Category Archives: Materials and Equipment

(December 21, 2010) — Just as walkie-talkies transmit and receive radio waves, carbon nanotubes (CNT) can transmit and receive light at the nanoscale, Cornell researchers have discovered.

Carbon nanotubes, cylindrical rolled-up sheets of carbon atoms, might one day make ideal optical scattering wires: tiny, mostly invisible antennae with the ability to control, absorb and emit certain colors of light at the nanoscale, according to research led by Jiwoong Park, Cornell assistant professor of chemistry and chemical biology. The study, which includes co-author Garnet Chan, also in chemistry, was published online Dec. 19 in the journal Nature Nanotechnology. The paper’s first author is Daniel Y. Joh, a former student in Park’s lab.

The researchers used the Rayleigh scattering of light — the same phenomenon that creates the blue look of the sky — from carbon nanotubes grown in the lab. They found that while the propagation of light scattering is mostly classical and macroscopic, the color and intensity of the scattered radiation is determined by intrinsic quantum properties. In other words, the nanotubes’ simple carbon-carbon bonded molecular structure determined how they scattered light, independent of their shape, which differs from the properties of today’s metallic nanoscale optical structures.

"Even if you chop it down to a small scale, nothing will change, because the scattering is fundamentally molecular," Park explained.

They found that the nanotubes’ light transmission behaved as a scaled-down version of radio-frequency (RF) antennae found in walkie-talkies, except that they interact with light instead of radio waves. The principles that govern the interactions between light and the carbon nanotube are the same as between the radio antenna and the radio signal, researchers found.

To perform their experiments, the researchers used a methodology developed in their lab that completely eliminates the problematic background signal, by coating the surface of a substrate with a refractive index-matching medium to make the substrate ‘disappear’ optically, not physically. This technique, which allowed them to see the different light spectra produced by the nanotubes, is detailed in another study published in Nano Letters.

The technique also allows quick, easy characterization of a large number of nanotubes, which could lead to ways of growing more uniform batches of nanotubes. Also read: Carbon nanotubes sliced, and leave the kinks in

The paper’s principal authors are former student Daniel Y. Joh; graduate student Lihong Herman; and Jesse Kinder, a postdoctoral research associate in Chan’s lab. Park is a member of the Kavli Institute at Cornell for Nanoscale Science. Both the Nature Nanotechnology and Nano Letters work were supported by the Air Force Office of Scientific Research and the National Science Foundation through the Center for Nanoscale Systems, Cornell Center for Materials Research, Center for Molecular Interfacing and an NSF CAREER grant.

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Carbon-nanotubes-CNT-sliced


December 17, 2010

(December 17, 2010) — Carbon nanotubes (CNT) have a diameter 1/50,000th the thickness of a human hair. Researchers at Brown University and in Korea have described the dynamics behind cutting single-walled carbon nanotubes. Tubes are compressed from both ends, causing atoms to shoot "sideways" off of the nanotube’s lattice structure.

Figure. High-intensity atomic-level sonic boomlets cause nanotubes to buckle and twist at compression-concentration zones. SOURCE: Kim Lab/Brown University

In a paper published this month in the British journal Proceedings of the Royal Society A, researchers at Brown University and in Korea document for the first time how single-walled carbon nanotubes are cut, a finding that could lead to producing more precise, higher-quality nanotubes. Such manufacturing improvements likely would make the nanotubes more attractive for use in automotive, biomedicine, electronics, energy, optics and many other fields.

"We can now design the cutting rate and the diameters we want to cut," said Kyung-Suk Kim, professor of engineering in the School of Engineering at Brown and the corresponding author on the paper.

The basics of carbon nanotube manufacturing are known. Single-atom thin graphene sheets are immersed in solution (usually water), causing them to look like a plate of tangled spaghetti. The jumbled bundle of nanotubes is then blasted by high-intensity sound waves that create cavities (or partial vacuums) in the solution. The bubbles that arise from these cavities expand and collapse so violently that the heat in each bubble’s core can reach more than 5,000 degrees Kelvin, close to the temperature on the surface of the sun. Meanwhile, each bubble compresses at an acceleration 100 billion times greater than gravity. Considering the terrific energy involved, it’s hardly surprising that the tubes come out at random lengths. Technicians use sieves to get tubes of the desired length. The technique is inexact partly because no one was sure what caused the tubes to fracture.

Materials scientists initially thought the super-hot temperatures caused the nanotubes to tear. A group of German researchers proposed that it was the sonic boomlets caused by collapsing bubbles that pulled the tubes apart, like a rope tugged so violently at each end that it eventually rips.

Kim, Brown postdoctoral researcher Huck Beng Chew, and engineers at the Korea Institute of Science and Technology decided to investigate further. They crafted complex molecular dynamics simulations using an array of supercomputers to tease out what caused the carbon nanotubes to break. They found that rather than being pulled apart, as the German researchers had thought, the tubes were being compressed mightily from both ends. This caused a buckling in a roughly five-nanometer section along the tubes called the compression-concentration zone. In that zone, the tube is twisted into alternating 90-degree-angle folds, so that it fairly resembles a helix.

That discovery still did not explain fully how the tubes are cut. Through more computerized simulations, the group learned the mighty force exerted by the bubbles’ sonic booms caused atoms to be shot off the tube’s lattice-like foundation like bullets from a machine gun.

Compression causes nanotubes to buckle and twist and eventually to lose atoms from their lattice-like structure. Source: Huck Beng Chew/Brown University

“It’s almost as if an orange is being squeezed, and the liquid is shooting out sideways,” Kim said. “This kind of fracture by compressive atom ejection has never been observed before in any kind of materials.”

The team confirmed the computerized simulations through laboratory tests involving sonication and electron microscopy of single-walled carbon nanotubes.

The group also learned that cutting single-walled carbon nanotubes using sound waves in water creates multiple kinks, or bent areas, along the tubes’ length. The kinks are "highly attractive intramolecular junctions for building molecular-scale electronics," the researchers wrote.

Huck Beng Chew, a postdoctoral researcher in Brown’s School of Engineering, is the first author on the paper. Myoung-Woon Moon and Kwang Ryul Lee, from the Korea Institute of Science and Technology, contributed to the research. The U.S. National Science Foundation and the Korea Institute of Science and Technology funded the work.

Also read: IBM constructs IC along single-walled CNT

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(December 13, 2010) — At the 2010 IEEE IEDM conference (12/6/10, San Francisco), Semiconductor Research Corporation (SRC) and researchers from Waseda University in Tokyo announced the development of the process and materials for precisely controlling both the amount and the position of channel dopants. The researchers say this advance should help extend the manufacturability of semiconductors beyond conventional doped-channel device technologies. The result is projected to enable near atomic-scale devices and single-dopant devices.

The paper, #26.5 ("Reliable single atom doping and discrete dopant effects on transistor performance") was co-authored by NTT Basic Research Laboratories and Tohoku University, and was presented by Waseda University. According to Dan Herr, SRC director of Nanomanufacturing Sciences, "Deterministic doping, per our single-ion implantation, is a key step for the extensibility of existing doped-channel CMOS devices at 16nm and beyond."

According to SRC, the findings demonstrate the impact of a very small number of dopant atoms on device performance, making the assumption of uniform dopant distribution incorrect. The naturally occurring non-uniform distribution causes significant variability in transistor characteristics, threatening further semiconductor miniaturization.

Listen to Hillenius speaking at IEDM: Play Now / Download (For iPod/iPhone users)

SRC’s EVP, Steve Hillenius, told ElectroIQ’s Debra Vogler, senior technical editor, that the research allows for a tool that enables precise doping profiles — literally putting individual atoms in a transistor channel. "As an analytical tool, it’s very useful in being able to make precise doping profiles and then studying the effects in moving one atom from one position to another in comparison with devices made with one distribution of dopants vs. another," said Hillenius (Figure). "Non-uniform doping across the channel is always a useful tool or knob to turn when designing transistors." He explained that by getting down to single ion doping, the researchers were able to do an extensive study of quantifying the effects on device characteristics depending on whether dopants were closer to the source, and then when they were closer to the drain. The researchers reported that the sub-threshold current is sensitive to the individual dopant location, and the sub-threshold current is always larger when the dopants are located at the drain side rather than at the source side.

Figure. Evaluation of electrical transport in FETS with discrete dopants.

"This research enables a real understanding of what the impacts are of process variations and very precise processing that will allow these effects to be done on a large scale," Hillenius told ElectroIQ. By doing so, the researchers are enabling device designers of processes for mass production to target a certain dopant profile to get the maximum performance out of a transistor.

Regarding its collaboration activities, Hillenius said that SRC is very happy with its collaboration and the high quality of research coming out of Waseda as well as with other universities around the world. "It’s only been the last few years that we’ve been funding research in Japan," said Hillenius. “This kind of research, in conjunction with the interests of our Japanese members, allow the university research and the students coming out to be very well suited to working in SRC member companies.”

With its Energy Research Initiative, SRC is also expanding research activities in the areas of energy and renewable energy applications. "We have a lot of hope of expanding such research in Japan," said Hillenius. The majority of members of this initiative are from countries other than the U.S. — only two U.S. companies are involved. 

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(December 11, 2010) — AT&S debuted a new technology to enable system-in-package (SiP) devices. AT&S’s embedded component packaging technology ECP is used to enable further miniaturiztion of electronic devices while enhancing their performance.

AT&S’s CEO Andreas Gerstenmayer states that high-end customers such as Texas Instruments are using this technology for new generation of PCBs for miniaturized components.

ECP is a highly efficient technology for integrating active and passive electronic components into printed circuit boards. It will be used in products that need to fit the largest possible number of features into the smallest possible space. A conventional component consists of a semiconductor core that has to be mounted on a circuit board substrate and appropriately packaged. ECP provides an efficient alternative to existing component packaging methods and enables the device to be both smaller and more powerful.

AT&S Austria Technologie & Systemtechnik Aktiengesellschaft (AT&S) a printed circuit board manufacturer, specializing in HDI microvia printed circuit boards, which are chiefly used in mobile devices. For more information, visit www.ats.net

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December 10, 2010 – Fujitsu Labs says it has developed a hybrid device that harvests energy and generates electricity from either heat or light, resulting in an economical device with potential use in sensor networks and medical technologies.

The technology, unveiled at this week’s IEEE International Electron Devices Meeting (IEDM 2010), addresses a key application sweetspot for such technology. Energy harvesting — converting energy from the surrounding environment to electricity, using anything from light, vibration, heat, even radio waves — removes the need for electrical wiring, power cords, and batteries, which could not only enable use of sensors in new applications and regions but also improve their use (and lower their costs) in existing ones.

The problem, though, is that energy harvesting can only put out a fraction of the power that batteries can, so more powerful devices need to be made. And since some types of devices may not work in some ambient environments (e.g. light or vibration), energy harvesting systems put together several types of these devices utilize multiple forms of external energy (e.g. heat and light, or light and vibrations). An ideal device, then, would combine the ability to convert multiple energy types.

Enter Fujitsu Labs, which says its single device can capture energy from either light or heat (the most typical forms of ambient energy), by connecting two types of semiconductor materials (P-type and N-type semiconductors) that can function as a photovoltaic cell or thermoelectric generator (Figure 1). It also can be manufactured from inexpensive organic materials to keep production costs low.

Figure 1: Single device featuring operation in both photovoltaic mode (left) and thermoelectric mode (right). (Source: Fujitsu Labs)

The technology doubles the energy-capture potential by using both ambient heat and light. In medical fields, for instance, sensors could monitor conditions such as body temperature, blood pressure, and heartbeats without batteries or electrical wiring; if neither energy source is sufficient to power the sensor, it can tap and utilize both sources. Another application: environmental sensing in remote areas for weather forecasting, where battery replacement or electric lines are problematic.

Fujitsu says it will continue to improve the hybrid device’s performance toward planned commercialization around 2015.

Figure 2: Prototype hybrid generating device manufactured
on flexible substrate. (Source: Fujitsu Labs)

 

(December 8, 2010) — During the IEEE International Electron Devices Meeting (IEDM 2010), held this week in San Francisco, researchers from the Institute for Microelectronics Stuttgart (IMS CHIPS), led by Joachim Burghartz, presented an improved version of their Chipfilm technology introduced in an IEDM 2006 Late News paper. The researchers now have a manufacturable process technology.

During the past three years IMS CHIPS developed this process in cooperation with semiconductor foundries operated by Robert Bosch GmbH, Micronas and Telefunken Semiconductors, and other partners within a large research project funded by the German federal ministry BMBF. Engineering for a wide process window was one particular focus during the Chipfilm technology development for the past three years. The researchers have finally succeeded in designing the array of anchors and the individual anchor structure for a process window suitable for industrial manufacturing.

Differently from wafer thinning techniques, the Chipfilm technology is based on narrow cavity formation underneath the chip areas on wafers above which the target chip thickness is set by precise epitaxial growth of silicon. As a result, ultra-thin chips (<20 μm) can be realized with excellent uniformity control across the wafer and from wafer to wafer. Such Chipfilm wafers can be used for the integration of microelectronic circuits like any conventional wafer substrate.

After circuit integration and etching of trenches along the chip edges, the ultra-thin chips can efficiently be detached by breaking residual anchors underneath the chips. Those anchors need to be designed on the one hand to provide high mechanical stability during wafer processing and on the other hand for fracturability after the trench etching at the end of the process sequence. Anchor fracture for chip detachment can be assisted by externally induced stress from bending the wafer to widen the process window.

In their presentation at IEDM 2010, they also show that the Chipfilm dies exhibit superior mechanical stability. A 20μm thin chip can be bent to a radius as small as 0.8mm, making Chipfilm technology particularly suited for applications in flexible electronics. But, due to the extendability to very small thickness with excellent thickness control, the Chipfilm technology may also be applicable for chip stacking in three-dimensional (3D) integrated systems. As such, the paper by IMS CHIPS is presented in the technical session "Advanced 3D Integration" at IEDM 2010.

The Institut für Mikroelektronik Stuttgart (IMS CHIPS) carries out industrial-oriented microelectronic research in silicon technology, customized circuits (ASIC), photo lithography and image sensor technology as well as being involved in professional development. Learn more at www.ims-chips.com

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December 7, 2010 – SEMI International is forming a standards committee to evaluate and create specifications and practices for 3D stacked ICs (3DS-IC), with initial efforts targeting three areas: bonded wafers, inspection/metrology, and thin wafer handling.

3D ICs that stack 2D die — most popularly using through-silicon vias (TSV) — are the next step of 3D integration beyond wire bonding and flip-chip, promising a fundamental shift for multichip integration and packaging with benefits of better performance, smaller footprints, and reduce cost and power consumption. They’re are already being used in CMOS image sensors, and are expected for use in IO SDRAMs in 2-3 years. But design and mechanical complexities need to be addressed, e.g. signal interference, manufacturing defects, and thermal management.

So, SEMI and SEMATECH have been working together to gather industry input and identify potential sweetspot topics for standardization, from 3D TSV integration challenges to gaps between existing technologies and future solutions. The proposed charter for the 3DS-IC Committee is to promote mutual understanding and improve communication between users and suppliers of materials, carriers, equipment, automation systems, and devices; enhance manufacturing efficiency, capability, and shorten time-to-market; and reduce manufacturing costs.

The work will initially consist of three Task Forces:

  • Bonded Wafer Pair: This group will create a standard for BWP using the SEMI M1 spec ("Specifications for polished single-crystal silicon wafers") as a starting point. SEMATECH’s Andy Rudack will lead this group.
  • Inspection and Metrology: Identify and create new standards (none currently exist) to address deficiencies for inspection and metrology created by 3DS-IC. This includes TSV depth, BWP thickness/TTV, microbump coplanarity, defect, and overlay. Leader: Semilab’s Chris Moore.
  • Thin wafer carrier: Identify and create new standards (none currently exist) for thinned wafer carriers to address deficiencies created by 3DS-ICs, including thin wafer handling and carriers (e.g. automation, shipping, process). Leader: Qualcomm’s Urmi Ray.

SEMATECH companies backing the effort include GlobalFoundries, HP, IBM, Intel, Samsung, and UMC; others supporting a formal 3DS-IC standards committee include Amkor, ASE, IMEC, ITRI, Olympus, Qualcomm, Semilab, Tokyo Electron, and Xilinx.

The 3DS-ICs standards committee’s inaugural in-person meeting will be held at SEMI’s Americas Spring Standards meeting (March 2011 in San Jose, CA). Interested parties wanting to join the committee or seeking more information can contact SEMI’s James Amano ([email protected]).

December 7, 2010 – As 2010 shapes up to be a record year for semiconductor equipment capex, so the following two years will be a fall back to Earth with low single-digit overall growth — though the group’s numbers indicate some clear market winners and losers.

In its semiannual market forecast, SEMI now sees an eye-popping 136% record surge in 2010 (following a -46% decline in 2009), up from a projected 104% in its July forecast issued at SEMICON West. But where SEMI once saw 9% growth in 2011 equipment sales, now it sees less than half that (4%), and only another 4% in 2012. SEMI president/CEO Stanley T. Myers in a statement expressed cautious optimism about the industry’s growth prospects, despite the pervasiveness of chips in everyday products.

2010 surging

Biggest increases in 2010 expectations since July are in the backend sector: both test and assembly/packaging are seen with about $600M more spending vs. the July update, about 22% more in terms of dollars; both segments are now at 155% growth (vs. 108%-109% in the July forecast). Wafer processing, still the overwhelming majority of spending, will see the biggest boost in terms of dollars ($3.65B), about 15% more than expected. Total chip tool spending is seen at $37.54B (vs. $32.5B in July), which is right around the same as 2004 levels, SEMI noted.

(Just a reminder, for perspective: backend spending is seen as a leading indicator of market cyclicality; generally speaking test/assembly/packaging are the first to go up when the market’s in an upturn.)

All regions are seeing higher growth than earlier predicted; five of the seven regions are seen doubling their spending in 2010 (and a sixth, Japan, will be at 98% growth). Most generous updates go to China (from 138% to 248% growth), with three other regions adding about 40 percentage points to their growth rates (Korea 188% -> 231%, ROW 109% -> 151%, Europe 98% -> 141%). Strictly in terms of dollars, Taiwan is still on top with just shy of $10B in spending, about 16% higher than No.2 South Korea (it was a 13% difference in the July outlook) and 88% more than North America (a 108% gap in July). SEMI tacked on over $1B in 2010 spending each for Korea and China, and at least three-quarters of a billion dollars for Taiwan and North America.

2011-2012 stalling

As usually happens, though, the higher numbers for 2010 come at the expense of the next year. SEMI now sees just 4% semiconductor sales growth in 2011, instead of the 9% it predicted back in July. Biggest hits come in the backend: test -5% (vs. 7% in the July forecast) and assembly/packaging (-17% vs. -5%), collectively losing $340M in sales next year.

Two regions, North America ($6B, 13% vs. 8%) and Europe ($2.9B, 25% vs. 9%), have more positive visibility into 2010 spending than six months ago. But Taiwan ($9.0B, -10% vs. 1%) and Korea ($8.28B, -4% vs. 8%) are actually seen spending less than in 2010, and other regions had their outlooks decreased (Japan $4.9B, 11% vs. 15%; RPW $4.08B, 13% vs. 26%; China $3.77B, 15% vs. 18%).

Mixed bag for 2012

Looking out to 2012, chip spending trends diverge significantly by SEMI’s calculations. Total chip tool spending will be flat at 4%, but spending on wafer processing tools will drop to just 2% growth to $30.8B. Meanwhile, though, backend will recover: 9% for test to $4.08B, and 11% for assembly/packaging to $3.31. And the "other" category will see the best growth of all:13% to $2.3B.

The major chip purchasing regions will be in the low single-digit growth (Taiwan 2% to $9.17B, Korea 5% to $8.72B, Japan 1% to $4.94B), while North America will decrease -3% to $5.81B. ROW, China, and Europe will crack (barely) double-digit growth at 10%-11%.

Two interesting points: ROW spent about $800M less than Japan in 2009 and 2010, but that gap will narrow to just $420M by 2012. And together China and ROW made up about 15% of global chip spending in 2009; next year they’ll move up to 20% — a collective increase of nearly $5.5B spending.

A team of researchers at the University of Maryland is working to harness and exploiting the "self-renewing" and "self-assembling" properties of viruses for a higher purpose: to build a new generation of small, powerful and highly efficient batteries and fuel cells.

The rigid, rod-shaped Tobacco mosaic virus (TMV) is a well-known and widespread plant virus that devastates tobacco, tomatoes, peppers, and other vegetation. But in the lab, engineers have discovered that they can harness the characteristics of TMV to build components for the lithium ion batteries of the future. Genetically modifying the virus to display multiple metal binding sites allows for electroless nickel deposition and self-assembly of these nanostructures onto gold surfaces.

 

They can modify the TMV rods to bind perpendicularly to the metallic surface of a battery electrode and arrange the rods in intricate and orderly patterns on the electrode. Then, they coat the rods with a conductive thin film that acts as a current collector and finally the battery’s active material that participates in the electrochemical reactions.

As a result, the researchers, brought together by Professor Reza Ghodssi, can greatly increase the electrode surface area and its capacity to store energy and enable fast charge/discharge times. TMV becomes inert during the manufacturing process; the resulting batteries do not transmit the virus. The new batteries, however, have up to a 10-fold increase in energy capacity over a standard lithium ion battery.

Caption: SEM image of Ni/TiO2 nanocomposite electrode (top), cross-section TEM image of an individual nanorod showing the core/shell nanostructure (Credit: University of Maryland, College Park).

"The resulting batteries are a leap forward in many ways and will be ideal for use not only in small electronic devices but in novel applications that have been limited so far by the size of the required battery," said Ghodssi, director of the Institute for Systems Research and Herbert Rabin Professor of Electrical and Computer Engineering at the Clark School. "The technology that we have developed can be used to produce energy storage devices for integrated microsystems such as wireless sensors networks. These systems have to be really small in size—millimeter or sub-millimeter—so that they can be deployed in large numbers in remote environments for applications like homeland security, agriculture, environmental monitoring and more; to power these devices, equally small batteries are required, without compromising in performance."

TMV’s nanostructure is the ideal size and shape to use as a template for building battery electrodes. Its self-replicating and self-assembling biological properties produce structures that are both intricate and orderly, which increases the power and storage capacity of the batteries that incorporate them. Because TMV can be programmed to bind directly to metal, the resulting components are lighter, stronger and less expensive than conventional parts.

Three distinct steps are involved in producing a TMV-based battery: modifying, propagating and preparing the TMV; processing the TMV to grow nanorods on a metal plate; and incorporating the nanorod-coated plates into finished batteries.

Specfically, the researchers integrated the TMV deposition and coating process into standard MEMS fabrication techniques as well as characterizing nickel–zinc microbatteries based on this technology. Using a microfluidic packaging scheme, devices with and without TMV structures have been characterized. The TMV modified devices demonstrated charge–discharge operation up to 30 cycles reaching a capacity of 4.45 µAh cm−2 and exhibited a six-fold increase in capacity during the initial cycle compared to planar electrode geometries. The effect of the electrode gap has been investigated, and a two-fold increase in capacity is observed for an approximately equivalent decrease in electrode spacing.

James Culver, a member of the Institute for Bioscience and Biotechnology and a professor in the Department of Plant Science and Landscape Architecture, and researcher Adam Brown had already developed genetic modifications to the TMV that enable it to be chemically coated with conductive metals. For this project they extract enough of the customized virus from just a few tobacco plants grown in the lab to synthesize hundreds of battery electrodes. The extracted TMV is then ready for the next step.

Scientists produce a forest of vertically aligned virus rods using a process developed by Culver’s former Ph.D. student, Elizabeth Royston. A solution of TMV is applied to a metal electrode plate. The genetic modifications program one end of the rod shaped virus to attach to the plate. Next these viral forests are chemically coated with a conductive metal, mainly nickel. Other than its structure, no trace of the virus is present in the finished product, which cannot transmit a virus to either plants or animals. This process is patent-pending.

Ghodssi, materials science Ph.D. student Konstantinos Gerasopoulos, and former postdoctoral associate Matthew McCarthy (now a faculty member at Drexel University) have used this metal-coating technique to fabricate alkaline batteries with common techniques from the semiconductor industry such as photolithography and thin film deposition.

While the first generation of their devices used the nickel-coated viruses for the electrodes, work published earlier this year investigated the feasibility of structuring electrodes with the active material deposited on top of each nickel-coated nanorod, forming a core/shell nanocomposite where every TMV particle contains a conductive metal core and an active material shell. In collaboration with Chunsheng Wang, a professor in the Department of Chemical and Biomolecular Engineering, and his Ph.D. student Xilin Chen, the researchers have developed several techniques to form nanocomposites of silicon and titanium dioxide on the metalized TMV template.  This architecture both stabilizes the fragile, active material coating and provides it with a direct connection to the battery electrode.

In the third and final step, Chen and Gerasopoulos assemble these electrodes into the experimental high-capacity lithium-ion batteries. Their capacity can be several times higher than that of bulk materials and in the case of silicon, higher than that of current commercial batteries. 

"Virus-enabled nanorod structures are tailor-made for increasing the amount of energy batteries can store. They confer an order of magnitude increase in surface area, stabilize the assembled materials and increase conductivity, resulting in up to a10-fold increase in the energy capacity over a standard lithium ion battery," Wang said.

A bonus: since the TMV binds metal directly onto the conductive surface as the structures are formed, no other binding or conducting agents are needed as in the traditional ink-casting technologies that are used for electrode fabrication.

"Our method is unique in that it involves direct fabrication of the electrode onto the current collector; this makes the battery’s power higher, and its cycle life longer," said Wang.

The use of the TMV virus in fabricating batteries can be scaled up to meet industrial production needs. "The process is simple, inexpensive, and renewable," Culver adds. "On average, one acre of tobacco can produce approximately 2,100 pounds of leaf tissue, yielding approximately one pound of TMV per pound of infected leaves," he explains.

At the same time, very tiny microbatteries can be produced using this technology. "Our electrode synthesis technique, the high surface area of the TMV and the capability to pattern these materials using processes compatible with microfabrication enable the development of such miniaturized batteries," Gerasopoulos adds.

While the focus of this research team has long been on energy storage, the structural versatility of the TMV template allows its use in a variety of exciting applications. "This combination of bottom-up biological self-assembly and top-down manufacturing is not limited to battery development only," Ghodssi said. "One of our lab’s ongoing projects is aiming at the development of explosive detection sensors using versions of the TMV that bind TNT selectively, increasing the sensitivity of the sensor. In parallel, we are collaborating with our colleagues at Drexel and MIT to construct surfaces that resemble the structure of plant leaves. These biomimetic structures can be used for basic scientific studies as well as the development of novel water-repellent surfaces and micro/nano scale heat pipes."

Funding for the research comes from the National Science Foundation, the Department of Energy Office of Basic Energy Sciences, the Maryland Technology Development Corporation, and the Laboratory for Physical Sciences at the University of Maryland. James Culver’s work is conducted in collaboration with Purdue University professor Michael Harris.

(December 6, 2010) — Bruker Corp. has announced at the Materials Research Society (MRS) Fall 2010 Meeting the release of a new generation of Atomic Force Microscopy (AFM) modes and measurement modules that transform Bruker’s AFM systems into turnkey solutions for nanoscale characterization in renewable energy research.

The company said the most significant of these new AFM accessories, the PeakForce Tuna module, enables very high resolution nanoelectrical characterization on fragile samples, including organic photovoltaics, lithium ion battery composites, and carbon nanotube-based device structures. Complementing this capability, Bruker said that its new offering for electrochemistry research provides solvent compatibility, ppm-level environmental control, and in-situ liquid scanning on an AFM.

The new modules expand the Bruker suite for nanoscale electrical and electrochemical characterization on samples requiring sensitive mechanical and environmental control. The PeakForce Tuna module uses a new current amplifier in conjunction with PeakForce Tapping to allow conductivity mapping on fragile samples such as organic photovoltaics, lithium ion cathodes, and carbon nanotube assemblies without the deleterious effects caused by sample damage and tip contamination.

"We are excited to offer ground-breaking new capabilities to scientists in growing areas of nanoelectrical characterization in materials research," said Dr. Mark R. Munch, president of the Bruker Nano Surfaces Business. "This new product release represents a significant advance in our continued drive to expand AFM technologies to energy markets by addressing customer needs for quantitative nanoscale characterization. We are gratified that these modules are among our first new product releases as part of Bruker. Building on our leadership position, they are a fitting continuation of the rapid stream of innovative new products that we have delivered over the past three years."

David Rossi, VP and GM of Bruker’s AFM Unit, added: "Our new suite of nanoelectrical and electrochemical products are part of our development team’s long heritage of AFM innovations in nanoscale research and they build on the foundation of PeakForce Tapping and ScanAsyst modes. We see unmet need for non-destructive and artifact-free nanoelectrical and electrochemical characterization in the growing arena of future energy generation and storage materials, and we are partnering with leading researchers and companies in those fields to deliver innovative products to enable their success."

Bruker Corp. is a provider of high-performance scientific instruments and solutions for molecular and materials research, as well as for industrial and applied analysis. More information is available at www.bruker-axs.com and www.bruker.com