Magnetotransport in mesoscopic carbon networks in the vicinity of metal-insulator transition

The magnetoresistance (MR) in the magnetic fields up to 35 T and the temperature dependencies of the resistance of honeycomb-shape carbon networks were measured in the temperature range 2-300 K. Two transport mechanisms were found in these systems: the hopping conductivity in the strong localization (SL) regime and weak localization (WL) in the diffusive transport limit. A crossover from SL to WL regime was observed with the temperature increasing. The temperature dependence of the resistance follows a typical for 3D-WL law Rsimilar toT(-n) in the temperature range 100-300 and 5-300 K for networks annealed at 950degreesC and 1150degreesC, respectively. The negative magnetoresistance (NMR) observed at T > 100 and 25 K, depending on the temperature of annealing of the samples, is related to quantum interference in the ATL regime. The positive magnetoresistance observed in the low-temperature range was due to the magnetic field induced shrinkage of the electronic wave functions. (C) 2002 Elsevier Science B.V. All rights reserved.