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Nobel-Worthy Graphene Work Promises Smaller, Greener Chips

By Richard Adhikari
Oct 5, 2010 11:36 AM PT

Physicists Andre Geim and Konstantin Novoselov of the University of Manchester in England have been awarded the Nobel Prize in Physics 2010 for what the committee described as "groundbreaking experiments" on graphene.

Nobel-Worthy Graphene Work Promises Smaller, Greener Chips

A sheet of graphene is just one atom thick, works as a superb conductor of electricity and heat, is almost transparent, but is so dense that no atoms can pass through it.

Graphene could lead to new, even faster semiconductors.

"This Nobel prize is for work on a fundamental building block of nanotechnology," Carl Howe, director of anywhere consumer research at the Yankee Group, told TechNewsWorld.

Graphene's Just Skinny Carbon

Graphene consists of carbon atoms joined together in a hexagonal pattern that's similar to chicken wire. It's only one atom thick and, as such, it is considered the first of a number of similar two-dimensional materials scientists have discovered since 2004, according to the scientific backgrounder compiled on graphene by the Royal Swedish Academy of Sciences. Others include single layers of Boron-Nitride and Molybdenum-disulphide.

Graphene has the properties of all three-dimensional (3D) objects -- length, width and depth -- even though that depth is one atom thick, so how can we consider it a 2D material?

"Although graphene's one atom thick, all the major properties of interest are or act along the sheet, so it's a 2D material," Brooks Hanson, deputy editor for physical sciences for the journal Science, told TechNewsWorld. "At one atom thick, it's as close to 2D as you can get."

The electronic structure of graphene is different from that of 3D materials. Its Fermi surface is characterized by six double cones. The Fermi surface is an abstract boundary used in condensed matter physics for predicting the thermal, electrical, magnetic and optical properties of metals, semimetals and doped semiconductors. Its shape is derived from the periodicity and symmetry of the crystalline lattice and from the occupation of electronic energy bands.

Doped semiconductors are those into which impurities have been intentionally introduced into an intrinsic, or extremely pure, semiconductor to change its electrical properties. The impurities introduced depend on the type of semiconductor used.

Properties of Graphene

The electrical conductivity of intrinsic graphene is low. However, when it's doped with electrons, through the creation of holes in the lattice or by adsorbing water or ammonia, its electrical conductivity may be raised to exceed that of copper at room temperature.

Graphene is practically transparent, absorbing only 2.3 percent of light falling on it. It maintains its 2D properties at room temperature, unlike low-temperature 2D systems based on semiconductors.

Graphene is substantially stronger than steel, very stretchable, and can be used as a flexible conductor. Its thermal conductivity is much higher than that of silver.

Everything Old Is New Again

It's not as if graphene has just been discovered. The material had already been studied theoretically in 1947 by P.R. Wallace as a textbook example for calculations in solid state physics. Wallace predicted graphene's electronic structure, among other things. Several other scientists wrote about graphene in the following years.

Before 2004, scientists thought it was impossible to isolate stable sheets of graphene. However, Geim, Novoselov and their collaborators managed to do this and published their results in the October 2004 issue of Science magazine.

They basically applied Scotch tape to a graphite crystal then transferred the thin layers they peeled off to a silicon substrate. Although this method had been suggested and tried by scientists previously, they couldn't identify any single-atom layers of graphene.

Geim and Novoselov succeeded by taking pictures of the layers they flaked off using Scotch tape with an atomic force microscope and managed to work on the graphene, patterning it into a Hall bar and attaching electrodes to it to measure the Hall effect.

The Hall effect is the potential difference on opposite sides of a thin sheet of conducting or semiconducting material in the form of a Hall bar through which an electric current is flowing. The current's created by a magnetic field applied perpendicularly to the Hall element.

The Hall effect can measure either the density of the carrier or the magnetic field. It differentiates between positive charges moving in one director and negative charges moving in the other.

Potential Uses for Graphene

Graphene makes experiments possible that give new twists to phenomena in quantum physics, the Royal Swedish Academy of Sciences stated.

Further, it may be used to create new materials and in electronics -- it's believed that graphene transistors will be "substantially" faster than the silicon transistors currently in use.

Graphene may make plastics more heat resistant and mechanically robust and let them conduct electricity. It may also be used in transparent touchscreens and light panels.

"You can, in theory, extend graphene beyond the boundaries set by the limitations of silicon, and thus make devices smaller," Rob Enderle, principal analyst at the Enderle Group, told TechNewsWorld.

"This could create vastly more complex microcomputers with huge implications for markets ranging from embedded medical equipment such as heart monitors to defense, where you may have intelligent bullets," Enderle added.

Graphene's strength, transparency and conductivity could let us "create near-impenetrable windshields with heads-up displays, next-generation military body armor with built-in health monitoring, TVs that seem to float on the wall or double as windows, letting you electronically change your view from real to artificial, and to architectural designs where the building itself may become a billboard," Enderle opined.

Graphene semiconductors would be more environmentally friendly than silicon ones, the Yankee Group's Howe pointed out.

"We dope silicon with lots of toxic metals to make it into the P or N versions of a semiconductor," Howe said. "Graphene, on the other hand, gets doped with water or ammonia, which are a lot less toxic."

Further, graphene's high conductivity means manufacturers may not need to deposit aluminum or copper wires onto graphene as they have to do with silicon when creating a semiconductor, Howe said. "We could be looking at an entire semiconductor industry developed around graphene," he suggested

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