Thermoelectric properties of a nanocontact made of two capped single wall carbon nanotubes (SWCNT) are calculated within the tight-binding approximation and by using Green’s function method. It is found that doped semiconducting nanotubes can have high Seebeck coefficients. This in turn leads to very high figures of merit $\left(ZT\right)$ for $p$-doped tubes which turn out to have also a large electrical to thermal conductivity ratio. Transport in the nanocontact device is dominated by quantum interference effects, and thus it can be tuned by doping (charge transfer and/or impurity potential) or application of a (nano-)gate voltage, or a magnetic field. Another reason for high $ZT$ in this device is the absence of phonon transport as there is barely a contact.

• Received 1 October 2005

DOI:https://doi.org/10.1103/PhysRevB.73.085406