Temperature dependences of conductivity and magnetoconductivity of multiwall carbon nanotubes annealed at different temperatures

Temperature (in range 4.2–300 K) and magnetic field (in fields up to 10 kG at 4.2 K) dependences of the conductivity of two sets of multiwall carbon nanotubes with different average diameters (8–10 nm and 20–22 nm) heated at various temperatures (1600, 2200, 2600, 2800 $^\circ$ C) were investigated. Temperature dependences for nanotubes with average diameter 20–22 nm is typical for quantum corrections to conductivity of the systems with interaction electrons in two dimensional conductors with local disorder. For nanotubes with average diameter 8–10 nm temperature dependences corresponds to one-dimensional variable range hopping conductivity (VRHC). The variation of annealing temperature of MWNTs influence on the contribution of corrections to conductivity and parameters of VRHC. The magnetoconductivity of MWNTs also depends on the annealing temperature and is less than that of highly oriented pyrographite. Annealed MWNTs with average diameter 20–22 nm has a positive magnetoconductivity.