Graphene!
vrajendr
“Given the fact that we're contemplating treating electrons just like light, you might ask why we don't simply build logic from photonic systems. Optical devices like lasers have long been an attractive way to make speedy computing circuitry. Instead of transistors, the systems use a combination of amplifiers, modulators, emitters, detectors, and waveguides to manipulate photons and perform computations.
Graphene offers a good compromise—electrons in a graphene switch will move much faster than they can in ordinary transistors, and at the same time, the devices themselves will take up much less space and consume far less energy than a photonic system.
As with a CMOS transistor, the basic unit for manipulating electrons in reconfigurable graphene logic is a simple straight p-n junction. These can be created by making a four-layer stack. At the very bottom, embedded into the substrate, two patches—or gates—made of conductive material are built. An insulating layer of oxide is placed on top, and then a rectangle of graphene is placed on top of that. Electrodes placed on top of the graphene, at either end of the rectangle, are used to supply a reference current to the device.
By applying a positive voltage on one gate, you can pull electrons from the nearest electrode into the graphene, creating an n-doped material. Applying a negative voltage to the other gate will draw holes from the other electrode into the graphene, creating a p-doped material. The resulting p-n junction isn't like the kind you'll find in a normal diode or transistor; it won't rectify current by allowing it to go in only one direction. Charge carriers pass freely across the barrier. But the junction does have the unique property of being angle dependent. The chance that an electron will get transmitted or reflected at the junction depends on its angle of approach.
It may not sound too profound, but this sort of behavior isn't really seen in the natural world—you can't focus light with a flat lens. But graphene bends a stream of electrons differently than the way most materials bend light: It has the electronic equivalent of what's referred to in optics as a negative index of refraction. An electron traveling through an n-doped region of graphene effectively takes on negative energy when it moves into a p-doped region, and conservation of momentum demands that it be bent in this counter intuitive way. So far, the only way to manipulate electromagnetic radiation in this fashion is to use artificial materials, which are often constructed by manipulating metal wires. It turns out that graphene is a natural electronic analogue to these meta materials.
Beyond focusing and defocusing electrons, graphene's refractive properties can also cause the total internal reflection of electrons. The material can be set up to accomplish this trick by taking advantage of the same angle dependence in a graphene p-n junction. For example, if the gates beneath a sheet of graphene are properly spaced, electrons sent toward a junction at a shallow angle—say, 45 degrees or less—won't be able to pass through the boundary; they will all be reflected. To let the electrons pass through the junction unimpeded, you simply reverse the voltage on one of the gates, creating a uniform n-n or a p-p device.
At the start, most of our research was theoretical. We realized that to make proper logic, we had to come up with designs that could actually perform logic operations, and we had to get a better understanding of how competitive they might be against state-of-the-art CMOS.
One of the first designs we explored was the simple binary switch. You could build such a switch with just a square of graphene. If you draw an imaginary diagonal across the square, you create two triangles of graphene. Under each of these triangles you place a triangular wedge of conducting material—such as copper or heavily doped silicon—that can be either positively or negatively charged. These buried wedges act as gates, altering the electronic properties of the graphene above them. If both wedges have the same charge, the switch is on, and an electron coming from one side of the graphene square can move in a straight line from one side of the square to the other. But if opposite biases are applied, the two graphene regions will become oppositely doped, and nearly all the electrons will be reflected at the interface. Now the switch is off.This simple device can be arranged in series to create a range of logic functions, including NOT, OR, and AND.”
samontoy
symay
Thanks,
Salomon.
matthias.engh
Here is a short visionary article on using graphene as capacitor and in that manner as energy storage:
http://ecogeek.org/component/content/article/3847
And for people with extra time on their hands..
An article on the story of graphene and possible uses:
http://www.independent.co.uk/news/science/the-graphene-story-how-playing-with-sticky-tape-changed-the-world-8539743.html