Magnetotransport in the amorphous carbon films near the metal-insulator transition

The low temperature electrical conductivity behavior of the amorphous carbon films in the non-metallic regime of the metal-insulator transition is studied in magnetic fields up to 7 T. The films are prepared from the pyrolysis of succinic anhydride in the temperature range 700-980 degrees C. A positive magnetoresistance (MR) is observed in films that are in the insulating regime and follows the variable range hopping (VRH) mechanism of conduction. In the VRH regime, at low temperatures B-2 dependence on the magnetoresistance is observed. The conductivity of the films in the critical regime follows the power law behavior. The MR is positive both at low and high field limits. At high fields the magnetoconductance is proportional to B-1/2 and is negligible at high temperatures. (c) 2007 Elsevier Ltd. All rights reserved.