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Shaahin G Shirazi

Why is the conductance of CNTs so high in this tool?

The conductance of CNTs in the curves extracted after simulation process is around 1e+7 Siemens or higher. But we know that the conductance of a ballistic SWNT with perfect contacts is (4e^2)/h which is equal to 155 micro Siemens. Is there an acceptable reason for these high values?

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    Eric Pop

    Thanks for pointing this out. You have found a small bug in the code. The conductance is calculated as eq 1 in our paper, Y. Zhao, A. Liao, E. Pop, IEEE Elec. Device Lett. 30, 1078 (2009), but the units are incorrectly listed here. The “conductance” plot window is actually plotting just mu*n, but the total G=q*mu*n/L (where n is in units of electrons per unit length, 1/m). So the “conductance” plot needs to be multiplied by a constant factor of q/L ~ 4e-14 C/m here.

    As a small side note, the 4q2/h conductance is for 4 ballistic channels in a SWNT. If multiple subbands are involved (i.e. Fermi level is in 2nd subband or beyond) and all are ballistic then the conductance can be higher than 4q2/h.

    In any case, we will need to update the plot window to reflect the missing q/L pre-factor. Otherwise please check the “guts” (physics) of the model against our paper listed above, and let us know if anything else seems odd. Thanks again,

    Eric Pop Assistant Professor Electrical and Computer Engineering University of Illinois at Urbana-Champaign 2258 Micro and Nanotechnology Lab T: + W:

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