1. Joined
    06 Mar '12
    Moves
    625
    06 Feb '14 10:135 edits
    I find this very interesting:

    http://phys.org/news/2014-02-ballistic-graphene-electronic-device.html

    "...Using electrons more like photons could provide the foundation for a new type of electronic device that would capitalize on the ability of graphene to carry electrons with almost no resistance even at room temperature – a property known as ballistic transport.

    Research reported this week shows that electrical resistance in nanoribbons of epitaxial graphene changes in discrete steps following quantum mechanical principles. The research shows that the graphene nanoribbons act more like optical waveguides or quantum dots, allowing electrons to flow smoothly along the edges of the material. In ordinary conductors such as copper, resistance increases in proportion to the length as electrons encounter more and more impurities while moving through the conductor.

    The ballistic transport properties, similar to those observed in cylindrical carbon nanotubes, exceed theoretical conductance predictions for graphene by a factor of 10. The properties were measured in graphene nanoribbons approximately 40 nanometers wide that had been grown on the edges of three-dimensional structures etched into silicon carbide wafers.

    For nearly a decade, researchers have been trying to use the unique properties of graphene to create electronic devices that operate much like existing silicon semiconductor chips. But those efforts have met with limited success because graphene – a lattice of carbon atoms that can be made as little as one layer thick – cannot be easily given the electronic bandgap that such devices need to operate.

    De Heer argues that researchers should stop trying to use graphene like silicon, and instead use its unique electron transport properties to design new types of electronic devices that could allow ultra-fast computing – based on a new approach to switching. Electrons in the graphene nanoribbons can move tens or hundreds of microns without scattering.

    "This constant resistance is related to one of the fundamental constants of physics, the conductance quantum," de Heer said. "The resistance of this channel does not depend on temperature, and it does not depend on the amount of current you are putting through it."
    ..."

    What! It doesn't " depend on the amount of current you are putting through it"! wouldn't that break ohms law! http://en.wikipedia.org/wiki/Ohm%27s_law
    Although materials that break ohm's law is nothing new, if its resistance doesn't depend on current, then I = V/R doesn't apply because it would mean R = (a constant ) in I = V/R ! Is that what they are really saying? From my studies of physics and electronics, until now, I would have thought that couldn't happen.

    "..."It seems that the current is primarily flowing on the edges," de Heer said. "There are other electrons in the bulk portion of the nanoribbons, but they do not interact with the electrons flowing at the edges."

    The electrons on the edge flow more like photons in optical fiber, helping them avoid scattering. "These electrons are really behaving more like light," he said. "It is like light going through an optical fiber. Because of the way the fiber is made, the light transmits without scattering."

    Electron mobility measurements surpassing one million correspond to a sheet resistance of one ohm per square that is two orders of magnitude lower than what is observed in two-dimensional graphene - and ten times smaller than the best theoretical predictions for graphene.

    ..."

    What! This is sounding too good to be true. If I am reading this right, if true, it could eventually lead to, for example, electric cables that have close-to-zero (only when compared with conventional materials ) electrical resistance at room temperature even though it doesn't superconduct.
    Although it does go on to say:

    "..Theoretical explanations for what the researchers have measured are incomplete. De Heer speculates that the graphene nanoribbons may be producing a new type of electronic transport similar to what is observed in superconductors.

    "There is a lot of fundamental physics that needs to be done to understand what we are seeing," he added. "We believe this shows that there is a real possibility for a new type of graphene-based electronics."
    ..."

    I will definitely be keeping a very close eye on this line of research for now on and wait to see if we can get some kind of confirmation of these results.
  2. Joined
    06 Mar '12
    Moves
    625
    06 Feb '14 11:183 edits
    mispost;

    "Although materials that break ohm's law is nothing new, if its resistance doesn't depend on current, then I = V/R doesn't apply because it would mean R = (a constant ) in I = V/R "

    is incorrect because it does 'apply' and should be:

    "Although materials that break ohm's law is nothing new, if its resistance doesn't depend on current, then I = V/R would mean R = (a constant ) in I = V/R (which means you can slightly simplify that to I = Vk where k is some constant for that material )"
  3. Subscribersonhouse
    Fast and Curious
    slatington, pa, usa
    Joined
    28 Dec '04
    Moves
    52619
    06 Feb '14 12:03
    Originally posted by humy
    mispost;

    "Although materials that break ohm's law is nothing new, if its resistance doesn't depend on current, then I = V/R [b]doesn't apply
    because it would mean R = (a constant ) in I = V/R "

    is incorrect because it does 'apply' and should be:

    "Although materials that break ohm's law is nothing new, if its resistance doesn't depend on current, th ...[text shortened]... ich means you can slightly simplify that to I = Vk where k is some constant for that material )"[/b]
    Well it makes sense, if R=zero, then I=E/R would be E/zero which doesn't work anymore.
  4. Joined
    06 Mar '12
    Moves
    625
    06 Feb '14 17:21
    Originally posted by sonhouse
    Well it makes sense, if R=zero, then I=E/R would be E/zero which doesn't work anymore.
    But R isn't exactly zero in this case, just arbitrarily 'small'.
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