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The Semiconductor Industry Association (SIA) today announced that worldwide sales of semiconductors reached $25.87 billion for the month of February 2014, an increase of 11.4 percent from February 2013 when sales were $23.23 billion. This marks the industry’s largest year-to-year increase in more than three years. Global sales from February 2014 were 1.5 percent lower than the January 2014 total of $26.26 billion, reflecting normal seasonal trends. Regionally, sales in the Americas increased by 18 percent compared to last February. All monthly sales numbers are compiled by WSTS and represent a three-month moving average.

“The trend lines remain positive for the global semiconductor industry, which has followed record revenues in 2013 with an encouraging start to 2014,” said Brian Toohey, president and CEO, Semiconductor Industry Association. “The Americas market continues to demonstrate impressive growth, while sales in Asia Pacific and Europe also increased substantially year-to-year, and the Japanese market continued its recent rebound.”

Regionally, year-to-year sales increased in the Americas (18 percent), Asia Pacific (12 percent), and Europe (9.6 percent). Sales decreased slightly in Japan (-0.2 percent), but February marked the region’s smallest year-to-year decrease since August 2012. Sales fell across all regions compared to the previous month, as February sales historically are lower than January sales due to seasonal trends.

“The U.S. semiconductor market has been a key driver of global market growth over the last year, and policymakers in Washington can help maintain this momentum by enacting measures that remove obstacles to continued growth,” Toohey continued. “One such obstacle is America’s dysfunctional immigration system, which was revealed again this week when scarce H-1B visas were rapidly claimed by employers. Lawmakers should recognize that outdated immigration policies hamper economic growth and innovation, and they should work together to enact meaningful immigration reform in short order.”

MEMS microphones, used in best-selling devices like Apple’s iPhone, face a resonant future as the market keeps climbing in the coming years, according to a new report from IHS Technology.

Global revenue for MEMS microphones is forecast to reach $1.04 billion this year, up a robust 24 percent from $836.9 million in 2013.

Less than a decade was needed for the MEMS microphone market to cross the billion-dollar threshold. While this year continues the galloping growth the industry has seen during the last few years, the rate of expansion is slowing as revenue has expanded.

Even so, the next few years will continue to yield solid results for the business, and revenue by 2017 will amount to a projected $1.37 billion, as shown in the attached figure, equivalent to a five-year compound annual growth rate (CAGR) of 18 percent from 2012 to 2017. Shipments at the end of the forecast window will equal 5.4 billion units, up from 1.9 billion in 2012.

MEMS mics

“The MEMS microphone segment has successfully capitalized on the value delivered by audible improvements in microphones to propel the industry forward,” said Marwan Boustany, senior analyst for MEMS & sensors at IHS. “Especially in an age in which devices are increasingly uniform, sound can be a real and important differentiator, in features such as voice command or crystal-clear audio in high-definition video—qualities that are possible only through high-performance MEMS microphones.”

Handsets and tablets account for the majority of MEMS microphone consumption, and Apple and Samsung are the biggest buyers at present, Boustany noted.

These findings are contained in the report, “MEMS and Sensors Report – Microphones – 2014,” from the Semiconductors & Components service of IHS.

Audibly improved: the difference matters

Two of the main measures for MEMS microphone quality are signal-to-noise ratio (SNR) and the maximum sound-pressure level (SPL). These define the lowest and highest sound levels, respectively—or dynamic range—that can be gauged by a microphone with a linear response. The measures apply to both analog and digital MEMS microphones, and have been used as the basis for microphone quality in marketing by firms such as Nokia and HTC.

At the top performance level, very-high-SNR microphones feature a signal-to-noise ratio level of greater than, or equal to, 64 decibels. These are the microphones projected to have the greatest growth in the coming years, with an estimated five-year CAGR of 40 percent from 2012 to 2017, IHS analysis shows.

In the past, low-SNR microphones, featuring a signal-to-noise ratio of less than 60 decibels, were the standard device in many handsets. Acceptable for phone calls, low-SNR microphones have shown their limitations in performance, as in cases where there is some distance between the source of the recorded sound and the microphone, such as for video recording and voice commands. In such instances, low-SNR microphones can miss out on  lower volume elements of the sound, which can result in a loss of data important for voice commands and a degradation of the richness in recorded sounds for video.

Low-SNR microphones are also not up to the task of ambient-noise cancellation, in which the microphones help to neutralize surrounding noise levels in order to better focus on the immediate sound intended for transmission or reception. Here, better-SNR microphones are the key factor as well to an improved listening experience, Boustany said.

Very-high-SNR microphones were first used in 2012 by Apple in the iPhone 5, and subsequent generations of the popular smartphone continued to utilize these MEMS microphones. After Apple, Samsung joined in, using very-high-SNR MEMS microphones in its S4 and Note 3 flagship handsets. Together the two brands made up 96 percent of revenue for the very-high-SNR MEMS microphone market in 2013.

Another advantage of very-high-SNR microphones is enhanced support for voice commands, helpful for Apple’s Siri or Google Now. The Motorola Moto X, for instance, includes multiple very-high-SNR microphones that improve the handset’s ability to capture voice commands.

Between the very-high-SNR and low-SNR categories sits a third class of MEMS microphones, the high-SNR devices with a signal-to-noise ratio between 59 and 64 decibels, which will be what lower midrange devices may choose to transition from low-SNR microphones. Growth of this segment during the next few years will be lower than that of very-high-SNR types, but higher than in the low-SNR segment that is headed for decline.

Finding their way into the most popular consumer gadgets

MEMS microphones are deployed the most in handsets and tablets, which last year accounted for 93 percent of revenue in very-high-SNR microphones. Apple and Samsung each have up to three microphones for their handsets that could possibly climb to four, and the multiple numbers no doubt help increase overall revenue for MEMS suppliers.

The rapidly growing tablet space is also a vigorous market driver, with the Apple iPad product line now outfitted with two microphones and with Samsung also adding multiple microphones to some of its tablets.

Very-high-SNR microphones are making inroads into hearing aids, too. The ReSound LiNX, for instance, uses two such devices, for noise cancellation and improved performance, with an additional beneficial capability that ties in Bluetooth connectivity with an iPhone—enabling the hearing aid to act as a headset as well.

High-performance MEMS microphones will also become increasingly prominent in the automotive space, helping support voice commands and hands-free calling. Harman has announced the use of two MEMS microphones for such use in Germany’s Daimler vehicles, to start in 2016.

Polymer materials are usually thermal insulators. But by harnessing an electropolymerization process to produce aligned arrays of polymer nanofibers, researchers have developed a thermal interface material able to conduct heat 20 times better than the original polymer. The modified material can reliably operate at temperatures of up to 200 degrees Celsius.

The new thermal interface material could be used to draw heat away from electronic devices in servers, automobiles, high-brightness LEDs and certain mobile devices. The material is fabricated on heat sinks and heat spreaders and adheres well to devices, potentially avoiding the reliability challenges caused by differential expansion in other thermally-conducting materials.

IMG_0695

“Thermal management schemes can get more complicated as devices get smaller,” said Baratunde Cola, an assistant professor in the George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. “A material like this, which could also offer higher reliability, could be attractive for addressing thermal management issues. This material could ultimately allow us to design electronic systems in different ways.”

The research, which was supported by the National Science Foundation, was reported March 30 in the advance online publication of the journal Nature Nanotechnology. The project involved researchers from the Georgia Institute of Technology, University of Texas at Austin, and the Raytheon Company. Virendra Singh, a research scientist in the Woodruff School, and Thomas Bougher, a Ph.D. student in the Woodruff School, are the paper’s co-first authors.

The new interface material is produced from a conjugated polymer, polythiophene, in which aligned polymer chains in nanofibers facilitate the transfer of phonons – but without the brittleness associated with crystalline structures, Cola explained. Formation of the nanofibers produces an amorphous material with thermal conductivity of up to 4.4 watts per meter Kelvin at room temperature.

The material has been tested up to 200 degrees Celsius, a temperature that could make it useful for applications in vehicles. Solder materials have been used for thermal interfaces between chips and heat sinks, but may not be reliable when operated close to their reflow temperatures.

“Polymers aren’t typically thought of for these applications because they normally degrade at such a low temperature,” Cola explained. “But these conjugated polymers are already used in solar cells and electronic devices, and can also work as thermal materials. We are taking advantage of the fact that they have a higher thermal stability because the bonding is stronger than in typical polymers.”

The structures are grown in a multi-step process that begins with an alumina template containing tiny pores covered by an electrolyte containing monomer precursors. When an electrical potential is applied to the template, electrodes at the base of each pore attract the monomers and begin forming hollow nanofibers. The amount of current applied and the growth time control the length of the fibers and the thickness of their walls, while the pore size controls the diameter. Fiber diameters range from 18 to 300 nanometers, depending on the pore template.

After formation of the monomer chains, the nanofibers are cross-linked with an electropolymerization process, and the template removed. The resulting structure can be attached to electronic devices through the application of a liquid such as water or a solvent, which spreads the fibers and creates adhesion through capillary action and van der Waals forces.

“With the electrochemical polymerization processing approach that we took, we were able to align the chains of the polymer, and the template appears to prevent the chains from folding into crystals so the material remained amorphous,” Cola explained. “Even though our material is amorphous from a crystalline standpoint, the polymer chains are highly aligned – about 40 percent in some of our samples.”

Though the technique still requires further development and is not fully understood theoretically, Cola believes it could be scaled up for manufacturing and commercialization. The new material could allow reliable thermal interfaces as thin as three microns – compared to as much as 50 to 75 microns with conventional materials.

“There are some challenges with our solution, but the process is inherently scalable in a fashion similar to electroplating,” he said. “This material is well known for its other applications, but ours is a different use.”

Engineers have been searching for an improved thermal interface material that could help remove heat from electronic devices. The problem of removing heat has worsened as devices have gotten both smaller and more powerful.

IMG_0728

Rather than pursue materials because of their high thermal conductivity, Cola and his collaborators investigated materials that could provide higher levels of contact in the interface. That’s because in some of the best thermal interface materials, less than one percent of the material was actually making contact.

“I stopped thinking so much about the thermal conductivity of the materials and started thinking about what kinds of materials make really good contact in an interface,” Cola said. He decided to pursue polythiophene materials after reading a paper describing a “gecko foot” application in which the material provided an estimated 80 percent contact.

Samples of the material have been tested to 200 degrees Celsius through 80 thermal cycles without any detectable difference in performance. While further work will be necessary to understand the mechanism, Cola believes the robustness results from adhesion of the polymer rather than a bonding.

“We can have contact without a permanent bond being formed,” he said. “It’s not permanent, so it has a built-in stress accommodation. It slides along and lets the stress from thermal cycling relax out.”

In addition to those already mentioned, co-authors of the paper included Professor Kenneth Sandhage, Research Scientist Ye Cai, Assistant Professor Asegun Henry and graduate assistant Wei Lv of Georgia Tech; Prof. Li Shi, Annie Weathers, Kedong Bi, Micheal T. Pettes and Sally McMenamin in the Department of Mechanical Engineering at the University of Texas at Austin; and Daniel P. Resler, Todd Gattuso and David Altman of the Raytheon Company.

A patent application has been filed on the material. Cola has formed a startup company, Carbice Nanotechnologies, to commercialize thermal interface technologies. It is a member of Georgia Tech’s VentureLab program.

Toshiba Corporation announced that it has brought a civil suit against Korea’s SK Hynix Inc. at the Tokyo District Court, under Japan’s Unfair Competition Prevention Act. The suit seeks damages for the wrongful acquisition and use of Toshiba’s proprietary technical information related to NAND flash memory, which Toshiba pioneered in 1987 and now jointly develops and produces with SanDisk Corporation of the U.S. SanDisk this week also filed a separate lawsuit against SK Hynix for theft of trade secrets.

Related news: SanDisk files lawsuit against SK Hynix for theft of trade secrets

Toshiba filed the suit on learning that a former employee of SK Hynix has been arrested in Japan for alleged criminal infringement of the Unfair Competition Prevention Act. The employee formerly worked for SanDisk in a NAND flash memory development project conducted in partnership with Toshiba at Yokkaichi Operations, Toshiba’s flash memory technology development and mass production base in Mie prefecture, Japan. The employee is alleged to have illegally taken Toshiba’s proprietary technical information in 2008, and to have subsequently provided it to SK Hynix.

A spokesman at the Tokyo Metropolitan Police Department said police officials arrested Yoshitaka Sugita on Thursday. The police allege that Mr. Sugita accessed and copied Toshiba’s trade secrets sometime during April 2007 and May 2008 when he was working inside Toshiba’s Yokkaichi plant in central Japan, and later handed the data to SK Hynix in July 2008.

SK Hynix is a business partner of Toshiba. However, the companies are also competitors in NAND flash memory, one of Toshiba’s core technologies, and given the scope and importance of the misappropriated technical data involved, Toshiba has no reasonable option other than to seek legal redress.

Moving forward, Toshiba will construct a more robust system for protecting its intellectual property and preventing its loss, and respond resolutely to unfair competition, in order to maintain the advanced technical competence that is the source of its competitive strength.

In this week’s Nature Communications, imec presents the development of fullerene-free organic photovoltaic (OPV) multilayer stacks achieving a record conversion efficiency of 8.4 percent.  This breakthrough achievement is an important step to bring organic photovoltaic cells to a higher level in the competitive thin-film photovoltaics marketplace.

imec image 01

Organic solar cells are an interesting thin-film photovoltaic technology due to their compatibility with flexible substrates and tunable absorption window.  Although the power conversion efficiency of organic solar cells has increased rapidly in the last decade, further enhancements are needed to make the production of organic photovoltaics more easily scalable into industrial production processes. Imec’s organic solar cells with record 8.4 percent power conversion efficiency were realized by introducing two innovations. Firstly, the implementation of fullerene-free acceptor materials resulted in high open-circuit voltages and useful absorption spectra in the visible spectrum. Secondly, high short-circuit currents were achieved by developing a multilayer device structure of three active semiconductor layers with complementary absorption spectra, and an efficient exciton harvesting mechanism.

Fullerenes are the dominant acceptor materials in current OPV cells due to their ability to accept stable electrons and their high electron mobility. However, the small absorption overlap with the solar spectrum limits the photocurrent generation in fullerene acceptors, and their deep energy level for electron conduction limits the open-circuit voltage. Imec implemented two fullerene-free materials as acceptor, increasing open-circuit voltages compared to OPV cells with fullerene acceptors.

To increase the efficiency of organic solar cells, complex tandem architectures are often proposed to combine the exciton harvesting of multiple photo-active materials. The imec team now proposes a simple three-layer stack to improve the spectral responsivity range. This device architecture comprises two fullerene-free acceptors and a donor, arranged as discrete heterojunctions. In addition to the traditional exciton dissociation at the central donor-acceptor interface, the excitons generated in the outer acceptor layer are first relayed by energy transfer to the central acceptor, and subsequently dissociated at the donor interface.  This results in a quantum efficiency above 75 percent between 400nm and 720nm. With an open-circuit voltage close to 1V, a remarkable power conversion efficiency of 8.4 percent is achieved. These results confirm that multilayer cascade structures are a promising alternative to conventional donor-fullerene organic solar cells.

These results were presented in Nature Communications.

The research leading to these results has received funding from the European Community’s Seventh Framework Programme.

The release today of the SEMI World Fab Forecast update reveals a 20 to 30 percent projected increase in semiconductor fab equipment spending in 2014. The uptick to 30 percent depends on specific fab projects in the Europe/Mideast and Asia regions, as detailed in the report. Figure 1 shows Total Fab Equipment Spending versus Installed Capacity without Discretes. For 2014, the report identified over 190 fab projects in 2014 spending on construction and/or equipment and over such 250 projects in 2015 (including Discretes, LED, Analog and Logic fabs).

fab graph

According to the SEMI data, double-digit fab equipment spending growth will occur in almost all industry segments.  The segment showing the largest increase is expected to be MPU, followed by Memory.  Analog, Logic and MEMS will share third place with about 30 percent growth each — off of a small spending base in 2013.  The Foundry segment spending is expected to grow by 15 percent.

The SEMI World Fab Forecast report shows an increase in DRAM related projects equipping, thus an increase in DRAM related equipment spending from about 7 percent growth in 2013 to 30 percent in 2014. Overall DRAM installed capacity is expected to remain flat (0 percent) in 2014, following a contraction in 2013.

Equipment spending is also expected to stabilize for both the Opto and the LED fab segments, from -16 percent spending declines in 2013 to -1 percent in 2014.  Equipment spending in the LED segment will decline -9 percent in 2014 following the -21 percent decline in 2013.  Construction spending for all Opto/LED facilities will increase by over 60 percent in 2014.  These investments will increase installed capacity for LED by 12 percent in 2014 and about 14 percent in 2015.

Using a bottom up approach, SEMI closely monitors the installed capacity of more 1,100 facilities.  Across the entire industry, installed capacity (without Discretes) grew by only 2 percent in 2013; this is expected to creep up to 3 percent growth in 2014 and in the 3-5 percent range in 2015.

The SEMI World Fab Forecast tracks over 190 fab projects in 2014 that are spending for construction projects and equipping facilities and over 250 such projects in 2015, including Discretes, LED, Analog and Logic fabs.  The report details that in 2013 seven new fabs and four R&D/Pilots facilities began construction. In 2014, six new fabs and one R&D fab are forecasted (with various probabilities) to begin construction.  Robust growth presents itself differently across segments of the industry; learn more about SEMI fab databases at: www.semi.org/MarketInfo/FabDatabase

The SEMI World Fab Forecast lists over 1,160 facilities.  There are 56 future facilities with various probabilities which have started or will start volume production in 2014 or later.  The report lists major investments (construction projects and equipping) in 196 facilities and lines in 2014, and a large number in 2015. Since the last fab database publication at the end November 2013, the SEMI has made 282 updates to 253 facilities (including over 250 Opto/LED fabs) in the database. There were 17 facilities added and 10 facilities closed.

The SEMI World Fab Forecast uses a bottom-up approach methodology, providing high-level summaries and graphs, and in-depth analyses of capital expenditures, capacities, technology and products by fab. Additionally, the database provides forecasts for the next 18 months by quarter. These tools are invaluable for understanding how the semiconductor manufacturing will look in 2013 and 2014, and learning more about capex for construction projects, fab equipping, technology levels, and products.

The Semiconductor Industry Association (SIA) today announced that worldwide sales of semiconductors reached $26.28 billion for the month of January 2014, an increase of 8.8 percent from January 2013 when sales were $24.15 billion, marking the industry’s highest-ever January sales total and the largest year-to-year increase in nearly three years. Global sales from January 2014 were 1.4 percent lower than the December 2013 total of $26.65 billion, reflecting normal seasonal trends. Regionally, sales in the Americas increased by 17.3 percent compared to last January. All monthly sales numbers are compiled by the World Semiconductor Trade Statistics (WSTS) organization and represent a three-month moving average.

“The global semiconductor industry has built on its record revenues from 2013 with an impressive start to 2014, led largely by continued strength in the Americas market,” said Brian Toohey, president and CEO, Semiconductor Industry Association. “Sales in January were up across most regions and nearly all product categories compared to last January, which bodes well for continued growth during the rest of 2014.”

Regionally, year-over-year sales increased in the Americas (17.3 percent), Europe (11.3 percent), and Asia Pacific (8.3 percent), but decreased in Japan (-4.7 percent). Sales were flat in Europe compared to the previous month, but decreased slightly in Asia Pacific (-0.6 percent), Japan (-2.3 percent), and the Americas (-3.5 percent). January sales historically are lower than December sales due to seasonal trends.

January 2014
Billions
Month-to-Month Sales
Market Last Month Current Month % Change
Americas 5.80 5.59 -3.5%
Europe 2.96 2.96 0.0%
Japan 2.93 2.86 -2.3%
Asia Pacific 14.96 14.87 -0.6%
Total 26.65 26.28 -1.4%
Year-to-Year Sales
Market Last Year Current Month % Change
Americas 4.77 5.59 17.3%
Europe 2.66 2.96 11.3%
Japan 3.00 2.86 -4.7%
Asia Pacific 13.72 14.87 8.3%
Total 24.15 26.28 8.8%
Three-Month-Moving Average Sales
Market Aug/Sept/Oct Nov/Dec/Jan % Change
Americas 5.71 5.59 -2.1%
Europe 3.05 2.96 -3.0%
Japan 3.11 2.86 -8.0%
Asia Pacific 15.22 14.87 -2.3%
Total 27.09 26.28 -3.0%

 

A microscope in a needle, a handheld device that prescribes corrective eyeglasses, and a device for heart attack diagnosis are winning projects in the 2014 SPIE Startup Challenge. Hosted by SPIE, the international society for optics and photonics, the pitch competition was held early this month in San Francisco during SPIE Photonics West, an annual event for the international optics and photonics community.

Jay Kumler of Jenoptik (left) and SPIE President Philip Stahl congratulate winner Robert McLaughlin of the University of Western Australia. (Photo: Joey Cobbs for SPIE)

Jay Kumler of Jenoptik (left) and SPIE President Philip Stahl congratulate winner Robert McLaughlin of the University of Western Australia. (Photo: Joey Cobbs for SPIE)

Cash prizes are funded by Founding Sponsor Jenoptik with additional support from Trumpf, Open Photonics, and Knobbe Martens. Finalist judges were Jenoptik’s Jay Kumler, Samuel Sadoulet of Edmund Optics, Jason Eichenholz of Open Photonics, Bruce Itchkawitz of Knobbe Martens, and Adam Wax of Duke University.

First-place winner Robert McLaughlin of the University of Western Australia received $10,000 plus an additional $5,000 in products from Edmund Optics. The university’s product, a microscope-in-a-needle, is a miniaturized optical coherence tomography (OCT) probe capable of 3D imaging that aims to reduce the number of repeat surgeries for breast cancer.

Second-place winner Nicholas Durr of Massachusetts Institute of Technology received $5,000. The product, PlenOptika’s QuickSee, is an innovative low-cost handheld device that provides eyeglass prescriptions at the push of a button. Durr also received the People’s Choice Award, which includes a fee waiver for SPIE Photonics West 2015.

Third-place winner Amos Danielli of MagBiosense received $2,500. The company’s product, a heart-attack diagnostic device and assay, offers laboratory-quality sensitivity combined with the rapid results and ease-of-use of a point-of-care system.

SPIE will provide support for winners to attend a week-long entrepreneur “boot camp” for further help in refining their ideas.

“Thanks to SPIE and the corporate sponsors, we have seen tremendous advancement in the quality of participants in the Startup Challenge. The businesses who participate are more developed, the technologies are more innovative, and the pitch quality gets better every year. It is an exciting event,” Kumler said. “The growth of the Startup Challenge suggests SPIE has a great opportunity to develop a photonics startup ecosystem that brings ideas, entrepreneurs, mentors, and investors together to advance our industry.”

Winners take home valuable new contacts as well as prizes, recognition, and pitching experience.

“It was an amazing experience. I met a lot of people and made good connections with judges, potential investors, and fellow applicants,” said Danielli. “After the competition, I was fortunate enough to be approached by Hamamatsu’s Head of Business Innovations Group. She suggested talking about future collaboration, which will be great because I’m using their components.”

The winners were chosen from among eight finalists in a public final round at Photonics West. Finalists had three minutes in which to deliver their pitches showcasing optics or photonics technologies or applications presented as the basis for viable new businesses.

Worldwide silicon wafer revenues declined by 13 percent in 2013 compared to 2012 according to the SEMI Silicon Manufacturers Group (SMG) in its year-end analysis of the silicon wafer industry. Worldwide silicon wafer area shipments increased 0.4 percent in 2013 when compared to 2012 area shipments.

Silicon wafer area shipments in 2013 totaled 9,067 million square inches (MSI), slightly up from the 9,031 million square inches shipped during 2012. Revenues totaled $7.5 billion down from $8.7 billion posted in 2012. “Annual semiconductor silicon shipment levels have remained essentially flat for the past three years,” said Hiroshi Sumiya, chairman of SEMI SMG and general manager of the Corporate Planning Department of Shin-Etsu Handotai Co., Ltd. ”However, industry revenues have declined significantly for the past two years.”

Annual Silicon* Industry Trends

  2008 2009 2010 2011 2012 2013
Area Shipments (MSI) 8,137 6,707 9,370 9,043 9,031 9,067
Revenues ($B) 11.4 6.7 9.7 9.9 8.7 7.5

*Shipments are for semiconductor applications only and do not include solar applications

Silicon wafers are the fundamental building material for semiconductors, which in turn, are vital components of virtually all electronics goods, including computers, telecommunications products, and consumer electronics. The highly engineered thin round disks are produced in various diameters (from one inch to 12 inches) and serve as the substrate material on which most semiconductor devices or “chips” are fabricated.

All data cited in this release is inclusive of polished silicon wafers, including virgin test wafers, epitaxial silicon wafers, and non-polished silicon wafers shipped by the wafer manufacturers to the end-users.

The Silicon Manufacturers Group acts as an independent special interest group within the SEMI structure and is open to SEMI members involved in manufacturing polycrystalline silicon, monocrystalline silicon or silicon wafers (e.g., as cut, polished, epi, etc.). The purpose of the group is to facilitate collective efforts on issues related to the silicon industry including the development of market information and statistics about the silicon industry and the semiconductor market.

Using electrons more like photons could provide the foundation for a new type of electronic device that would capitalize on the ability of graphene to carry electrons with almost no resistance even at room temperature – a property known as ballistic transport.

Research reported this week shows that electrical resistance in nanoribbons of epitaxial graphene changes in discrete steps following quantum mechanical principles. The research shows that the graphene nanoribbons act more like optical waveguides or quantum dots, allowing electrons to flow smoothly along the edges of the material. In ordinary conductors such as copper, resistance increases in proportion to the length as electrons encounter more and more impurities while moving through the conductor.

Related news: GA Tech: Graphene could replace Cu for IC interconnects

The ballistic transport properties, similar to those observed in cylindrical carbon nanotubes, exceed theoretical conductance predictions for graphene by a factor of 10. The properties were measured in graphene nanoribbons approximately 40 nanometers wide that had been grown on the edges of three-dimensional structures etched into silicon carbide wafers.

“This work shows that we can control graphene electrons in very different ways because the properties are really exceptional,” said Walt de Heer, a Regent’s professor in the School of Physics at the Georgia Institute of Technology. “This could result in a new class of coherent electronic devices based on room temperature ballistic transport in graphene. Such devices would be very different from what we make today in silicon.”

Walt de Heer in his lab in the Howey Physics building.

Walt de Heer in his lab in the Howey Physics building.

The research, which was supported by the National Science Foundation, the Air Force Office of Scientific Research and the W.M. Keck Foundation, was reported February 5 in the journal Nature. The research was done through a collaboration of scientists from Georgia Tech in the United States, Leibniz Universität Hannover in Germany, the Centre National de la Recherche Scientifique (CNRS) in France and Oak Ridge National Laboratory – supported by the Department of Energy – in the United States.

For nearly a decade, researchers have been trying to use the unique properties of graphene to create electronic devices that operate much like existing silicon semiconductor chips. But those efforts have met with limited success because graphene – a lattice of carbon atoms that can be made as little as one layer thick – cannot be easily given the electronic bandgap that such devices need to operate.

De Heer argues that researchers should stop trying to use graphene like silicon, and instead use its unique electron transport properties to design new types of electronic devices that could allow ultra-fast computing – based on a new approach to switching. Electrons in the graphene nanoribbons can move tens or hundreds of microns without scattering.

“This constant resistance is related to one of the fundamental constants of physics, the conductance quantum,” de Heer said. “The resistance of this channel does not depend on temperature, and it does not depend on the amount of current you are putting through it.”

What does disrupt the flow of electrons, however, is measuring the resistance with an electrical probe. The measurements showed that touching the nanoribbons with a single probe doubles the resistance; touching it with two probes triples the resistance.

graphene-nanoribbons

“The electrons hit the probe and scatter,” explained de Heer. “It’s a lot like a stream in which water is flowing nicely until you put rocks in the way. We have done systematic studies to show that when you touch the nanoribbons with a probe, you introduce a method for the electrons to scatter, and that changes the resistance.”

The nanoribbons are grown epitaxially on silicon carbon wafers into which patterns have been etched using standard microelectronics fabrication techniques. When the wafers are heated to approximately 1,000 degrees Celsius, silicon is preferentially driven off along the edges, forming graphene nanoribbons whose structure is determined by the pattern of the three-dimensional surface. Once grown, the nanoribbons require no further processing.

The advantage of fabricating graphene nanoribbons this way is that it produces edges that are perfectly smooth, annealed by the fabrication process. The smooth edges allow electrons to flow through the nanoribbons without disruption. If traditional etching techniques are used to cut nanoribbons from graphene sheets, the resulting edges are too rough to allow ballistic transport.

“It seems that the current is primarily flowing on the edges,” de Heer said. “There are other electrons in the bulk portion of the nanoribbons, but they do not interact with the electrons flowing at the edges.”

The electrons on the edge flow more like photons in optical fiber, helping them avoid scattering. “These electrons are really behaving more like light,” he said. “It is like light going through an optical fiber. Because of the way the fiber is made, the light transmits without scattering.”

The researchers measured ballistic conductance in the graphene nanoribbons for up to 16 microns. Electron mobility measurements surpassing one million correspond to a sheet resistance of one ohm per square that is two orders of magnitude lower than what is observed in two-dimensional graphene – and ten times smaller than the best theoretical predictions for graphene.

“This should enable a new way of doing electronics,” de Heer said. “We are already able to steer these electrons and we can switch them using rudimentary means. We can put a roadblock, and then open it up again. New kinds of switches for this material are now on the horizon.”

Theoretical explanations for what the researchers have measured are incomplete. De Heer speculates that the graphene nanoribbons may be producing a new type of electronic transport similar to what is observed in superconductors.

“There is a lot of fundamental physics that needs to be done to understand what we are seeing,” he added. “We believe this shows that there is a real possibility for a new type of graphene-based electronics.”

Georgia Tech researchers have pioneered graphene-based electronics since 2001, for which they hold a patent, filed in 2003. The technique involves etching patterns into electronics-grade silicon carbide wafers, then heating the wafers to drive off silicon, leaving patterns of graphene.

In addition to de Heer, the paper’s authors included Jens Baringhaus, Frederik Edler and Christoph Tegenkamp from the Institut für Festkörperphysik, Leibniz Universität, Hannover in Germany; Edward Conrad, Ming Ruan and Zhigang Jiang from the School of Physics at Georgia Tech; Claire Berger from Georgia Tech and Institut Néel at the Centre National de la Recherche Scientifique (CNRS) in France; Antonio Tejeda and Muriel Sicot from the Institut Jean Lamour, Universite de Nancy, Centre National de la Recherche Scientifique (CNRS) in France; An-Ping Li from the Center for Nanophase Materials Sciences at Oak Ridge National Laboratory, and Amina Taleb-Ibrahimi from the CNRS Synchotron SOLEIL in France.

This research was supported by the National Science Foundation (NSF) Materials Research Science and Engineering Center (MRSEC) at Georgia Tech through award DMR-0820382; the Air Force Office of Scientific Research (AFOSR); the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy, and the Partner University Fund from the Embassy of France. Any conclusions or recommendations are those of the authors and do not necessarily represent the official views of the NSF, DOE or AFOSR.