Intel Experimenting With Nanotubes 85
illeism writes "C|Net is reporting on Intel's experimentation with nanotubes in processors. From the article: 'The chip giant has managed to create prototype interconnects — microscopic metallic wires inside of chips that link transistors ... Carbon nanotubes ... conduct electricity far better than metals. In fact, nanotubes exhibit what's called ballistic conductivity, which means that electrons are not scattered or impeded by obstacles.'"
Re:Power is Heat (Score:5, Informative)
I'm also tempted to suggest that the empty space between tubings could be flooded with some sort of coolant to eliminate the temperature gradient; but I have my doubts about the feasibility of that. At such a small level, you'd have a lot of difficulty trying to fit atoms into that space. In addition, you'd probably do more to damage the circuitry than heat removal. Still, that doesn't place micro-heatpumps woven into the circuits entirely out of the question. Just mostly.
In any case, we're already using WAY too much power to keep up these ridiculous clock speeds. Forcing chip-makers to scale the power usage back a bit wouldn't be all that bad of a thing. Especially if they're getting replacement speed increases from the smaller interconnects and lower resistance of the nanotubes.
Re:Don't let random people write science articles (Score:5, Informative)
Are you serious, or are you just trolling? As a blatant counterexample, there are non-metallic superconductors, which conduct electricity infinitely better than a metal. So sure, metals conduct (with non-zero resistance) and have some common characteristics, eg their fermi energy typically lies in the middle of a band (unlike semiconductors or insulators), ratio of thermal to electrical conductivity is relatively constant, etc.
But there are many things that also conduct fairly well at room temperature, such as doped silicon (an insulator). However, cool down silicon and the resistance increases (not enough thermal energy to excite electrons above the bandgap). Cool down a metal and its resistance will decrease (to a limiting factor). Cool down a superconductor and it undergoes a phase transition to a state of infinite conductivity.
Carbon nanotubes are actually extremely interesting in this regards, they can look metallic or insulating, depending on the chirality (ie, how the graphene plane is rolled into a tube). The metallic ones (with the fermi energy in the middle of a band) have quite long mean-free paths. Hence electrons can travel through the tube without scattering (this is the ballistic travel mentioned in the slashdot blurb). This limits the nanotubes resistance to the quantum resistance of about 25 kOhm. (Actually, the tube's resistance is 1/4 this resistance, as there are four quantum conducting channels because the graphene plane has two independent sites in its unit cell, and each site can have two values of electron spin).
Even some the insulating (or semiconducting) carbon nanotubes (or the graphene plane itself) are really cool. Due to the layout of the graphene plane, the band structure isn't pseudo-parabolic (as in a standard insulator) but conical (two cones meeting at a point), like a Minkowski light cone, or MCP from TRON. In the right orientations, the Fermi energy lies exactly at the intersection, and believe it or not, the excited states look EXACTLY like relativistic massive particles. The speed of light is mapped to the speed of sound instead, in this system. Really cool stuff, there are tons of future applications for nanotubes and graphene studies due to the interesting band structure, we've only really begun to break the surface.
Re:Don't let random people write science articles (Score:3, Informative)
Conductivity is a function of:
A) Number of possible free electron states (positions) - function of temperature
B) Mean time to collision for given electron - function of temperature
C) [free] Electron density - function of temperature
Note that higher temperatures mean:
B) greater vibrational or translational properties of the material which obstruct the paths of free electrons.. So B is inversely proportional to temperature.
C) greater number of electrons are excited and thus broken from their atomic bonds (or at least lower atomic orbitals) and thus a greater number of electrons are available to participate in conduction. So C is directly proportional to temperature
Any material that
A) has free electrons (non-atomicly bound OR in covalent orbitals / orbitals shared between atoms)
B) has a non-infinite potential barrier between geometric positions
C) is above absolute zero
Naturally, the wider the path (radially), the greater the number of electrons and the greater the number of electron states, so the greater the conductivity.. It's 1 to 1 or linear growth.
As for length, the conductivity is an intrinsic measure, so length is somewhat irrelevant. However as a matter of practicality, on a large scale, the longer a path a given set of electrons have to travel, the more collisions will occur and thus the greater number of energy dispersals will occur and thus a greater amount of waste-heat. So you get an effectively greater measurement of resistance the longer the wire. This too is linear..
But length is usually a function of practical design (gotta connect two geographically distinct items).. Width, on the other hand is often a function of technology (how small can I make it) AND because width directly affects conductivity (gotta be wider to conduct more electrons), the intrinsic conductivity of the material dictates that for a given requirement of current and voltage, you must have a certain width for a given material.
However, not all geometries are created equally. The shape of the material, (which includes the curvature.. gentle curves v.s. right angles) affects the electro-static properties of the material. Indeed the mean-free-path to collision is different around the edges/boundries of a material, so obviously curved wire will have different properties than straight wire. Likewise the type of material adjacent to the conductor dramatically affects it's properties.
So to your original statement about water.
A) Water is a naturally polarized particle, so it can easily support attraction of free electrons.
Ionized water (e.g. salt-water) has even greater electron attraction
B) Water is anamorphic (non structured, and constantly moving), so the mean-time-to-collision is pretty short.. This restricts conductivity significantly.
C) Water is not naturally ionized - it doesn't give off a free electron in it's natural state at room-temperature, so there are very few actual electrons available to conduct. Salt, on the other hand DOES give off a free electron when ionized in water. Likewise acids are ionized giving off free electrons. Thus lead-acid batteries use water with lots of free electrons, and thus conduct electricity reasonably well. Note that it's the storage of electrons, not the conductivity of electrons that makes these batteries useful. In fact the collisions due to high current conduction heats up the water.. This is how car batteries can explode, and this is why you should never open up the battery ports immediately after a car has been running for a long time.
Re:3D Microprocessors (Score:3, Informative)
Sparc T1: 8 Cores w/4 threads [wikipedia.org] (Maximum thoroughput: 32 simultaneous processes)
16 Core POWER5 [ibm.com]
Cell Processor: 1 Primary + 8 Sub-Processors [wikipedia.org]
Intel Promises 80 cores [com.com]
We're at a LOT more than "four".