Thermoelectrical random stick network method and its application to carbon nanotube films

Electrical and thermal circuit analyses on a random stick network were combined to develop the simulation method to calculate the thermoelectric response of carbon nanotube (CNT) films. The experimental results were successfully reproduced with respect to the gate-voltage dependence of both the electrical conductivity and Seebeck coefficient of CNT-film field effect transistors for various mixing ratios of semiconducting/metallic CNTs. The Seebeck coefficient increases monotonically with the semiconducting CNT content and the rate of increase in the Seebeck coefficient is strongly dependent on the chemical potential (i.e. the carrier density). The thermoelectric response of aligned CNT films was also investigated. The Seebeck coefficient of an aligned CNT film was determined to be isotropic (i.e. independent of measurement in the directions parallel and perpendicular to the CNT alignment), although the electrical conductivity in the direction parallel to the CNT alignment was much larger than that in the perpendicular direction.