I'd like to draw your attention to this article, which is published in the last Nature issue.

Single-crystal metallic nanowires and metal/semiconductor nanowire heterostructures

YUE WU1,*, JIE XIANG1,*, CHEN YANG1, WEI LU1 & CHARLES M. LIEBER1,2

Substantial effort has been placed on developing semiconducting carbon nanotubes and nanowires as building blocks for electronic devices—such as field-effect transistors—that could replace conventional silicon transistors in hybrid electronics or lead to stand-alone nanosystems. Attaching electric contacts to individual devices is a first step towards integration, and this step has been addressed using lithographically defined metal electrodes. Yet, these metal contacts define a size scale that is much larger than the nanometre-scale building blocks, thus limiting many potential advantages. Here we report an integrated contact and interconnection solution that overcomes this size constraint through selective transformation of silicon nanowires into metallic nickel silicide (NiSi) nanowires. Electrical measurements show that the single crystal nickel silicide nanowires have ideal resistivities of about 10 µ cm and remarkably high failure-current densities, >108 A cm-2. In addition, we demonstrate the fabrication of nickel silicide/silicon (NiSi/Si) nanowire heterostructures with atomically sharp metal–semiconductor interfaces. We produce field-effect transistors based on those heterostructures in which the source–drain contacts are defined by the metallic NiSi nanowire regions. Our approach is fully compatible with conventional planar silicon electronics and extendable to the 10-nm scale using a crossed-nanowire architecture.

Unfortunately I cannot read further, but I'd certainly do if I had an access.

The same group (Lieber's) has also been working on developing biosensors using nanowires. Basically, since the conductance of the nanowire is dependent on surface impurity, it can detect even a single binding molecule.

So this means to put these in chips, we'd have to clean each nanowire perfectly and keep them perfectly clean?! Same goes for nanotubes!

Smaller wires have larger resistivity. Ultrathin insulators can conduct by leakage or tunnelling. Is it possible that small enough nanowires become as resistive as tunneling insulators?

hello, all

just to correct some misconceptions here...

the impurities to which you refer are electron donating dopants, not dirt or what have you...if you put in an impurity such as potassium (a 1s1-type groupI metal), you've doped in an extra electron, making the nanotube conductive...as we all know, potassium is all too happy to sit there as a cation (just like in KCl or KI, or any other potassium salt) and give up it's precious electron so easily - what a slut!

secondly, the conventional notion of diam v. resistivity does not apply here, since the method of conduction is completely different from typical copper conduction (where the medium is effectively a 2-space electron sea). carbon nanotubes are relying more on the excited states of the electron in the graphene matrix (the carbon lattice from which the nanotubes are constructed) than the ballistic path to conduct.

angrily spinning my solids...

Carbon nanotube conductance: isn't it 2e^2/h per wall?

Isn't that how STM works?

Solid Spin:

Could you expand on your discussion as to why the electron conduction mechanism in Cu is different from the others. I'm curious as to why you would not expect surface scattering to become more dominant with reducing diameters - something to do with non-ballistic transport?