Thermoelectric power of aligned and randomly oriented carbon nanotubes

Thermoelectric power was used to elucidate the electrical transport propert ies of aligned and randomly oriented carbon nanotube systems in the tempera ture range 77-450 K. A weakly negative thermoelectric power, comparable wit h that of a graphite flake, was observed for a macroscopic bundle of multiw all carbon nanotubes with individual axes aligned parallel to the main axis . However, mats of randomly oriented multiwall carbon nanotubes gave a stro ngly positive thermoelectric power, as did mats of single-wall nanotubes. T his is evidence of the importance of intertube contacts in the interpretati on of the thermoelectric power data for carbon nanotube systems. Models for thermoelectric power behavior incorporating contact effects are described.