The new technology has the potential to dramatically increase the driving range of electric vehicles and eventually transform highway travel, according to the researchers. Their results are published in the journal Applied Physics Letters (APL).

“Our vision is that you’ll be able to drive onto any highway and charge your car,” said Shanhui Fan, an associate professor of electrical engineering. “Large-scale deployment would involve revamping the entire highway system and could even have applications beyond transportation.”

Driving range

A wireless charging system would address a major drawback of plug-in electric cars – their limited driving range. The all-electric Nissan Leaf, for example, gets less than 100 miles on a single charge, and the battery takes several hours to fully recharge.

A charge-as-you-drive system would overcome these limitations. “What makes this concept exciting is that you could potentially drive for an unlimited amount of time without having to recharge,” said APL study co-author Richard Sassoon, the managing director of the Stanford Global Climate and Energy Project (GCEP), which funded the research. “You could actually have more energy stored in your battery at the end of your trip than you started with.”

The wireless power transfer is based on a technology called magnetic resonance coupling. Two copper coils are tuned to resonate at the same natural frequency – like two wine glasses that vibrate when a specific note is sung. The coils are placed a few feet apart. One coil is connected to an electric current, which generates a magnetic field that causes the second coil to resonate. This magnetic resonance results in the invisible transfer of electric energy through the air from the first coil to the receiving coil.

“Wireless power transfer will only occur if the two resonators are in tune,” Fan noted. “Objects tuned at different frequencies will not be affected.”

In 2007, researchers at the Massachusetts Institute of Technology used magnetic resonance to light a 60-watt bulb. The experiment demonstrated that power could be transferred between two stationary coils about six feet apart, even when humans and other obstacles are placed in between.

“In the MIT experiment, the magnetic field appeared to have no impact on people who stood between the coils,” Fan said. “That’s very important in terms of safety. ”

Wireless charging

The MIT researchers have created a spinoff company that’s developing a stationary charging system capable of wirelessly transferring about 3 kilowatts of electric power to a vehicle parked in a garage or on the street.

Fan and his colleagues wondered if the MIT system could be modified to transfer 10 kilowatts of electric power over a distance of 6.5 feet – enough to charge a car moving at highway speeds. The car battery would provide an additional boost for acceleration or uphill driving.

Here’s how the system would work: A series of coils connected to an electric current would be embedded in the highway. Receiving coils attached to the bottom of the car would resonate as the vehicle speeds along, creating magnetic fields that continuously transfer electricity to charge the battery.

To determine the most efficient way to transmit 10 kilowatts of power to a real car, the Stanford team created computer models of systems with metal plates added to the basic coil design.

“Asphalt in the road would probably have little effect, but metallic elements in the body of the car can drastically disturb electromagnetic fields,” Fan explained. “That’s why we did the APL study – to figure out the optimum transfer scheme if large metal objects are present.”

Using mathematical simulations, postdoctoral scholars Xiaofang Yu and Sunil Sandhu found the answer: A coil bent at a 90-degree angle and attached to a metal plate can transfer 10 kilowatts of electrical energy to an identical coil 6.5 feet away.

“That’s fast enough to maintain a constant speed,” Fan said. “To actually charge the car battery would require arrays of coils embedded in the road. This wireless transfer scheme has an efficiency of 97 percent.” Wireless future

Fan and his colleagues recently filed a patent application for their wireless system. The next step is to test it in the laboratory and eventually try it out in real driving conditions. “You can very reliably use these computer simulations to predict how a real device would behave,” Fan said.

The researchers also want to make sure that the system won’t affect drivers, passengers or the dozens of microcomputers that control steering, navigation, air conditioning and other vehicle operations.

“We need to determine very early on that no harm is done to people, animals, the electronics of the car or to credit cards in your wallet,” said Sven Beiker, executive director of the Center for Automotive Research at Stanford (CARS). Although a power transfer efficiency of 97 percent is extremely high, Beiker and his colleagues want to be sure that the remaining 3 percent is lost as heat and not as potentially harmful radiation.

Some transportation experts envision an automated highway system where driverless electric vehicles are wirelessly charged by solar power or other renewable energy sources. The goal would be to reduce accidents and dramatically improve the flow of traffic while lowering greenhouse gas emissions.

Beiker, who co-authored the APL study, said that wireless technology might one day assist GPS navigation of driverless cars. “GPS has a basic accuracy of 30-40 feet,” he said. “It tells you where you are on the planet, but for safety, you want to make sure that your car is in the center of the lane.” In the proposed system, the magnetic fields could also be used to control steering, he explained. Since the coils would be in the center of the lane, they could provide very precise positioning at no extra cost.

The researchers also have begun discussions with Michael Lepech, an assistant professor of civil and environmental engineering, to study the optimal layout of roadbed transmitters and determine if rebar and other metals in the pavement will reduce efficiency.

“We have the opportunity to rethink how electric power is delivered to our cars, homes and work,” Fan said. “We’re used to thinking about power delivery in terms of wires and plugging things into the wall. Imagine that instead of wires and plugs, you could transfer power through a vacuum. Our work is a step in that direction.”

This article was written by Mark Shwartz, communications/energy writer at the Precourt Institute for Energy at Stanford University.

Contact: Mark Shwartz
mshwartz@stanford.edu
650-723-9296
Stanford University

Because there is no standard method for setting up passwords, each Web site employs its own set of requirements and restrictions. After investigating the pros and cons of design-related features of the requirement and restriction practices of 90 popular Web sites, the authors found that more than half the sites failed to display password guidance prior to the first attempt. Users may receive multiple error messages if their chosen passwords do not line up with system requirements, which can lead to confusion and frustration for the user and increased operating expenses for system administrators.

The authors offer a number of recommendations for Web designers seeking to improve the user experience: Provide users with password requirements prior to their first attempt; use clear and concise language to communicate the password requirements; present, at a minimum, length and character requirements; and avoid placing password requirements in the entry box.

“This study helps us gain more insight into the current state of password practices and helps create more intuitive and empathic interactions,” said Moshfeghian. “Intuitive password practices lead to increased user trust and thus user sustainability. In short, the optimal goal is to humanize interfaces, make them as intuitive as possible, and bridge the gap between users and interfaces.”

Enhancing user experience through effective password practices can have many benefits. A more user-friendly registration process may produce a larger number of successfully registered accounts, which can translate into increased sales and a more recognizable brand. Fewer failed registration attempts can result in reduced system maintenance, security, and password recovery costs.

For more information on this article, contact HFES Communications Director Lois Smith (lois@hfes.org; 310/394-1811).

The Human Factors and Ergonomics Society is the world’s largest nonprofit individual-member, multidisciplinary scientific association for human factors/ergonomics professionals, with more than 4,500 members globally. HFES members include psychologists and other scientists, designers, and engineers, all of whom have a common interest in designing systems and equipment to be safe and effective for the people who operate and maintain them. Watch science news stories about other HF/E topics at the HFES Web site. “Human Factors and Ergonomics: People-Friendly Design Through Science and Engineering”

Plan to attend the HFES 56th Annual Meeting, October 22-26: http://www.hfes.org/web/HFESMeetings/2012annualmeeting.html

Contact: Lois Smith
lois@hfes.org
310-394-1811
Human Factors and Ergonomics Society

In the study, researchers from the Institute of Materials Research and Engineering (IMRE), a research institute of the Agency for Science, Technology and Research (A*STAR) in Singapore, and Imperial College London in the UK have made T-rays into a much stronger directional beam than was previously thought possible, and have done so at room-temperature conditions. This is a breakthrough that should allow future T-ray systems to be smaller, more portable, easier to operate, and much cheaper than current devices.

The scientists say that the T-ray scanner and detector could provide part of the functionality of a Star Trek-like medical ‘tricorder’ – a portable sensing, computing and data communications device – since the waves are capable of detecting biological phenomena such as increased blood flow around tumorous growths. Future scanners could also perform fast wireless data communication to transfer a high volume of information on the measurements it makes.

T-rays are waves in the far infrared part of the electromagnetic spectrum that have a wavelength hundreds of times longer than those that make up visible light. Such waves are already in use in airport security scanners, prototype medical scanning devices and in spectroscopy systems for materials analysis. T-rays can sense molecules such as those present in cancerous tumours and living DNA, since every molecule has its unique signature in the THz range. They can also be used to detect explosives or drugs, for gas pollution monitoring or non-destructive testing of semiconductor integrated circuit chips.

Current T-ray imaging devices are very expensive and operate at only a low output power, since creating the waves consumes large amounts of energy and needs to take place at very low temperatures.

In the new technique, the researchers demonstrated that it is possible to produce a strong beam of T-rays by shining light of differing wavelengths on a pair of electrodes – two pointed strips of metal separated by a 100 nanometre gap on top of a semiconductor wafer. The structure of the tip-to-tip nano-sized gap electrode greatly enhances the THz field and acts like a nano-antenna to amplify the wave generated. In this method, THz waves are produced by an interaction between the electromagnetic waves of the light pulses and a powerful current passing between the semiconductor electrodes. The scientists are able to tune the wavelength of the T-rays to create a beam that is useable in the scanning technology.

Lead author Dr Jing Hua Teng, from A*STAR’s IMRE, said: “The secret behind the innovation lies in the new nano-antenna that we had developed and integrated into the semiconductor chip.” Arrays of these nano-antennas create much stronger THz fields that generate a power output that is 100 times higher than the power output of commonly used THz sources that have conventional interdigitated antenna structures. A stronger T-ray source renders the T-ray imaging devices more power and higher resolution.

Research co-author Stefan Maier, a visiting scientist at A*STAR’s IMRE and Professor in the Department of Physics at Imperial College London, said: “T-rays promise to revolutionise medical scanning to make it faster and more convenient, potentially relieving patients from the inconvenience of complicated diagnostic procedures and the stress of waiting for accurate results. Thanks to modern nanotechnology and nanofabrication, we have made a real breakthrough in the generation of T-rays that takes us a step closer to these new scanning devices. With the introduction of a gap of only 0.1 micrometers into the electrodes, we have been able to make amplified waves at the key wavelength of 1000 micrometers that can be used in such real world applications.”

The research was led by scientists from A*STAR’s IMRE and Imperial College London, and involved partners from A*STAR Institute for Infocomm Research (I2R) and the National University of Singapore. The research is funded under A*STAR’s Metamaterials Programme and the THz Programme, as well as the Leverhume Trust and the Engineering and Physical Sciences Research Council (EPSRC) in the UK.

Contact: Simon Levey
s.levey@imperial.ac.uk
44-020-759-46702
Imperial College London

Quantum computers are expected to play an important role in future information processing since they can outperform classical computers at many tasks. Considering the challenges inherent in building quantum devices, it is conceivable that future quantum computing capabilities will exist only in a few specialized facilities around the world – much like today’s supercomputers. Users would then interact with those specialized facilities in order to outsource their quantum computations. The scenario follows the current trend of cloud computing: central remote servers are used to store and process data – everything is done in the “cloud.” The obvious challenge is to make globalized computing safe and ensure that users’ data stays private.

The latest research, to appear in Science, reveals that quantum computers can provide an answer to that challenge. “Quantum physics solves one of the key challenges in distributed computing. It can preserve data privacy when users interact with remote computing centers,” says Stefanie Barz, lead author of the study. This newly established fundamental advantage of quantum computers enables the delegation of a quantum computation from a user who does not hold any quantum computational power to a quantum server, while guaranteeing that the user’s data remain perfectly private. The quantum server performs calculations, but has no means to find out what it is doing – a functionality not known to be achievable in the classical world.

The scientists in the Vienna research group have demonstrated the concept of “blind quantum computing” in an experiment: they performed the first known quantum computation during which the user’s data stayed perfectly encrypted. The experimental demonstration uses photons, or “light particles” to encode the data. Photonic systems are well-suited to the task because quantum computation operations can be performed on them, and they can be transmitted over long distances.

The process works in the following manner. The user prepares qubits – the fundamental units of quantum computers – in a state known only to himself and sends these qubits to the quantum computer. The quantum computer entangles the qubits according to a standard scheme. The actual computation is measurement-based: the processing of quantum information is implemented by simple measurements on qubits. The user tailors measurement instructions to the particular state of each qubit and sends them to the quantum server. Finally, the results of the computation are sent back to the user who can interpret and utilize the results of the computation. Even if the quantum computer or an eavesdropper tries to read the qubits, they gain no useful information, without knowing the initial state; they are “blind.”

The research at the Vienna Center for Quantum Science and Technology (VCQ) at the University of Vienna and at the Institute for Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences was undertaken in collaboration with the scientists who originally invented the protocol, based at the University of Edinburgh, the Institute for Quantum Computing (University of Waterloo), the Centre for Quantum Technologies (National University of Singapore), and University College Dublin.

Publication: “Demonstration of Blind Quantum Computing” Stefanie Barz, Elham Kashefi, Anne Broadbent, Joseph Fitzsimons, Anton Zeilinger, Philip Walther. DOI: 10.1126/science.1214707

Contact: Stefanie Barz
stefanie.barz@univie.ac.at
University of Vienna

Stephanie B. Velegol and colleagues explain that removing the disease-causing microbes and sediment from drinking water requires technology not always available in rural areas of developing countries. For an alternative approach, Velegol looked to Moringa oleifera, also called the “miracle tree,” a plant grown in equatorial regions for food, traditional medicine and biofuel. Past research showed that a protein in Moringa seeds can clean water, but using the approach was too expensive and complicated. So Velegol’s team sought to develop a simpler and less expensive way to utilize the seeds’ power.

To do that, they added an extract of the seed containing the positively charged Moringa protein, which binds to sediment and kills microbes, to negatively charged sand. The resulting “functionalized,” or “f-sand,” proved effective in killing harmful E. coli bacteria and removing sediment from water samples. “The results open the possibility that … f-sand can provide a simple, locally sustainable process for producing storable drinking water,” the researchers say.

The authors acknowledge funding from the National Science Foundation, and the U. S. Environmental Protection Agency.

Contact: Michael Bernstein
m_bernstein@acs.org
202-872-6042
American Chemical Society

Experiments and atom-by-atom supercomputer models of the wires have found that the wires maintain a low capacity for resistance despite being more than 20 times thinner than conventional copper wires in microprocessors.

The discovery, which was published in this week’s journal Science, has several implications, including:

• For engineers it could provide a roadmap to future nanoscale computational devices where atomic sizes are at the end of Moore’s law. The theory shows that a single dense row of phosphorus atoms embedded in silicon will be the ultimate limit of downscaling.
• For computer scientists, it places donor-atom based silicon quantum computing closer to realization.
• And for physicists, the results show that Ohm’s Law, which demonstrates the relationship between electrical current, resistance and voltage, continues to apply all the way down to an atomic-scale wire.

Bent Weber, the paper’s lead author and a graduate student in the Centre of Excellence for Quantum Computation and Communication Technology at the University of New South Wales, was thrilled with the finding.

“It’s extraordinary to show that Ohm’s Law, such a basic law, still holds even when constructing a wire from the fundamental building blocks of nature – atoms,” he says.

The innovation of the Australian group was to build the circuits up atom by atom, instead of the current method of building microprocessors, in which material is stripped away, says Gerhard Klimeck, a Purdue professor of electrical and computer engineering and director of the Network for Computational Nanotechnology.

“Typically we chip or etch material away, which can be very expensive, difficult and inaccurate,” Klimeck says. “Once you get to 20 atoms wide you have atomic flucuations that make scaling difficult. But this experimental group built devices by placing atomically thin layers of phosphorus in silicon and found that with densely doped phosphorus wires just four atoms wide it acts like a wire that conducts just as well as metal.”

The goal of the research is to develop future quantum computers in which single atoms are used for the computation, says Michelle Simmons, director of the Centre of Excellence for Quantum Computation and Communication Technology at the University of New South Wales and the project’s principal investigator.

“We are on the threshold of making transistors out of individual atoms,” Simmons says. “But to build a practical quantum computer we have recognized that the interconnecting wiring and circuitry also needs to shrink to the atomic scale.”

Hoon Ryu, a Purdue graduate who is now a senior researcher with the Korea Institute of Science and Technology’s Supercomputing Center, said the practicality of the research is exciting.

“The metallic wire is in principle quite difficult to be scaled into one- to two-nanometer pitch, but in both experimental and modeling views, the research result is quite remarkable,” Ryu says. “For the first time, this demonstrates the possibility that densely doping wire is a viable alternative for the next-gerenation, ultra-scale metallic interconnect in silicon chips.”

To assist the Australian researchers, Klimeck’s research team ran hundreds of simulations to study the variability of these nanoscale structures.

“Having the throughput capability for a highly scalable code is important for doing that, and we have that capability here at Purdue with http://nanoHUB.org,” Klimeck says. “We ran hundreds of cases to understand the potential landscape of these devices, so this was computationally intensive work.”

Klimeck says that in addition to the project’s scientific and engineering implications, he found the collaboration the most rewarding aspect.

“It is an exciting collaboration,” he says. “We were doing simulations of experimental work, which was based on a theoretical model. So we were bringing the three legs of modern science together in one project. Plus, our graduate students are able to stay in contact and work with each other despite working in various locations around the world. It’s hard to think of a better example of how science is done today.”

Writer: Steve Tally, 765-494-9809, tally@purdue.edu, Twitter: sciencewriter

Media contacts: Greg Kline, 765-494-8167, gkline@purdue.edu
University of New South Wales media contact: Mary O╒Malley, 0438 881 124, m.omalley@unsw.edu.au

Sources: Michelle Simmons, 0425 336 756 michelle.simmons@unsw.edu.au
Gerhard Klimeck, 765-494-9212, gekco@purdue.edu
Hoon Ryu, elec1020@gmail.com

Related websites:
Centre of Excellence for Quantum Computation and Communication Technology at the University of South Wales: http://www.cqc2t.org
Network for Computational Nantechnology, nanoHUB, Purdue University: https://www.ncn.purdue.edu/
Michelle Simmons: http://www.cqc2t.org/biography/98
Gerhard Klimeck: http://nanoHUB.org/klimeck

IMAGE CAPTION:

Wires just one atom tall have been created by inserting a string of phosphorus atoms in a silicon crystal by a team of researchers from the Univeristy of New South Wales, Melbourne Univeristy and Purdue University. This image from a computational simulation run of the wires shows electron density as electrons flow from left to right. The wires are 20 times smaller than the smallest wires now available and measure just four atoms wide by one phosphorus atom tall. (Purdue University image/Sunhee Lee, Hoon Ryu and Gerhard Klimeck)

http://news.uns.purdue.edu/images/2012/klimeck-phosphorus.jpg

Abstract on the research in this release is available at: http://www.purdue.edu/newsroom/research/2012/120105KlimeckPhosphorus.html

Contact: Steve Tally
tally@purdue.edu
765-494-9809
Purdue University

Ridding water of trace metals “is really hard to do,” said Joseph Calo, professor emeritus of engineering who maintains an active laboratory at Brown. He noted the cost, inefficiency, and time needed for such efforts. “It’s like trying to put the genie back in the bottle.”

That may be changing. Calo and other engineers at Brown describe a novel method that collates trace heavy metals in water by increasing their concentration so that a proven metal-removal technique can take over. In a series of experiments, the engineers report the method, called the cyclic electrowinning/precipitation (CEP) system, removes up to 99 percent of copper, cadmium, and nickel, returning the contaminated water to federally accepted standards of cleanliness. The automated CEP system is scalable as well, Calo said, so it has viable commercial potential, especially in the environmental remediation and metal recovery fields. The system’s mechanics and results are described in a paper published in the Chemical Engineering Journal.

A proven technique for removing heavy metals from water is through the reduction of heavy metal ions from an electrolyte. While the technique has various names, such as electrowinning, electrolytic removal/recovery or electroextraction, it all works the same way, by using an electrical current to transform positively charged metal ions (cations) into a stable, solid state where they can be easily separated from the water and removed. The main drawback to this technique is that there must be a high-enough concentration of metal cations in the water for it to be effective; if the cation concentration is too low – roughly less than 100 parts per million – the current efficiency becomes too low and the current acts on more than the heavy metal ions.

Another way to remove metals is through simple chemistry. The technique involves using hydroxides and sulfides to precipitate the metal ions from the water, so they form solids. The solids, however, constitute a toxic sludge, and there is no good way to deal with it. Landfills generally won’t take it, and letting it sit in settling ponds is toxic and environmentally unsound. “Nobody wants it, because it’s a huge liability,” Calo said.

The dilemma, then, is how to remove the metals efficiently without creating an unhealthy byproduct. Calo and his co-authors, postdoctoral researcher Pengpeng Grimshaw and George Hradil, who earned his doctorate at Brown and is now an adjunct professor, combined the two techniques to form a closed-loop system. “We said, ‘Let’s use the attractive features of both methods by combining them in a cyclic process,’” Calo said.

It took a few years to build and develop the system. In the paper, the authors describe how it works. The CEP system involves two main units, one to concentrate the cations and another to turn them into stable, solid-state metals and remove them. In the first stage, the metal-laden water is fed into a tank in which an acid (sulfuric acid) or base (sodium hydroxide) is added to change the water’s pH, effectively separating the water molecules from the metal precipitate, which settles at the bottom. The “clear” water is siphoned off, and more contaminated water is brought in. The pH swing is applied again, first redissolving the precipitate and then reprecipitating all the metal, increasing the metal concentration each time. This process is repeated until the concentration of the metal cations in the solution has reached a point at which electrowinning can be efficiently employed.

When that point is reached, the solution is sent to a second device, called a spouted particulate electrode (SPE). This is where the electrowinning takes place, and the metal cations are chemically changed to stable metal solids so they can be easily removed. The engineers used an SPE developed by Hradil, a senior research engineer at Technic Inc., located in Cranston, R.I. The cleaner water is returned to the precipitation tank, where metal ions can be precipitated once again. Further cleaned, the supernatant water is sent to another reservoir, where additional processes may be employed to further lower the metal ion concentration levels. These processes can be repeated in an automated, cyclic fashion as many times as necessary to achieve the desired performance, such as to federal drinking water standards.

In experiments, the engineers tested the CEP system with cadmium, copper, and nickel, individually and with water containing all three metals. The results showed cadmium, copper, and nickel were lowered to 1.50, 0.23 and 0.37 parts per million (ppm), respectively – near or below maximum contaminant levels established by the Environmental Protection Agency. The sludge is continuously formed and redissolved within the system so that none is left as an environmental contaminant.

“This approach produces very large volume reductions from the original contaminated water by electrochemical reduction of the ions to zero-valent metal on the surfaces of the cathodic particles,” the authors write. “For an initial 10 ppm ion concentration of the metals considered, the volume reduction is on the order of 106.”

Calo said the approach can be used for other heavy metals, such as lead, mercury, and tin. The researchers are currently testing the system with samples contaminated with heavy metals and other substances, such as sediment, to confirm its operation.

The research was funded by the National Institute of Environmental Health Sciences, a branch of the National Institutes of Health, through the Brown University Superfund Research Program.

Contact: Richard Lewis
Richard_Lewis@brown.edu
401-863-3766
Brown University

The approach could enable engineers to build faster, more compact and efficient integrated circuits and lighter laptops that generate less heat than today’s. The transistors contain tiny nanowires made not of silicon, like conventional transistors, but from a material called indium-gallium-arsenide.

The device was created using a so-called “top-down” method, which is akin to industrial processes to precisely etch and position components in transistors. Because the approach is compatible with conventional manufacturing processes, it is promising for adoption by industry, said Peide “Peter” Ye, a professor of electrical and computer engineering at Purdue.

A new generation of silicon computer chips, due to debut in 2012, will contain transistors having a vertical structure instead of a conventional flat design. However, because silicon has a limited “electron mobility” – how fast electrons flow – other materials will likely be needed soon to continue advancing transistors with this 3-D approach, Ye said.

Indium-gallium-arsenide is among several promising semiconductors being studied to replace silicon. Such semiconductors are called III-V materials because they combine elements from the third and fifth groups of the periodic table.

“Industry and academia are racing to develop transistors from the III-V materials,” Ye said. “Here, we have made the world’s first 3-D gate-all-around transistor on much higher-mobility material than silicon, the indium-gallium-arsenide.”

Findings will be detailed in a paper to be presented during the International Electron Devices Meeting on Dec. 5-7 in Washington, D.C. The work is led by Purdue doctoral student Jiangjiang Gu; Harvard doctoral student Yiqun Liu; Roy Gordon, Harvard’s Thomas D. Cabot Professor of Chemistry; and Ye.

Transistors contain critical components called gates, which enable the devices to switch on and off and to direct the flow of electrical current. In today’s chips, the length of these gates is about 45 nanometers, or billionths of a meter. However, in 2012 industry will introduce silicon-based 3-D transistors having a gate length of 22 nanometers.

“Next year if you buy a computer it will have the 22-nanometer gate length and 3-D silicon transistors,” Ye said.

The 3-D design is critical because the 22-nanometer gate lengths will not work in a flat design.

“Once you shrink gate lengths down to 22 nanometers on silicon you have to do more complicated structure design,” Ye said. “The ideal gate is a necklike, gate-all-around structure so that the gate surrounds the transistor on all sides.”

The nanowires are coated with a “dielectric,” which acts as a gate. Engineers are working to develop transistors that use even smaller gate lengths, 14 nanometers, by 2015.

However, further size reductions beyond 14 nanometers and additional performance improvements are likely not possible using silicon, meaning new designs and materials will be needed to continue progress, Ye said.

“Nanowires made of III-V alloys will get us to the 10 nanometer range,” he said.

The new findings confirmed that the device made using a III-V material has the potential to conduct electrons five times faster than silicon.

Creating smaller transistors also will require finding a new type of insulating layer essential for the devices to switch off. As gate lengths shrink smaller than 14 nanometers, the silicon dioxide insulator used in conventional transistors fails to perform properly and is said to “leak” electrical charge.

One potential solution to this leaking problem is to replace silicon dioxide with materials that have a higher insulating value, or “dielectric constant,” such as hafnium dioxide or aluminum oxide.

In the new work, the researchers applied a dielectric coating made of aluminum oxide using a method called atomic layer deposition. Because atomic layer deposition is commonly used in industry, the new design may represent a practical solution to the coming limits of conventional silicon transistors.

Using atomic layer deposition might enable engineers to design transistors having thinner oxide and metal layers for the gates, possibly consuming far less electricity than silicon devices.

“A thinner dielectric layer means speed goes up and voltage requirements go down,” Ye said.

The work is funded by the National Science Foundation and the Semiconductor Research Corp. and is based at the Birck Nanotechnology Center in Purdue’s Discovery Park. The latest research is similar to, but fundamentally different from, research reported by Ye’s group in 2009. That work involved a design called a finFET, for fin field-effect transistor, which uses a finlike structure instead of the conventional flat design. The new design uses nanowires instead of the fin design.

Writer: Emil Venere, 765-494-4709, venere@purdue.edu

Source: Peide Ye, 765-494-7611, yep@purdue.edu

Note to Journalists: An electronic copy of the paper is available from Emil Venere, Purdue News Service, at 765-494-4709, venere@purdue.edu

Transistors that exploit a quantum quirk

Today’s computers have no less than a billion transistors in the CPU alone. These small switches that turn on and off provide the famous binary instructions, the 0s and 1s that let us send emails, watch videos, move the mouse pointer… and much more. The technology used in today’s transistors is called “field effect;” whereby voltage induces an electron channel that activates the transistor. But field effect technology is approaching its limits, particularly in terms of power consumption.

Tunnel-FET technology is based on a fundamentally different principle. In the transistor, two chambers are separated by an energy barrier. In the first, a horde of electrons awaits while the transistor is deactivated. When voltage is applied, they cross the energy barrier and move into the second chamber, activating the transistor in so doing.

In the past, the tunnel effect was known to disrupt the operation of transistors. According to quantum theory, some electrons cross the barrier, even if they apparently don’t have enough energy to do so. By reducing the width of this barrier, it becomes possible to amplify and take advantage of the quantum effect – the energy needed for the electrons to cross the barrier is drastically reduced, as is power consumption in standby mode.

Mass production is imminent

“By replacing the principle of the conventional field effect transistor by the tunnel effect, one can reduce the voltage of transistors from 1 volt to 0.2 volts,” explains Ionescu. In practical terms, this decrease in electrical tension will reduce power consumption by up to a factor of 100. The new generation microchips will combine conventional and tunnel-FET technology. “The current prototypes by IBM and the CEA-Leti have been developed in a pre-industrial setting. We can reasonably expect to see mass production by around 2017.”

An essential technology for a major European project

For Ionescu, who heads the Guardian Angels project (a project vetted for a billion Euro grant from the EU), tunnel-FET technology is without a doubt the next big technological leap in the field of microprocessors. “In the Guardian Angels project, one of our objectives is to find solutions to reduce the power consumption of processors. Tunnel-FET is the next revolution that will help us achieve this goal.” The aim: design ultra-miniaturized, zero-power electronic personal assistants. Tunnel-FET technology is one of the first major stages in the project’s roadmap. IBM and the CEA-Leti are also partners in the project.

Contact :

Adrian Ionescu, Nanoelectronic Devices Laboratory, EPFL, adrian.ionescu@epfl.ch or 41-21-693-39-78 / 41-21-693-39-79

Lionel Pousaz, Media and Communication Service, lionel.pousaz@epfl.ch or 41-79-559-71-61

Reference :

Nature : Tunnel field-effect transistors as energy-efficient electronic switches

Link:

http://www.nature.com/nature/journal/v479/n7373/full/nature10679.html

When the rover Curiosity heads to space as early as Saturday, it will carry the most advanced payload of scientific gear ever used on Mars’ surface. Those instruments will get their lifeblood from a radioisotope power system assembled and tested at Idaho National Laboratory. The Multi-Mission Radioisotope Thermoelectric Generator is the latest “space battery” that can reliably power a deep space mission for many years.

The device provides a continuous source of heat and power for the rover’s instruments. NASA has used nuclear generators to safely and reliably power 26 missions over the past 50 years. New generators like the one destined for Mars are painstakingly assembled and extensively tested at INL before heading to space.

“This power system will enable Curiosity to complete its ambitious expedition in Mars’ extreme temperatures and seasons,” said Stephen Johnson, director of INL’s Space Nuclear Systems and Technology Division. “When the unit leaves here, we’ve verified every aspect of its performance and made sure it’s in good shape when it gets to Kennedy Space Center.”

The power system provides about 110 watts of electricity and can run continuously for many years. The nuclear fuel is protected by multiple layers of safety features that have each undergone rigorous testing under varied accident scenarios.

The INL team began assembling the mission’s power source in summer 2008. By December of that year, the power system was fully fueled, assembled and ready for testing. INL performs a series of tests to verify that such systems will perform as designed during their missions. These tests include:

• Vibrational testing to simulate rocket launch conditions.
• Magnetic testing to ensure the system’s electrical field won’t affect the rover’s sensitive scientific equipment.
• Mass properties tests to determine the center of gravity, which impacts thruster calculations for moving the rover.
• Thermal vacuum testing to verify operation on a planet’s surface or in the cold vacuum of space.

INL completed its tests in May 2009, but by then the planned September 2009 launch had been delayed until this month because of hurdles with other parts of the mission. So INL stored the power system until earlier this summer, when it was shipped to Kennedy Space Center and mated up with the rover to ensure everything fit and worked as designed.

The system will supply warmth and electricity to Curiosity and its scientific instruments using heat from nuclear decay. The generator is fueled with a ceramic form of plutonium dioxide encased in multiple layers of protective materials including iridium capsules and high-strength graphite blocks. As the plutonium naturally decays, it gives off heat, which is circulated through the rover by heat transfer fluid plumbed throughout the system. Electric voltage is produced by using thermocouples, which exploit the temperature difference between the heat source and the cold exterior. More details about the system are in a fact sheet here: http://www.inl.gov/marsrover/.

Curiosity is expected to land on Mars in August 2012 and carry out its mission over 23 months. It will investigate Mars’ Gale Crater for clues about whether environmental conditions there have favored the development of microbial life, and to preserve any evidence it finds.

NASA chose to use a nuclear power source because solar power alternatives did not meet the full range of the mission’s requirements. Only the radioisotope power system allows full-time communication with the rover during its atmospheric entry, descent and landing regardless of the landing site. And the nuclear powered rover can go farther, travel to more places, last longer, and power and heat a larger and more capable scientific payload compared to the solar power alternative NASA studied.

“You can operate with solar panels on Mars, you just can’t operate everywhere,” said Johnson. “This gives you an opportunity to go anywhere you want on the planet, not be limited to the areas that have sunlight and not have to put the rover to sleep at night.”

INL is one of the DOE’s 10 multiprogram national laboratories. The laboratory performs work in each of DOE’s strategic goal areas: energy, national security, science and environment. INL is the nation’s leading center for nuclear energy research and development. Day-to-day management and operation of the laboratory is the responsibility of Battelle Energy Alliance.

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Contact: Teri Ehresman
teri.ehresman@inl.gov
208-521-9882
DOE/Idaho National Laboratory