Temperature dependent resistance of as-grown and chemical treated single walled carbon nanotubes films.

Single Walled Carbon Nanotube (SWCNT) films were directly synthesized via Floating Catalyst Chemical Vapor Deposition (FCCVD) method. Temperature dependent resistance measurements were carried out on the as-grown and chemical treated SWCNTs films. A "U" shaped curve was obtained for each sample, with a significant variation in the crossover temperatures between the as-grown and treated samples. A heterogeneous model was adopted to interpret the experimental data, revealing the coexistence of anisotropic 1D metallic conduction, conventional metallic conduction and fluctuation assisted tunneling. Our results implied very low barriers, verifying the good intertube and interbundle contacts in the directly synthesized SWCNTs films. We speculated that oxidization and acid treatments would affect the overall configuration of the films, leading to the changes in the temperature dependence of resistance. In addition, Raman and absorption spectra indicated that oxidization and acid process would cause moderate changes in the hole carrier concentration of the films.