 A nanometer-scale step is etched into the silicon carbide crystal by a fluorine-based reactive ion etch (RIE). (B) The crystal is heated to about 1200-1300 degrees Celsius (at low vacuum), inducing step flow and relaxation to the etching. (C) When the crystal is further heated to about 1450 degrees Celsius, a graphene nanoribbon forms. (D) From there the source and drain contacts, graphene nanoribbon channel, aluminum oxide gate dielectric and metal top gate are added.)
MAKING GRAPHENE NANORIBBONS: The process for tailoring of the silicon carbide crystal for selective graphene growth and device fabrication is illustrated, starting with the top left figure. (A) A nanometer-scale step is etched into the silicon carbide crystal by a fluorine-based reactive ion etch (RIE). (B) The crystal is heated to about 1200-1300 degrees Celsius (at low vacuum), inducing step flow and relaxation to the etching. (C) When the crystal is further heated to about 1450 degrees Celsius, a graphene nanoribbon forms. (D) From there the source and drain contacts, graphene nanoribbon channel, aluminum oxide gate dielectric and metal top gate are added.
Image: COURTESY OF WALTER DE HEER
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For years researchers have held out hope that graphene would be the material to pick up the mantle in the electronics industry when silicon hits its limits as the material of choice for making devices smaller, faster and cheaper. Yet, turning graphene's promise into a reality has been difficult to say the least, in part because of the inherent difficulty of working with a substance one atom thick.
Methods of cutting graphene into useable pieces tend to leave frayed edges that mitigate the material's effectiveness as a conductor. Now, a team of researchers at Georgia Institute of Technology led by Walter de Heer claims to have made a significant advance in that area by developing a technique for creating nanometer-scale graphene ribbons without rough edges. (A nanometer is one billionth of a meter.)
Graphene has, of course, made headlines throughout the scientific world this week, thanks to the awarding of the Nobel Prize in Physics to two researchers at the University of Manchester in England who in 2004 pioneered a way of isolating graphene by repeatedly cleaving graphite with adhesive tape. The Nobel Prize committee recognized Andre Geim and Konstantin Novoselov "for groundbreaking experiments regarding the two-dimensional material graphene."
Unlike the approach taken by Geim and Novoselov, de Heer and his team in the past have created graphene sheets by heating a silicon carbide surface to 1,500 degrees Celsius until a layer of graphene formed. The graphene was then cut to a particular size and shape using an electron beam. "This was a serious problem because cutting graphene leaves rough edges that destroy a lot of graphene's good properties, making it less conductive," says de Heer, regents' professor in Georgia Tech's School of Physics.
De Heer's new approach, described October 3 in Nature Nanotechnology, is to etch patterns into the silicon carbide and then heat that surface until graphene forms within the etched patterns. (Scientific American is part of Nature Publishing Group.) In this way graphene forms in specific shapes and sizes without the need for cutting. "The whole philosophy has changed," he says. "We're not starting with an infinite sheet of graphene; we're growing it where we want to grow it."
The researchers claim to have used the technique to fabricate a densely packed array of 10,000 top-gated graphene transistors on a 0.24-square-centimeter chip, a step toward their ultimate goal of creating graphene components that can be integrated with silicon for new generations of electronics. Such a consolidation would be a key milestone towards making microprocessors able to operate at terahertz speeds, 1,000 times faster than today's chips (whose speeds are clocked at billions of hertz). Another goal is to reduce heat generation as an increasing number of transistors are packed onto each chip. Such advances would continue to validate Moore's law even as silicon circuits reach their miniaturization limit. "In principle, graphene can overcome silicon's limitation," de Heer says. "If we completely succeed [only] time will tell."
Graphene and silicon will be able to coexist much the same way that airplanes and freight ships are used for transporting cargo. "They move at different speeds, but both are important because they have different costs," de Heer says. "I think a similar thing will happen in electronics."
De Heer is also quick to acknowledge that, although the study of graphene dates back to the 1970s, the field still has a long way to go. He and his team are now investigating how the ribbons they created will perform over time and to what degree their new approach improves on cutting pieces of graphene out of larger sheets.
With so many open questions about graphene's viability, de Heer says he was surprised that the Nobel selection committee recognized graphene at this time. The technology has tremendous potential but only a fraction of that potential has been realized to date. "It's a little early," he says. "If you ask me the bottom line—What has graphene accomplished?—it's still trying to find its way."
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Reply | Report Abuse | Link to thisStudent’s Discovery Advances Nanotech Research
http://www.utdallas.edu/news/2010/10/6-6101_Students-Discovery-Advances-Nanotech-Research_article.html
Keep in mind that a 1,000 fold increase in processor speed would not produce a 1,000 fold increase in application performance, unless system memory, buses, disks and other peripheral devices and, especially internet connection speeds, were similarly increased.
Reply | Report Abuse | Link to thisNo need to get excited about next Christmas: graphene processor development may simply allow future performance enhancements to continue historical achievements.
As I understand, humanity's contribution to atmospheric co2 is a product of combusting hydrocarbon compounds to extract their energy stored over eons. It is the effects of increasing atmospheric co2 that is considered to produce global warming. I doubt that any significant amount of atmospheric co2 can be sequestered during the production of graphite or graphine products. There is no relationship between reducing atmospheric co2 and employing carbon materials in high tech products. Might make a fun premise for a science fictions story: self replicating intelligent carbon based nano life forms clean up the Earth after humans have gone...
Reply | Report Abuse | Link to thiscool discovery....i guess we get to wait and see if they do anything with it...
Reply | Report Abuse | Link to thisFollowing the same reasoning, perhaps the best thing we could do to fight global warming would be to switch from pens to pencils and carbon filter a lot of water, just in case graphene electronics circuitry and carbon nanotubes don't pan out. Sorry, I'm just not seeing it.
Reply | Report Abuse | Link to thisIf we can make it one foot thick, we might b able to get that "ladder" concept off the ground all the way to the ISS. As long as money is of no importance that is.
Reply | Report Abuse | Link to thisFirst, I am no chemist and may simply be missing the obvious. Second, you have not explained how employing carbon in products will sequester carbon from the atmosphere, reducing global warming, or even the ocean.
Reply | Report Abuse | Link to thisAs I understand, most of the graphite required to produce graphene, carbon nanotubes, carbon fiber reinforced plastics, synthetic diamonds, pencil leads and other carbon compositions is extracted from strip mines like coal. Any other methods used to extract graphene from the sea or air could also be used in the production of pencil leads, for example.
My guess is that any process that could extract graphite from the atmosphere or oceans for the purpose of producing graphene would require the expenditure of a great deal of energy in the process.
Without explaining, at least in principle, economically viable methods of achieving your very large scale CO2 sequestration objectives, I have to consider them to be impractical or fictional science. Probably I'm simply ignorant: please explain.
ennui...i keep forgetting about that concept...carbon is the material to do it...now, how to string it together for 23k miles and to use as a lift...probably would generate huge amounts of electricity as a side benefit...
Reply | Report Abuse | Link to thisIt seems to me that sequestering carbon is a self solving problem. The more CO2 in the air, the better plants grow. The better plants grow, the more Carbon they use and thus sequester.
Reply | Report Abuse | Link to thisIt will be interesting to see if graphene will have a meaningful application eventually.
Yes, it's simple chemistry not science fiction. But doing it on a large scale to reduce or just stop increasing atmospheric CO2 is uneconomical. The simpler and more economical solution is to reduce burning fossil fuels, replace them with renewable and nuclear energies, and plant more trees.
Reply | Report Abuse | Link to thisPhotosynthesis is a natural chemical reaction that takes atmospheric CO2 and combines it with water to form carbohydrate and oxygen.
CO2 + H2O -> C6H12O6 + O2
The topic of this article is the promise of graphene nano-electronics, not planet-wide carbon sequestration. You're not creating any good will among your fellow scientists hi-jacking the comments section with irrelevant comments.
Reply | Report Abuse | Link to thisSimilar to nanotubes, we've figured out how to make some horribly poor yield of an amazing material. That's good enough for physicists to measure its properties and then extrapolate "if we could make a CPU out of this..." but the work of perfecting production yields until it's suitable for commercialization seems less glamorous. There probably won't be a Nobel Prize for graphene production techniques, but there probably is a lot more money to be made. I hope one of these methods works out (e.g. SiC decomposition or copper foil CVD) but I wouldn't bet much on a graphene-based commercial product in the next decade. We're doing some tricks and twists with Silicon, but it's the same basic stuff from 1954. I hope I'm wrong - I'll try to be wrong on that one.
Artificial leaf is not commercially viable. Scientists doing research on this should tell us how much it costs to convert 1 kg of atmospheric CO2 to hydrocarbon and oxygen using their technology. Compare this to the cost of planting trees that converts the same weight of CO2. I put my money on plants.
Reply | Report Abuse | Link to thisWe can start by not destroying our forests. Better, create more forests by planting trees. If there isn't enough land, we can cultivate algae in the oceans which cover over 70% of the earth. Algae also sequesters CO2 and it can be used as biofuel.
Better still, stop burning fossil fuels and replace them with renewable energies. Earth receives 7,000 times more solar energy (230 watts/sq.m.) than the world's total energy consumption (0.03 W/sq.m.)
With good battery to store energy, a 100-sq.m. solar cell on the house roof can provide 100% of the 4 KW power need of an average household. And we still have hydro, wind, geothermal and nuclear which are all existing technologies.
Graphene, artificial leaf, etc. are great new technologies. But for reducing atmospheric CO2, I put my money on proven technologies.
Yes, biofuel is more expensive than fossil fuel. But it is cheaper than hydrocarbon fuel extracted from atmospheric CO2 using artificial leaf technology.
Reply | Report Abuse | Link to thisA farmer uses 1,000 sq.m. land for housing, 1 hectares for food crops to feed his family, and 100 hectares for tree planting. Reforestry works. I know bec. one of our foundations is involved in reforestry and my colleague is an agroforestry expert.
There are many species of algae. Some are harmful or toxic. Others are not. We can use non-toxic algae like seaweeds for biofuel.
The clouds are made up of water. The atmosphere is 99% nitrogen and oxygen. CO2 is only 0.039% and hydrocarbon (methane) is 0.00018%. It is cheaper to extract methane from natural gas underground and biogas manure than from the atmosphere.
Water vapor is the most significant greenhouse gas, 30x more H20 molecules in the atmosphere than CO2. But the role of clouds in climate change is uncertain. They can be positive or negative feedback bec. they absorb terrestrial infrared radiation but they also increase albedo as they reflect incoming sunlight.
Reply | Report Abuse | Link to thisIf there is an economical way to capture all greenhouse gases in exhaust systems, by all means we should do it. But there is none so far. My favored solution is to stop burning fossil fuels and shift to renewable energy. Sunlight is the ultimate free lunch. It's easier to turn it into useful energy than extracting minute traces of hydrocarbon in the atmosphere for fuel.
Eventually renewable energy will be the only viable solution. Our fossil fuel reserve will be depleted in 60 yrs. more or less. Uranium ore will also be depleted sooner or later. The earlier we accept this fact, the better. We can still live in denial for 60 yrs.
Btw, I'm a firm believer in nuclear fusion. This and renewables are the energy of the future.
We've been experimenting with nuclear fusion for 60 yrs. The ITER fusion reactor in France is now being built at a cost of 15 billion euros. It will produce 450 MW net power in 2018. But making it cost competitive is a big challenge.
Reply | Report Abuse | Link to thisBtw, the idea of using graphene to replace silicon in electronics industry to reduce atmospheric CO2 will not work bec. the one-atom thick graphene uses very little carbon.
The diameter of a carbon atom is 1.5x10^-10 m. One sq.m. of graphene uses 4.4x10^19 carbon atoms. A graphene sheet as big as the total surface area of the earth (5.1x10^14 sq.m.) would use 2.3x10^34 C atoms. A gallon of gasoline contains 10^26 C atoms.
So the earth-sized graphene sheet contains the same no. of C atoms as 197 million gallons of gasoline. U.S. alone consumes 386 million gallons of gasoline a day. It will have little effect on atmospheric CO2.
Our present world economy is already carbon based. 85% of the world's energy consumption come from fossils fuels. Many believe this is the cause of global warming. I think we should move away from carbon as source of energy. There are many non-carbon energy sources: solar, wind, hydro, geothermal, nuclear.
Reply | Report Abuse | Link to thisBut we want to still stick to carbon in the future, the most efficient way to extract hydrocarbon large scale and turn them to energy is fossil fuels from underground, and biofuels from plants and animals.
I believe the focus of research should be new energy sources like nuclear fusion, not reinforcing the old carbon economy by new technology. It's like genetic engineering the horse to produce more horsepower. Why don't we just get rid of the horse and build a Lamborghini?