Giant Thermopower Effects from Molecular Physisorption on Carbon Nanotubes

Results are presented of in situ studies of the thermoelectric power and four-probe resistance of single-walled carbon nanotube films during the adsorption of cyclic hydrocarbons ${\mathrm{C}}_6{\mathrm{H}}_{2n}$ ($n=3–6$). The size of the change in these transport parameters is found to be related to the $\pi$ electron population of the molecule, suggesting the coupling between these $\pi$ electrons and those in the nanotube wall may be responsible for the observed effects. A transport model for the SWNT film behavior is presented, incorporating the effects of a new scattering channel associated with the adsorbed molecules.