nuts. Food processing is a major consumer of energy in California.

The EEC also plans to send engineering and science doctoral and post-doctoral students and faculty through a targeted business development curriculum, to give them the tools to build business models and conduct market research around their own work. "We do see that a lot of the doctoral-level students are interested in seeing their work have a significant impact on society, which means getting it out into the market for widespread adoption," says EEC program manager Benjamin Finkelor.

The EEC was launched with a $1 million grant from the California Clean Energy Fund and a matching campus grant of $1.3 million. PG&E Corp. has pledged $500,000 over five years, as well.

If the EEC is focused on technologies that reduce energy consumption, the campus’ Bioenergy Research Group is tackling the issue from the supply side, developing renewable fuels made from biomass to power vehicles in the future in addition to other energy and product uses. That research just got a lot more mileage thanks to a recent $25 million grant over five years from Chevron. What is an oil company doing funding research into the competition? Professor Bryan Jenkins, co-chair of the UC Davis Bioenergy Research Group explains.

"Clearly over the next few decades we are going to see an increasing tightening of supplies of petroleum and conventional fuels and increasing attention to environmental impacts of energy demand," says Jenkins. "Chevron, along with many other companies, is interested in identifying alterative supplies, including biofuels."

Like the EEC and the Energy for the Future Initiative, Chevron's biofuels grant will focus many of the campus’ existing strengths on energy research. "Much of the work that has been done historically on agricultural crops is now being directed at improving and identifying new crops and other biomass sources for the production of bioenergy. Work of this type is likely to be proposed under the Chevron grant," says Jenkins, adding that continuing work in biomass production, processing, conversion, and materials is also likely to be proposed under the grant.

Sperling points out that the campus' increased focus on energy does not merely build upon Davis' well-established research areas, but also its historic roots. "Davis is very much what we call engaged. It still looks to its land grant roots of being an engaged university and trying to be committed to doing research in the public interest; this commitment to a major energy research initiative resonates at all levels and in all ways," Sperling says. <!-- InstanceEndEditable -->

 

For more information:

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Energy for the Future Initiative

UC Davis Energy Efficiency Center

UC Davis Center for Entrepreneurship

UC Davis Institute for Transportation Studies

UC Davis Bioenergy Research Group

Chevron to Fund Major Biofuel Research Projects at UC Davis (UC Davis News, September 19, 2006)

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