[Alan McDougall (OP)]

Graphene will it be used for computer chips etc? It is a very thin substance with some very interesting properties, do you guys know anything about it?

[evan_au]

Electrons move very quickly through single-layer graphene, which means that it could potentially be used to process signals at very high frequencies. This is a promising characteristic for the future of electronics, in which the trend over time has been to move towards higher and higher frequencies. This allows computers to run faster, communications links to carry more data and wireless networks to operate in currently-unused parts of the electromagnetic spectrum.

However, there are some practical constraints which scientists and engineers are working to overcome:

• It is hard to make good electrical connections from graphene to more conventional materials like aluminium, copper, gold and silicon
  
• Conventional logic gates save a lot of power by having two complementary gates - one turns on when the other turns off. However, graphene does not directly support a high-gain complementary structure
  
• Behaviour changes when you cut it into wires
  
• When you make 3-dimensional circuits, capacitance increases and speed reduces
  
• ...and there are many engineering challenges in reliably manufacturing graphene into the detailed, complex shapes required for dense, high-speed circuitry.

But the range of unique properties of graphene ensures that it will start appearing in applications near you over the next few years.
See: http://en.wikipedia.org/wiki/Graphene#Integrated_circuits

[tomizett]

So does a higher drift velocity mean higher propagation speed?
What determines the speed of propagation - rings a bell that it's todo with the characteristic impedance, the ratio between impedance and capacatance per unit length (or something like that).
Does the drift velocity relate to electrical resistance at all (or is it not that simple)?

[evan_au]

The technical term is electron mobility (or in general, carrier mobility). See: http://en.wikipedia.org/wiki/Electron_mobility

The conductivity=1/resistance is the product of carrier mobility and carrier concentration.

In a transmission line or cable, the velocity of propagation of an electromagnetic wave is determined by the permeability and permittivity of the cable, which is affected by its geometry and it construction materials. The speed of light in a vacuum is determined by the permeability and permittivity of free space.

However, when the size of the components is far less than the wavelength of operation, the behaviour of electrons and holes is of greater interest, and the drift velocity is a key parameter affecting the speed of components fabricated from that material.

[Alan McDougall (OP)]

The technical term is electron mobility (or in general, carrier mobility). See: http://en.wikipedia.org/wiki/Electron_mobility

The conductivity=1/resistance is the product of carrier mobility and carrier concentration.

In a transmission line or cable, the velocity of propagation of an electromagnetic wave is determined by the permeability and permittivity of the cable, which is affected by its geometry and it construction materials. The speed of light in a vacuum is determined by the permeability and permittivity of free space.

However, when the size of the components is far less than the wavelength of operation, the behaviour of electrons and holes is of greater interest, and the drift velocity is a key parameter affecting the speed of components fabricated from that material.

Thanks for your informative posts, you have really filled in some serious gaps in my knowledge!

[evan_au]

A recent story in Nature revealed a new technique for building graphene nanowires on a Silicon Carbide substrate.
These wires had electrical resistance 1000 times lower than graphene wires formed by cutting bulk graphene sheets.
This translates into circuits that can charge and discharge 1000 times faster (ie higher clock frequency for a computer), and 1000 times less heat dissipation (ie the chip won't melt at these high clock frequencies).
The results were so good that they exceeded theoretical predictions by a factor of 10...
See: http://www.nature.com/news/graphene-conducts-electricity-ten-times-better-than-expected-1.14676