Thermoelectric power behavior in carbon nanotubule bundles from 4.2 to 300 K

Thermoelectric power (TEP) properties of carbon nanotubule bundles were measured in the range 4.2--300 K. It was found that the TEP is positive over the whole temperature range, and increases with the increase of temperature. Above 30 K it can be well described by a formula S(μV)=0.181T-(61.8+0.092T)e^-308.3/T, which is derived based on a two-band model. This result supports the theoretical prediction for both kinds of nanotube bundles, metallic and semiconducting. Below about 30 K, the fitting curve clearly deviates from the experimental data, which may indicate some possible changes of electronic structures, an electron weak localization effect, for example.