The eletrical transport properties of SWNTs has been recently studied has raised some controversy. The conductance of a tube is quantized, and a nanotube acts as a ballistic conductor. Nanotubes also have a constant resistivity, and a tolerance for very high current density.
In 1998, Stephan Frank et al. experimented on the
conductance of nanotubes. [5] Using a SPM, he carefully contacted nanotube
fibers with a mercury surface. His results revealed that the nanotube behaved as a ballistic conductor
with quantum behavior. The MWNT conductance jumped by increments of 1 G0 as additional
nanotubes were touched to the mercury surface. The value of G0 was found to be
1/12.9 k
-1, where G0= 2e2/h . The
coefficent of the conductance quantum was found to have some suprising integer and non-integer values,
such as 0.5 G0.
Later, in 1999, Sanvito, Kwon, Tománek, and Lambert, [4] used a scattering technique to calculate the ballistic quantum conductance of MWTNs. They found that their results explained these unexpected conductance values found by Frank in 1998. Sanvito et al. stated that some of the quantum conductance channels were blocked by interwall reactions. Also, the interwall reactions of MWNTs were found to redistribute the current over individual tubes across the structure nonuniformly.
Relatively early in the research of nanotubes, Thess et al. calculated the resistivity
of ropes of metallic SWNTs to be in the order of 10-4 -cm at 300 K.
[2] They did this by measuring the resistivity directly with a four-point
technique. One of their values they measured was 0.34 x 10-4, which they noted
would indicate that the ropes were the most highly conductive carbon fibers known, even factoring in
their error in measurement. In the same study his measurements of the conductivity, Frank et al.
[5] was able to have reach a current denisty in the tube greater than
107 A/cm2. Later, Phaedon Avouris [12] suggested
that stable current densities of nanotubes could be pushed as high as 1013 A/cm2.
