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TWO-DIMENSIONAL CARBON, OR GRAPHENE
Posted on Saturday, March 18, 2006 @ 11:40:50 UTC by vlad
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PHYSICS NEWS UPDATE: TWO-DIMENSIONAL CARBON, OR GRAPHENE, has many of the interesting properties possessed by one-dimensional carbon (in the form of nanotubes): electrons can move at high speed and suffer little energy loss.
According to Walt deHeer (Georgia Tech), who spoke at this week's meeting of the American Physical Society (APS) in Baltimore, graphene will provide a more controllable platform for integrated electronics than is possible with nanotubes since graphene structures can be fabricated lithographically as large wafers.
Single sheets of graphene were only isolated in 2004 by Andre Geim (Univ. Manchester). In graphene, electron velocity is independent of energy. That is, electrons move as if they were light waves; they act as if they were massless particles.
This extraordinary property was elucidated in November 2005 through experiments (see background article in the Jan. 2006 Physics Today) using the quantum Hall effect (QHE), in which electrons, confined to a plane and subjected to high magnetic fields, execute only prescribed quantum trajectories.
These tests were conducted by groups represented at the APS meeting by Geim and Philip Kim (Columbia Univ.). The QHE studies also revealed that when an electron completes a full circular trajectory in the imposed magnetic field, its wavefunction (encapsulating the electron's quantum wave nature) is shifted by 180 degrees.
This modification, called "Berry's phase," acts to reduce the propensity for electrons to scatter in the backwards direction; this in turn helps reduce electron energy loss. Geim reported a new twist to this story. Studying QHE in graphene bilayers he observed a new version of QHE, featuring a doubled Berry's phase of 360 degrees. Also, Geim drew a comparison to certain cosmologies in which multiple universes can co-exist, each with its own set of physical constants; in graphene, he said, where electrons move in a light-like way, with a fast speed (but one somewhat less than the speed of light in vacuum), the parameter which sets the scale of the electromagnetic force, namely the fine structure constant (defined as e^2/hc), has a value of roughly 2.0 rather than the customary 1/137.
The goal now is to learn more graphene physics and then worry about applications. For example, Walt deHeer reported that a plot of resistance versus applied magnetic field had a fractal shape. DeHeer said that has so far has no explanation for this.
As for applications, he said that on an all-graphene chip, linking components with the usual metallic interconnects (which tends to disrupt quantum relations) would not be necessary. Thus the wave nature of electrons could be more fully exploited for quantum-information purposes. De Heer's group so far has been attempting to build circuitry in this way; they have made graphene structures (including a graphene transistor) as small as 80 nm and expect to get down to the 10-nm size.
The American Institute of Physics Bulletin of Physics News Number 769 March
17, 2006 by Phillip F. Schewe, Ben Stein, and Davide Castelvecchi
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Re: TWO-DIMENSIONAL CARBON, OR GRAPHENE (Score: 1) by RoseName on Wednesday, November 24, 2010 @ 06:19:11 UTC (User Info | Send a Message) | Thanks for a very exciting read! My research work has a lot to do with the issue. It is called "Future Applications of Graphene" to be more exact. If you are interested, I downloaded a video from a search engine. It's called http://filecraft.com [filecraft.com] SE if I am not mistaken. Here is its main idea. With the rise and rise of mobile computing, hardware companies are going
to spend more R&D money on things like graphene - it's a plentiful
enough substance (it's made of carbon, for crying out loud, and you can
get your own using a piece of sticky tape and a pencil!) and it has
astounding mechanical, electrical and piezoelectrical properties (i.e.:
by bending the device shown in the vid, you'd be able to MAKE
electricity). It's only a matter of time 'til we can buy these sorts of
things. [filecraft.com]
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Re: TWO-DIMENSIONAL CARBON, OR GRAPHENE (Score: 1) by jameslees on Sunday, February 06, 2011 @ 19:16:36 UTC (User Info | Send a Message) | Thanks for the site i have also found videos on on graphene on http://www.mediafilelinks.com [www.mediafilelinks.com] check it out if you studying the same class.
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Re: TWO-DIMENSIONAL CARBON, OR GRAPHENE (Score: 1) by DavidK on Tuesday, November 01, 2011 @ 16:59:49 UTC (User Info | Send a Message) | It is really a feat that another structure in the carbon family is explored and can be put into applications in the industries either in mobile and in the field of technology where it can be applied. Have quote wikipedia what is "graphene". Tampa Car Accident Lawyer [www.thetampainjurylawyers.com]
"The term graphene was coined as a combination of graphite [en.wikipedia.org]and the suffix -ene [en.wikipedia.org] by Hanns-Peter Boehm [en.wikipedia.org], [2] [en.wikipedia.org] who described single-layer carbon foils in 1962. [3] [en.wikipedia.org] Graphene is most easily visualized as an atomic-scale chicken wire [en.wikipedia.org] made of carbon atoms and their bonds. The crystalline or "flake" form of graphite consists of many graphene sheets stacked together.The carbon-carbon bond length in graphene is about 0.142 nanometers [en.wikipedia.org]. [4] [en.wikipedia.org] Graphene sheets stack to form graphite [en.wikipedia.org] with an interplanar spacing of 0.335 nm, which means that a stack of three million sheets would be only one millimeter thick. Graphene is the basic structural element of some carbon allotropes [en.wikipedia.org] including graphite, charcoal [en.wikipedia.org], carbon nanotubes [en.wikipedia.org] and fullerenes [en.wikipedia.org]. It can also be considered as an indefinitely large aromatic [en.wikipedia.org] molecule, the limiting case of the family of flat polycyclic aromatic hydrocarbons [en.wikipedia.org]." wikepedia |
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