(a) Thermopower versus time for a mat of SWNTs at K initially saturated with air at ambient conditions. The sample is under dynamic vacuum when open symbols are used and dark symbols representing intervals when N2 and He are present. N2 is introduced at B and D; He is introduced at F and H. Vacuum pumping is applied at A, C, E, G, and I; (b) four probe resistance ratio of SWNT mat at 500 K versus time. Data normalized to sample resistance at A. Points A through I have the same meaning as described for (a). Shown in the inset is the time dependence of the temperature during the admission of each gas and subsequent pumping [38].
