Lattice to replace chips in computers to come
For more than half a century, computers have been obeying "Moore's Law," a principle named after Gordon Moore, the co-founder of chip maker Intel.
Under it, the number of transistors that can be incorporated in a chip has doubled every 18 months or so, which explains the extraordinary rise in processing speed and memory capacity at the heart of modern gadgets.
The "law" was predicted by Moore to endure until the mid-1970s, yet it is still going strong -- but not for much longer.
As early as 2015, according to the gloomiest estimates, engineers working in silicon and other existing materials will run smack into another law: the limits of miniaturisation, when too many circuits cramped into too small a space leads to higher temperatures which in turn crimps efficiency.
This is why graphene, the material that on Tuesday unlocked the Nobel Prize for Russian-born physicists Andre Geim, 51, and Konstantin Novoselov, 36, has been greeted with such excitement.
Graphene is a novel form of carbon that comprises a single layer of atoms arranged in a honeycomb-shaped lattice.
Even though the substance is chemically very simple, it is a stellar performer in strength, in conducting electricity and dissipating heat.
That makes it a fabulous candidate to replace semiconductor chips -- and explains why microchip giants such as IBM and Intel have been investing heavily in a material that today only exists in tiny flakes.
"Diamonds may be a girl's best friend but graphene gives an unexpected and a wholly new way to put the electron in carbon country," said Marshall Stoneham, president of the Institute of Physics in London.
Graphene transistors would in theory run at far higher speeds and cope with much higher temperatures than silicon counterparts.
As graphene is nearly transparent, it would also be suitable for making touch screens, light panels and possible solar cells.
Plastics with graphene added to them can become heat-resistant and -- thanks to the robustness of the carbon lattice -- mechanically strong. They could be incorporated as composite materials in the satellites, planes and high-performance cars of the future.
"Graphene has become known as a wonder material," Geim, a professor at the University of Manchester, northwestern England, said last year as he accepted an honour at Britain's prestigious Royal Society.
"Not only is it the thinnest material in the Universe, but also the strongest ever measured. It can sustain current densities a million times higher than that of copper, shows record thermal conductivity and stiffness and allows the investigation of quantum relativistic phenomena in a bench-top experiment.
"The full list is long and is yet to be completed."
Graphene was aired as a theoretical substance in 1947, but for decades, many physicists thought it would be impossible to isolate, suggesting that such thin crystalline sheets were bound to be unstable.
Showing smartness and arguably the cheapest technology around, Geim and Novoselov in 2004 extracted graphene by painstakingly using ordinary sticky tape to pick up a flake from a piece of graphite -- the carbon form found in pencils.
Graphene still remains firmly a laboratory substance, produced only in flakes of a fraction of a millimetre, which of course is far too small to be useable in electronics.
But in January this year, European scientists demonstrated how graphene production could be scaled up by "growing" one layer on another on silicon carbide.Discovery of mighty carbon yields Nobel
NEW YORK — It is the thinnest and strongest material known to mankind — no thicker than a single atom and 100 times tougher than steel. Could graphene be the next plastic? Maybe so, says one of two scientists who won a Nobel Prize on Tuesday for isolating and studying it.
Faster computers, lighter airplanes, transparent touch screens — the list of potential uses runs on. Some scientists say we can't even imagine what kinds of products might be possible with the substance, which hides in ordinary pencil lead and first was extracted using a piece of Scotch tape.
Two Russian-born researchers shared the physics Nobel for their groundbreaking experiments with graphene, which is a sheet of carbon atoms joined
Watch a video about Alfred Nobel.
together in a pattern that resembles chicken wire.
Andre Geim and Konstantin Novoselov of the University of Manchester in England used Scotch tape to rip off flakes of graphene from a chunk of graphite, the stuff of pencil lead. That achievement, reported just six years ago, opened the door to studying what scientists say should be a versatile building block for electronics and strong materials.
"It has all the potential to change your life in the same way that plastics did," said Geim, 51, a Dutch citizen. "It is really exciting."
Michael Strano, a chemist at the Massachusetts Institute of Technology, said trying to predict its uses would be "folly."
"We can't even imagine the uses we're going to find," he said.
But he and others have some ideas. Graphene's electrical properties mean it might make for faster transistors, key components of electronic circuits, and so lead to better computers, the Nobel committee said.
As a single layer of carbon atoms, it's tiny, which could pay off in more powerful cellphones, several scientists said.
And because it's practically transparent, it could lead to see-through touch screens and maybe solar cells, the committee said. It might also pay off for big TV screens.
Its tremendous strength could produce new composite materials that are super-strong and lightweight for use in building airplanes, cars and satellites, the committee said.
Joseph Stroscio, a physicist at the National Institute of Standards and Technology, said he had thought it would take a few more years of scientific appraisal before graphene would win a Nobel. But its potential applications and the brand-new behavior it presents for basic physics have drawn strong interest since the 2004 breakthrough, and the prize is well-deserved, he said.
It might take five or 10 years before graphene shows up in products such as cellphones, he said.
Novoselov, 36, is the youngest Nobel winner since 1973 of a prize that normally goes to scientists with decades of experience. He holds British and Russian citizenship.
Paolo Radaelli, a physics professor at the University of Oxford, marveled at the simple methods the winners used.
"In this age of complexity, with machines like the supercollider, they managed to get the Nobel using Scotch tape," Radaelli said.
The chemistry prize will be announced today, followed by literature Thursday, the peace prize Friday and economics Monday.
Read more: Discovery of mighty carbon yields Nobel - The Denver Post http://www.denverpost.com/headlines/ci_16263630#ixzz11ZQb3xdGGraphene transistors promise 100GHz speeds
Researchers are running into the physical limits of speed and scaling in silicon transistor technology, forcing them to look elsewhere for next-generation devices. The leading candidate to replace silicon being pursued by, well, pretty much everyone, is graphene. Graphene, single sheets of graphitic carbon, is exciting because it is a single atom thick and has remarkably high electron mobilities (100 times greater than silicon), making it ideally suited to atomic-scale, high-speed operation. Also, graphene's electrical properties can be controlled, switching it among conducting, semiconducting and electrically insulating forms. That means graphene-only (or, more likely, graphene-mostly) devices are, in principle, possible.
In this week's Science, researchers from IBM demonstrate graphene-based field effect transistors (FETs) that may operate at much higher speeds (100GHz) than Si FETs. Graphene layers were thermally grown on two-inch SiC wafers and the FETs were formed using standard Si fabrication techniques with HfO2 as the gate oxide. That's a rather significant point—the researchers actually created an entire wafer of these devices.
The smallest gate length demontrated in the paper was 240nm, quite large compared to current generation Si (32nm), but the graphene was one or two layers (meaning one or two atoms) thick in all the tested devices—a considerable improvement over Si.
High frequency operation, colloquially referred to as the speed of the transistors, was the key property examined in the paper. As operating frequency increases, electrons have less time to respond to the electrical fields that drive transistors, which will eventually cause the transistor to fail because the electrons simply can't conduct across the material fast enough.
The graphene FETs in this work were tested up to 30GHz and, extrapolating those results, the authors showed that the FETs would operate, albeit poorly, up to 100GHz. Similarly sized Si devices are limited to 30GHz operation. Assuming these devices can be scaled, they will undoubtedly present a dramatic speed increase over current generation Si.
Because the graphene used in this study was conductive (i.e. no band gap), the demonstrated voltage-current characteristics were strange compared to Si. Specifically, current continued to increase linearly with drain voltage up to device breakdown. Si-based transistors typically have a point, called the threshold, at which a current cannot increase despite increasing drain voltage.
This study is a mixed bag of promise and hype. The 100GHz speed touted in the article's title is an extrapolation—no such properties were actually measured. Also, the electron mobilities, the key property for high frequency operation, that the authors measured in the fabricated devices were pedestrian compared to graphene's potential, probably due to the thermal process used to synthesized the graphene layer. Future devices could dramatically outperform these FETs if wafer-scale fabrication can replicate some of the better electron mobility measurements of graphene.
Graphene devices have grown by leaps and bounds over the past few years, and they are probably the best bet to eventually replace silicon. Demonstrations like this are important because they show that wafer-scale production is possible, and the properties, while not ideal, are truly impressive, in that they're already beginning to push the limits of Si technology.